WAR 2 1970

Reference not to

taken froin the liL^^jy.

BUILDING SCIENCE SERIES

20

Durability of

Insulating Glass
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UNITED STATES DEPAKTMENT OF COMMERCE • Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

Proceedings of a Seminar on the

Durability of Insulating Glass

Held at the National Bureau of Standards

Gaithersburg, Maryland, November 14-15, 1968

Henry E. Robinson, Editor

Building Research Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

Sponsored by

The American Society for Testing and Materials, Committee E-6

The Building Research Institute

The Construction Specifications Institute

and

The National Bureau of Standards

Building Science Series 20

' (

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NATIONAL BUREAU OF STANDARDS

MAR 2 1970

Abstract ^fj,

^ ' A two-day seminar on the Durability of Insulating Glass was attended by some 130 persons on November 14 and 15, 1968. The seminar was held at the Gaithersburg, Maryland, facilities of the National Bureau of Standards and featured fourteen speakers who participated in

panel discussions or delivered individual papers. Numerous agencies interested in design, manufacture, specification, purchase, installation or maintenance of windows were represented at the seminar.

Among the topics considered in the panel discussions were: (1) The need for reliability

and durability of insulating glass; (2) manufacturers' test methods ; (3) proposals for future

action. The Canadian experience with an accelerated test method and acceptance program was

presented and discussed, as were the Norwegian accelerated test methods and their correlation

with field experience. A review of current practices leading to new test methods and standards was also presented, and a "round robin" program that would compare various test methods now employed in the industry was proposed. Affirmative interest in participating in the

proposed round robin was expressed by about a score of manufacturers present at the seminar.

Key words: Accelerated laboratory tests; double-glazed window units; factory-sealed insulating glass units ; field performance tests, correlation with laboratory tests ; sealant performance ; test methods ; standardized testing.

Library of Congress Catalog Card No. 76-605058

II
Foreword

The use of factory-sealed double-glass insulating units is increasing in both Government and

privately owned buildings. Seal failure on some of the units leads to moisture penetration of

the air space, with ultimate fogging and loss of clear vision through the unit. Such failure is of concern to users, fabricators, and specifiers of insulating units.

To provide a first forum for exchange of information and suggestions for assuring improved seals, the National Bureau of Standards jointly with a subcommittee of ASTM Committee E-6, and with the Building Research Institute and the Construction Specifications

Institute, Inc., sponsored a Seminar on Durability of Insulating Glass, held November 14 and

15, 1968, at Gaithersburg, Maryland. Registered attendance totaled about 130 persons, including contingents from two other countries.

This publication contains the proceedings of the sessions of the Seminar, and the texts of

thirteen papers or panel presentations contributed at the Seminar.

Lewis M. Branscomb, Director

m

Contents

Page Abstract ii Foreword iii

Introductory remarks—James R. Wright 1

Introductory remarks—Willis MacLeod 2

1. Panel Discussion I Introduction of the First Panel—Robert W. McKinley 3

1.1. The roles of architects, manufacturers, and contractors in the prevention

of early failure of insulating glass units. Harold J. Rosen 3

1.2. The need for a method to evaluate the performance life of insulating glass

units. Lynford K. Snell, Jr. 5

1.3. Problems resulting from early failure of insulating glass units. Willard E. Bryant 7

1.4. Discussion Session I 9

2. Canadian Experience With an Accelerated Test Method and Acceptance Program 11

2.1. The development of evaluation procedures for factory-sealed double-glazing

in Canada.

K. R. Solvason and A. G. Wilson 11

2.2. Discussion Session II 17

3. Norwegian Experience With Accelerated Test Methods and Their Correlation With Field Experience 19

3.1. Norwegian experience with accelerated test methods for sealed glazing units and their correlation with field experience. Tore Gjelsvik 19

3.2. Discussion Session III 25

4. Panel Discussion II Introduction of the Second Panel—Robert W. McKinley 27

4.1. Test methods for evaluating organically sealed insulating glass units. Joseph S. Amstock 27

4.2. Manufacturers' test methods : Correlation with field experience ; expected

field life. James D. Gwyn 35

4.3. Test methods and field experience with double-glazed units. R. J. Mazzoni and G. H. Bowser 37

4.4. Insulated glass sealants—function and types. James A. Box 43

4.5. Discussion Session IV 47

5. A Review of Current Practices Leading to New Test Methods and Standards 49

5.1. An exploratory study of laboratory testing methods and standards for factory-sealed double-glazed window units. Henry E. Robinson 49

5.2. Discussion Session V 59

V
Contents (continued)

Page

6. Proposals for Future Action—Panel Discussion III Introduction of the Third Panel—Henry E. Robinson 61

6.1. Proposals for future action. Lynford K. Snell, Jr. 61

6.2. Proposals for future action. Roger O'Shaughnessy 62

6.3. Proposals for future action—Round robin comparison of test methods.

Robert W. McKinley 63

6.4. A manufacturer's experience with insulating glass. O. C. Stout 65

6.5. Discussion Session VI 67

7. Biographies of Speakers 77

VI
Proceedings of a Seminar on the

Durability of Insulating Glass

Introductory Remarks

James R. Wright'

National Bureau of Standards,

Washington, D. C. 20234

Introductory remarks were made by the author to the attendees of a seminar on the Durability of Insulating Glass. The National Bureau of Standards Building Research

Division was a cosponsor of the seminar held at the NBS on November 14-15, 1968.

Key words : Accelerated testing ; insulating glass units ; standardized testing.

Gentlemen : In welcoming you here to participate in the seminar on Durability of Insulating Glass, of which the National Bureau of Standards is privileged to be a co-sponsor with

ASTM Committee E-6, the Building Research Institute, and the Construction Specifications

Institute, I am much impressed that one type of product, among the hundreds that compose the

fabric of a building, should receive such manifest attention and consideration, looking toward

improved durability in service applications. That is not to say that many other products might

not also benefit from similar attention ; I point out simply that in the case of insulating glass

units, a worthy and necessary step forward is being attempted here and now. I wish you

success and effective action in this direction.

The seminar program is designed to bring you contributions from architects, builders,

and large users of insulating glass. The contributions are from : four sources primarily con- cerned with testing methods for evaluating units ; four sources of similar interests as producers of units or component materials; and one source from a leading manufacturer of

windows who is well aware of his dependence, and the dependence of his customers, on the

quality of insulating glass units that he can incoi-porate in his finished product. These contributions will be made richer by those from highly respected laboratories of two other countries—from the Division of Building Research of the National Research Council of Canada,

and from the Norwegian Building Research Institute. It is gratifying to have representatives

from these organizations here, and we welcome them cordially.

With the wide spectrum of information that will be put before you, we can be encouraged

as to the prospects for useful action stemming from this seminar. Nevertheless, one must not

expect automatic success. As I visualize it, yours is one of the more difficult of technological

tasks—to ascertain, on a sound and reliable basis, by means of accelerated laboratory tests, in

as short a time as possible, the prospective durability in service of sealed insulating glass

units. The goal, of course, is assured, satisfying performance for periods up to or beyond

the expected life of a building. The fact that this seminar has been convened, and so well

attended, attests that this goal has not been generally and adequately met at this point in

time.

Speaking now as Chief of the Building Research Division of the National Bureau of

Standards, I can say that the Division has had considerable experience in accelerated tests to ascertain durability of building materials in service, and we know something of the problems, and the efforts needed to solve them. One instance that may be cited is a project undertaken to study the durability of asphalt roofing materials, accomplished by means of a research

associateship sponsored by the Asphalt Roofing Industry Bureau, research programs sponsored by NBS, and related projects sponsored by other Federal agencies. We have learned

much from this combined research effort, and have replaced tests requiring months to produce qualitative data with tests that yield quantitative results in a few hours. The Materials

Durability Section of the Building Research Division conducts studies on the durability of

plastics, organic coatings, polymeric coatings, metals, and inorganic building materials.

However, time does not permit more than a mention of this fact.

J Chief, Building Research Division.

1
Out of this experience, I would suggest to you that a concerted effort by your industry,

however or whenever launched, would be the most promising course of action. It is interesting

that the program of certification established by Sealed Insulating Glass Manufacturing Association could be a nucleus for such an undertaking, provided that developmental or evolutionary research was given ample support.

In closing these introductory remarks, I would like to mention an important practical

matter that must be well appreciated among you. The cost of laboratory testing of one manufacturer's lines of sealed insulating units is at present quite considerable, and the testing

capability required to test all manufacturers' products in a reasonable time does not exist at present. There is, therefore, an urgent need to develop standardized testing methods, and apparatus capable of standardized testing of large numbers of units, effectively, uniformly,

quickly and at lowered costs. I would suggest to you that contributions in this direction, that

might be accomplished through the action of this seminar, would well justify it, quite apart

from the cooperative understanding and concerted effort that it is hoped the seminar will

engender.

Introductory Remarks

Willis MacLeod

American Society for Testing and Materials,

Philadelphia, Pennsylvania 19103

Introductory remarks were made by the author to the attendees of a seminar on

the Durability of Insulating Glass. The American Society for Testing and Materials

(ASTM) was a cosponsor of the seminar held at NBS on November 14-15, 1968.

Key words : Insulating glass units, standards, uniform test methods.

It is indeed a privilege to welcome you on behalf of the American Society for Testing

and Materials which, along with the National Bureau of Standards, the Building Research

Institute, and the Construction Specification Institute is a cosponsor of this Seminar on the

developing technology in research and testing of insulating glass window units in building

and housing construction.

The American Society for Testing and Materials, organized in 1898 and incorporated in

1902, was formed for "the promotion of knowledge of the materials of engineering and the

standardization of specifications and methods of testing." There are about 16,000 members in

the Society and 100 main technical committees which develop standard methods of test and

specifications for materials and products and recommend practices. The Index of ASTM

Standards lists more than 4,000 standards and specifications covering the materials of engineering. These are developed under procedures representing a consensus of the producing,

consumer, and general interest participant in the technical committee having jurisdiction

for the standards. For this reason, a large majority of the present U.S.A. Standards was

developed by ASTM.

The Durability Task Group, Subcommittee VIII of ASTM Committee E-6 initiated the

Seminar.

Our distinguished Chairman of the Seminar Committee, Mr. McKinley, is a member of

ASTM Committee E-6 on Methods of Testing Building Construction which originated and

has spearheaded this project presenting to you a program of knowledgeable and competent

authorities including our colleagues from Canadian and Norwegian Building Research on the

subject of double glazed window unit durability. It is our expectation that these presentations and deliberations will lead to the development of uniform test methods for measuring in meaningful terms the serviceability and durability of insulated glass units in order to insure

levels of serviceability commensurate with the several types of building construction in which

they are used. ASTM is organized and stands ready to respond to any conclusions resulting

from the Seminar.

2
1. Panel Discussion I

Introduction of the First Panel

Robert W. McKinley

Thank you^ Mr. MacLeod. Mr. MacLeod''s realization of the need for this Seminar

helped very much to get things launched and to obtain ASTM sponsorship.

I hope that members of the Building Research Institute and of the Construction Specifications Institution Jioill understand if we do not take time now to detail their help. We do

appreciate their sponsorship. The program now is under way. You will find the qualifications

of our first panel summarised in the biographical sketches that came in your registration

packet. I call upon our first panel., the members of which are: Mr. Harold J. Rosen., Chief.,

Specifications Department^ Skidmore, Owings, and Merrill, Architects and Engineers; Lynford K. Snell, Jr., Architect, Federal Housing Administration, Washington, D.C.; Willard

Bryant, Assistant Director Technical Services, National Association of Home Builders,

Washington, D.C.

Our primary target during the seminar is an exchange of information and an understanding . . . and we''re starting with the consumers, the users of insulating units, in order

that we may understand what they believe their needs to be and what we may do to help

them satisfy those needs.

Mr. Rosen.

1.1. The Roles of Architects, Manufacturers, and

Contractors in the Prevention of Early Failure of

Insulating Glass Units

H. J. Rosen^

Skidmore, Owings & Merrill,

New York, New York 10022

Architects, manufacturers, and contractors can play distinct roles in the prevention

of product failure. If each fulfills his own obligations, as set forth in the AIA policy statement of a few years ago, he will be contributing to the life of the product. Another

way to diminish the problem of failure would be for these three parties to join together

in research for methods of preventing such failure. Key words : Design ; installation ; materials failure ; production.

1. Introduction

Mr. Chairman, for the next two days apparently

; you are going to hear a good deal in depth and in

detail about the problems of insulating glass . . .

i and I would think that although the program

!{ indicates that I am to talk about how one gets

II involved with additional cost as a result of a

I failure of insulating glass, that I can best address

j myself to the subject if I speak about the area of

I, involvement of each of us—architects who design,

I manufacturers who produce, and contractors who

I install. I think if we all understood our relationship and our responsibility, we would have an area

of agreement and perhaps in that way reduce the

I problem,

ij

' Chief, Specifications Department.

Now, where does responsibility lie when materials failure occurs? It is with the architect who

selects the material, the manufacturer who produces and furnishes it, or the contractor who installs it? Each of the parties has an obligation to the owner in selecting, furnishing, and installing

the product. Too many times we think only in

terms of a product failure involving the product

itself because of certain inherent defects. We fail to recognize that product failure can also be at- tributed to a poor design on the part of the architect or improper installation on the part of a

contractor. T\Tio is responsible for fogging of in- sulating glass when it occurs after three or four

years of service? 'Who is to be responsible for

cracking of insulating glass after the one year

guarantee runs out? Architects and engineers are prone to think that their judgment is infallible

3
and that they can do no wrong. But they should

also remember that a judicial decision in a court

of law will be resolved on the pertinent facts of

a particular case. Thus architects, manufacturers,

and contractors fare no better or worse than any- one else when they enter into contractual rela- tionships. We cannot resolve here today a hypothetical case of who is responsible for insulating

glass that has "gone sour" for one reason or

another. We can join in research for methods of

preventing materials failures rather than try to

fix responsibility after a failure occurs.

2. Architect's Role

Now what is the architect's role in the selection

of materials ? When a man practices architectural

engineering, he is expected to have an adequate

knowledge of the science of design and construction and to exercise reasonable care, judgment, and

technical skill to see that the design is properly

executed and the work properly done. Court decisions have held that an architect is responsible

for proper selection and application of materials,

and for adequate research, and that reliance on

advertising literature of the manufacturer or

o<:lier respresentations of the manufacturer, do not

necessarily protect the architect. About two or

ihree years ago, the AIA issued what it calls a

policy statement on building product development and uses, and it makes the following observations concerning the obligations of each of the

parties : Now first, with respect to what the architect is obligated to do—He is expected to inform

himself with respect to the properties of the

products he specifies, though he is entitled to rely on manufacturers' written representations. He is advised to seek the technical opinion of the re- search or application engineering departments of

the manufacturer when his intended use is not

clearly included in the printed data of the manufacturer. He is further responsible for uses con- trary to supplementary written information on

proper use in installation procedures of the manufacturer. The architect's use of a product and its installation should extend to its compatibility

with and relationship to adjacent materials and

assemblies, notwithstanding the manufacturer's

similar obligations. Now the AIA hasn't any

guide rules on what to do when we arei con- fronted with two major insulating glass manufacturers, each advocating a different method for

installing insulating glass in a structural neoprene

gasket. Perhaps if you want to ask me separately

what I think about it, I'll give you that kind of

information.

3. Manufacturer's Role

Now how about the role of the manufacturer?

The AIA in the same policy statement suggests

that manufacturers be guided by the following

rules : The manufacturer should supply the architect with all essential data concerning his product, including pertinent information which would

involve its installation, use, and maintenance.

Particularly important is information on the

product's compatibility and interfitting with in- terrelated products, as well as precautions and

specific warnings on where the products should

not be used, based on conditions of known or anticipated failures. TVHienever the manufacturer

has specific knowledge of a new proper use of his

product, he should furnish such information in

writing to the architect. The manufacturer is ex- pected to recognize that he is responsible for the

failure of his product to perform in accordance

with his written data supplied by him or his au- thorized representative, as well as for misrepresentations of such data. And, finally, the manufacturer is expected to investigate the relationship of his prodvict to other components likely or

logically expected to be used in association with

his product. Such information should be available to the architect. 4. Contractor's Role

Now, how about the contractor ? A contractor's basic responsibility is to perform substantially ac- ' cording to the drawings and specifications set forth by the architect. A contractor who has, in

fact, performed substantially and built the building accordingly, would be absolved from any legal

responsibility.

Now the AIA policy statement sums up the contractor's obligations as follows : It is the respon- ji sibility of the contractor to inform himself con- k cerning the application of the product he uses

| and to follow the directions of the architect and '< manufacturer . . . and in the event of disagreement, between the contract documents and the

manufacturer's directions, the contractor is ex- pected to seek written instructions from the archi- i tect before proceeding with the installation.

If the contractor has knowledge of, or reason to believe the likelihood of a failure, he is expected

to transmit such information to the architect and 1 ask for written instructions before proceeding

with the work. This policy statement outlines the

AIA's position.

5. Conclusion

Today's sophisticated construction techniques , and esoteric materials require knowledgeable per- ^ sons on the staffs of architectural, manufacturing,

»

and construction firms. These skilled people must

be able to cope with the problems related to build- I ing products and their incorporation into complex ^ designs. To reduce the problems the following , do's and don'ts are suggested as a guide to select- ing materials and reducing the possibility of a ' materials failure. ^ Do be certain that the manufacturer knows how [ his material or equipment will be used. Don't use ' an unfamiliar material unless it is known to have ' been used successfully in installations similar to the proposal under review. Don't rely on a manu- . facturer's statements and claims as the only basis

for using the material.
1.2. The Need for a Method to Evaluate the

Performance Life of Insulating Glass Units

Lynford K. SneU, Jr/

Federal Housing Administration,

Washington, D. C. 20412

The FHA's interest in insulating glass is growing as the product's use is growing.

This agency has reviewed various specifications for evaluating units, but there is no

consensus on a procedure which can be used successfully. A reliable method of estimat- ing service life of glass units is badly needed.

Key words : Durability ; test method : sealed insulating glass unit.

1. Introduction

j In reviewing the docket on the subject of sealed

insulating glass units the other day, I found that

as far back as mid-1964, shortly after I started

I with FHA, several of our field offices had ex- pressed concern and asked for guidance in select

I ing suitable sealed insulating glass units.

]j The increase in the number of manufacturers

and types of manufacture, coupled with the ab-

' sence of a way to evaluate the performance life of

these units, amplified the need to pursue efforts

I toward some type of solution. This was added to

I our list of project assignments in March 1965.

1 2. The Need for a Test Procedure

I FHA has reviewed various specifications for

evaluating sealed insulating glass units. There

^ were, and still are, differences of opinion on a

, procedure which can be successfully used. Our

* interest, of course, is in a procedure to measure

j (estimate) the service life (durability) of these

' units.

I Large areas of glass are used widely in today's

i architecture, and as the consumer demands furI ther sophistication in the control of his environ-

' ment, the additional comfort provided by sealed

; insulating glass units will result in increased use

I of these products.

One generally considers glass to be a very dur-

' Architect, Architectural Division.

able building material; excluding breakage, it is one of the few products capable of lasting the

useable lifetime of a building. Based on the foregoing premise, it would indeed be tragic to dis- cover suddenly that unanticipated failures necessi- tate replacement.

The Methods and Materials section of FHA's

Architectural Division is responsible for providing our field offices with the best technical advice

possible and in many ways is comparable to the

specification department of an architectural firm.

When there are concerns about product performance, ways and means must be devised and measures taken to provide protection commensurate

with the estimated risk. During the next two days, we will all have the

opportunity to review and discuss various

methods used to measure or estimate the durability of sealed insulating glass units.

For several years FHA has been trying to determine if there is one test method for insulating glass that can be depended upon for estimating service life. If there is a margin of error in

using such a method, what percentage of success can be expected ? In view of the fact that there is uncertainty about an acceptable test method, we

can understand why specification writers sometimes use empirical precautionary measures.

It may be advisable for FHA to consider re- serves for replacement of units that fail in programs where such reserves are required. In regard

to single family programs there are no reserves; consequently, the homeowner will face the ex- pense of replacing these units on his own.
3. Conclusion

Several articles have been published in recent months relative to the liability of the architect,

engineer, and manufacturer in regard to building

materials and systems. Who is to be placed in the

position of ultimate responsibility? The architect

who makes the selection? Or the manufacturer

who has offered evidence of performance for his

product ? The selection and use of new materials and sys- tems could be seriously deterred by attempting to single out a source of responsibility.

It would seem to me more logical to think in

terms of a team effort wheteby responsibility is reasonably distributed and ultimately placed. I

believe if we can show that we have exercised the

best of our current knowledge in arriving at such

decisions, such as by selecting an appropriate test method, then we will be able to endure criticism

that may arise from our decision.

If we share an interest in development and in- novation (in other words in progress), then we

must share in assuming the probable risk and

responsibilities of this adventure.

6
1.3. Problems Resulting from Early Failure

of Insulating Glass Units

Willard E. Bryant

National Association of Home Builders,

Washington, D. C. 20034

Appropriate standards and test methods would improve the quality of insulating

glass units and also the meaningfulness of manufacturers' warranties. As the situation

is now, the builder is not fully protected from loss of money, time, and labor, or from

loss of business resulting from failure of units even though the units are covered by

warranties.

Key words : Insulating glass industry, product evaluation, product failure, warranties.

1. Introduction

1 I think it is important to make one comment

|! before I get into my discussion. Much of what I

'j have to say is equally true of many, many other

jl building products so I'm not taking a potshot at

I the insulating glass industry.

The major problem with regard to durability,

1 other than accidental breakage, is the failure of

i the seal with its attendant and very attention-

,j producing element of fogging or vision-obstructil ing moisture. Due to limited time, I won't go into

ji detail on the topics but I believe you can break

li the builder's viewpoint down into two categories

I involving periods of time: The first, you might

1 call the short term, which would be the time when

l{ the house or the building is under construction

or if there is a one-year warranty period. And the

i second, the longer term, is when the unit is under

Ij the manufacturer's warranty.

2. Failure Problems

j The short term problem presents the builder

I with a number of questions rather than answers, and these concern how meaningful the warranties

are. In other words you have a 5-, 10-, 20-year

warranty . . . are these warranties really indicative of the expected life of the unit, and are there

I meaningful test procedures to back up these warj ranties? When a builder purchases an insulating

unit, how does he know what he's really getting?

Of course, as with any other products on the

market, he pretty much has to rely on the manufacturer. Let's assume that during the time when

it's the builder's responsibility, that a unit does

fail. Now what can the builder expect to happen ? Well typically the manufacturer will replace the

i unit.

' Assistant Director of Teclinical" Services.

This is only a partial answer because the builder

still has to take it down to his dealer, bring it back, and reinstall it. Therefore, merely replacing

a unit that fails does not compensate the builder

for all his costs. I think this is really the most

important aspect of the problem because the

warranty doesn't really protect the builder insofar

as his total cost is concerned, and therefore it in

itself is not a completely adequate means of re- course. Now to take the longer range aspect, where the

unit is now under the manufacturer's warranty.

As far as we are concerned, there is a single

problem in this area. If a unit does fail say after

2, 4, or 5 years, w-ho gets the blame? Well, I'm

sitting here, and because the buyer bought the

house from me, I'm responsible to that buyer. And

I'll tell you, this is not a very satisfying answer

to give to one of your buyers—"W^ell, it's not my

responsibility any more, you have to go see the

manufacturer." So, in effect, the builder's public

image suffers as a result of this. Now I think it's important to realize for this particular aspect,

that the average home mortgage today is slightly over 7 years, and this means that repeat business

to a home builder is equally as important as it is to any other business, and the manner in which

the manufacturer backs up his product is ex- tremely important. I think the fact that the glass

unit is typically manufactured by someone other

than the window manufacturer has a tendency to compound the problem.

3. Conclusion

Now the question is : What are some of the conclusions or solutions to this problem. I have made

a short list, and they are not necessarily in order

of importance, but I thought I would put them

forth to you.

First is an establishment of appropriate standards and test methods. Second Avould be a certification program. Third would be The issuance
of adequate installation instructions, which I believe Mr. Rosen briefly commented on, as to how

to properly install and where not to install such

windows. I think in general there has to be a method of evaluating existing products that are on the market. This won't go over very big, but I think that the solution to the failure problem,

from the builder's standpoint, is that perhaps the

manufacturers and the dealers should consider

some method of servicing, or at least evaluating,

failures on the job site, particularly with regard

to establishing responsibility as to Avhether it was

improperly installed, improperly manufactured

or whatever the case might be. And, in addition,

I believe that the producers of glass, and the window manufacturers should cooperate to the fullest degree to produce a window unit that will give

the desired end results.

8
1.4. DISCUSSION SESSION I

Mr. McKinley: Thank you, Mr. Rosen, Mr.

Snell, and Mr. Bryant. You have presented a

challenge. We hope to develop a fruitful response

from the audience.

I would like to have a question put first to Mr.

Bryant since his comments are most recent and

fresh in your mind. A second question to Mr.

Snell. A third question to Mr. Rosen. Having

those questions presented we'll all adjourn for

coffee. That will start what Mr. Rosen referred

to at breakfast as "the fracas". Wlio has a question for Mr. Bryant ? Yes sir ? The question : What

are the builders doing to evaluate units ? The sec- ond question, this one for Mr. Sn6ll (FHA). Yes

sir? The question : How are insulating glass units

now being selected ? Thank you very much. Coming from Canada I think it's very important be- cause they do have a unit testing system. I hope

you'll talk about that with Mr. Snell also. Now

who wants to present a problem to Mr. Rosen.

Yes sir? Clark D. Moore : I'd like to ask Mr. Rosen what

his criteria are for using insulating glass with

reflective coatings as opposed to just standard

reflective glass?

Mr. McKinley : A very perceptive question. I think most of you know that there is something new in the insulating glass market referred to as a reflecting unit. That's an excellent question for

Mr. Rosen.

Mr. Bryant, I wonder if you'd care to give us your response to the question put to you earlier. W. Bryant: I believe the question is, "What

have the home builders done to evaluate insulating glass units?" There is no easy answer to this

and I am not trying to be evasive at all. You in

the glass industry have one product with which

you are concerned. I don't think anybody's ever taken the time and effort to tabulate the total number of different products that go into housing

construction so the answer to the question as to what w^e have done is, quite frankly, "nothing in

the way of research." Now we do have a research

foundation which is a totally owned subsidiary

of NAHB and which does research into products

built for us and for manufacturers. But I think

really the solution is that there has to be a much

greater dialogue between the builder, the dealer,

the manufacturer, supplier, etc., as to where the

problems lie. As a National Trade Association, we

only hear of the problems that are told to us. If

Ave had received an enormous number of complaints about insulating glass quite possibly there

would have been a research project by this time.

As I say, it's very difficult to give you a definitive answer to your question but I think that everybody needs to really get together and discuss the

entire issue, and this is true for many products. I think we often fail to appreciate the viewpoints

and the problems of each other with regard to any

product.

Mr. McKinley: Thank you, Mr. Bryant. Mr.

Snell.

Mr. Snell : Very briefly, I believe the question was, "How do we now select units?" and I think

I can limit my answer to "Hopefully".

Mr. McKinley: Thank you. I think that is understandable to all of us. Mr. Rosen.

Mr. Rosen : I think the question that was posed was "What are the criteria for using insulating

glass with reflective coatings, as opposed to just

standard reflective glass?" I think that the answer

to that question, and to all questions of that same

nature—how do you make a determination of a material to use—depends upon what the industries themselves have done. When there are standards available for the specification writer to use

in the determination of whether a material meets an ASTM standard, a Federal specification or a USASI standard, he utilizes them, and if he

wishes he can modify them too. But he has a basis

for making some sort of a decision that is con- cerned with an industry acceptance of a specific

standard. We're now^ dealing with a product for

which we have no standards whatever. Hopefully, our Canadian friends and our Norwegian friends

may have some answers for us with respect to the

type of criteria that should be established for in- sulating glass and for insulating glass having

reflective coatings. This would perhaps be the

start or the basis for the beginning of a standard

somewhere, promulgated by ASTM or USASI or some other organization that has an interest in

developing that kind of a standard.

Mr. McKinley : Thank you, Harold. May I ask

that you continue the discussion over coffee, or at lunch or dinner with all of the speakers. We do

thank you three for your contribution. You've

launched this Seminar most effectively.

Mr. McKinley : Earlier we mentioned formal

technical sponsorship of several well-known or- ganizations. I think it's significant that our audi- ence includes a heavy representation of fabricators of insulating units from all over the world

with specific emphasis on fabricators from Canada. Following the next paper, because they've

had specific experience, we will ask them to com- ment as specifically as they can, and. with as much

vigor as they care to, about their Canadian

experience.

The next paper is entitled, "The Development

of Evaluation Procedures for Factory-Sealed

Double-Glazing in Canada." The authors are Mr. A. Grant Wilson, Head, Building Services

Section, National Research Council of Canada,

and Mr. K. R. Solvason, Research Officer, Division of Building Research, National Research

Council of Canada. Mr. Solvason will present the

paper. Following his presentation, there will be an opportunity for discussion.

9

2. Canadian Experience With an Accelerated Test Method

and Acceptance Program

2.1. The Development of Evaluation Procedures

for Factory-Sealed Double-Glazing in Canada*

K. R. Solvason and A. G. Wilson'

National Research Council of Canada,

Ottawa 7, Canada

The Division of Building Research, National Research Council of Canada began a

long process of developing test methods for evaluating insulating glass units. The primary requirement was the maintenance of a low dew point temperature in the air space

which, in turn, required an adequate sealing system. The test methods indicate the re- sistance of the seals to failure from stresses in service. A national standard has been

accepted in Canada and insulating glass units made there have steadily increased in quality since the program began.

Key words : Ambient pressure : dew point temperature ; Canadian Government Specifica- tions Board (CGSB) standard; factory-sealed double-glazing units; high humidity cycle;

mechanical stress ; moisture transfer ; organic sealants, ultraviolet radiation ; water

vapor diffusion ; weather cycling apparatus.

1. Introduction

Over the past 10 years a large number of manufacturers of factory-sealed double-glazing units

have entered the Canadian market, and there has

been an increasing use of these components in both

residential and commercial buildings. In 1961,

when the Dominion Bureau of Statistics first began to keep records on their use, the total value

of annual production was about 9 million dollars

;

by 1965, the last year for which records are published, the value had risen to about 16 million

dollars. The development and availability of new or- ganic sealing materials applicable to the construction of sealed glazing units has been one of

the factors that has led to this growth, and all of

the new manufacturers have utilized an organictype sealing arrangement.

The appearance of such large numbers of

brands of sealed double-glazing for which there was no history of field performance presented a

difficult problem to the Central Mortgage and

Housing Corporation (CMHC). This Crown

Company has responsibility for administering the

National Housing Act of Canada, including the

determination of requirements for acceptability

of materials and components used in houses constructed under the Act. Because there were no

published standards or test methods for sealed

double-glazing units, the Corporation asked

DBR/NRC to assist in developing a basis for

* This paper Is a contrlbntlon from the Division of Buildlnp: Research, National Research Council of Canada, and is published with the approval of the Director of the Division.

^ Building Services Section, Division of Building Research,

establishing their acceptability as quickly as

possible.

2. Developing a Test Program

During the early stages of the study that fol- lowed, discussions with experienced manufacturers provided much valuable background information. The provision and maintenance of a low

dewpoint temperature in the air space was quickly

identified as the major criterion of performance.

A low dewpoint temperature is necessary to avoid

condensation and eventual fouling of the glass

surface from leaching of sodium salts, which are a normal component of soda-lime glass. A test method, described in Reference [1],^ to measure

the relative dewpoint temperatures of the air

space was established; initial measurements

showed a wide variation among units, a number

having high values of moisture content.

It was evident from calculations of the amount

of moisture required to produce excessive dewpoint temperatures that only very small amounts

of moisture transfer to the air space could be

tolerated over the service life of a unit, even when

desiccants were employed. Moisture is transferred

to the space by diffusion of water vapor, or, if a

leak exists, as a result of the movement of liquid

water or air caused by pressure differences across the seal. These pressure differences are induced by

temperature or barometer pressure changes, or by

wind action, and result in the transfer of large

amounts of moisture if leaks are present. Thus,

2 Wilson, A. G., and Solvason, K. R., Performance of sealed double-glazing units, J. Can. Ceram Soc, 31, 68-82 (1962).

11
the unit must be hermetically sealed with materials having a high resistance to water A^apor

diffusion and must remain sealed throughout its

life. The primary problem of evaluation is, therefore, the determination of the adequacy of the

seal. In service, stresses leading to seal failures (and

glass breakage) are imposed on double-glazing

units in several ways : by pressure differences between the air space and surrounding air due to temperature and barometer pressure changes; by

differential expansion or contraction of components caused by unequal thermal expansion coeffi- cients and differential temperatures ; by wind pressures; and by forces that may develop due to faulty installation. Sealing systems must withstand the repeated action of these forces and must

also retain the necessary physical properties under

normal conditions of exposure over their required

service life. The development of methods to determine the

resistance to chemical degradation of the sealing

system under service conditions was regarded as a long-term problem and efforts were, therefore,

concentrated on developing methods of evaluating

the ability of the sealing systems to withstand re- peated cycles of stress without developing leaks. Attention was directed towards methods that

could be applied to the units as a whole, rather

than to the individual components, because the

performance of the unit depends upon the interrelation of components and manufactviring techniques.

It was decided that for this purpose it was

necessary to accelerate both the effects of various

kinds of mechanical stresses that could occur in

service and the moisture transfer process, particularly that due to total pressure differences across the seal, so that tests could be conducted in a rea- sonable time. It was also considered desirable to

stress the sealing systems over the range of temperatures that could occur in service in order to expose weaknesses associated with temperaturedependent properties of sealants. The test established for this purpose consisted of exposing one

side of the specimens to room conditions controlled to 73 °F (23 °C) and 50 percent relative

humidity (RH) while exposing the other side to

a simulated weather cycle of : heating to 125 ±

5 °F (52 ± 3 °C) over a period of 90 min, air

circulation alone for 26 min, water spraying at 75 ± 5 °F for 5 min. air circulation alone for 60

min, and cooling to' -25 ± 5 °F ( -32 ± 3 °C)

over a period of 60 min. The apparatus is shown

in figure 1. The dewpoint temperature of the air space

'

after exposure to the weather cycle was taken as the criterion of seal adequacy.

Because of the possibility of wide variations in

quality from faults in the assembly process, it Avas decided that several specimens of each brand

shoukl be tested. Owing to space limitations and

the large numbers of specimens involved, there

Figure 1. Weathering apparatus for sealed douMe-glazing units.

was considerable incentive to use small specimens.

A size of 14 by 20 in. (35.5 by 51 cm) was se- lected, somewhat arbitrarily as a practical minimum.

The size (the small dimension, particularly),

the air space thickness, the glass thickness, and

the rigidity of the edge, all influence the air pres- sure differences developed between the air in the

space and ambient. The pressure difference, in

turn, largely determines the stress imposed on

the sealing system under the conditions of test. A rise in air temperature within the space results in an increase in pressure, a glass deflection and,

hence, an increase in volume. The pressure rise and deflection are interrelated, so that on small

units the deflection is relatively small and the

pressure rise relatively large. A larger pressure

rise occurs with thick glass than Avith thin, be- cause of the smaller deflection. Both pressure rise and deflection increase as the air space thickness

increases. The shape of the deflection curve on the

glass is influenced by the rigidity of the edge

arrangement. Larger pressure increases occur with

rigid edges as this arrangement results in a smaller mean deflection (and hence a smaller vol- ume increase).

Exposure in the weather cycling apparatus

sometimes results in breakage of glass adjacent to the spacer on units having rigid sealing arrangements. As there was no evidence of such occur- rences in the field, it had to be assumed that this

effect was peculiar to the unit size, glass thickness, and rate of change in the cycle. The weather

cycling apparatus was, therefore, deemed unsuitable for tests on units having all-glass edges or

glass-to-metal seals.

12
The structural arrangements at the edges of

various units utilizing an organic-type seal are very similar. Brands with several years of good

field performance withstood many cycles in the

apparatus, whereas units having poor field per- formance records failed in relatively few cycles.

The apparatus, therefore, provides a good basis

of comparison of different units of this type, provided that the unit size, glass thickness, and air

space thickness are the same. Thirty-two oz(4

mm) glass and a i/^-in. (1.3 cm) air space were

selected for purposes of acceptance testing.

Some tests were conducted on 20- by 28-in (51

by 71 cm) and 28- by 40 in. (71 by 102 cm) (approx) units to assess the influence of size. It was

possible to test only a few units because of space

limitations. The larger sizes did, however, withstand many more cycles than the smaller ones. There was no way of comparing combined

effects of stresses and moisture transfer potentials

produced in the weather-simulating apparatus

with those in service, and it was not possible to

relate laboratory exposure directly to field conditions. It was accepted from the beginning that the

test provided only a basis for comparing the behavior of sealing systems under conditions of

fluctuating mechanical stress and temperature

comparable to those that might occur in service. Tests were therefore conducted on specimens of

most of the units on the market, including a few

for which there was some history of field per- formance. In addition, a simple initial screening

test to identify gross leaks in the seal was

adopted ; this consisted of determining the ability

of a unit to maintain a deflection of the two panes

induced by a small change in ambient pressure. While these initial laboratory tests were being

conducted, a few specimens of each brand were

exposed to outdoor weather, mounted in a vertical

position on a plywood support facing south, and

dewpoint temperatures were measured periodically (fig. 2). The primary purpose was to expose

the specimens to ultraviolet radiation to determine whether the sealing systems were sensitive

to failure from this cause. The results of these initial studies have been

reported [1]. Based on the results, CMHC established initial requirements for acceptability. In

tests on 18 specimens submitted by the manufacturers, at least 17 were required to pass the initial screening seal test and to have dewpoints no

higher than 30 °F (-1 °C). Twelve of the speci- mens were exposed to 320 cycles (2 months) in

the weather cycling apparatus and at least ten were required to have dewpoints no higher than

30 °F at the end. Results of tests on 33 sets of

units were as follows : units from 23 sources passed the initial seal test on first submission

;

units from 10 sources failed and 9 subsequently

passed on re-submission. Of the 32 sets that ulti- mately passed the initial seal test, at least 17

failed the weather cycle based on the above requirements. Fourteen of 32 sets mounted on the

outdoor racks had at least' one failure after one

year of exposure.

Following the establishment of these acceptance

requirements in 1961 DBR began to conduct tests on a commercial basis for manufacturers, who

were required to submit a detailed description of

the units in applying to CMHC for acceptance.

No attempt was otherwise made to ensure that

specimens submitted by manufacturers for qualification testing represented typical production.

Acceptance of products by CMHC was therefore

based on the ability of manufacturers to meet the current test requirements rather than on any positive assurance that the units being marketed met

these requirements.

Figure 2. Outside exposure racks.

At this time, development was begun on a further qualifying test procedure involving exposure

of the units to an elevated temperature cycle (70

to 130 °F) (21 to 54 °C) and high humidity

atmosphere. One of the purposes of the test was

to provide a high average water vapor pressure, not present in the weather cycling apparatus, in

order to obtain some indication of the resistance

of the sealing systems to water vapor diffusion.

In addition, there was need for a simpler qualifying test because of the large volume of testing

and the limited capacity of the weather cycling

apparatus; and for an inexpensive apparatus

that could be reproduced by manufacturers for use in product development. The final form of

the apparatus is shown in figure 3. Again, the

dewpoint temperature of the air space, following exposure to the elevated temperature cycle, was taken as the criterion of seal adequacy.

During the development phase, an extensive

series of tests was conducted to compare the per- formance of a number of sets of imits exposed to

13
WATER

SPRAY

ELECTRIC HEATER

45° F. (7° C ) COOLING WATER COOLING COIL

4^ INDICATES AIR B CIRCULATION 40 CREATED by SPRAY

HEATER and COOLING WATER

VALVE CONTROLLED

by TIMER

Figure 3. High, humidity cycling cabinet.

both the weather cycle and the high humidity

cycle. In general, brands that failed in the

weather cycling apparatus in less than 320 cycles

failed in the high humidity cycling apparatus in

less than 24 cycles (4 weeks) ; brands that withstood more than 320 cycles of the former, usually

withstood over 8 weeks of exposure in the latter. Exposure to the high humidity cycle did not cause abnormal failures, such as breakage of the glass

adjacent to the spacers, in units having rigid

edges. The apparatus was therefore used in evaluating sealing systems of this type as well as those

with organic seals. In 1963 CMHC included exposure of six speci- mens to the high humidity cycle as a part of its acceptance requirements, and the number of speci- mens in the weather cycle was reduced to six. In

1964, the requirements for acceptance were re- viewed in relation to the range of test results being obtained. It was apparent that the majority

of manufaqturers could produce units that provided initial dewpoint temperatures below —40

°F (—40 °C) and values after weather and

humidity cycling below 0 °F (-18 °C). It was

observed during the weather cycle that condensation sometimes occurred between panes with ref- erence dewpoints above 0 °F ( — 18 °C). As a

result, CMHC altered the initial and final dewpoint requirements to —40 °F (—40 °C) and

0 °F ( — 18 °C), and a new round of qualification

testing was begun on this basis.

3. Development of a Standard

As a result of widespread recognition of the

qualifying tests being used for CMHC acceptance,

they were accepted as the basis of a national

standard, preparation of which was begun in 1965

imder the auspices of the Canadian Government

Specifications Board (CGSB). The CGSB Committee on Sealed Double-Glazing Units consisted

of representatives of sealed glazing manufacturers, sealant suppliers, and government users. Consideration was initially given to establishing re- quirements for two grades of units, one based on

the existing CMHC requirements and a second,

higher grade based on initial and final dewpoint

temperatures of -60 °F (-51 °C) and -40 °F

(—40 °C). Results of the most recent qualifying

tests for CMHC at that time indicated that a large percentage of the manufacturers were capable of making units that could meet the requirements of the higher grade. At the urging of the

industry representatives, the Committee decided

to include only the higher grade.

The Committee was concerned that the tests developed for CMHC acceptance did not include one to determine the likelihood of glass staining

by the condensation of organic vapors evolved

from the sealing system. Staining problems had

been experienced with many early brands. Tests on individual components were considered, but

preference was given to a single test on an as- sembled unit. The "Ultraviolet Exposure Fogging" test (fig. 4) was developed for this purpose.

Test units are heated to about 150 °F (71 °C) so that if volatiles are present in the sealing system

components or have been absorbed by the desiccant they will be driven off and condense on the

glass area cooled by the cooling plate. An ultraviolet lamp is used for heating because it was

suspected that a breakdown of components of the

sealing system might occur under ultraviolet ex- posure. Very faint deposits can be detected if an

appropriate lighting and viewing technique is used. Deposits appear to be produced by traces of oil on spacers, small amounts of resin binder on mineral wool used to retain the desiccant in

spacers, certain glass cleaning agents, and some

plastic inserts for spacer corners, as well as by the

sealants used.

14
NOTE: 22"«22"x22" (56 cm.) BOX CONSTRUCTED of PLYWOOD ond LINED with ALUMINUM FOIL

Figure 4. Ultraviolet fogging test apparatus.

To assess the implications of the method, tests were conducted on specimens, from all manufacturers, that had met the other test requirements.

Among some 174 units, no deposit was visible on

54, a faint deposit was visible on 42, a medium

deposit was visible on 43, and a heavy deposit Avas

visible on 35. The results indicated that many manufacturers

could produce units having no deposit or only a

faint deposit. Furthermore, there was no evidence

of field problems on brands having only faint

deposits. A viewing arrangement was therefore

developed in which a faint deposit is not apparent

but a medium deposit is readily visible. CGSB Specification 12-GP-8 is now being

applied widely in the specification of sealed

double-glazing for federal government buildings.

The test apparatus has been reproduced by the

testing laboratories of the Department of Public

Works and results of tests in accordance with the

standard are being used by an Inter-Departmental

Qualification Board to develop a list of qualified

brands. The results of laboratory as well as out- door exposure tests indicate a steady and marked

improvement in the quality of units produced

since the program was started. Interim results for 33 sets of units received before 1961 are given in Reference [1]. Only five of

these sets would have passed the 1964 CMHC re- quirements and three sets the CGSB require- ments. Six units from 29 of the sets were exposed

outside and dewpoint temperatures measured

periodically. After one year all units had fa^iled on seven sets; after two years all had failed on

14 sets; after three years all had failed on 21

sets; and after six years all had failed on 22 sets. After seven years only one set was free of fail- ures. Stains from materials in the sealing system

appeared on at least three sets. At least two of

the failures resulted, from a rapid degradation

of the sealant, presumably from ultraviolet radiation. The results for some 67 sets of units received

from November 1960 to July 1963, analyzed on

the basis of the standards set by CMHC in 1964

(-40°F (-40 °C) initial dewpoint and

0 °F ( -18 °C) after weather cycle) and on the

basis of the present CGSB specification (— 60 °F

(-51 °C) initial and 0 °F (-18 °C) after

weather cycle), are as follows:

1964 CMHC CGSB

Pass 18 27% 11 17%

Failed seal leakage 7 10% 7 10%

Failed initial dewpoint 16 24% 18 27%

Failed weather cycle 26 29% 31 46%

Units from 37 of these sets were exposed outdoors. Seventeen failed in 2 to 5 years; ten show

essentially no change in dewpoint; stains are

visible in six. The results for units received from August

1963 to July 1965 are as follows:

1964 CMHC CGSB

Pass 36 37% 20 20%

Failed seal test 14 14% 14 14%

Failed initial dewpoint 21 22% 25 26%

Failed high humidity

cycle 6 6% 10 10%

Failed weather cycle 6 6% 11 11%

Failed in both H.H. and W.C. 15 15% 18 19%

Units from this group were exposed outdoors

in November 1964 and to date only three of 16

have failed. One set has evidence of staining.

Units received from July 1965 to the present

time performed as follows on the basis of the

CGSB standard:

Pass 58 44%

Failed seal test 10 7%

Failed initial dewpoint 10 7%

Failed high humidity cycle 18 14%

Failed weather cycle 8 6%

Failed both H.H. and W.C. 29 22%

After one and a half years' outdoor exposure on two units each of 39 sets, one unit in each of

three sets has failed; and three of the sets show

signs of staining.

These figures include the results of tests carried

out for manufacturers for purposes of product

development and qualification by Central Mortgage and Housing Corporation. Some of tht

sealing systems were never marketed or were marketed for only a brief period. A substantial

improvement in quality of specimens submitted

since the program began is, nevertheless, apparent.

Approximately 9 percent of the units received up

to November 1960 would have passed the current CGSB requirements; 17 percent received from

November 1960 to July 1963 ; 20 percent received

15
from August 1963 to July 1965; and 44 percent

received from July 1965 to the present. Essentially, all of the units currently marketed in- corporate a design that has met the test requirements of the Canadian Government Specifications

Board standard. Although there has been no

formal survey of field performance, the incidence

of seal failure reported to the Division has greatly

decreased. It seems, therefore, reasonable to as- sume that the average quality of units has greatly

improved since the beginning of the research

program.

4. Conclusion

The procedure for evaluating sealed doubleglazing now in wide use in Canada appears to provide a reasonably good basis for judging the

quality of assembly and the relative ability of the

various sealing systems to withstand mechanical

stresses in service. It is mainly deficient in not

identifying the effects of aging on the required

physical properties, and some further consideration of this is desirable.

The severity of the acceptance requirements set by CMHC were gradually increased during the

period of development of procedures, so that there was continuing pressure on the industry for improvement of the product. Competent manufacturers have responded and there has been a major

increase in the average quality of units since the

program began, to the benefit of both customer

and producer. The CGSB standard now provides

a good technical basis for specifying sealed

double-glazing and for further development and

improvement of both the methods of test and the

product.

16
2.2o DISCUSSION SESSION II

H. E. Robinson : Has your group been able to get field information or experience as to the

durability or failure of units in service in Canadian buildings ? Mr. McKinley : Grant, would you like to re- spond ? A. G. Wilson : I think the answer is, as far as we're concerned, that we haven't had any planned

program of getting information from the field. Most of our contact with conditions in the field has come directly from the manufacturers. We

have enjoyed a very good relationship with all the

manufacturers, have gotten to know them very

well, and we've received from them some sort of

feeling for the situation in the field, but we

have had no planned program of our own. The feedback mechanism of Central Mortgage

and Housing Corporation as far as I know is again not a planned one, and I think the answer

is that there is not good information on the

statistics of failure in the field. We have been

brought into a number of situations, mainly in

the earlier days, when there were certain specific

types of units that were involved in widespread

failures. We have this kind of evidence, but we

don't have any statistics on what is happening in a general way in respect to units as they are presently being manufactured.

Mr. McKinley : Mr. Rosen.

Mr. Rosen : Mr. Moderator, here's a question to you as a representative of one of the major American glass companies. In manufacturing insulating glass units, have you taken advantage of the

Canadian program to utilize the Canadian standards of testing for units?

Mr. McKinley : Yes, like most manufacturers, we have submitted units for Canadian approval

tests. We find them effective. Mr. McKinley: Yes, Mr. O'Shaughnessy.

Mr. R. O'Shaughnessy : Mr. Wilson, in the Canadian programs do all manufacturers submit

units to you or only those who are selling units

in programs in which government monies are in- volved? Is there a mandatory program for this

before sales can be made to the public?

Mr. Wilson : The incentive for manufacturers

to submit the units to us in the first instance, aside

from their interest in getting assistance with their

own developments, was to get acceptance or list- ing by the Central Mortgage and Housing Corporation. And there is a very strong incentive

because a very large percentage of the housing

units which are constructed in Canada are constructed under the National Housing Act. This means that their mortgages are guaranteed by the

federal government, although the mortgage money

usually comes from pi-ivate sources. So there's a strong incentive for any major producer to have

his product listed by the Central Mortgage and

Housing Corporation. This means that a very

large percentage of the manufacturers submitted

units for this reason. Participant: One of the tests you described

the fogging test—appears quite severe for some

types of units. How can excessively severe, or unrealistic, tests be guarded against?

Mr. Wilson : This is one of those things we are very much concerned about. We are always aware

of the fact that some condition imposed in an

accelerated test may be completely ridiculous and

that units that can withstand it may be practically impossible to make. We try to avoid ruling

good products off the market because of some unrealistic test condition. To get back to the fogging

situation, there has been a' considerable amount of

evidence of fogging in the field, and I think some

manufacturers almost went broke replacing units

that were showing stains. To avoid getting back

into this situation the CGSB committee decided

that they should have some test to insure that this

didn't happen. As I said, one of the things we are most concerned about in a test like this is to avoid unnecessary tests, or tests so severe that

they rule out all the good products on the market.

Mr. McKinley : Thank you.

Mr. Solvason: I might comment further that

practically all the manufacturers in Canada can produce units that meet the requirements of

CGSB, so while this testing as I said involves a

fair number of development tests, eventually

practically every manufacturer in Canada be- comes able to produce sets that will meet the re- quirements. If something is sent in that doesn't

quite meet them, the manufacturer goes back to try and find out what's wrong with his operation

and straightens that out, until eventually he can

get a product out that will meet the requirements.

Mr. McKinley: Yes?

Mr. Robinson : Are the units that are placed out on the board for field exposure samples those that

have previously passed the laboratory weathering

test? Mr. Solvason : The later sets that have gone on

the field are samples of those which have passed

the laboratory tests so that of the samples that

are out on the board, there are none from sets that failed in the weathering test. The selection

put outside was a fairly good selection, much

better than the overall selection as reported in

the weathering test. Mr. McKinley : Yes ? Participant: Does CMHC require periodic re- submission of units for testing in order to keep

their acceptance list current?

Mr. Wilson : The Central Mortgage and Housing Corporation, and I shouldn't really be speaking for them, because we're not representatives

for them although we are fairly aware of their

requirements, does not have any fixed period for

17
resubmission of products for their acceptance list. In the case of sealed glazing units, there was a requirement from CMHC for resubmission much

more often than would normally be the case, be- cause as Mr. Solvason said, the information on

unit performance, the tests themselves, and particularly the requirements that were being used

by CMHC were gradually evolving. As these

changed, and as information came in, and as they

began to know more about what was reasonable

and what was possible, they would ask for resubmissions in the history that Mr. Solvason has

given you. The most recent has been in connection

with the CGSB specification which came out in 1966. Subsequent to that, all of the units in

Canada wanting CMHC acceptance have been

reexamined.

Participant: How does CMHC police its ac- ceptance list? Mr. Wilson: I'll begin trying to respond on

behalf of CMHC. The Corporation operates on

an honor system, believe it or not. They have no

policing systems. They have certain requirements

for listing and one is that the listing is only good

so long as the manufacturer is manufacturing the

product on which the original acceptance was

based. That's understood by the manufacturer

when he gets his product listed. If he chooses to ignore that, I suppose it's a matter for his conscience to begin with. Of course, there is always

the concern that he might be found out, in which

case I suspect, it would be rather difficult for him

to get on the list again. CMHC doesn't, as I say, run any sort of continuing certification program.

When a manufacturer is listed on the CMHC list,

all this indicates is that the manufacturer has

shown he could meet whatever happened to be the

CMHC requirements for listing at that time.

Mr. McKinley : I think we might temporarily

postpone further discussion of this paper until

perhaps around the luncheon table. The Canadian

fabricators have said on the one hand, that they

do endorse the views that have been expressed

and yet in this insurance idea they are going

beyond the present situation. That has a great

deal of significance for us here. I would like to thank Mr. Solvason and Mr. Wilson again for

their contribution.

The gentleman who in many respects has gone

to the greatest trouble to join us and share with

us his experience is our next speaker. His subject

is "Norwegian Experience with Accelerated Test

Methods for Sealed Glazing Units and Their Correlation with Field Experience." It's a pleasure to introduce Mr. Tore Gjelsvik, Senior Research

Officer, The Laboratory, Norwegian Building

Research Institute, who has flown all the way

from Trondheim and arrived promptly on schedule. Mr. Gjelsvik, we are very much pleased to welcome you, sir. Mr. T. Gjelsvik: Mr. Chairman, ladies and

gentlemen. I am very glad to be here to talk a

little to you about our accelerated test methods

and also something of our experience from field studies. But before I start I have to say a few

words about our Norwegian Building Research

Institute, which is somewhat different from your

Building Research Institute here in the United

States. We are doing research into building programs and we are testing materials and constructions.

18
3. Norwegian Experience With Accelerated Test Methods and

Their Correlation With Field Experience

3.1. Norwegian Experience With Accelerated

Test Methods for Sealed Glazing Units and

Their Correlation With Field Experience

Tore Gjelsvik

Norwegian Building Research Institute,

Trondheim, Norway

The Norwegian program was begun 10 years ago, starting with the design of an

apparatus for accelerated aging tests. The device was built after scientists analyzed

actual stresses on insulating units. Carried on concurrently with the laboratory tests were field studies. The most important of these was made in 1963 and involved 2,040

units. In general there is a good correlation between lab tests and field studies.

Key words : Accelerated test program, climatic strains, dew formation time, dewpoint

temperature, field studies, glass-to-metal seal, glued seal, mechanical stresses, pulsation

stresses, visible damage.

1. Introduction

The work on the subject of sealed glazing units

I at the Norwegian Building Research Institute

' started back in 1958, independent of similar work

j in other countries. The first part of the project was sponsored by a Norwegian company, and led

I to the construction of an apparatus for accelerated

I aging. At that time, the accelerated aging tests

i constituted the whole test program,

j Systematic field studies were introduced in

I 1959, to check the results of the accelerated tests

I and to gain more general experience. The results

' of the field studies and the information available

I from other sources have resulted in successive

modifications of the accelerated aging tests. The

test program has been changed, and the apparatus

; itself improved several times. The basic apparatus

has, however, been the same all the time.

2. Stresses on the Edge Seal

The actual strains on the edge seal of sealed

[ glazing units were thoroughly examined before

the apparatus for accelerated aging was designed.

I The following types of strains were considered

as actual

Transportation stresses Assembling stresses Variations in atmospheric pressure

Temperature changes

Wind stresses Sunlight

Water

Mechanical stresses caused by vibrations.

Details shall not be given here, reference is made

to earlier publications [1], [2].^

Of the types of stresses mentioned above, trans- portation and installation strains must be con- sidered as more or less arbitrary. Transportation

strains can easily be reduced by suitable measures, and with the present installation recommendations

[3], the assemblage strains can be virtually eliminated. The real climatic strains must be said to be

variations in the atmospheric pressure, changing

temperatures, wind and sunlight. Water and vi- brations can certainly be of importance in special

cases, but whether they shall be included in normal

test methods or not, is an open question.

In general, there seems to be agreement between

scientists in the different parts of the world about

the types of strains acting on sealed glazing units.

The importance of the different types of strains,

however, is judged to be somewhat different by

different scientists. This is unpleasant, perhaps,

but not really surprising. Some of the strains on

sealed glazing units are fairly well known, while

for others, the available information is rather

limited. The different judgment is then only a natural result of the differences in the basic material. The situation is now considerably better than

in 1958, but still an accelerated test program has

to a high degree to be based on common sense.

1 Figures in brackets indicate the literature references at tlie end of tliis paper.

19
1. Frame

2. Casement

3. Sealed glazing unit

4. High pressure fan

5. Hot chamber

6. Regulating valves

Figure 1. Apparatus for climatic strains on sealed glazing units.

7. High pressure supply pipe

8. Return pipe

9. Pulsating damper

10. Manometer

11. Cold air fan

12. Cold chamber

13. Main sliding damper

14. Sliding damper

15. Cold air supply pipe

16. Return pipe

3. Apparatus and Test Procedures

On the basis of earlier considerations, the Norwegian Building Research Institute (NBRI)

decided in 1958 to build an apparatus where in- stalled units could be subjected to temperature

changes and pulsating wind pressure. It was

found that variations in the atmospheric pressure

could be omitted, as the stresses derived from the

two other factors would be considerably stronger.

On the other hand it was thought desirable to in- clude sunlight. This factor, however, for practical

reasons, had to be dropped. Water was also left out, as at that time it was considered possible to avoid the entry of water into the rebate with perfect installation. The last factor, vibrations, was more or less unknown at that time.

A unit size of 120 X 170 cm with about 12 mm

air space and a glass thickness of about 4 mm

was estimated to correspond most correctly to actual conditions.

Figure 1 shows the NBRI apparatus for cli- matic strains on sealed glazing units. Actually,

the apparatus on the figure is the second main

version from the period 1963-66, with several

improvements compared with the original version

of 1959. The principle, however, is the same for

both.

The system consists of three frames made of

teak wood. In each frame four casements can be

attached, each bearing one sealed glazing unit

120 X 170 cm, or a higher number of smaller

units. When the installation is completed, closed

chambers are formed, in which air with adjustable

pressure and adjustable temperature can be cir- culated. In other words, the air in the closed

chambers represents the outdoor climate. The

complete apparatus is located in the laboratory

which represents the indoor climate with a temperature of about +20 °C.

The apparatus can be adjusted in two ways. One

method is to let a high pressure fan supply the

air to the chambers. A pulsating damper regulates the air supply, so that the pressure within

the chambers pulsates, like wind gusts. The pulsating damper had in the beginning a frequency

of 6 periods per minute, but was changed to 5 periods per minute after the first series of tests, in 1960. The maximum super-pressure within the

chambers during the wind gusts can be varied

between 10 and 100 mm water column, corres- ponding to wind force Beaufort No. 5 to 11. The

temperature inside the chambers, measured centrally in front of the units, can be varied between

4-10 and +55 °C. The lowest temperatures are

20
reached by adding in cold air from the cold

chamber.

The second method is to let a low pressure fan

blow cold air directly from the cold chamber

through a larger set of pipes. In this way the

temperature inside the chambers can be lowered

to about —10 °C. The super-pressure, however, is insignificant, and pulsation is not possible. By

changing from a hot to a cold period, and vice

versa, the units can be subjected to temperature

changes.

The installation of the units in the apparatus

has in the period 1959-1966 been done with plastic

glazing compounds, in the first series of tests without spacers, later with spacers to avoid extrusion. In the first series of tests the wind stresses were

started at a moderate level, and gradually in- creased step by step. The details of this program

appear in NBRI Report No. 33 [1]. In the later

tests, from 1961 to 1966, the stresses have been in

accordance with a somewhat revised test program.

In carrying out this program, an attempt was made to include 20-yr wind stresses in comparatively exposed places. The wind pressure and air

temperature were fixed to follow a day-cycle consisting of 4 hours cooling at a low and constant

air pressure to an outside air temperature of about — 10 °C, followed by a 20-hr period with 5 wind

gusts per minute under simultaneous heating to a prescribed temperature level. The actual temperatures, the maximum wind pressures during the

wind gusts and the number of day-cycles at each

period of strain are indicated in table 1. This 45-

day program has been repeated once, making a

total effective operation time of 90 day-cycles.

Table 1

double-glazing unit

Period of strain I II III IV V

Day-cycle number 1-10 11-30 31-34 35-44 45 Maximum pressure during the windgusts,

mm water column 40 25 70 15 100

Corresponding to wind

force Beaufort No. 8 7 10 5 11

Air temperature, °C 25 35 15 50 15 The units have always been inspected regularly

for visible damage during the operation of the

tests. Dewpoint measurements have been taken at regular intervals. Finally the units have been

taken out for inspection. Usually they have also

been taken apart and the edge seal examined in

detail. All dewpoint measurements have been carried out with the apparatus developed at the NBRI

Laboratory in Trondheim. Figure 2 shows a cross- section of the cooler. This is made of brass and the

cooling surface is polished and nickel and chrome

plated. When dewpoint measurements are taken,

the cooler is filled with a mixture of dry ice and

location of thermocouple

cooler

Figure 2. Dewpoint measurement on douMeglazing unit.

alcohol, having a temperature of —75 °C. Originally the method was based on thermocouples

glued to the outside glass surfaces. Later on, the

method was further developed [4] and investigated. The thermocouples are now left out, and

the measurements simply taken by placing the

cooler against the glass with good thermal contact, and measuring the time from the contact is obtained till visible condensation can be detected

by an experienced observer. This "dew formation

time" is then converted to real dewpoint temperature with the help of the curves in figure 3.

90

' 80

70

60

° 50

AO

30

20

10

-AO -35 -30 -25 -20 -15 -10 -5 0 'J

Real dew point temperature , °C Figure 3. Dew formation time versus real dewpoint

temperature, NBRI measuring method. (Unit

temperature +20 °C, glass thickness 3 to 6 mm.

21
The NBRI dewpoint method is a typical

dynamic method, suitable to give very fast readings with an acceptable accuracy. In practice,

readings are usually taken in less than one minute,

while dew formation times above two minutes

occur very rarely. The measurements are also

carried out with the units in a vertical position,

and this makes the method specially suitable for

measurements in the field. The only drawback is that the method is dependent on a well trained

observer. Inexperienced people will usually see the

condensation too late, and this will result in dewpoint readings which are too low and too good.

4. Field Experience

Systematic field studies were organized by the

NBRI in 1959, 1960, and 1963. The most important is the west coast field study of 1963. In this

study, an attempt was made to cover all types of

units which had been on the Norwegian market,

and units of different age, as far back as possible.

The final result was 2040 units, divided into 10

different brands and installation years from 1951

to 1963. The investigations covered inspection for

visible damage as well as dewpoint measurements,

and the results have been treated statistically [5]. It is not possible to give all details here, but the

main conclusions of the report are the following

:

The study has clearly shown that it is not an

easy job to manufacture durable sealed glazing units. Even large, reputable companies

have failed to do so, and have obviously put

their units on the market before they have

been sufficiently thoroughly developed and

tested. For all t3'pes of units there has so far been a wide variation in the dewpoint temperature

of new units. Although the manufacturing of

sealed glazing units is an industrialized process, it has still maintained its character of

manual work. Extreme care in the dehydrating of the units as well as all other steps in the production seems to be necessary to obtain units of uniform quality with low

dewpoints.

The average damage frequency for the units

covered by the study is rather high. The old

production of certain types of units is responsible for this high figure. For the rest of the

units the number of damaged units is comparatively low, and has been found to be

either a result of special strains or quite

simply failures in the production.

Even the intact units of the improved types

are not absolutely tight, at least not those

with a direct glass-to -metal seal or a glued

seal. For these types there is an increase in

dewpoint with age of unit, indicating certain

leakage rates. The units must be considered to have a finite span of life. The rate of increase , in dewpoint temperature is, however, so low

that the expected span of life is fully accept- J able. , Very small units as well as oblong units with : one really short side are weakened more in rapidly than the normal and bigger sizes.

| The special strains mentioned above include i vibrations and other types of rapid pulsating ^ mechanical stresses. Units installed in doors \ with a heavy traffic frequency may be weakened rapidly or even have the edge seal broken. Units installed adjacent to such doors 1 may also be weakened or broken down if the

frames are not sufficiently rigid to reduce the [ transmission of vibrations from the doors.

When properly installed, units in doors with | moderate traffic seem to serve all right.

Heavy and gusty wind has proved to have a weakening influence similar to vibrations

from doors. Units broken down by wind | stresses have, however, not been found in ' practice so far.

Prolonged contact with water has been the reason of early seal failure of several units,

particularly those with a glued seal. This has

been the case especially with units installed

in top and bottom hung windows, and to a

certain extent also horizontally pivoted windows. The improved types of units seem to be

less sensitive to prolonged contact with liquid water. There is, however, every reason to take

appropriate precautions. Rebates and beads ; must be properly dimensioned to give the [' necessary clearances and edge coverage. Bottom bead and sash or frame as well as the

glazing compound must be sufficiently sloped

to shed water, even when the windows are put in a ventilating position. The glazing

must be as perfect as possible, preferably in- corporating a two-stage sealing system with

ventilated and drained rebates. It is probable

that the results of the field study might have

been better if better installation methods had

been used.

Field studies have also been carried out in the

years after 1963, but none of these studies has

been of the same order as that on the west coast. The experience gained in the later studies fully

supports the conclusions drawn on the material

from 1963. It has been planned to go out to the

west coast again and check the same units once more, but so far it has not been possible to get any

support for such a project from the manufacturers involved.

22
5. Results of Laboratory Tests and

Their Correlation With Field Experience

The major part of the accelerated agmg tests in

the period 1959-1966 has been carried out with

units 120 X 170 cm. The first series in 1959 were

run on a tentative basis, while the later tests have

followed a fixed program. These tests cover a

total of 26 sets of units from 18 different sources. The results can be divided into visible damage

in the units and changes in the dewpoint.

The visible damage comprises cracks in the

glass, cracks in the metal seal, and displacement

of the metal seal. Cracks in the glass have occurred in different

types of units. It has appeared, however, that the

cracks have always started at the edge of a spacer block. The reason has been that the bead

has been forced back so hard that the unit and

spacer have jammed. Similar cracks have also

occurred in practice. Mounting with spacers must

always be carried out with some care. Some types

of all-glass units must either be installed with

special types of spacers or entirely without such.

Cracks in the metal seal have occurred only in

units with a direct glass-to-metal seal. The cracks

have been localized to the central part of the long

sides of the units, in some cases also to the short

sides. In the laboratory tests the cracks have oc- curred at a comparatively late stage, after the

units have been subjected to prolonged strains. In

practice, however, they have so far only occurred

in units installed in doors with a heavy traffic frequency or close to such doors. The cracks have

always had the appearance of typical fatigue

breaks at the weakest and most heavily strained

part of the edge seal, and are undoubtedly due to pulsation stresses. Displacement of the metal seal is characteristic

of certain periods of production in some types of

units with glued seals. Deflections up to 2 cm have

been measured in practice, in the laboratory as much as 7 cm. The changes in dewpoint during the laboratory

tests have differed greatly for different types of

units. Some typical cases are shown in figure 4. Curve A is typical of a good unit where the

dewpoint is not influenced significantly by the

stresses. In Curve B there is first a certain in- crease, which may be due to changes in temperature, separation of water from the adhesives during curing, etc. Also units with this type of dewpoint curve have, however, to be considered as good. In Curve C, the situation is quite different.

I Here the dewpoint rises so rapidly towards the

I critical limit that the units undoubtedly have conj siderable leaks. Curve D must be considered as

' showing a real production failure, as the dewpoint

has been much too high from the outset. Something between Curves B and D can be judged

I somewhat differently, according to where the curves start and end.

Curves A-D represent units without visible

damage. In the case of units with visible cracks in

the metal seal, the dewpoint will follow Curve E

and suddenly rise above the critical limit when

the cracks have occurred. For units with displacement of the metal seal, there will be a corresponding rapid increase, as for instance Curve F. The field experience [5] has confirmed that the

dewpoint of good units will rise slowly in course

of time as in Curves A and B. For bad units, the

dewpoint can easily rise above the critical limit, as in Curves C, D, and E, and result in condensation. Units with a much too high incipient dewpoint. Curve F, have also occurred.

F

D

:ritical limit

B

E

A

10 20 30 AO 50 60 70 80 90

Effective running time . day cycles

• FiGUBE 4. Typical examples of measured dewpoint temperatures.

The correlation between the results of the laboratory tests from 1959 to 1966 and the field experi- ence has in many ways been surprisingly good.

The types of damage that have occurred have been

exactly the same, and the dewpoints have developed in a completely parallel way. Some fac- tors have, however, indicated that the strains have

not been on just the right level. In the units with

a direct glass-to-metal seal, cracks in the metal

spacer, as mentioned before, did develop in the

later part of the laboratory tests. In practice, such

cracks have only been found in units installed in

doors or adjacent to doors, while the great mass of

units have shown good performance. A more detailed analysis showed that the wind loads used

in the period 1959-1966 had been too high. The

test program was therefore taken up for revision. This was coordinated with the development

of the draft Scandinavian specification.

23
6. Draft Scandinavian Specification

of 1967

This specification was worked out by the four

leading manufacturers in Scandinavia in joint

cooperation with the NBRI. The specification is much influenced by the American SIGMA specification, but is otherwise completely redrawn to take into account Scandinavian experience.

One point worth noting is the inclusion of initial tests, which cover visual inspection, measure- ment of initial dewpoint, and control of initial

seal. The purpose is to avoid running expensive

and time-consuming aging tests with units which

are not of a reasonably high quality.

The accelerated aging tests are based on the

NBRI method, but with several modifications. The

size of the unit has been reduced to 120 X 82 cm,

i.e., about half the original size, by mounting a crossbar in the sashes. On the other hand, ultraviolet radiation has been included. The actual

UV-lamps are fluorescent black light tubes with

radiation mainly between 3000 and 4000 A. The

units are also mounted with the bottom edge in a metal tray. This is filled with water once a day so that the bottom edge is subjected to wetting and

drying cycles. The number of temperature changes

has been maintained and the temperature strains even slightly increased, while the number of wind

gusts have been reduced to about half. The present

accelerated aging test program amounts to 50-day

cycles. Details are given in table 2. Table 2

Period of strain I

Day-cycle number 1-8

Temperature changes

per day cycle 2 Maximum pressure during the wind gusts, mm water column 40

Corresponding to wind force Beaufort No. 8

Air temperature, °C 25

II III IV V

9-27 28-29 30-49 50

2 111

25 70 15 100

7 10 5 11

35 15 55 15

The most important novelty in the revised program is perhaps the wetting and drying cycle.

The reason for this is that the field studies have

clearly shown that water will sooner or later reach

the edge seal. Then the combination of humidity

and ultraviolet radiation becomes of importance.

7. Future Plans

Testing in accordance with the draft Scandinavian specification has now been going on for

1^2 years. A total of 31 sets from 23 different sources has been tested in Trondheim. The experi- ences gained in these comprehensive tests have

shown that some improvements in the aging tests are desirable. First of all, the black light tubes

should be replaced with the American type of

sunlight tubes specified by the SIGMA organization. Further, the wetting and drying cycle should

be made a little more effective. Finally, the size of

unit should be increased, at least a bit towards the

original NBRI size 120 X 170 cm. The available

material shows that 142 X 121.4 cm will probably

be a future common Norwegian and Swedish

standard size. This size is recommended as the

basis for type testing. For control testing, it is also desirable to have possibilities to test units of

different sizes, at least sizes deviating a little from the base size. A completely new apparatus

for accelerated aging tests has now been outlined

at the NBRI laboratory. This new apparatus will

be completely different from the old apparatus,

but perform the same basic functions. The apparatus is expected to be far more effective, and

all the desired improvements can be realized.

There also seems to be a real chance to obtain a temperature of about +70 °C in Period IV, as originally wanted by the Scandinavian manufacturers.

8. References

[1] Gjelsvik, Tore, Tests with factory-sealed double- glazing window units. Norwegian Building Research

Institute, Report No. 33, Oslo 1962 (in English).

[2] Gjelsvik, Tore, Laboratory testing of sealed glazing

units. RILEM Bulletin No. 35, June 1967. Norwegian

Building Research Institute, Reprint No. 145, Oslo

1967 (in English).

[3] Sealed glazing units. Installation in frame or sash

of wood or directly into wooden framework. Architectural Data Sheet NBI( 31).202.2. Norwegian

Building Research Institute, April 1965 (in Nor- wegian).

[4] Gjelsvik, Tore, Humidity in the dehydrated air space of sealed glazing units. Norwegian Building

Research Institute, Report No. 48, Oslo 1967 (in

English )

.

[5] Gjelsvik, Tore, Performance of sealed double-glazing

units in severe Norwegian climate. The west coast

field study 1963. Norwegian Building Research Institute, Report No. 44, Oslo 1965 (in English).

24
3.2. DISCUSSION SESSION III

Mr. McKinley : Thank you. I think, we can all join in genuine admiration of Mr. Gjelsvik's

ability to speak to us in our own language. We

have about 15 minutes before lunch is due and I am sure that there are many questions you would

like to present to Mr. Gjelsvik. Yes sir? Participant : I would like to know if the report

that you referred to several times, your No. 44

' report, is available in English?

Mr. Gjelsvik: We have some of our reports

available in English and in English only. The

numbers I have referred to are Reports Nos. 33,

44, and 48 and Reprint No. 145, and all of them

are available in English.

Mr. McKinley : Very good. I am sure that Mr.

Gjelsvik will be glad to give you detailed refer- ences later on. Yes sir? Participant : I would like to know what types of

units were tested in your programs, and I would

also like to know what drying agents were used. T. Gjelsvik: The units I have referred to and

that we have tested during the period of years

have not only been manufactured in Norway. In

fact, only a few of them were manufactured

there. Most of them came from abroad, from Denmark, Sweden, Germany, France, or England and we also had one set from the United States and

one from Canada. The manufacturing methods

are completely different. We have, I would say,

all types of units. We have had the all glass units

made in the United States, we have had units

with the glass to metal seal made in different

countries, and we have had a fairly large number of units with the edge seal made with completely different types of sealing materials and

different types of space and edge construction.

The desiccants have partly been silica gel and

partly activated alumina.

Mr. McKinley : Yes sir, Mr. O'Shaughnessy.

R. O'Shaughnessy : You have evidently been

taking the opposite method, not method but procedure, in using large units versus the small units we use. Have you in your tests correlated some

difference in the test results utilizing the same

test with the different size units? T. Gjelsvik : Our test method is very strong, at

least partly, on simulating gusty wind pressures, and applying variable wind pressures on ex- tremely small units would be really nonsense. So we have generally tested the fairly large units. We

have not only tested the size mentioned but also some smaller sizes, but most of the units have

been the large size. We have field experience with

different sizes of units and, in general, we have

found a reasonably good correlation. But we also

found that the very small units are weaker and

much more likely to fail than the larger sizes in

practice.

Mr. McKinley: Yes?

R. Fentress: When you have your wind gust

test as part of your test, how long a duration of

the different gusts do you put on ? T. Gjelsvik : Well, as I said before, we are using

five wind gusts a minute. The units are subjected

to the pressure pulsations throughout the 24 hours

of the day, except for the few hours when units are being cooled to 14 °F on one side. R. Fentress : The peak wind load is sustained

how long?

T. Gjelsvik : The top of the peak lasts only for a part of a second. The shape of the wind gust is approximately sinusoidal.

Mr. McKinley: Mr. Robinson?

Mr. Robinson : Mr. Gjelsvik, in view of the ex- tensive field investigations that you have made, I would like to know if you found any correlation or difference in the failure or breakage rate of

windows that face north and have little sun upon

them as compared to those that face the sun ? T. Gjelsvik : We tried to find if there was any

real difference, but we were not able to prove any

difference.

Mr. McKinley : Yes sir, Mr. Beatty ? J. A. Beatty : In view of the requirement of the

Canadian specification for 32 oz. glass, do you

specify one particular thickness of glass to make

your evaluation of units, and can you make the same evaluation on other thicknesses of glass? T. Gjelsvik : Well, to be able to get results which

you can compare directly, you should always use

the same thickness of glass. If you use a different

thickness you can never be sure how you should

interpret the final results. When we tested a very

large size of units, we always specified the glass

thickness of 4 mm which corresponds roughly to your double strength. When Ave wrote the Scandinavian specifications, we reduced the size of

unit and we reached a size where most manufacturers would supply the units with glass thickness

of only 3 mm, but some of these manufacturers do

not make units with 3 mm, they make it with at

least 4 mm, so in fact we have run into trouble due

to this. And that's one of the reasons we want to increase the size of units again. We want to get

up into sizes where all manufacturers will supply

the units with the same glass thickness and that

will be 4 mm.

Mr. McKinley: Do we have perhaps one more

question? Yes sir? Mr. Robinson : Would you agree, sir, that you

can affect your test results by making the glass

thinner rather than thicker on the sizes of units

that you are talking about? By this I mean that

you would reduce the pressure difference from

inside to outside because of the greater deflection

of thinner glass near the central area of the unit.

25
T. Gjelsvik : If you reduce the glass thickness

you will put heavier strength on the units and if you increase the thickness you will, of course, reduce it. But I must admit that we have not made

any really systematic study of that problem.

Mr. McKinley : As we all adjourn for lunch, I want to thank Mr. Gjelsvik once again, I want to thank Mr. Backman from Sweden who contributed the fabricator's view, and I want to thank

all of you.

26
4. Panel Discussion II

Introduction of the Second Panel

Robert W. McKinley

As we get underway this afternoon, the theme for our second panel discussion is, Manufacturers'' Test Methods; Correlation with Field Experience; Expected Service Life. The

panel toill step forward: Mr. Joseph S. Amstock, Technical Manager, Eastern Division, Products Research and Chemical Corporation. Mr. Amstock has been very active in SIGMA. He

is Chairman of the SIGMA Standards Committee. Mr. James D. Gwyn, Assistant Director,

Research Products, Lihhey-Owens-Ford Company, Toledo, Ohio. Mr. Renato J. Mazzoni,

Head, Building Materials, Glass Research Laboratory, PPG Industries, and Mr. James A.

Box, Industrial Products Development Manager, The Tremco Manufacturing Company,

Cleveland.

Now, as in the case of our panel discussion this morning, we have asked each of these

gentlemen to make a brief presentation, and toe then loill invite questions from the audience.

4.1. Test Methods for Evaluating Organically

Sealed Insulating Glass Units

Joseph S. Amstock'

Products Research & Chemical Corporation,

Gloucester City, New Jersey 08030

The performance of a sealed insulating glass unit in service is dependent on many

factors. These include : dewpoint temperature ; bond integrity of the sealant to glass, and

spacers ; thermal stress and strain ; extremes in temperature and weather ; exposure to moisture and ultraviolet radiation ; type of glazing compounds used ; method of glazing

;

and workmanship during installation. Key words : Accelerated weathering ; dewpoint temperature ; moisture vapor transmission (MVT) ; polysulflde sealant; sealant adhesion; sealed insulating glass units; test methods.

1. Introduction

Fifteen years ago the polysulflde sealants were

not expressly designed for the insulating glass

industry. As the industry grew, the requirements

changed and PRC embarked on an intensive re- search program to develop a sealant system speciflcally for insulating glass.

The polysulflde unit consists of a hollow Tshaped spacer separating two or more lights of

glass. A desiccant is used to dry the air space. The

unit is then sealed with an organic sealant based on a liquid polysulflde rubber polymer. This type

of unit may have the edges protected with a metal

wrap or tape, if desired. A majority of American

and European manufacturers have adopted this

method (fig. 1).

What was needed ? —"V\Tiat did we look for and

what tests did we utilize to screen these products ?

• Manager, Market Development.

Some basic tests for screening the sealants were

first used prior to determining what objective

tests should be performed on a sealed unit to determine its service life. Aside from the normal handling characteristics

of the sealant which were required by the manufacturers, it was an acknowledged fact that one of

the most important characteristics of a well made

insulating glass unit is the adhesion of the sealant

to the glass and metal as well as the retention of

that initial adhesion after prolonged exposure to

ultraviolet radiation, rain, and other material

elements.

2. Tests

Several pieces of 1 X 5 in double strength

glass which has been thoroughly cleaned are bonded to 1 x 10 in pieces of high strength aluminum foil. These test panels (fig. 2) are allowed

to cure for 7 days at room temperature. At the

end of this period an initial test is run for peel

strength.

27
POLYSULPHIDE SEALANT

Figure 1. Polysulflde unit.

Variation of aging and exposure ranges were

adopted from 2 days to 30 days. Sets of these

glass/ aluminum samples are exposed as follows:

Room temperature

Oven aging at 70 °C.

Water immersion at 50 °C.

UV/Water—Ambient

Linseed oil Generally the samples are tested for peel adhesion

after exposure at 2-day, 6-day and 30-day intervals. For the purpose of long term experimentation the samples are tested additionally at 30-day

intervals up to one year. Over a six month period several hundred peel

adhesion coupons were tested. Values averaged

12 to 15 pounds per inch width after six months

exposure to the above mentioned aging conditions

for the conventional manganese dioxide-cured

polysulflde systems. For a system which is highly

resistant to various glazing compound vehicles

(generally vegetable oil based), the values were in

the magnitude of 30 to 34 pounds per inch width.

In addition to the long-term study of adhesion,

moisture vapor transmission (MVT) data were

obtained using ASTM E 96 test method. MVT

rates range from 0.354 g/mV24 hr to 0.533

g/m^/24 hr. The average specimen thickness used was 35 mils to correlate to the normal thickness of

sealant between the spacer and the glass.

FiGUEE 2. Test panels—glass/aluminum samples.

Based on these preliminary data of peel adhesion values and of MVT rates, sealed insulating

glass units were then made and subjected to tests for seal integrity, initial dewpoint, accelerated

weathering (dewpoint rise) fogging for both

architectural and refrigeration applications and

resistance to glazing compounds.

It should be noted that the data being presented

are for commercially built sealed insulating glass

units, not laboratory samples. Therefore, the type

of workmanship generally used was indicative of

what can actually be obtained in field units and

makes the results more realistic. Our study in- volved several hundred sealed units of all descriptions.

3. Type of Study

The initial seal test was adopted to determine

the seal integrity or seal leakage prior to subjecting the units to long-term accelerated interior

weathering. The units, after being subjected to vacuum (3 in of mercury) for 2.5 hr, must show

no signs of seal leakage and must not deviate

from the zero deflection reading by more than 15

percent. This test has also proved to be a valuable

research tool in determining glass deflection,

effects on various thicknesses of glass, and the

capabilities of sealants to withstand strain and

stresses. This change of 3 in Hg represents an altitude

of 3,000 feet, so you can readily see the severity of

this initial test. Figure 3 illustrates the test chamber used for

checking the seal integrity. In this phase of our

test program we evaluated 450 organically sealed

insulating glass units. The failure rate was ap- proximately 10 percent ; these failures were attribiited generally to poor workmanship. There Avas no

significance as to the type of cured polysulfide

(Pb02 or Mn02).

28
Figure 3. Test chamber used for checking seal integrity.

4. Dewpoint Temperature

Chamber's Technical Dictionary defines dewpoint temperature as the temperature at which a given sample of moist air will be saturated and

deposit dew. Water or moisture vapor trans- ferred to the air space is evident by a rise in

dewpoint temperature. Dewpoint is a function

only of the volume of the air space and the amount

of water sealed into or transferred into it. The reason for using dewpoint temperature

measurements was to find a means of correlating

the MVT values and transposing these into actual

moisture vapor transferred into a sealed unit.

Moisture can be transferred to the air space by

diffusion of water vapor througja the sealing material. The amount transferred depends upon vapor

transmission or the vapor permeability of the

sealant, the length of the path of sealant, and the

vapor pressure differential. We have attempted through laboratory data

and field experience to give you the best possible

MVT rate material, yet keeping in mind many of

the other requirements needed of a good sealant

system.

Two important facts must be known when dis- cussing dewpoints. The first is the type and

amount of desiccant used in fabricating the unit.

Secondly, it is necessary to readily distinguish a measured dewpoint from an actual dewpoint

temperature. Figure 4 shows an approximate

calibration curve for various glass thicknesses.

The measured dewpoint temperatures are recorded

from the thermometer in the vessel on the glass
WATER CAPACITY

OF DESICCANTS

g -

4 6 a 10 12 LBS. OF WATER/100 LBS. DESICCANT Figure 5. Curves indicate the moisture content for a given dewpoint protection.

surface and actual dewpoint readings are those

measured by a thermocouple cemented on the

interior glass surface in the air space.

Table 1

Sealant cure system Group

Number of specimen Results MnOs A

B

C

86

56

93

All units passed the —60° F. temperature requirement

althougli the majority were

greater than

—100° F. PbOj A

B

C

43

51 Four units failed to meet the —60° F. requirement in Group C.

Misc. 88 Four units failed to

is used. The test procedure can be obtained from

the author.

In order to determine the MVT correlation, we

built a limited number of sealed units in the

laboratory with moisture probes inserted in the

air space. This probe was attached to a meter

which reads the free water vapor in grains of

meet the —60° requirement.

Figure 5 is the moisture isotherms of silica gel

and molecular sieve. These curves indicate the

moisture content for a given dewpoint protection.

As many of you are aware, these two materials

and variations of these are the most common desiccants in use today.

For those manufacturers of insulating glass who

wish a simple and inexpensive method of establishing a quality control system, the dewpoint

temperature reading method is unique. It is quite

reproducible and can be learned readily by a

novice. Figure 6 illustrates the type of vessel that

Figure 6. Vessel used for dewpoint temperature reading

method.

30
10 f

0 +70 DEW POINT TEMPERATURE °F

FiGUKE 7. Correlation of measured dewpoint versus free water for a given volume of air space.

water. At the same time, we continued to take

dewpoint readings and have been able to correlate measured dewpoint versus free water for a given volume air space. We are continuing to run

this study on new improved sealant systems'.

Figure 7 gives you some early values of these

studies.

5. Accelerated Interior Weathering

In attempting to correlate the short-term field experience of most manufacturers, and a test for

evaluating the hermetically sealed unit, an ac- celerated interior weathering test was developed

to check a unit in a variety of environmental conditions. This test included freezing, thawing, rain

exposure, ultraviolet radiation exposure and high

humidity, all on a uniform programed cycle. We

were looking for variations of performance based on the different formulations of sealants we

developed.

What were we measuring ? (a) Adhesion after exposure to ultraviolet

radiation (uv).

(b) Adhesion after exposure to water.

(c) MVT as measured by dewpoint temperature rise after high humidity exposure.

(d) Seal fatigue due to flexing caused by

barometric pressure differentials. The apparatus is pictured in figure 8. This equipment has been adapted from that used at National

Research Council—Canada for several years. However, we have modified it by the addition of

a series of black lights and uv sunlamps, to closely

approximate that of natural uv. We have included

a water pump which would give us an equivalent

of an inch of rain per hour. In addition, we have

also opened up the distance between lights of

glass giving a greater air flow around the sealed

units.

Figure 8. Apparatus for interior weathering test. A typical cycle consists of:

2 hr at -20 °F followed by

1 hr recovery at room temperature followed

by

1 hr of uv exposure followed by

1 hr of rain exposure followed by

2 hr at 120 °F. and 100 percent relative

humidity followed by

1 hr recovery at room temperature.

Dewpoint readings are taken at five-day intervals

to record the rise in temperature. Table 2 shows

the number of units tested and their values after

120 cycles.

31
Table 2

Sealant cure Group Dewpolnt temperature system

Less —100 °F - 79 "F -59 °F

than to to to Above

100 "F -80 "F - 60 °F -30 °F -30 °F MnOa A 80 20 4 4 4 B 50 36 14 14 15 0 43 22 PbOj A 10 2 4 —

T> QO in 4 2 0 2 6

Misc. 18 4

Table 3

Sealant cure Group Dewpoint temperature system

Less -100 °F -79 °F -59 °F

than to to to Above

100 "F -80 °F -60 °F -30 °F -30 "F MnOa A 50 24 16 2 6

B 20 30 6 4 10 C 12 20 4 4 PbOs A 8 4 2 2 8 B 6 6 2 2 2 C 2 4 4

Misc. 12 8 2 7

In addition to the accelerated interior weathering test, duplicate test units, unglazed, are placed

outdoors at a 45 deg. angle facing south. Periodic

dewpoint readings are taken in order to compare

these with the readings on the accelerated interior

weathering.

6. Fogging

Fogging tests in both architectural and refrigeration type units were developed to check the

sealant against depositing a permanent layer of

contaminate on the inside surface of the glass.

These tests are for a 14-day duration at 150 °F.

If no fogging occurs after that period, the units are considered to have passed the requirements of

the test. Many sealant manufacturers attempt to produce a more economical product by the addition

of various low cost dilutes, etc. This type of test weeds out the poor sealant. Many times fogging

will show up during the accelerated weathering

cycle. Figures 9 and 10 illustrate the apparatus

used in this test.

Figure 9. Apparatus for fogging test. Figure 10. Apparatus for fogging test.

32
123'i5672 5 10 12 WEEKS

DAYS FiGUBE 11. Chart illustrating weight loss of various sealant systems after exposure to oil at a 50° C. temperature.

Curve A—Polysulfide sealant without barrier coat ; Curve B—Polysulfide sealant with aluminum pigmented barrier coat

;

Curve C—Polysulfide sealant with nitrile rubber coatinp; ; Curve D—Polysulfide sealant with barrier coat, clear ; Curve E—Polysulfide sealant with nitrile rubber coating and aluminum barrier coat ; Curve F—Polysulfide sealant with nitrile rubber coating and barrier coat, clear ; Curve G—Oil resistant polysulfide sealant and latex barrier coat. Curve H—Oil resistant polysulfide sealant without barrier coat.

7. Glazing

Certain oil-based glazing compounds, used to

install insulating glass units, have an effect on

polysulfide sealants used in their manufacture. To

check if a sealant is compatible, we have developed

three specific tests.

1. The first we call static testing; it is done

by taking the actual glazing compound and

glazing a 6 X 6 in test unit into an aluminum sash and subjecting the unit for at

least 30 days at 158 °F. The test sample is inspected for bleeding once a week. Bleeding shows up generally as a clear droplet

of oil on the air space side of the glass.

Sometimes the sealant is attacked causing

reversion of the compound, or cracking,

discoloration, etc.

2. The second method is of a dynamic nature, where a cross section of a sealed unit

is fabricated. The sealed portion is ex- posed to both the glazing compound and

ultraviolet radiation while being flexed at 60 cycles/minute. The flexing is equivalent

to barometric pressure changes of 2,000

feet. As yet we have not been able to cor33
relate the static versus the dynamic

method, but these studies are continuing.

3. Method three is a direct immersion of a

sealed unit in the respective oil vehicle at 158 °F. This test is the most dramatic and

without a doubt the one which produces

the quickest results. A simple test on the sealant system alone is ac- complished by means of weight loss. The sample

of cured sealant is subjected to various glazing

oil vehicles for a definite time period at an ele- vated temperature.

Figure 11 is a chart illustrating the weight loss of various sealant systems after exposure to oil at a 50 °C. temperature. Curve H is based on

results of a new development on a sealant which is highly resistant to oil. Those who do not wish to pay a premium for a highly resistant sealant can use a series of barrier

coats. A barrier coat is used to prevent bleeding of

these oils through the sealant. The coating is applied after the sealant has become tack-free.

The system of sealant and barrier coat provides

protection against defective installation techniques and materials. One sure way of eliminating

this problem at its source is to specify a compatible glazing compound.

8. Conclusion

The insulating glass industry is in a great

growth period, and, from all indications, this

growth will continue. This means that more manufacturers will be making more units than ever

before. Now there are formal means at the dis- posal of all manufacturers to check the quality of

their units— a new specification with a certifica- tion program. Component parts have been improved over the years and more improvements will

be forthcoming. All are aimed at product improvement so that extended warranties may be

offered.

It looks as though the future of our industry is assured.

The author wishes to thank the PRC Laboratory staff for their assistance in furnishing and

compiling the data.

34
4.2. Manufacturers' Test Methods: Correlation

With Field Experience; Expected Field Life

James D. Gwyn

Libbey-Owens-Ford Company,

Toledo, Ohio 43605

Laboratory test procedures used by Libbey-Owens-Ford Co. to evaluate insulating

glass are chosen to simulate the cyclic temperature and moisture effects which may

occur for actual windows. Because the edge seal construction of the insulating glass contains no organic materials, ultraviolet radiation produces no deleterious effects and

this item is not normally included in the testing. Testing is conducted in chambers

capable of producing rapid changes in temperature and relative humidity when required.

Many test-cycle configurations and test durations are used, depending upon the time

available and other factors. Most commonly the procedure recognized by General Services Administration is employed. This procedure requires the insulating glass to be subjected

to 175 continuous weathering cycles each consisting of alternate exposure to 48 hours at

0° F and 48 hours at 14.^° F and 95 percent relative humidity. At the conclusion the dewpoint of the air space must not exceed —18° F. During testing the glass is not moved,

thereby eliminating the damage which may occur to the glass or seal when two separate

test chambers are used. The long period required to conduct the above test precludes its use as a routine pro- cedure for acceptance of insulating glass. Development of a shorter test procedure which

also reflects the weatherability of insulating glass units is needed. Investigations in this area are presently underway.

Key words : Accelerated weathering ; field experience ; insulating glass units ; outdoor

weathering ; pressure changes ; test cycles.

1. Introduction

Before discussing our test methods and the ex- perience we have had with our insulating glass

units in the field, I believe it will be helpful if I

briefly describe their construction. The edge seal construction is of especial interest. In the fabrication of the units, the glass is first washed,

cleaned, and dried after which metallizing and

tinning are applied to the glass surface around the

periphery. This forms an integral bond much

stronger than the cohesive strength of the glass

itself. To the metallized and tinned glass is applied a lead calcium alloy separator strip formulated to withstand movement that may occur in an

insulating glass unit. As a point of interest, this

alloy is the same as that used for protecting out- door telephone cables; therefore, its long term

weathering properties have been thoroughly tested

and are well recognized. The lead separator is soldered to the metallizing using a specially designed soldering iron and a compatible soldering

material.

The construction described to this point is that

which was used for many years in our insulating

glass. Field experience was excellent and trouble

occurred only in cases where the sash was grossly

misdesigned or other improper conditions were

excessive in one way or another. Even though fail- ures were rare, we felt improvements should be

made so that the chances of failure "were even

further reduced.

To arrive at this goal we developed several

improvements. One of these is the application of a

wax coating to the outside of sealing materials to prevent any electrolytic contact between these

materials and the surrounding aluminum or steel sash. Besides this, a polyethylene freeze tube was

installed. This was to accommodate for any moisture that may penetrate to the edge of the unit

and subsequently freeze. Expansion upon freez- ing would be taken up by a partial collapse of the

freeze tube. A third item was the addition of an aluminum edge channel. This channel is expendable. Its only function is to provide protection of

the edge of the units during handling and glazing. Should this channel for some reason entirely

corrode once the glass is in place, the hermetic

seal would not be affected.

2. Testing

Testing of our insulating glass units begins with

the material suppliers who are required to furnish

materials to rigid specifications and perform pre- scribed tests. We conduct similar tests in our

laboratories to make certain that the materials

meet specifications. We realize the important item

for an insulating glass unit is not the performance

of individual parts but the performance of the

assembled unit and the majority of our tests are on this basis. In our laboratory we have two cyclic test cabi- nets for accelerated weathering. In these the temperature and relative humidity are automatically

controlled and if desired can be preprogramed.

35
The primary advantage of these cabinets compared with earlier ones used by ourselves and

others is that the insulating glass is not manually

moved from a cold chamber to a warm chamber

during each cycle. If the tests involve a large

number of cycles, there is a good chance of damaging the glass when it is moved negating the re- sults of the tests. We have used various test cycles and have

found no short duration test that remotely reflects the field performance. Most short duration

tests tend to be unduly severe causing damage that

could never occur in the field or are not severe enough thus giving misleading results. Of the

many weathering cycles studies we have found

two which we believe will result in failure of in- ferior insulating glass units. One of these consists of an 8-hr cycle with a dwell time of 48 min

at 145 °F and 48 min at 0 °F, the relative humidity maintained at 95 percent when the temperature is above 40 °F. Heating and cooling is at a uniform rate. We believe that for a sampling of

6 test units, not more than one unit should have an

air space dewpoint above 0 °F after 200 cycles.

Passing this test does not necessarily mean the

unit is adequate but if the unit is grossly inadequate it should fail. Another test similar in many respects consists

of a 6-hr cycle with 30 min dwell time at 120 °F

and 30 min at 20 °F. Again, the relative humidity

is maintained at 95 percent when the temperature

is above 40 °F. We believe a sampling of 6 units

should withstand at least 600 cycles of this test with not more than one unit above 0 °F dewpoint.

In the early stages of our testing we studied

the effect of ultraviolet radiation on the edge seal of our units and found no effect. Therefore, units

of our manufacture which we evaluate are not

subjected to ultraviolet radiation. Of course with

mastic type units ultraviolet testing is very neces- sary since these units are affected to some degree

by extended exposure to ultraviolet radiation.

Besides the various cyclic tests we conduct in our test cabinets, we also conduct what we call a "huff and puff" test. The apparatus used for this

consists of two insulating glass units with a nar- row air space between. To this air space is at- tached an air line and necessary pressure regulating and timing controls. The pressure is fluctu- ated within the space causing the units to bow in- wardly and outwardly as the pressure is changed.

The purpose of this test is to simulate gust wind

loading to see if the edge separator materials are

affected. The amount of pressure and the frequency of fluctuation depend on the particular

goal of the test. We also test units by exposing them to outdoor

weathering. At present we have about 4,000 units

in our two outside test areas. They are not glazed

in openings but are open to the weather on both

sides allowing rain and snow to reach the edge

channel and exposing the edge seal to all weather

factors. We have had units exposed up to 12 years

in this type of testing.

3. Conclusion

In attempts to correlate our laboratory tests with actual field experience we have found no

conclusive correlation. We do know, however, that

duplicate units of those which have weathered for

12 years and are still in good condition will withstand in excess of 1000 cycles of the 120 °F to 20

°F cycle test previously described . The two cyclic tests described earlier are, of

course, much too long for quality control. The

shorter one requires about 70 days to complete.

Obviously there is a strong need for a test method

requiring less time while accurately reflecting

field experience. This is an overwhelming task to accomplish. After exhaustive testing we have a

fair idea of the service life to be expected in

climates similar to Toledo. We don't Imow precisely what should be expected for other climates

such as might be found in Minneapolis, Miami, or Phoenix.

Because of the lack of supportable correlation

between laboratory tests and field experience, the

expected service life of our insulating glass units

is not definitely determined. We have manufactured insulating glass units for over 30 years and

even the early units which lacked the many later improvements have performed well to the best of our knowledge. We have no precise records of

these early units but do have information regarding units produced up to about 20 years ago. The

largest installation of over 20 years ago was one

containing 14,000 units and to date the units are performing satisfactorily. A small stock of re- placement glass was ordered with the original

glass and has been adequate for replacement for

breakage and other types of failure.

At present our insulating glass is warranted for

20 years. Based on our field experience, accele- rated tests, and outdoor weathering of units, we

are confident that the 20 year warranty is fully

justified.

36
4.3. Test Methods and Field Experience

With Double-Glazed Units

R. J. Mazzoni and G. H. Bowser

Glass Research Laboratory,

PPG Industries,

Creighton, Pennsylvania 15030

Performance criteria for double-glazed units intended to assure building owners of a

satisfactory period of performance in service must cope with field environments through

accelerated testing procedures. Quantitative knowledge of performance variability and a minimum acceptable standard of satisfactory performance are essential ingredients of any program of this kind. The accelerated testing program we use includes:

1. Temperature cycling

2. Water vapor diffusion

3. Solar radiation

4. Outdoor exposure

5. Water immersion

We have tested large numbers of units manufactured in our own plants and by others according to these procedures.

A significant difference in performance among groups of units tested has been observed.

Differences in the sealant composition and performance, in manufacturing procedures, in type and conditions of desiccant used are factors which explain the wide range of per- formance demonstrated by superficially similar units. Our service experience, because of the long guarantee which has been in effect for many

years, is based both upon our replacement records and upon formal field exposure studies. Correlation between accelerated test procedures and field tests in recent years has been

good. We believe that this correlation provides sufficient justification for establishing a minimum performance level in the accelerated tests. Key words : Accelerated lab tests ; dewpoint measurement ; double-glazed insulating

units ; exponential distribution ; field performance ; outdoor aging tests ; organic seal units ; pressure tests ; polysulfide rubber sealants ; temperature cycling test ; water vapor

diffusion.

1. Introduction

During the past decade, serious attention has

been devoted increasingly by government agencies

to the problem of evaluating in-service life of

double-glazed insulating units. I believe that the

Canadian [3,4]^ and Scandinavian [1,2,6,7,8,9]

Government Agencies first recognized this need

several years ago. Perhaps this is explained

because of the severe winter climates in their

regions and the greater proportional use of double-glazing. Domestic interest is growing and it

is apparent from the interest demonstrated in this

Seminar that progress will be made.

We hope in this paper to point out the importance of tight correlation between accelerated lab- oratory testing and orderly monitoring of field performance at the job site. The foundation for

this work was described in an earlier ASTM

paper [5].

From the very beginning of our participation

in the Insulating Glass Market over twenty years

1 Figures In brackets indicate the literature references at the end of this paper.

ago, it was apparent that a sophisticated and ex- tensive testing and development program would

be needed. T\niile close correlation between accel- erated laboratory tests and field performance has

been acquired over a period of years, our initial experience, including both success and failure,

taught us that product reliability on the job

could be determined in advance by accelerated

tests that simulate environment factors encountered in service.

To make accelerated testing practical, it was

important to evaluate test unit sizes. Based on

careful studies of stresses in glass and the edge

seal joints, we arrived at a standard test unit size of approximately 14 X 20 in with a i/^-in air

space and glass thickness of % in or less. We learned early that a great deal of time and

effort could be saved if certain very rapid "screen- ing tests" could be applied to eliminate test units

of poor design or careless fabrication. These

screening tests include dewpoint measurements

and pressure differential tests of seal tightness.

Generally, test units with air space dewpoints

above 0 °F are obvious indications of seal leakage

and should be discarded since their performance

is so poor as to result in early failure.

37
FiGUEE 1. Chamber for 120° to 20° F. cycling test.

2. Accelerated Tests

Figure 1 shows the 120 to 20 °F cycling test equipment. The units are mounted above a 1-in

pool of water to maintain high humidity throughout the test. Within the cabinet, the atmosphere is cycled from 120 to 20 °F. This test is controlled

automatically to give four 6-hr cycles each day, seven days a week.

This test checks the ability of the sealant to withstand pressure loading caused by temperature fluctuations and expansion and contraction

forces between dissmilar materials.

A relatively simple test and one which can

readily check the water vapor diffusion characteristics of the sealant is carried out at 110 °F and

90 percent relative humidity (see fig. 2). Air

temperature is thermostatically controlled at 110

°F and a pan of water in the bottom of the cabi- net maintains the high humidity throughout the

test. The specimens are supported on wood frames

and continuously exposed to conditions in the

cabinet.

The sunlamp test is used to obtain ultraviolet

light exposure (see fig. 3). RS 275 watt sunlamps

are positioned 14 in above and perpendicular to the specimens, and the light is directed on Test

Unit corner areas. The aluminum surface below

the specimens reflects the radiation to the oppoFiGURE 2. 90 percent relative humidity chamber in 110° F. room.

site surface. We have found this test to be very

effective when it is followed by the 120 to 20 °F

temperature cycling test. The 130 to -30 °F cycling test, shown in figure

4, includes a circular table that rotates automatically according to a predetermined time schedule.

Specimens are glazed into each of the five 4X4

ft panels which are mounted vertically on the

table so that the exterior surfaces of the units are exposed to conditions within test chambers loFiGURE 3. RS 275 watt sunlamp test.

38
Figure 4. Indexing taUe for 130° F. to 30° F. cycling

test.

cated at fixed positions around the table. The

opposite surfaces are exposed to prevailing room

conditions. Each specimen is subjected to four

complete cycles each day, six day a week. Speci- mens are exposed sequentially to (1) —30 °F, (2) room conditions (70 to 90 °F), (3) 130 °F, (4)

water spray, and (5) room conditions (70 to 90

°F).

Figure 5 shows how the specimens are mounted

in the outdoor exposure rack. The units are facing

south and inclined at a 45 -degree slope to prevailing conditions at Harmar Twp., Pa., and Fort

Lauderdale, Fla.

Water immersion, Fadeometer, Weatherometer,

elevated temperature and pressure tests are useful also. Our field testing program includes exposure of

test units in the outdoor wall of our Creighton,

Pa., laboratory building and full-size production

unit installation in buildings selected geographically for exposure conditions. To provide statistical validity, a large number of units in many differ- ent installations is required. Let me show typical

data for organic seal units obtained from specific

field tests. For reference, let me remind you of the

data first presented in our earlier ASTM paper

[5]. The following data are in addition to those

data.

FiQTJBE 5. Specimens mounted in outdoor exposure rack.

3. Accelerated Test Results

Curves in figures 6, 7, and 8 are for seven groups of units from five manufacturers obtained

within the past four years. Most of the unit

groups were sealed with polysulfide rubber seal- ants. These are representative of most organic

sealed units. The minimum number of units in

each group was 18 distributed among four to five accelerated tests. The data presented are from the

120 °F to 20 °F cycling, 110 °F -90 percent R.H.

(relative humidity) and the combination ultraviolet and 120 °F to 20 °F cycling tests. Recommended exposure periods for these tests are made

relative to 20-yr service life with 10 percent or less failure potential. The basis for these recom- mended periods will be discussed later. The significant difference in performance obtained among groups tested in the 120 °F to 20

°F cycling test can be seen in figure 6. The mean

Figure 6. RS sunlamp and 120° F. to 20° F. test.

39
life in this test can be as low as 300 cycles and

extend to over 5000 cycles. Group D shows no

change from the initial —80 °F dewpoint after

2300 cycles. Factors explaining the wide range in

performance are (1) differences in sealant composition and performance, (2) manufacturing procedures, and (3) type and condition of desiccant

used. Ineffective fabrication process control is another contributing factor. Groups B, C and G

from the same manufacturer were obtained within

a period of 18 mo. For 20-yr service life in the building we would

like to see a minimum exposure period of about

1200 cycles with an allowable average change in

dewpoint of less than 30 °F from an initial of — 60 °F. This requirement was met by Groups C,

D and F. A similar scattering of results was obtained in

the 110 °F, 90 percent R.H. test (see fig. Y). For

some types of sealants, this water vapor diffusion

test is more severe than the 120 °F to 20 °F temperature cycling test. This test reinforces the data

obtained in the 120 °F to 20 °F test. Group G had

a mean life of only 40 days, while Group D is still performing well after 600 days.

Groups B, C, and G utilize molecular sieve as the desiccating medium. This desiccant has the

capacity for maintaining lower dewpoints than

silica gel but the opposite is true at the higher

dewpoints. We expect 20-yr units to perform sat- isfactorily up to 300 days in this test. Figure 8 shows ultraviolet effect on sealant. While all specimens showed no change in dewpoint from initial dewpoint, the relatively poor

resistance of the sealant to ultraviolet radiation

becomes evident when followed by short exposure

periods in the 120 °F to 20 °F cycling test. For

Groups B, E and H, this test was 12 to 20 times more severe than the 120 °F to 20 °F cycling test alone. However, Groups D and F were unaffected

by the ultraviolet exposure and the former has

0 400 800 1200 1600 2000 2400 CYCLES Figure 8. +120° F. to +20° F. test.

now received a total of 1400 cycles with no change

from the initial dewpoint of —80 °F.

Experience with this two-part test indicates 500

hr in the RS Sunlamp exposure followed by the

120 °F to 20 °F cycling test produces similar re- sults to the outdoor aging test. We would recom- mend the total exposure be 1000 hr in the RS Sunlamp exposure and 500 cycles in the 120 °F to 20 °F test.

4. Field Test Program—Correlation with

Accelerated Tests

Figures 9, 10, and 11 will cover the results obtained in the service tests. The four groups of units in the laboratory wall

test also were 14 X 20 in and were glazed in steel sash using elastic glazing compound (see fig. 9).

These groups are from the same manufacturers as those in the accelerated tests but obtained at different times. The number of units in each group

and the disposition of failures are also indicated.

PERFORMANCE

IN 120 - 20°F TEST

TIME - YEARS Figure 7. 110° F. — 90 percent R.H. test. Figure 9. Laboratory wall.

40
The total life of Groups B, E and H glazed in

1962 ranged between 64 to an estimated 87 mo

with failures recorded as early as 18 mo. These

results substantiate the relatively poor performance obtained in the accelerated aging tests. The

types of failure were the same as those in the

ultraviolet exposure followed by the 120 °F to 20 °F cycling tests. The performance of these groups in the 120 °F

to 20 °F test after 500 hr exposure to ultraviolet can be found in this same chart. A rough correlation indicates that 500 hr ultraviolet and 100

cycles in the 120 °F to 20 °F tests is equivalent

to approximately 2 to 7 yr exposure in the wall. Looking at it another way, the performance of

Groups B, E and H would have to be upgraded

by a factor of six to eight to insure reliability for

a period of 20 yr at a mortality level of 10 percent

or less. Group D with three failures in six years

and no additional failure in 7i/^ yr has the potential for an extended life. Results of a field study started in 1960 are shown in figure 10. The letter designation again

indicates the same manufacturer as for the ac- celerated and wall test units. Some of these sites have been abandoned because of gross failures or

other problems.

Figure 11 shows the correlation between the ac- celerated tests and the field study. The total life of six of the nine sites ranges between four to an

estimated ten years which parallels that obtained

in the laboratory wall test for the same type of

unit. Once again the Group D units are showing

a superior performance with an estimated life span greater than 20 yr. This correlation gives

further justification to the recommended 1000

hours of ultraviolet and 500 cycles in the 120 °F

to 20 °F cycling test.

Dew Point Results °F Location

Year of InstallationNo. of

Units Specimens Checked

Date Checked Avg Range

Date Checked Avg . Range Avg. Increase

Range

N. Y. (E) 1962 115 14 1963 5 -10,31 1965 + 21 5,31 16 1, 38

Pa. (B) 1961

1963

340

62

7

6 1963 50 -15 18,50

-35,6

1965 all

40 failed

-22,50 37 13, 64 111. 1963 400 9 1963 -40 1967 40 30,50

(5 failures)

80 70, 90

W. Va. (B 1959

1962

28

22 136 1964 8 -60 -10,50 1967 50 -28

8,50 -50,442

32

4 , 10, 48

64 Wash. 1965 900 16 1965 -40 1966 -40 -40,-30 0 0, 10 111. 1965 200 28 1965 -40 1968 -25 -40,0 15 0, 40 Mich. (D) 1963 102 11 1963 -40 1966 -40 0 111. (D) 1960 1700 15 1960 -50 1966 -50 0 Ohio (D) 1962 45 14 1962 -50 1966 -50 0

Figure 10. Field study.

FIG. 11 - FIELD STUDY VS ACCELERATED TESTS

Speci- Dew Point Results "F Failure-Accelerated Tests-Cycles

Location

Yr. Instof

. Units mens Checked

Date Check Avg. Date Check Avg. Increase

Avg. FailureYears 120°-20"'F 500 hrs Sunlamp

120''-20°F Pa. (B) 1961

1963

340

62

7

6 1963 50 -15 1965 all failed

40 37

4

5 est . 1100 60

W. Va. (B) 1959

1962

28

22 13

6 1964 8 -60 1967 50 -28

42

32

8 10 est . 1100 60

N. Y. (E) 1962 115 14 1963 5 1965 + 21 16 6 est . 1300 110 111. 1963 400 9 1963 -40 1967 40 80

5 failed

4

111. 1965 200 28 1965 -40 1968 -25 15 10 est . 1500 Wash. 1965 900 16 1965 -40 1966 -40 0 Mich. (D) 1963 102 11 1963 -40 1966 -40 0 20 est . 5500 140 no failure

111. (D) 1960 1700 15 1960 -50 1966 -50 0 20 est . 5500 140 no failure Ohio (D) 1962 45 14 1962 -50 1966 -50 0 20 est . 5500 140 no failure

Figure 11. Field study versus accelerated tests.

41
5. Statistical Analysis of Field Data

A statistical analysis was made of our field data

in an attempt to predict the probability of failure

of a 20-yr period. In this analysis, the performance of millions of units was involved with field follow-up work covering more than 17 yr. We

have found that an exponential distribution fits the available data and describes probability of

failure. This is given by F (x) — 1 — exp. (x/d)

where x is the time to failure. 6 is the mean value

and F (x) is probability of failure within time x

(see fig. 12).

If mean failure time is 50 yr, the proportion of

defective units one can expect to develop in 10 yr

is about 18 percent of an original population in- stalled at time 0. In 20 yr the percentage will in- crease to about 33 percent. If the mean life is 100

yr, then the percentages will decrease to 9.5 percent and 18 percent requiring replacing in 10- and

20-yr spans, respectively. Therefore, a manufacturing unit needs to know the risk of failure with

the guarantee period desired.

FIG. 12 - STATISTICAL ANALYSIS TO PREDICT PROBABILITY OF FAILURE

F (X) = 1 - EXP (-x/e)

X = TIME TO FAILURE

e = MEAN FAILURE TIME

F (x) = CUMULATIVE PROBABILITY OF FAILURE

FOR e = 50 YEARS F (X)

X = 10 YEARS 18%

20 YEARS 33%

FOR 9 = 100 YEARS F (x)

X = 10 YEARS 9.5%

20 YEARS 18%

Figure 12. Statistical analysis to predict proiaiility of

failure.

An attempt to translate this statistical analysis

to the 120 °F to 20 °F cycling test (since the type

of failure is the same as that encountered in service) suggests that assuming a probability of fail- ure of 10 percent in 20 yr the number of test cycles

should be over 700. However, statistically it is necessary to use 25 samples or more to get meaningful and reliable estimates. Earlier, I recom- mended 1200 cycles in this test to compensate for

the small number of samples generally used. This

analysis shows what can be done once field information becomes available.

This type of correlation analysis is needed to determine the minimum acceptable standard for

satisfactory performance.

6. Conclusions

A significant difference in performance among

groups of units tested has been observed in the

accelerated tests. Differences in the sealant compositions and performance, in manufacturing procedures, in type and condition of desiccant used

are factors which explain the wide range of per- formance. Ineffective fabrication process control is another contributing factor. The formal field testing studies show relative

performance differences similar to those obtained

in the accelerated aging tests. The total life of

several test sites ranged between 4 to an estimated

10 yr while the life span of those with high quality imits is estimated to be greater than 20 yr. The good correlation obtained between accel- erated test procedures and field tests provides

sufficient justification for establishing a minimum

performance level in the accelerated tests. Our

recommendation for a minimum exposure period

in the accelerated tests to insure reliability for

extended periods should include

:

1200 cycles—120 to 20 °F temperature cyc- ling test 300 days—110 °F, 90 percent R.H.

1000 hr RS Sunlamp Test and 500 cycles in

the 120 to 20 °F

Allowable average change in dewpoint should

be less than 30 °F from an initial of -60 °F

dewpoint.

Our experience with long guarantee periods

further substantiates these minimum requirements.

7. References

[1] Sealed Glazing units, types and properties. Architectural Data Sheet NBI (31). 103, Norwegian

Building Research Institute, April 1965 (in Norwegian).

[2] Gjelsvik, Tore, Tests with factory-sealed double- glazed window units. Norwegian Building Research

Institute, Report No. 33, Oslo, 1962 (in English).

[3] Wilson,' A. G., Solvason, K. R., Nowak, E. S., Eval- uation of factory sealed double-glazed window units. ASTM Special Technical Publication No. 251, 1959

(in English).

[4] Wilson, A. G., Solvason, K. R., Performance of

sealed double-glazed units. Research Paper No. 168

of the Division of Building Research, National Research Council of Canada, Ottawa 1962 (in English).

[5] Mazzoni, R. J., King, L. K., Performance of double- glazed units in accelerated and service tests. Material Research & Standards, Vol. 5 (1965), No. 10, pp. 517-524 (in English).

[6] Bastiansen, Alf., Sealed glazing units in Norwegian

climate. Bygg, No. 2, 1961, pp. 29-36. Norwegian

Building Research Institute, Reprint No. 53, Oslo, 1961 (in Norwegian).

[7] Gjelsvik, Tore, Performance of sealed double-glazing

units in severe Norwegian climate. The West Coast

Field Study 1963. Norwegian Building Research Institute, Report No. 44, Oslo, 1965 (in English).

[8] Gjelsvik, Tore, Durability of sealed glazing units. Byggmesteren, No. 24, 1965, pp. 19-20, 23, 27-28, 31- 32 and 34-36. Norwegian IBuilding Research Institute, Reprint No. 115, Oslo, 1965 (in English).

[9] Gjelsvik, Tore, Laboratory testing of sealed glazing

units. Norwegian Building Research Institute, Reprint No. 145, Oslo, 1967.

42
4.4. Insulated Glass Sealants

Function and Types

James A. Box^

The Tremco Manufacturing Company,

Cleveland, Ohio 44104

The purpose of this article is to review the sealants available to manufacturers of insulated glass units and point out the service properties that are necessary and available

in current sealants. I primarily want to point out how we believe optimum performance

from the sealant standpoint can be obtained for long term service. Key words : Butyl-polyisobutylene ; insulated glass units ; laboratory tests ; optimum

performance ; polysulflde sealants ; sealant performance ratings ; standardized test chamber.

1. Introduction

There are two major families of sealants used

in the fabrication of insulated glass sealants: (1)

chemically curing, two-package, gun-applied

materials typified by polysulfides, and (2) pre- extruded, noncuring, elastomeric tapes typified by

butyl-polyisobutylene tapes. Each of these serves the required functions, each having its own strong

points and weaknesses. Both types may be used

singly or in combination obtaining varying degrees of performance.

To best analyze the sealant problem and then

accomplish a logical conclusion or selection of

sealant types, let's take a look at what we expect

the sealant to do for the insulating glass unit.

First, the sealant must hold the unit together.

Structural rigidity is nearly always accomplished

through the sealant. There are other methods of

doing this, where the unit may be held together

by some mechanical means such as a spring steel surrounding band, but the usual method is to

utilize the sealant. The next most important function the sealant

must perform is to act as a barrier to gases and

vapors, preventing or reducing, to an acceptable

level, their entry into the interior air space of the

unit.

An additional property necessary in sealants

used in constructing insulating glass units is the

ability to compensate for thermal and barometric movement of individual glass unit members. A last, and obvious requirement of the sealant,

is that it must be compatible with the fabricator's

production methods and cost allowances.

Now, let's enumerate the performance properties or qualities necessary in sealants to achieve

the functions we have just outlined, and, for the

moment, we will not consider the unit which

utilizes a mechanical means for structural

rigidity.

' Industrial Product Development Manager.

1. The sealant must develop satisfactory adhesion to the various components or adherends which usually are aluminum (mill

finish or anodized), galvanized steel, stainless steel, and, obviously, glass.

2. It must be resistant to the weathering it will

encounter in service; moisture and temperature variations between minus 40 °F.

and 200 °F., and particularly important,

ultraviolet energy.

3. Flexibility, or perhaps a better term, controlled internal mobility, is necessary to compensate for movement between the

joining members of the unit.

4. It must have the lowest possible transmission rates of moisture and other volatile

materials. An added desirable quality is to be nonvolatile itself.

5. Application qualities vary with the type

material and are too numerous to go into

their details here but pumpability, mixability of two package materials, non- slump qualities, cut-off and extrudability

are all extremely important but, to a

large extent, are defined by individual

fabricator's requirements.

2. Performance Ratings of Sealants

Initially, we divided the sealants into two

major families : two-package, pumpable materials

which chemically cure in place, and extruded

materials which initially, at least, are pressuresensitive in their adhesive properties. Taking

these two types of sealants, which can be typified

by polysulfides in the one case and butyl-polyisobutylene tapes on the other, let us take a look

at what each of these has to offer in the construction of a typical insulated unit which does not

rely on a mechanical means for holding the unit

together.

43
2.1. Structural Rigidity

Structural rigidity is easily accomplished by

pumpable sealants. Two part polysulfides can be

made which rapidly cure to a reasonable hardness and adequately hold the unit together. The

necessary adhesion and cohesion can be built into

these sealants without too much difficulty. Extruded tapes, on the other hand, demonstrate

good adhesion but the cohesive properties are only poor to fair. The problem with extruded

tapes is really one of flow under pressure. Even

though it is possible to formulate a material

which will not be squeezed completely out of the

joint between the glass and the interior core or

separator, the perfect material which will not

permit lateral movement of the glass and at the same time accomplish all the other necessary

properties of adhesion, compressibility, etc., has

not been made satisfactorily to our knowledge.

2.2. Barrier Properties

Barrier properties of the pumpable materials

should be rated as good. Using the same refer- ence, top-quality extruded materials must be

rated as excellent or outstanding. Using the same

evaluation methods, the extruded materials have

a 20 to 40 fold advantage. This is the primary

advantage of using the butyl-polyisobutylene

type tapes. It is an inherent property of the base

polymers used in the formulation of these materials and it offers an advantage that has not been

met by the best two package pumpable materials.

2.3. Resistance to Weathering and Ultraviolet Energy

Resistance to weathering and ultraviolet energy

of top-quality two-package insulated glass polysulfides is good. This requires sophisticated for- mulating knowledge and is available in some cur- rently marketed polysulfides. Traditional polysulfides used in construction or industrial applications do not fill the bill. They are more than

adequate for the job they have but do not have

the long-term lieat and ultraviolet resistance

necessary for insulated glass service. The resist- ance possible with top-quality butyl-polyisobutylene tapes to ultraviolet energy and heat is excellent.

2.4. Resistance to Fogging

Fogging of the interior surfacees of an insulated unit is caused by two general weaknesses:

(1) moisture traveling through or under a seal- ant, and (2) volatiles emitting from the sealant. Either or both of these are then condensed and

deposited on the interior glass surfaces. The

moisture problem has just been discussed under

barrier properties, but the fogging caused by volatiles coming from the sealant itself is an equally

serious possibility.

Two-package, pumpable sealers which have

been used up until quite recently would be rated

poor to fair. Recent materials have been made

which are definite improvements in this characteristic of volatile emission. Depending on how

the material is evaluated, the new generation of

sealants just emerging can be rated as good for

this characteristic.

The second major strength of an extruded butyl-polyisobutylene tape is the absence of the risk

in causing a fogging condition because of volatiles which might come from the sealant itself. The materials used in formulating this type of

material do not contain low molecular weight

fractions which would permit a fogging condition to occur.

2.5. Handling

From the handling standpoint, both materials can be rated as good. Each have their own characteristics of pumping, mixing, extruding, and

placement.

If we look at the composite picture made by

the ratings assigned to both types of materials

related to the required performance qualities, it

is apparent why the use of both sealants in the

fabrication of high quality units has been developed and used. Wliere one sealant does not measure up to an excellent rating, the other does.

By using both sealants, it is possible to obtain an excellent rating and performance for each of

the necessary qualities. One sealant complements

the other with the end result being a higher quality imit than is possible when using either sealant

individually.

3. Methods of Evaluating Performance

A brief description of methods used in evaluating these qualities is in order. To a large extent, it is necessary to rely upon laboratory data.

Facts concerning field failure are not widely publicized for the normal reasons. When a failure

occurs, none of the parties involved is particularly anxious to have the information circulated

and so it is difficult to know where or when fail- ures in service occur unless your organization is directly involved. Sealant companies, therefore, are hampered in relating field failures to laboratory evaluations of their materials because, after

all, when the question is asked, the answer usually is, who has any failures?

So, specific data are difficult to obtain. In addition, the conditions in service are not imiform.

Location, ambient weather conditions, thermal

movement, handling of the units prior to installation, and the installation itself is seldom the same

and so there is seldom a uniform base from which

to draw conclusions.

The various sealant qualities listed are neces- sary and are a concern or they would not be de44
j manded by their users. Specifications such as

I NRC's 12GrP8 and the Sigma Specification con-

, tain requirements which measure barrier qualij ties, weathering resistance, and fogging proper-

, ties because they are recognized problems by the

1 people who are in the business of making and

, using insulated units.

The laboratory tests which are most meaningful to us in sealant development are quite simple

i in principle. We use test applications of the sealj ants involved on the substrates the fabricator is using. Exposure of these test applications to long

term high temperature conditions, ultraviolet

I energy, both dry and in the presence of moisture,

j is a very empirical and reliable test. What adheres to one aluminum alloy will not necessarily

j adhere to another. A sealant may have excellent

I resistance to ultraviolet energy but as soon as

j moisture is introduced along with the ultraviolet

energy, the sealant can fail adhesively.

I Resistance to pressure buildups in the interior

of an insulating imit can be simulated with a

I standardized test chamber where pressures can be

} controlled and exerted on the sealant which is unsupported other than by its own adhesion and

cohesive forces. The barrier qualities can most reliably be

tested by use of the ASTM Test Method E-96.

Procedure E of this method is most severe. Results from this test must be tempered with the

sample size involved and the conditioning of the

sample prior to the test. A sealant tested at a 20 mil thickness may have an MVT rating of 2 grams (H20)/24 hr/m^ but when tested at differ- ent thickness or aged in a weatherometer prior to

testing, the MVT value wall vary. One study

made with a two-part polysulfide, which was

tested at various thicknesses before and after

j weatherometer exposure, showed the barrier

i properties degrading from 3 to 20 at 20 mils

thickness. I would like to go into a little more detail on

the individual laboratory test that we use in

evaluating our sealants before we think they are ready to go into a unit and then be tested in the

unit itself. Adhesion and cohesion is rated by

the normal method using overlap shears made up

of adherends of the aluminum or stainless steel or glass involved. A two part polysulfide should

typically give an overlap shear value of over

100 pounds per square inch. A butyl-polyisobutylene tape w-ill give a very low value, and it should fail cohesively. Actually, it does not contribute anything to the structural rigidity and

the value that it gives is not really important.

Barrier Droperties. as mentioned, are measured by

the ASTM E-96 Method and a good polysulfide

underneath the conditions stated in Procedure E

(0 to 90 percent relative humidity) at a 20 mil

thickness un-aged, should give values between

two and five grams of moisture through a square

meter area in 24 hours. losing the same set of

conditions, a butyl-polyisobutylene tape will give

a value of .1 to .2 gram.

Resistance to ultraviolet is best tested on glass

and, in this case, polysulfides should give at

least a 60 day resistance to ultraviolet in a dry

condition and 30 days in a wet condition. The

manner of testing is to simply put a casting of

the sealant down onto the glass, expose it 12

inches away from the sun lamps, periodically

peeling off the polysulfide. A cohesive failure

should result. Fogging resistance can be tested

in a chamber which contains the polysulfide or

other test material. The air temperature is kept

at 160 °F. A glass plate on top of the vessel is cooled at 50 °F. by circulating water. Volatiles

that are inside the compound which could come

out after it is in the unit, will be condensed on

the glass surface.

4. Conclusion

In summary, there are a set of qualities desired

in any insulated glass sealant which, simply

stated are:

1. Adhesion/Cohesion

2. Ultraviolet and Heat Resistance

3. Flexibility

4. Low Permeability

5. Nonfogging

Two-package sealants and pre-extruded tapes

both have advantages and a portion of the qualities necessary. It is necessary to use both types of

materials in a single unit and obtain the optimum performance for each property or quality

desired. If the butyl-polyisobutylene sealants are not used, it is not possible to obtain the optimum

combination of service performance properties of

low permeability, non-fogging, and long term re- sistance to degradation.

Because of the variations in field use and conditions, and the elusiveness of reliable data con- cerning field failures, it is necessary to rely primariljr on laboratory tests which measure the

qualities required for good, long-term, performance.

Performance of Sealants in Insulated Glass Units

Performance

quality

Pumpable

sealants Extruded

tapes

1. Structural rigidity

(a) Adhesion

(b) Cohesion

Excellent

Excellent GoodPoor to fair

2. Barrier property Good Excellent

3. Resistance to u.v. and weathering Good Excellent

4. Nonfogging Poor to fair Excellent

5. Handling in production Good Good

45

4.5. DISCUSSION SESSION IV

Mr. McKinley: Could we now have questions

from the floor for our four speakers? Mr.

Beavers ? Mr. Beavers: I have a question for Mr. Amstock. If a manufacturer uses an accelerated cure

of a polysulfide sealing system, is the performance of the seal impaired in any way ? Mr. McKinley : Thank you. May we have a

question for Mr. Gwyn?

Participant: Can Mr. Gwyn give us any in- formation on the effect of using reflectivelycoated glass in sealed double-glazed units?

Mr. McKinley : Thank you. A question for Mr.

Mazzoni ? Participant: Has Mr. Mazzoni's company con- ducted tests recently on polysulfide sealed doubleglazed units?

Mr. McKinley : Thank you. One for Mr. Box ? Participant : Could Mr. Box expand his pre- vious remarks to include discussion of other

types of sealants than those made by his com- pany for insulating-glass units?

Mr. McKinley: Thank you. Sir?

Participant: (Inaudible)

Mr. McKinley : I belive the question is, hoAv can we cope with glazing problems, and it is di- rected to all four speakers. Thank you.

Let's go and get a cup of coffee and be back here

at 4:00 o'clock. On your way, if you would like to pick up an extension to your registration list Mr. Cook has these at the registration desk.

Mr. Amstock: I will attempt to answer Bill Beavers' question first. His question was: if a manufacturer accelerates the cure of the polysulfide system, does he get a degradation of the

seal? On the contrary, most good polysulfide

seals manufactured will gain properties such as adhesion, resistance to UV and moisture and

combinations of them because of this accelerated cure by heat. Again, most manufacturers have

the capability of adjusting application time or cure rate by means of different retarders in their

system and this by no means will detract from

the ultimate properties of the cured sealant sys- tem, or the performance of the sealed unit. And

if I may answer my glazier friend back there,

who claims that he has quite a bit of breakage or

failures because of glazing techniques.

Participant : Almost everybody in the industry

has.Mr. Amstock : Well, I can't agree with you fully on that one, I'm sure there are a lot of problems

in the field because of this condition. I don't

know if you Avere there, but yesterday the

SIGMA organization had a lengthy meeting on

glazing techniques for installing lights into the

sash or building as well as a discussion on the

various types of compounds that are used. I would say that with the type of potential specification that was discussed, which is a very diffi- cult one to develop, and the experience that we've

had from the two major glass suppliers, I think

this will be resolved. Again many glaziers, and

I've seen it happen in the field, just slap the unit

in as though they could hardly care less about

clearances or setting blocks. This is the responsibility of the glazier himself or the foreman or supervisor on his job, and of no one else. I would think that breakages due to poor glazing practices should not be charged to the manufacturer of the glass, or to the component manufacturer, because I personally couldn't accept

that type of logic in such cases. Mr. McKinley : I think you've uncovered a very

practical side of our problem and I believe when we get to the wind-up this is one of the items

that ought to be on our list. Thank you for the

question, and thank you, Joe. Dan Gwyn : The question that was asked me

has to do with a reflective copper film and really

doesn't pertain to this meeting. I talked to the

young man back there. ... I think he is satis- fied with the answer. It has nothing to do with

the edge seal of our unit.

R. W. McKinley : Very good. Do you care to comment on the glazing question?

J. D. Gwyn : I certainly am not the best one

to discuss glazing but I have the strong impression that my company, as well as PPG, has, and

offers, detailed information on glazing. I^ do

know that w^e have a department which looks into

all large buildings that are under consideration,

as far as sash is concerned, to see the glazing

matters appear satisfactory.

Mr. McKinley: Perhaps it is time to move

along. Mr. Mazzoni.

Mr. Mazzoni : The question put to me was, "Have Ave done any recent testing on polysulfide

double glazed units?" I Avould like to point out

that I purposely did not identify any type of

unit that we have in there, at least I tried not to. The main purpose of the paper was to try to

correlate the accelerated test data with the field data and, once having a correlation, to use this as a basis for projecting, from the results of the

accelerated test of any new material that may be

used, an estimate of how Avell the material will

do in the field, because you can't very well have

field data come to you all the time. In other

Avords, if you have made a variation you can't practicably put this into the field and wait five years or ten years. So the prime purpose of the

paper was to show that there is some kind of a

correlation that can be made with a PPG type

accelerated test and the service type test. Mr. McKinley : Thank you, Ray. Mr. Box.

J. A. Box : The general question to me was,

""\'\niy didn't I include discussion of other types

of sealants in my remarks? I hesitate to say

47
specifically why in many cases because we don't

manufacture these other types of sealants for

insulating units so I would be knocking someone

else's line of products. The reason we don't use them is because we think that what we're using

for insulating glass is the best. There are many sealants that are excellent for

various specific applications, but they are not

suitable for sealed double-glazed units because

of the combination of properties required for this

application. Among essential characteristics

needed are satisfactory rate of cure, very low

vapor permeability, adhesion, strength, low creep, and resistance to uv. For one reason or another,

many otherwise good sealants are therefore

screened out as regards use for insulated glass

units.

As far as the glazing question is concerned,

I'd like to say that the way the unit is glazed is also a source of a lot of problems.

Mr. McKinley : Yes, Mr. Orbeson.

Mr. Orbeson : I would like to comment in part on this glazing problem. Concerning the information that we have published, let's say that in a general way, we will work with any manufacturer of glazing materials or sash to develop his

methods to fit our units, but why should we publish a book of lengthy practices on some 203

installation methods—to help our competitors.

Mr. McKinley : I think our panel deserves a

real hand ... I want to thank each of you and

I'm sure your questions will not end as you step

back into the audience.

Mr. McKinley : Very early in the game, one of

the reasons for focusing our attention on the National Bureau of Standards was the possibility

that the next paper might be available. The subject is "An Exploratory Study of Laboratory

Testing Methods and Standards for FactorySealed Double-Glazed Window Units." Our

speaker is Henry E. Robinson, Chief, Environmental Engineering Section, National Bureau of

Standards.

48
5. A Review of Current Practices

Leading to New Test Methods and Standards

5.1. An Exploratory Study of Laboratory Testing

Methods and Standards for Factory-Sealed

Double-Glazed Window Units

Henry E. Robinson

National Bureau of Standards, Washington, D. C. 20234

Failure of edge-seals of factory-sealed double-glazed insulating glass window units to exclude moisture from the air space of the unit leads to permanent fogging, obscuring

view through the unit. A review was made of three fairly well standardized extant

laboratory methods for accelerated testing of such units aimed at evaluating the intrinsic

initial quality and prospective in-service durability of the seals. In addition, visits were made to four laboratories with extensive experience in such testing for detailed discus- sion of test methods. Among the information sought was evidence of the degree of posi- tive correlation between the results of the accelerated tests and long-time satisfactory

performance of units in service. It is tenable to conclude that units that fail the present

accelerated tests would not have had satisfactory durability in service. However infor- mation at present as to a positive correlation between successful test performance and

long-time service performance is too limited to enable predictions as to service durability

generally for the spectrum of units now marketed. In part, a correlation is impeded by

the fact that the present test methods have not been in use for a period as long as the

desired life of a unit, i.e., the useful life of a building. Current trends in the development and needs of accelerated testing methods for such

units are discussed, and an apparatus is suggested for satisfying them. Certain research

possibilities offered by the suggested apparatus are outlined. Key words : Accelerated laboratory tests ; correlation of test and service performance

;

double-glazed window units ; durability of edge-seals ; insulating-glass ; factory-sealed

;

permanent fogging of insulating-glass.

1. Introduction

i In the last two decades there has been an acI celerating use of factory-sealed double-glazed

insulating window units in buildings. Several

factors have combined to promote increasing use

of such units. Among these are decreased discom-

' fort near windows and less condensation on them

in winter, reduction of air conditioning loads in

j summer, reduced noise transmission, neat and

) unitary installation, improvements in materials

i and factory production, and architectural tendenI! cies toward use of increased areas of fenetration.

j Nevertheless, cases of failure of factory-made

seals to exclude moisture from the air space of

' the units have occurred sufficiently to concern producers and users alike. Such failure leads in a

relatively short time to permanent fogging or

filming of the inaccessible glass surfaces and per- manent obscuration of clear view.

Users will expect that units should have an in-

! service durability equal to the life of a building,

barring accidental damage, and producers must

j expect that they must provide it. Thus, during the

development of sealed units, manufacturers and

others have developed various tests of accelerated

types, by which to evaluate the quality and durability under the accelerated test conditions, of the

factory-made seals of the units. Undoubtedly

these have contributed to improvement of seal designs and materials, and quality control in

production.

At the present stage, in addition to the accel- erated tests adopted and used in-house by individual manufacturers for their own guidance,

there are in use in North America two principal

specifications of testing methods and requirements—that of the Canadian Government Specifications Board (12-GP-8) [1] ^ and that of the

Sealed Insulating Glass Manufacturers Association (65-7-2) [2]. Testing of units according to each specification is now available to manufacturers generally, at designated laboratories.

1 Fifjures in brackets indicate the literature references at the end of this paper.

49
This exploratory study was conducted for the

Federal Housing Administration of the Department of Housing and Urban Development. The

purpose of the study was to make a review of extant laboratory procedures, arid to summarize

information obtained in visits to four laboratories ^ having extensive experience in the manufacturing and/or testing of sealed insulating units.

Among the information sought was data showing

the degree of positive correlation between the

results of accelerated tests and long-time satis- factory in-service performance of units. It had

to be concluded that although some manufacturers have actively pursued efforts to establish cor- relations for some time, and perhaps in some

instances had some favorable results, no general

correlation applicable to the broad spectrum of

marketed units had been established. Two strong

reasons for this are that there are not many in- stallations of ten or twenty year age for which

consistent performance data have been accumulated, and that practically no units installed for

such lengths of time had first been tested or screened by means of the current accelerated tests. It is to be noted that with the availability and

use of the developing test methods and specifications for sealed insulating units, the latter essential for developing correlations is more likely to be satisfied. Practical considerations concerning the accel- erated testing of sealed insulating units are dis- cussed in this paper, and some suggestions are made as to ways in which improvements might be

made in respect to accelerated test conditions and

testing apparatus.

2. Statement and Discussion

of the Problem

Factory-sealed double-glazed insulating glass

units are intended to provide a permanently hermetically-sealed space between the glass panes

containing air at a moisture content or dewpoint

so low that no moisture will condense on the

inner surfaces of the panes under use-conditions.

In general, three different types of edge construction are used for commercial factory-sealed

insulating units. These are:

1. Fused-edge^ in which the two sheets of glass are fused together at the edge.

2. Glass-to-metal, in which the glass near the

edge is metallized and soldered to the edges

of a thin lead alloy strip spacer.

3. Organically-sealed, in which the glass at the

edges is glued to a spacer strip by means of an organic sealant or adhesive. The spacer

may be of steel, aluminum, or an organic

material and is usually hollow and filled with

a desiccant which, through small holes, is exposed to the interior air.

" Please see acknowledgements, page 56.

In the last two types of construction, a U-shaped

external channel of metal or tape is often applied

to the outer edges of the unit to protect the glass

edges and sealants, and to help hold the glass

panes together. In the first two types of construction, the air space is purged with clean, very

dry, air through a small hole in the seal after

assembly, after which the hole is sealed. For

units containing desiccant, the desiccant is relied on to dry the space air after assembly. Most

units are sealed at room temperature and barometric pressure; for units to be used at substantial altitudes, final sealing at the ambient pres- sure may be effected after shipment.

There are significant differences among the

constructions in regard to edge-rigidity. The

fused-edge units are rigid at the edges ; the glassto-metal units are not wholly rigid, due to bending of the thin spacer strip; organically-sealed

units can range from rigid to nonrigid, depending on the materials used, but probably most are nonrigid at the edge. The rigidity at the edge

affects the deflection of the glass panes nearer

the center of the unit, which in turn affects pres- sure differences between the air space and the exterior. Such pressure differences may be due to change in air space mean temperature or to barometric or wind pressures. Other things being

equal, interior pressures depart less from the

exterior pressure when the unit size is increased,

and when the air space thickness is decreased.

This factor makes it questionable whether the

force tending to separate the panes due to a given

condition favoring an interior pressure excess, per foot of edge, increases with the size of the

unit. With rigid edges, greater stresses are developed in the glass near the edge ; with nonrigid

edges, glass rotation about the spacer may cause

separation from the sealant. It is apparent however that in evaluating sealed units by laboratory

tests it is desirable that more than one size of

unit should be tested. Avoidance of condensed moisture on the inner

surfaces is an essential requirement for satisfactory performance. This is not simply because of

the obscuration of clear vision by the condensation (which might be endured for brief occasional periods), but because the condensation will

eventually leach soluble salts from the glass and

leave a permanent scumming or cloudy film on the

inaccessible glass surface.

Ideally, a once-dry hermetically-sealed unit

should remain dry indefinitely. In actuality, the

seal may be or become imperfect, allowing moist

air or water to enter the air space as a result of

pressure differences, or the material of the seal may not be wholly impermeable to the inward

diffusion of water vapor as a result of water

vapor pressure differences. These are the practical problems to which laboratory tests of sealed

units must be addressed. The test must subject

units to conditions adequately simulating, and ac50
celerating, the stressing conditions which units in

service must withstand for periods up to the life of a building. Presumably, tests adequate to ex- amine units in regard to the important aspects of

performance will cause failure of inferior units,

and pass better units. The very important practical question that remains to be answered is what

intrinsic durability in service can be realistically

predicted for units that pass the imposed tests.

3. Literature Review of

Extant Test Methods

The references listed on page 58 present detailed descriptions of various test methods that

have been developed for laboratory testing of

factory-sealed units. The process has been one of

evolution, which undoubtedly is not completed.

The extensive work carried out, and still in progress, at the Division of Building Research of the

National Research Council at Ottawa [3,4] has

eventuated in the Canadian Standard 12-GP-8

for sealed units [1], which sets forth specific tests and testing procedures, and establishes certain re- quired performances for sealed units in Canadian

service in buildings.

Some of the larger manufacturers of factory

sealed units in this country have been engaged in

developing tests, and in testing such units, for

many years, antedating the work at Ottawa.

Some of this work has been published [5], and

some of it undoubtedly has influenced the development of Interim Specification SIGMA No.

65-7-2 [2].

In many respects the testing methods of the

Canadian Standard 12-GP-8 and of SIGMA No.

65-7-2 are similar, but there are distinct differ- ences also. For both, test units are approximately

of the same size (14 by 20 inches).

Both use measurements of the deflection of the

glass panes, when a unit is subjected to an exterior pressure lowered by about 0.1 atmosphere,

to detect initial leaking-seal failure, with similar

limits for indicating failure.

Both measure the initial dewpoint of the air

in the airspace, using similar apparatus and

with the same higher limit for an acceptable

desiccant-containing unit ( — 60 °F). They differ

in that 12-GP-8 calls for conditioning the unit

at 70 °F for one week before the dewpoint

measurement, while No. 65-7-2 allows a minimum conditioning period of only two hours at 73.5 °F. For units containing desiccant, a long

conditioning period is preferable to assure equilibrium of air moisture content and desiccant.

Both methods subject one face, and the edges,

of the sealed units to repeated cycles of temperature change, with intervals of water spraying on that side, and with the other face exposed to

air at 73 °F. The testing apparatus is essentially

similar for both methods. Following a required

number of cycles of exposure, both methods re- quire that the air space dewpoint not exceed a

specified value. The similarities and differences of

the two tests are indicated below.

Canadian

12-GP-8

SIGMA

65-7-2

Test method, paragraph No. 4.2.4 5.2.4

Test is applied to: Organic-seal units only All types

Cycle events: 90 min to 125 °F

25 min air circul. 5 min 75 °F water spray

60 min air circul. 60 min to -25 °F

2 hr at -20 °F

1 hr at 73 °F

1 hr at 75 °F water spray

1 hr uv rad. 2 hr at 120 °F 100% RH

1 hr at 73 °F

Cycle duration, hr. 4 8

No. of cycles required 320 120

Total hours of test 1280 960

Max. dewpoint, after test -40 °F -30 °F

The temperature range, and rates of temperature change of the units, are greater in the Canadian test than in the SIGMA test, as are also the number of cycles, duration of the test, and

the restriction on allowable dewpoint. However,

in several ways the SIGMA test may be more

searching: in providing for 60 min of water

spray versus 5 min in 12-GP-8. and in providing

2-hr exposure at 100 percent RH at 120 °F, not

required in paragraph 4.2.4 of 12-GP-8 (but see below). In addition, the SIGMA test cycle in- cludes 1 hr of ultraviolet radiation at a time when

the units are wet from water spraying, which may

be a matter of importance for organically sealed

units. It should be noted that both methods call for (dry) ultraviolet exposure in other tests (paragraph 4.2.3 of 12-GP-8, and 5.2.5 of 65-7-

2) , which are conducted rather similarly. The Ca51
nadian requirement is that there shall be no evi- dence of fogging of the cooled area of the unit

after 7 days of uv exposure; the SIGMA re- quirement is the same for 14 days of exposure.

Both the Canadian and the SIGMA test methods

apply (dry) uv exposure tests to all types of

sealed units. There seems no reason to subject to uv the inorganically sealed units.

The Canadian Standard includes a HighHumidity Cycling test (paragraph 4.2.5), not

required in 65-7-2, although the 2-hr exposure to 100 percent RH at 120 °F in the test of paragraph 5.2.4 of the latter subjects the units to similar inwardly-directed vapor pressure differ- ences. The Canadian high-humidity cycling test

is probably more severe, in the direction of vapor

diffusion into the air space, because of higher

temperatures (to 130 °F) and vapor pressures. On the other hand, the exposure to high humidity in the SIGMA test occurs with the unit subject to a considerable temperature difference

(s;25 °F) pane-to-pane, which may strain edgeseals, while the Canadian test is conducted with

substantially equal temperatures pane-to-pane.

Other comparisons between the two methods

include the following:

Canadian

12-GP-8 SIGMA

65-7-2 No. of units in a test-set 18 12

Est. min time to complete

tests, weelcs 15 11 Failures permitted per

test-set, units 1 1 Max dewpoint allowed at end of test —40° F —30° F

A considerable amount of testing and investigation of sealed units has been done at the Norwegian Building Research Institute, some of

which is reported in English [6,7]. A rapid translation to English of a draft interim Scandinavian

Specification, adopted 21 June 1967 by representatives of the Norwegian Building Research Institute and several Scandinavian window manufacturers, has been available for study. It appears

to be largely based on N.B.R.I. work.

The testing methods it specifies include, as do

the tests above, initial seal tests under moderate

vacuum, and initial dewpoint determinations,

made on 10 units comprising a set. The units are large : approximately 32 by 48 inches in size. An

"accelerated aging" test is conducted for 51 days,

with five different "periods of strain", each in- volving one or two selected cycles of air temperature change daily on one side (changes range

from (14 °F to 59 °F) to (14 °F to 131 °F), with

almost continuous exposure to ultraviolet radiation (some occurring with the loAver edge of the

unit in water), and with j^ulsating pressures simulating wind gusts exerted on the face subject to

temperature change, the other face being exposed

to air at 72 °F. The pulsations occur at a fre- quency of 5 per minute, with a maximum pressure

magnitude established for each of the "periods of , strain" within a range from 0.6 to 3.9 in of water ' column. The units are subjected to the pressure

pulsations during most of the twenty-four hours

of the day, except for the few hours when air

temperatures on one side of the units are being

j cooled to 14 °F. Six units of the set of ten are subjected to this test. The maximum dewpoints

allowable are —4 °F initially, and 14 °F after the 1 accelerated aging test. No requirement as to the

limits of effects due to uv exposure is stated. Fail- ure of more than one unit in the initial dewpoint

test fails the set; all six units must pass the ac- i celerated aging test. Assessment of the Norwegian testing method is difficult, in part because it differs considerably

from the other cycling tests described. The large

size of the unit is also a factor difficult to evaluate with the information available. Although the

pressures exerted, on windows by wind gusts are normally not large compared to those due to barometric pressure or temperature changes, the

many pulsations imposed on the units, at unit mean temperatures ranging approximately from

66 °F to 102 °F, must subject the edges and seals to considerable working over a range of shear and

stress conditions. It should also be noted that the

pulsations are exerted on the face of the unit

when it is subject to a pane-to-pane temperature

difference. The duration of uv exposure used seems extreme, but no data are available as to in- cident intensity on unit edges. The apparatus

used for the accelerated aging test is large and

complex, and differs from any known to be used on this side of the ocean. In view of the large

amount of work done by N.B.R.I. in development

of sealed-unit testing methods, and their extensive field studies of sealed-unit performance, the

1967 adoption of the draft as an interim Scandinavian specification suggests that the method is considered to be meaningful.

In addition to the extant test methods dis- cussed above, data have been presented giving

results of laboratory and some service exposure

tests conducted by a manufacturer [5] on a

variety of factory-sealed units of 14 by 20 in size. The laboratory test methods were approximately

similar to those of the Canadian and SIGMA

tests, including initial seal and dewpoint tests, and accelerated aging tests involving (a) 6-hr

temperature change (120 °F to 20 °F, isothermal,

in high humidity) ; (b) 6-hr cycles of temperature change (130 °F to -30 °F on one side, 60

to 80 °F on other), with a period of water spray;

and (c) steady temperature exposure of the entire unit to 110 °F and 90 percent RH. In addition, units were exposed to outdoor weather and

sun at 45-deg slope facing South at Southern and ' mid-Northern sites. Considerable differences in

[
laboratory test performance were found among

units of different manufacturers, and among units

of some manufacturers at different times, es- pecially for some types of organically sealed

units. Failures of organically sealed units were

generally associated either with water vapor

diffusion, or loss of adhesion to glass, or both. In

this connection, advice was received that the polysulphide sealants used in the units involved were

relatively poor in water vapor impermeability, as compared with much better polysulphide sealants

that are now available. Fused-edge units per- formed Avithout failure in the laboratory tests; some glass-to-metal units failed by seal faik;re

in the 130 °F to -30 °F, one-sided, test in a

relatively short time. Failure was based on a rise of air space dewpoint to 0 °F. Performances of

various kinds of units in field service and in a laboratory exterior wall were roughly in keeping

with the results of the laboratory cycling tests. Mazzoni and King [5] conclude with suggested

and recommended performance tests and limits. !The recommendations include the usual initial

tests, and call for the cyclic 120 °F to 20 °F test and of the steady 110 °F, 90 percent R.H. ex- posure test. They include also exposure to artificial uv radiation or outdoor exposure to strong

sunlight.

In summarizing this review, it is noted that none of the extant methods contains recommendations or representations that success in meeting

the laboratory tests assures a particular expectation of satisfactory durability in service. This is not surprising. Only many years of field service can provide the essential durability information

needed, and the units involved should also have

I been tested for their evaluation by the selected

laboratory test methods; failures due to other

than intrinsic qualities [8,9] must be screened out ; and some statistical size for the investigation

is necessary. The accelerated and service test information

provided in [5] is favorable in indicating fairly

good agreement between laboratory and service

performance, but is too limited to provide quantitative correlations pertinent to present needs.

On the other hand, although positive quantitative correlations between field service durability

and successful performance in the laboratory

, tests are not available, it seems tenable to conclude

/ that units failing present accelerated laboratory

tests do not have reasonable service performance

expectation.

4. Visits to Laboratories Engaged in

Testing Sealed Units

Techi:;ical discussions were held with professional personnel of the four laboratories listed on page 56. All discussions were conducted in a helpful atimosphere of cov;rtesy. candor and in- formative exchange ; in all instances laboratory

facilities and operations were viewed, and in two

the factory production of sealed units was observed in detail. A summary of the obtained in- formation significant for the purposes of this

study is given below, without attribution.

4.1. Evaluative Methods

The test methods previously discussed were

used in some degree, and with various differences

in the four laboratories visited as to cycle-period, or events, or number of cycles of exposure.

There are certain differences in aim and objectives among the laboratories, which affect the

tests being conducted. The BRD-NRC Canadian

laboratory has responsibility for testing units in

accordance with Standard 12-GP-9, by a standard procedure, although other test research is also carried on. The industry laboratories are less constrained to a standard procedure for much of

their work, and therefore adopt variations or nonstandardized procedures and methods considered useful for specific purposes. As a result,

although it is probable that the industry laboratories could effectively conduct the standardized

Canadian or SIGMA tests, it was my impression that they did not routinely do so. What is more important is the general trend,

the directions in which laboratory testing is going. The nonisothermal weather-cycling test

(e.g., the 12-GP-8 Paragraph 4.2.4 test) is in use, but ultraviolet exposure is added to it, as in the

SIGMA specification. At all laboratories, there

is recognition of the importance of uv as regards

organically-sealed units, and it is evidenced by

use of both outdoor solar exposures and artificial uv irradiation in the laboratory. The importance

of concomitant water during uv exposure is generally appreciated, although it is not yet included

in all uv exposvires now called for. Use of uv to develop failures due to volatiles released from

organic sealants, which cause fogging of the air

space surfaces, is general. The test is much more

severe when the unit is at a high temperature, as

it appears to be in the Canadian test (150 °F,

paragraph 4.2.3). In one instance it was stated

that the high temperature alone is severe in con- nection with fogging by volatiles. This condition

applies with special force to units used in refrigerated food display cabinets, which often are heated at the edges.

Although it is among the oldest of tests, there

appears to be an increased use of isothermal highhumidity tests over cycles of temperature change.

By means of such tests, units are subjected to positive and negative internal pressures, relative to the barometer, and consequently to stresses of

the seals, under conditions favoring vapor or

liquid entry through the seal to the air space. Being isothermal (although the temperature of

the unit is cycled), the unit is not subjected to the same stresses as one having the two panes of

glass at different temperatures. The tests seem

effective in causing failures of units, even when
the units are kept at a steady temperature, without cycles. Clearly, the high-humidity isothermal

tests are well aimed at testing the vapor permeance of the seal, and possibly the adherence of the

sealant to the glass.

All laboratories used the initial vacuum deflec- tion tests, and the initial dewpoint test, to screen out imperfect seals before more expensive testing was undertaken. At one laboratory it was sug- gested that the deflection test was not essential,

provided that the units had a satisfactorily low

initial dewpoint. The point is well taken, but the vacuum test may have a useful value in examining the stresses developed in the sealed unit, or in

subjecting a seal to forces tending to part the two

glass panes.

It was plain that all laboratories put considerable weight on outdoor solar exposure tests, either on racks (isothermal) or in test or field fenestrations. Programs of periodic monitoring

of the dewpoint of installed fenestrations are under way by several laboratories, and it seems

clear that producers rely strongly upon such findings in evaluating the confidence with which

durability guarantees can be advanced.

It is desirable to emphasize that there are dis- tinct differences among sealed insulating units

that compound the problem of evaluating them.

Inorganically sealed units are not subject to uv

degradation, as organically sealed units may be. On the other hand, the inorganically sealed units

may be more severely stressed at edges by unavoidable nonuniformity of temperatures in service, while organically sealed units mav be ser- iously affected by chemical incompatibility with

caulkings, glazing compounds, etc., especially in the presence of water. Field fenestration monitoring should provide comparable durability data

for all kinds of sealed units, if all types are in- cluded, but requires too much time for present

purposes.

Because of the possible vulnerability of organically sealed units to chemical effects, it is neces- sary to examine such effects under laboratory

conditions where chemical attack is subject to controlled conditions not attainable in field or

service situations. Such investigations were dis- cussed at one laboratory, but probably are carried on at several. Among such investigations at one

laboratory were

:

(a) flexings in air of short lengths of organically sealed joints with uv exposure;

(b) use of vacuum deflections of joints to find

best sealant properties, and dimensions of

seal spacers and joints;

(c) exposure of samples of sealants to a variety of solvents, fluids and oils, at selected

temperatures, to evaluate chemical effects and changes;

(d) applications to organically sealed edges of

various caulking compounds and materials

for observation of chemical effects, and use

of sealers to separate caulking and edge to reduce chemical effects;

(e) improvements in organic sealants due to formulations or fillers which result, for

example, in much lower vapor permeance

of seals of current availability.

One result of such investigations, it was stated,

is that a specification that would yield excellent

sealants is possible, but for commercial reasons may not find easy acceptance. However, it was

also stated that even though excellent sealants can be supplied, some manufacturers may fail to do what is additionally necessary to assure satis- factory units, in respect to such matters as quality

of glass, or glass edges; uneven sealant application; dirty (or not clean) glass; added solvents;

poor temperature or chemical or desiccant control; or mismatched expansion coefficients of

spacers and glass.

The importance of these manufacturing matters as regards production of satisfactory units i] was strongly indicated during the tours made to J see factory production of sealed units. Organization to promote and realize close quality control was plainly a result of experience and much ii effort, and was regarded as a primary responsij bility.

'

4.2. Practical Considerations in Laboratory Testing

of Units

The cost of conducting the tests called for in

the Canadian and SIGMA standards is high,

being estimated variously as from $1,500 to $3,000 per set of units. In part, the high cost is due to the cost of apparatus such as the Canadian

Weather Cycling equipment, which accepts only

24 units, and the time required to install units for

test. This apparatus also imposes constraints on

the size of units that can be installed. The highhumidity test chambers, with or without temperature cycling, are preferable in respect to acceptance of a variety of unit sizes, speed of

installation of units, and number of units that can be accommodated, provided that the exposures satisfactorily examine the units. However,

there may be some question as to the uniformity

of conditions from place to place in such chambers. The matter of test-unit size is important for

several reasons. Testing a range of sizes of the same unit design seems advisable until it is known that size is not a material factor. Further,

there are disadvantages in having a single standard test-unit size (14 by 20 in) that is not a stock or common size generally procurable oA^er the

counter. Specific orders to manufacturers for the

test-size units might well receive special production attention. It is also desirable that the test- ing equipment be able to test units of various

sizes which might be involved in field service

fenestration monitoring programs.

54
5. Recommendations and Conclusions

1. Procurement of factory-sealed double-glazed

units for architectural service should be based on

successful performance in meeting laboratory

tests of the kinds reviewed in this study.

2. At present two fairly well evolved specifications are available for conducting laboratory

tests of sealed units—the Canadian Government

Specifications Board 12-GP-8, and the Sealed

Insulating Glass Manufacturers Association In- terim Specification SIGMA No. 65-7-2. The two

specifications are approximately similar, with some differences in detail, and in requirements.

Some sealed-unit manufacturers have the equipment for the SIGMA tests; a certifying laboratory for SIGMA tests is now available to manufacturers.

3. It has not been fully established that success of units in meeting the requirements of these

specifications assures their intrinsic in-service

durability for a predictable term of years. It is tenable to conclude that sealed units that fail to meet the requirements of these specifications do

not have reasonable service performance expectation.

4. Further evolution of the specifications and

test methods is to be expected. Among modifications thought desirable are : ability to test a range

of sizes of sealed units; increased use of ultraviolet irradiation in the presence of water or high

humidity, at least for organically sealed units;

increased exposure to high humidity at edges of

units, preferably with temperature cycling ; better assurance that all units under test are subjected

uniformly to substantially the same test conditions.

5. It is recommended that in view of the present

high cost of the specification tests, and the large

testing capacity that will be needed if test data

are required for sealed-unit procurement, a strong

.effort should be made to simplify the testing, and

to evolve testing apparatus and methods that in- crease testing capacity and lower the unit cost of

tests.

6. Comment

The recommendation that procurement of

sealed units be based on satisfactory performance

in meeting laboratory tests is based on the general experience that the necessity of meeting a

suitable performance specification upgrades product quality. This requirement is especially desirable when the service demands on the product are

severe, as they are for sealed glazing units. A

further advantage is that by excluding units of

poor intrinsic quality, the gradually accumulated

in-service performance and durability experience

with only accepted units will provide more defi- nite information leading' to improvement of the

testing specification. The clarification of problems, and solutions to them, should be made easier, and product improvement be advanced.

7. Proposal for Improved Testing

Apparatus

Following up Recommendation 5, exploratory

consideration has been given by the author to a

possible testing apparatus that might meet the

needs expressed in Paragraphs 4 and 5 above. The

apparatus is illustrated schematically in figure 1. In brief, it would consist of a circular chamber

subjecting many individual imits to isothermal

exposure to high humidity with cycled temperatures from about 35 °F to 125 °F, somewhat

similar to the Canadian 12-GP-8 (Paragraph

4.2.5) High Humidity Cycling Chamber. The

units would sit on edge on supports forming a

lai'ge wheel turning slowly on bearings about a

UV TUBE

Section A-A

-HEATER -REFRIGERATION COIL

Section B-B

PUMP

FiGTjEE 1. Schematic draicing of apparatus for labora- tory testing of insulating glass units. Air tem- peratures in apparatus are governed by controlled temperature of the continuous recirculated water

sprays in cylinder at center ; air circulation is In- duced by the sprays. The specimen-holding turntable Is rotated slowly by the drive at top.

55
-4 ONE CYCLE ^

TIME

Figure 2. A possible cycle of temperatures in the apparatus: W, of the spray-water ; A,

of the air in the apparatus; II, of a unit undergoing test.

vertical pipe axis, and would be exposecf, as they

passed, to uv irradiation from suitably disposed

lamps. Chamber conditions would be cycled by

control of the temperature of continuous recir- culated water sprays causing air circulation

downward through an open cylinder at the wheel

axis. A possible cycle of temperature variations

in the apparatus is shown in figure 2. By placing

the units on a slowly turning wheel, uniformity

of exposure conditions for all units would be

improved. Loading on of units would be done

through a door in the side of the chamber; it is believed that some 100 units, of various sizes,

could be accommodated. The diameter of the

chamber would be 10 or more feet, depending on maximum size of units to be tested. Although the apparatus, as pictured, is in keeping with the presently strong tendency toward

vapor-pressure testing of factory-made seals, and

does so in a way assuring uniformity of exposure conditions, it does not strain the seals, be- cause individual units are substantially isothermal. However, it may be desirable to be able to subject unit seals to edge-strains during the ex- posure tests. A means to do this in the apparatus

is readily developed, as follows.

Suppose two units were sandwiched closely to- gether, with a gasket or perhaps even a pad of

material between them. Exposed in the apparatus,

the outer pane of each would respond in temperature to the time-varying ambient temperatures

established in the apparatus. The inner pane of

each, however, would be heated or cooled chiefly

by heat exchange with the outer pane across the

air space. Thus, the temperature of the inner

pane would lag that of the outer, and the temperature difference between them would cause dimensional strains on the unit seals. An esti- mate of the maximum pane-to-pane temperature

difference thus set up can be made approximately, on the basis of reasonable assumptions, as

set forth in the appendix (section 8). The analysis shows that substantial pane-to-pane temperature differences can be developed twice in each

cycle.

One advantage of thft possibility is that it enables a determination of the importance of

strain at unit edges in accelerated testing of fac- tory-sealed units. The Canadian weather cycling

test, the SIGMA test, and the Norwegian accel- erated aging test all include edge-strains as significant variables. Using the proposed apparatus,

half of a set of units can be exposed to isothermal

test conditions, and the other half to the same

ambient conditions with edge-strains superimposed by means of pane-to-pane temperature

differences, to varying degrees if desired, all with

uniformity of ambient exposures and uv irradiation. Further, it enables experimental consideration of the effect of unit size on the performance

of the factory-made seals, since the edge-strain

developed for similar pane-to-pane temperature

differences probably depends on unit size. These research possibilities—and there are more

that can be developed—make it desirable to ex- plore an apparatus of this type. There seems no

reason to doubt that the apparatus can be duplicated so that tests in one would be comparable to those in another.

The author wishes to acknowledge the helpful

assistance and information obtained from the

officers and technical personnel of the following

four laboratories visited in connection with this

study during the period November 1967 to January 1968

:

The Division of Building Research of the National Eesearch Council of Canada, Ottawa,

Canada.

Pittsburgh Plate Glass Company, Pittsburgh,

Pa.

Products Research and Chemical Corporation,

Gloucester City, New Jersey.

Libbey-Owens-Ford Glass Company, Toledo,

Ohio.

56
8. Appendix. Calculation of

Pane-to-Pane Temperature Difference

Assume that two similar sealed insulating

glass units, IJi and U^, are sandwiched together

with a gasket at the edges, or a pad of suitable

material of thickness, a, between them, and that

the sandwich is then placed in the proposed ap- paratus for cyclical exposures. Figure 3 shows a

cross-section of the assembly. The temperature, 7", of the outer pane of a unit and that, of the

inner pane, are cyclical functions of time due to the temperature variations in the apparatus. The

thermal resistance of the air space from pane to pane is taken as R iExO.7 deg F/(Btu/hr ft")

for most units). The heat capacity from the air- space surface of the inner pane to the centerline

of the sandwich is designated as C (Btu/ft- deg

F), which can be estimated when circumstances

are selected.

Figure 3. Partial cross section of two units sandwiched

together with a pad between.

It is assumed, as a reasonable approximation,

that T varies sinusoidally with time, i.e.. = ^ sin U (la)

27r where A is the amplitude of T, and ^ ~ p where

P is the cyclic period, in hours.

Then

or, dv

T—v _ pdv

dt

A solution is mA

+ mv = mA sin ht (2a)

V m sin ht — h cos ht + Be~"

J2 -|_ After sufficient time the transient term will

vanish, and

V m? ["sin ht — h cos hfX

A h^ m

and

T-v = m? sin ht + hm cos ht (3a)

A h^ + w? h"^ + m? = sin ht + k cos ht

1 + P

/, h %tRG\ .

To find the extreme values of

-.—, we obtain the A '

derivative with respect to ^, and set it equal to zero

d_ IIT—v\ T-v\ hk"^ cos ht — hk sin ht ^

dt \ A ] 01 -fF

whence tan ht-^, — yfc, or 5^m' = ^-rc tan k + rnr

T—v

Evaluating for this value of &^m' we find

(^)max

min

= sm o^M'=sm I arctan--p—| (5a)

Similarly, it is found that for v, the extreme

A

values occur when tan htu" — ~i and that

k

(1) * ' max

min

= sin htM"= sinl arc tan

For numerical illustration, values of (Tv) max

are tabulated below for three cases. In the first, the units are separated slightly by a gasket at the

edges, with no interposed pad. In the second and

third, pads of i/4-in and 1-in cement-asbestos

board, respectively, are used to form the sandwich. In all cases, the cycle period was assumed

to be 4 hr, and the amplitude A was taken as 45

deg F.

Case C , (^) (T-^l

• ' mnv Btu/ff deg F deg F.

No pad 0.26 0.29 0.28 12.4 1/4-in C.A. 0.47 0.52 0.46 20.6

1-in C.A. 1.09 1.20 0.77 34.6

The pane-to-pane temperature differences

shown in the last column above are of magnitudes

similar to those to which units are subjected in

service.

57
9. References

[1] Canadian Government Specifications Board Standard

for Factory-Sealed Double-Glazing Units, 12-GP-8 (15

July 1966).

[2] Interim Specification for Sealed Insulating Glass

Units, SIGMA No. 6.5-7-2, Sealed Insulating Glass Manufacturers Association (1967 Edition).

[3] Wilson, A. G., Solvason, K. R., and Novak, E. S., Evaluation of factory-sealed double-glazed window

units. Research Paper No. 85 (NRC .5270) of the Division of Building Research, National Research

Council, Canada (19.59). [4] Wilson, A. G., and Solvason, K. R., Performance of sealed double-glazing units. Research Paper No. 168 (NRC 7042) of the Division of Building Research,

N. R. C, Canada (1962).

[5] Mazzoni, R. J., and King, L. K., Performance of double-glazed units in accelerated and service tests, ASTM Materials Research and Standards, 5, No. 10, 517-524 (Oct. 1965).

[6] Gjelsvik, Tore, Performance of sealed double-glazing

units in severe Norwegian climate—the West coast

field study 1963, Norwegian Building Research Institute, Report No. 44, Oslo, (1965) (In English).

[7] Gjelsvik, Tore, Laboratory testing of sealed glazing

units, Norwegian Building Research Institute, Reprint No. 145, Oslo (1967) (In English).

[8] Solvason, K. R., and Wilson, A. G., Factory-sealed

double-glazing units, Canadian Building Digest, CBD

46 (Division of Building Research, NRC Canada,

Oct. 1963).

[9] Garden, G. K., Glazing design, Canadian Building

Digest, CBD 55 (Division of Building Research,

NRC Canada, July 1964.)

58
5.2. DISCUSSION SESSION V

Mr. McKinley : Thank you very much, Henry.

I am sure that you have not only provided a very

important and objective review of the several

methods, but now have challenged all of us with a proposal that may speed testmg, increase reliability and reduce costs. We have about 15 minutes

remaining so Henry can respond to the first questions that come to your mind.

We'll see if we can lead into some of the first reactions. Perhaps it would be a good idea to

start with Mr. Wilson or Mr. Solvason and ask

if they care to comment.

Mr. Wilson : I'll say a few things just to give

Dick Solvason a chance to get his mind clear so that he can say something worthwhile. I think

both Dick and I fully support many of the things

that Henry has said. A test method for certifica- tion purposes has got to be simple, has got to be

capable of handling large numbers of units, it's got to be an economic proposition and I think

that if one can demonstrate that this isothermal

kind of apparatus that Henry has described,

which is not too dissin^ilar from some of the other

kinds of apparatus we have heard about, is adequate, then it does provide a very good answer

because it's capable of handling large numbers of

units and therefore may be able to provide, hopefully, an economic way of going about certifica- tion. I'm sure we both agree that it's extremely

desirable to be able to introduce ultraviolet

effects in the presence of water; I know Dick's

been thinking about this. We've been under great

pressure in Canada to get on with the business

of getting some sort of standard method that can

be used by the manufacturers and by the users. We've responded to this pressure and have not

conducted as much by way of research as we

would have liked because we had this primary

responsibility to fulfill. I think we both agree, as I'm sure the other people doing tests would agree, that ultraviolet exposure in the presence of water

is a very desirable feature in a testing program at

this stage.

Dick, do you wish to add anything?

Mr. Solvason : Henry made a couple of comments about the dew points after weathering

tests. In general, these don't make very much

difference because when a unit fails in these kinds

of weathering tests it begins to fill up with water

so that it doesn't matter very much whether the

dewpoint cutoff is made —30 or —40 °F.

Another comment I want to make is that most

of the test methods that are in vogue at the pres- ent time are really a mechanical-stressing type of

test conducted with fairly high water vapor pres- sure differences so that they will accelerate the

mechanical stressing of the units and give a

little higher water vapor diffusion rate. I would

like to point out fv;rther that the accelerated tests

may serve to demonstrate whether a manufacturer can make a unit that will stand up mechanically when it is new, but that little information is provided as to the effect of time and

exposure on the materials in the sealing system

itself. When the accelerated tests are finished, the

units are still only 4 or 5 months old at the most. This does not tell us anything about what they're

going to be like 5 years later, or 10 years later, or 20 years later. Mr. McKinley: Thank you, Dick. I wonder if Ted Pritsker from the Dallas Laboratories would

care to comment?

Mr. Pritsker: For the apparatus described,

what would be the duration of one cycle of ex- posure ? Mr. Robinson : I think the apparatus described

could be operated on a 4-hour cycle or thereabouts; it hasn't been built so I can't be more

specific. I think a 4 or 6 hour cycle would be

quite feasible. It may perhaps depend on the

temperature range that you want to cover and the

equipment you can lay your hands on to get that

job done.

In connection with what Dick Solvason just

finished saying, it is true that the units may be

only 4 or 5 months old when the test is finished. I wonder if anyone here has taken new units,

exposed them let us say to solar radiation for a 6-month or one-year period, and then put them

through the laboratory tests. I think this would

be possibly worth doing.

Mr. McKinley : Thank you very much. I was

going to ask Dan Gwyn if he wished to say a word.

Mr. Gwyn: (Inaudible)

Mr. McKinley: Ray Mazzoni, do you wish to say a word?

R. Mazzoni : (Inaudible)

Mr. McKinley : Henry, do you have something

to add?

Mr. Robinson : I would like to say a few things

that touch upon what has just been said by sev- eral people. First, the apparatus described is not

offered with an idea of it being "the answer." It

is to indicate to you one way of producing conditions, and uniformity and control of conditions,

which it appeared to me from the study are needed in testing these units. I can not guarantee

or assert that this apparatus will do as well as any present one. I think it has a good chance of

being made to work by suitably selecting temperature ranges, and so on, so that it would be

effective. But this would have to be showTi.

I would add the thought that one of the essentials in your growing industry is to have enough

jl^est facilities and it's unlikely that any one place

would have enough. First of all, the geographic

distribution of the country is too great. There59
fore, I believe it is quite essential or desirable

that a standardized or standard apparatus be developed which can be reproduced on the Pacific

Coast, Gulf States, or anywhere else, and replicated so that manufacturers can be assured of

comparability of results obtained at various

places. This is an evident need that requires co- operative attention and solution by the whole in- dustry and its customers. R. W. McKinley : Yes, Mr. Orbesen.

G. Orbesen: Mr. Robinson, you have referred

several times to the Canadian test method, and

the SIGMA test method. Is there not a GSA

specification for insulating glass units ? Mr. Robinson : The Public Buildings Service of

GSA has an Interim Guide Specification for glazing (PBS 4-0885 (INT), June 1967) which sets up requirements for insulating glass units (Paragraph 2.1). Few details are given concerning

testing procedure or equipment. It requires that

units withstand one of two optional alternative

tests. It will be of interest that one option calls for tests of 250 days, and of one year, duration;

the other option requires 700 days for completion.

I have no information as to who has conducted I certifying tests under this guide specification.

R. W. McKinley: Yes, Roger? i Mr. O'Shaughnessy : Have you worked on any

costs involved for the suggested apparatus?

Mr. Robinson : No. I think the cost could vary

by 2 to 1 depending on who has the building of it.

60
6. Proposals for Future Action —Panel Discussion III

Introduction of the Third Panel

Henry E. Robinson

The clock is moving and toe have a full schedule. Pd like to ask the meeting to come to order. We are about to have., I think., the action fart of this Seminar take place.

Up to noio toe have been getting educated and have discussed various aspects of the questions. The motif for today is, I think, action. The title of this part of the program is ^'Proposals for Future Action.'''' Action is the key toord but the agenda noio is soliciting proposals. To

put these before you, the program calls for a panel tohich toill consist of Mr. Lynford K.

Snell, would you take position . . . ; Mr. Roger O''Shaughnessy, President of the Card'mal

Insulated Glass Company; Mr. Robert W. McKinley of PPG Industries ; and Mr. C. C. Stout, Treasurer and Product Development Manager of the Andersen Corporation.

This panel is convened to give you in short form their suggestions as to vjhat course of

action this Seminar and your industry might consider. I say again the motif of this session

is action. After the four panel members have made their suggestions, I think tve toill not

have time for much discussion because toe toill have a coffee break.

After the coffee break, I hope that the fifth member of the panel, yourselves, toill stoing

into act'ion and help us to define and understand tohat should be done and vohat might be

done.

I voill call upon the first member of the panel, Mr. Lynford K. Snell, to start off.

6.1. Proposals for Future Action

Lynford K. Snell, Jr.^

Federal Housing Administration,

Washington, D. C. 20412

I believe FHA's needs are two-fold—an immediate one and the desire for a future or longer

I range plan.

' I think that this seminar and FHA's study

with NBS have indicated that no one test method

can be viewed as the ultimate answer and that more development work is needed. I would suggest that this be done as soon as possible.

Perhaps our immediate need could be fulfilled by use of the Canadian or SIGMA test method on

a temporary basis, while we move toward the

^ Architect, Architectural Division.

development of an improved testing method

which could be nationally recognized.

I do believe that by using one of the existing

test methods we would have a temporary stopgap measure, whereby, at least the very poor

units could be eliminated. Perhaps additional

effort could be placed on standards for sealant

systems.

As to longer range plans and desires; perhaps

development using ASTM—NBS—Industry

Government cooperation is appropriate. I believe

those who follow will expound on some possible

suggestions along this line.

61
6.2. Proposals for Future Action

Roger O'Shaughnessy

Cardinal Insulated Glass Co.

Minneapolis, Minnesota 55440

Mr. Roger O'Shaughnessy did not present a formal paper and no transcript of his remarks is available. Some of his ideas, however, appear in

the discussion following Mr. Stout's paper.

62
6.3. Proposals for Future Action

Round Robin Comparison of Test Methods

Robert W. McKinley/ Chairman

PPG Industries, Inc. Pittsburgh, Pennsylvania 15222

Preceding speakers and discussions have made it clear that there are a variety of test methods, facilities, and procedures now in use by various organizations which have, in at

least some respects the same general objective, namely ; reliable accelerated evaluation

of insulating glass unit performance.

Key words : ASTM ; insulating glass unit ; round robin ; test farms ; test methods.

1. Introduction

At present accelerated testing methods rely, at

least in interpretation, calculation, and application of their results on judgmental processes not

necessarily constrained by similar guidelines.

Since the original purposes of these methods have

varied as their creators, important differences in

results are to be expected. It is indeed fortunate

that there exists such a wide experience from

which to draw. Practical correlation of accel- erated test results with on-the-job performance is difficult at best, and impossible without experience.

Within the durability task group of subcommittee VIII, ASTM Committee E-6, the preparation of a durability test method for glazed sash

has been proposed. Drafts have been circulated

and discussed. It seems appropriate, therefore,

that we propose and perhaps undertake a comparison of existing test methods for insulating units.

2. Proposal for Comparing Test Methods

For your consideration and discussion, it is our

proposal that the durability task group plan and

conduct a round-robin program of test method

comparisons. Such a program might include the

following features:

(1) Assemble a group of representative manufacturers, laboratories and test farms. Encourage interested manufacturers to as- semble a number of units following their

usual production practice. Insofar as possible, these units should represent product

characteristics typical for their process. They should be of a size selected to facili- tate testing.

(2) Identify each such test specimen permanently with a non-proprietary code

(ASTM NO. ). Omit or remove

proprietary labeling.

(3) On ASTM order, each manufacturer would

ship (at no charge) fifteen (15) of these

test specimens to each laboratory and/or

test farm and retain fifteen (15) as control samples.

(4) Each participating laboratory and test farm w^ould test samples (submitted by

ASTM) following its usual procedure and

report results to ASTM in a uniform

fashion. A suggested data format follows.

Task group E would assemble and analyze the

results and prepare a formal report. This might

be published in Materials, Eesearch, and Standards. It would report on the test methods—not on the test units.

1 Manager, Technical Services, Glass Division.

63
ASTM COMMITTEE B-6

SUBCOMMITTEE VIII TASK GROUP ON DURABILITY

EOUND ROBIN REPORT

TEST METHOD EVALUATION

DURABILITY OF INSULATING GLASS

Date:

Laboratory/Farm :

Address :

Engineer in Charge :

Telephone Number :

Test Method:

Usual Purpose of Test :

Number of LTnits previously tested : .

Results normally reported :

Means of correlation with on-the-job performance:

Facilities and Equipment :

Procedure : ( Start with receipt of test samples at laboratory and go all the way through to describe storage after tests are completed.)

RESULTS

ASTM Test Unit No. Performance Criteria

64
6.4. A Manufacturer's Experience with Insulating Glass

C. C. Stout^

Andersen Corporation,

Bayport, Minnesota 55003

In this paper the author reviews the growth in the use of insulating glass in buildings

and presents data from his company's experience in regard to replacement cost for field failures, which was approximately 0.1 percent of annual sales. Good performance of units over the life of a building was described as the result of production of insulating

glass units aimed at value rather than price.

Key words : Field performance ; insulating glass ; replacement cost ; service procedure.

1. Introduction

The following comments indicate our belief

that insulating glass has become an important

customer benefit to producers of window units

and sliding doors.

The figures that will be presented to you are

not intended to impress you, but I hope they will

add some validity to this presentation.

I represent a window and sliding door manufacturer that has had experience in the marketing of insulating glass since 1946. At that time

our insulating glass interests were principally at our distributor level. These distributors had

started to supply otir picture units glazed with

insulating glass. We've been very active in the

sale of insulating glass since 1953.

2. Growth of Insulating Glass Production

During the past fifteen years over 10 million

window units and sliding doors produced at our

plant have been factory glazed with hermetically

sealed insulating glass. Over 60 percent of all sash and door panels that we produce are glazed

with insulating glass.

Insulating glass now represents over one-third

the cost of all materials used in our products. It

is the XUMBER OXE component that we use

in the products Ave produce today.

Wlien we started glazing our products with in- sitlating glass, our suppliers and our company

believed there was a joint responsibility to proA'ide the end user with a product that would give

satisfactory performance. "\Ye wanted a low inci- dence of field failures and, most important, to back up the product in the event of failures.

3. Incidence of Failure

Our field experience records have been compiled on both an annual and cimiulative basis. Our record of field failures has been excellent.

1 Treasurer—Product Development Manager.

The causes of field complaints are: Stress cracks

Seal failures

Glass quality

Scratched glass

Collapsed air space

The following data covers the years from 1956

through 1967, a period of 12 years. On the basis

of cumulative replacements, it has cost the

Andersen Corporation approximately $40,000 a year as an average over the past 12 years. Our sales over the past 12 years have averaged

$41 million dollars per year. Cost of replacement

to the Andersen Corporation is approximately

0.1 percent of annual sales. This figure represents our company's replacement cost. Our insulating

glass suppliers share in the overall replacement

cost. This is divided 75 percent by Andersen and

25 percent by our suppliers.

Our experience shows that if failures occur, they develop the first year or two after installation. We find the incidence of failures based on

percent of glazed sash to be the same for both

ventilating and stationary openings.

4. Comment

To successfully back up a product, you commit yourself to a policy and then administer that

policy eifectively. Field complaints on insulating

glass are followed up by our Service Department

which operates under our Sales Department.

Over the years we've developed a procedure to service insulating glass complaints by good coor- dination between our distributors, dealers, and

our field sales and service people.

Although we use a much larger share of glass

edge type of insulating glass, we've had satisfactory field experience with non-glass edge type of

insulating glass.

"With the increased use of tempered insulating glass in sliding doors, we will use more of

the non-glass edge type of insulating glass.

We expect our suppliers to produce tempered

insulating glass that provides field performance

equal to ottr past experience.

65
We believe that under normal exposure glass is a permanent material. We also believe that when

glass is used to produce insulating units, the

product should be permanent and last for the

life of the building.

A five-, ten-, or twenty-year warranty, in our judgment, does not appear to be the solution to satisfactory field performance of insulating glass.

There's not much satisfaction to the end user

when a product fails during the sixth, eleventh! or twenty-first year. Producing insulating glass that has value and

not price would appear to provide the best as- surance of good performance during the life of ii the building. We have learned from experience j that when a firm makes a product that performs 1 well, and provides adequate adjustment for prodj uct failures, the product can be marketed suc-j

cessfully. |

66
6.5. DISCUSSION SESSION VI

j H. E. Robinson : Thank you, Mt. Stout. I think

, it goes without saying that you have helped us

all look through clear glass at a clear picture,

namely: "Value rather than price." Mr. Stout's

position should receive our earnest attention

because of his dual consumer and producer concern in this matter. Before the break for coffee which is due

shortly, I would like simply to summarize the

suggestions and proposals that have been made to us so far, so that we can chew them along with

the coffee that we take. Mr. Snell has recommended, in view of the immediate needs of his agency and undoubtedly of

GSA and other governmental agencies, that our

position should be to adopt what is now availI able, which is the SIGMA specification in this

I country, or the Canadian Specification, so that

j at least there can be a beginning of exclusion of

poor units. He has also suggested the importance

, perhaps of developing some sort of specification

I on sealant systems or materials which others of

I our speakers have indicated are near or could be

I effected. He has also suggested the cooperation of

' governmental agencies, of the SIGMA organization and of the industry and possibly NBS to improve the current testing methods and require-

[ ments of the specifications. Mr. O'Shaughnessy

[ has expressed the actions on the part of SIGMA

recently and in the past to tighten the present

SIGMA specification in several respects, to re- vise some of its test cycles in ways which he feels will improve them and perhaps give them more

impact, as far as accelerated testing is concerned.

He has mentioned the efforts they have made to summarize the available information on glazing

and to make recommendations with respect to both mechanical and chemical aspects. And he

proposes for us the adoption of the SIGMA

effort and its glazing recommendations. This is a

i matter for you to consider. Mr. McKinley has

proposed a Round Robin series of tests, not of

units, but of the testing methods and procedures

now being used, which could be initiated perhaps

by the Task Group of ASTM E-6, Subcommittee

VIII. Mr. Stout's information which we just

heard, I found very interesting myself, especially his mention that generally fogging failures occur early, in the first or second year, which

sounds very much as though the first or second

year period of use represents a screening test for

the quality of units being supplied to him. Mr.

Stout did not say how they purchase their glass,

whether on specifications or otherwise, nor did he

indicate directly hoAv they control the glazing

practices in their own production. These are matters some of you may wish to discuss with Mr.

Stout.

I leave the matter with you at this point. We

will come back in 20 minutes after coffee and then

I hope the floor will make itself heard.

I hope you all enjoyed your coffee as much as I did. Before we consider and discuss the suggestions we have already received, does any member of this Seminar have a suggestion other than

those we have heard . . . for action by this

Seminar?

H. E. Robinson: Sir?

Participant : Just one request and that is in all of these testing procedures, for the southern half

of the United States, please include some kind of

testing procedure for reflective glass.

H. E. Robinson: Thank you. Your request is noted. Are there others, or another? Mr.

O'Shaughnessy ? R. O'Shaughnessy : We are involved in a rather

major effort right here. Since these reflective products are new and are just coming onto the

market, it may be well in the future to consider

the various tests that already are being performed

by professors at various universities and then to

institute some type of program whereby we can

consolidate the information and proceed from

there, but I think the immediate proposal is a bit

beyond our realm.

H. E. Robinson : I think it's one we should keep

in mind and develop possibly in the way you

suggest.

I think we can subdivide the present situation

in the way that Lyn Snell did, into the immediate need, and the longtime need or program

which your industry may require.

For the immediate need it appears that the

chief suggestion we have is that an extant test method, as it now appears or is being modified,

such as the SIGMA test method, might be the

quickest avenue to action to improve the product

at the present time for the purposes of large and

other purchases. For FHA, GSA, the government

generally, I think that the pressure is in this

direction. Wliether this is equally so for private

purchases, I don't know. I gather from the ex- pressions here that the architects would be of

similar mind. ^^Hiether this is the avenue they

would prefer I cannot myself say . . . I'd be glad

to have the audience give its views in that connection.

It was mentioned by Lyn Snell that possibly

now is the time to start developing a specification

for the sealant system components. This is an

element which your industry may wish, to consider. We have not dwelt on it much at this meeting but in some way action on this should be

taken, whether by SIGMA or an ASTM group,

I am not able to recommend at this moment. I think you should consider that.

67
It was also suggested that there should be as much cooperation as possible among governmental agencies, companies, SIGMA, and NBS

perhaps to try and improve the testing methods.

The chief avenue that to us at least appears

possible and appropriate here is that of the re- search associateship. Although this was discussed

at the dinner last night, I'm going to ask Dr.

George Gordon, who is here, to briefly summarize

the nature of such arrangements and perhaps to answer any questions that may come from the

floor. Dr. G. Gordon : For the benefit of some of you

who weren't here last evening and who didn't hear

Dr. Kushner's talk about NBS in general and,

particularly, about the research associate program, let me say a couple of things that may be

repetitious to some. First, I am speaking as one who until yesterday was utterly ignorant of the

technical problems that affect the insulating

window industry. Now that I have learned something of your problems at this Seminar, I would

like to describe our research associateships as something that might be useful and acceptable to your industry in solving some of these problems.

Before that, hoAvever, I'd like to state something

about NBS and its relation to the voluntary

standards or engineering standardization methods

of this country. With very few exceptions, and

these are prescribed to us by Congress, we do not make engineering standards. In no case do we

police or enforce engineering standards. We do

not certify products or procedures and our sole responsibility in this area is to provide technical

backup useful in the making of these standards.

Dr. G. Gordon : One of the methods that has

been found extremely useful, for a period of

about 39 years, is what we call the Research Associate Program. Very briefly, the Research Associate Program is an arrangement by which a company, an association, or perhaps a g^oup of

individual companies, can send a person here to work for a period of 6 months, a year, 2 years, sometimes longer, not as an employee of the National Bureau of Standards but working here

Avith our people, under our supervision, and producing research or engineering results in the same way that one of our emj^loyees does. This man

comes here with his salary paid by the sponsoring

organization. We supply supervisory assistance,

clerical help, laboratory space, and ordinary supplies and equi])ment. If there is need for extra- ordinary services like computer work, large

amounts of shop Avork, or special equipment, a

special fund is set up by the sponsor here from

Avhich AA-e clraAv and pay for these special services. What are the advantages to the sponsor of

having a man Avorking here instead of someAvhere

else? First, the associate has access immediately

and continuously to a A^ery Avide range of technical competence that Ave have here at the Bureau. Not only competence, but special facilities.

For example, as it might affect the insulating

windoAv industry we have, of course, the Building Research Division, but aside from that in other Institutes Ave have a large group working

on glass, Ave have in the Polymers Division people

Avho are deeply involved with adhesive problems,

Ave have expertise in the use and application of

sealants, and Ave now have half a dozen widely

scattered outdoor exposure sites which would be

available for the use of the program ... all the

Avay from Puerto Rico to Alaska . . . and any

other parts of the Bureau that could be useful are

available. Well, what are the advantages to NBS . . . Avhy do we like to see this program

used? I think it is pretty obvious that it is not

because we Avant to stick our noses into the standards making process and do anything like set up

a government standard . . . that isn't it at all. We need the input though from industry and it often comes most usefully through a research

associate. We need the input that allows us to plan more efficiently for industrially-related work

that Ave have been given the mandate to do by our

original legislation. I'd be less than candid if I

didn't admit to the fact that a research associateship helps us beef up our own research effort a

little bit. The presence of an associate here adds

to the amount of research that we can do in the

face of financial limitations. Se Ave see it as a good

thing for the sponsor, Ave see it as a good thing

for ourselves.

In setting up a research associateship the first step is to identify the problem that a research

associate can Avork on here that fits somehoAV into

something of mutual interest that Avould be an on- going piece of engineering work. Second, of

course, is to find a suitable man to come as a re- search associate. The third is to find the money

to support him, his salary.

Once a problem is identified, and a man is located, setting up an associateship is quite a simple thing to do. The paper work is very

simple and a man can come to work here almost

immediately. We like to keep a project fairly

short, say 1 or 2 years, Avith a well-defined beginning and end . . . Ave like to make sure that

fairly frequent revieAvs take place involving our NBS people, the research associate himself, and

his superAdsor, and representatives of the sponsoring body . . . and Avith that procedure we

usually find that we have a program that is satis- factory to everybody concerned. More and more

Ave are trying to bring programs here that have

real substance to them. There haA^e been cases

in the past AA'here programs continued on and on and lost their effectiveness. I think this is fairly

easily avoided by being careful to describe the

program especially at the very start, and to keep

a close Avatch on AA'hat's going on. Briefly, to illus- trate Avhat Ave are doing, I Avill give you a couple

of examples Avithin the Building Research Division. For example, the Porcelain Enamel Institute, Avhose members are generally quite small

68
j companies, have had a program here for 2 to 3

i years involving the examination of the mechanaj ism of spalling of porcelain enamel from various

II metal substrates under different physical and

a chemical conditions, with the idea that on the

basis of this research satisfactory accelerated test methods can be set up and used as the basis of

standards of performance for porcelain enamel.

We have another group supported and sponsored by the Manufacturing Chemists Associa-

' tion for 4 years now, involved with determining

r the weatherability of plastics used in buildings,

' including the effect of outdoor climatic condi-

\\ tions, such as solar radiation, moisture, and tem-

» perature.

' These are just a couple of examples. We have

? them ranging all the way over into much more

I scientifically oriented directions as well, but these, I think, will give you some idea of the kind of

program that could be applicable here. If there

are any questions, I'd be happy to try to answer

them.

W. MacLeod : Do you have any research associate program that involves joint sponsorship,

such as by industry, a trade association, and governmental agencies other than NBS?

Dr. Gordon : Not currently, no. Mr. Robinson: George, would it be feasible to do that? Dr. Wright?

Dr. Wright: I might answer Mr. MacLeod's

question. We don't have a research associateship

that is jointly sponsored in just that way but we

do have programs that involve government agencies, ourselves, research associates, and so on. I might cite one in our Structural Engineering

Section—our Masonry Research Program. We

have a program involving various facets of

masonry research. This is supported No. 1 by

our own NBS research dollars; No. 2 by three

agencies of the government, the Army, Navy and

Air Force; No. 3 by a Dow Chemical Company

Research Associateship; No. 4 by a grant from

the National Concrete Masonry Association. So

there's an illustration of how many groups can

get together to carry out one particular type of

research. And a key point, I think, in any re- search associate program, particularly from the

standpoint of a sponsor, is that as a part of an

integrated program of that type, everything developed in it is open to you.

Dr. Gordon : Another possibility, even though

it doesn't have all the advantages of a research

associateship here, is the furnishing of a grant in

dollars to NBS so that we with one of our own

employees can carry out work of interest to an

outside organization or group. I say it isn't quite

as advantageous to the outside organization be- cause our own employee presumably stays here, he

doesn't go back to the industry, and the maintenance of long continuing contacts is not as easy as

if you had one of your own people here for a period.

Mr. O'Shaughnessy : If I may address Mr.

McKinley and yourself directly, m Mr. McKinley's program for future action, would the ASTM

in its round-robin on test metliods be able to work in conjunction with a research associate, as

it possibly would wish to do?

Mr. McKinley : I would picture the sponsored

research associateship as a very flexible and in- clusive kind of thing. The focal point for con- ducting this round robin then could be here at NBS. For example, the National Bureau of

Standards Test Farms from Puerto Rico to Alaska might be useful. You know the question

has come up, what about the differences in weather exposure. In my ASTM proposal I mentioned Test Farms specifically. If this kind of

ASTM program can be started it would greatly

expedite results. I would think that the research associate would

mean that the test program would move much

more rapidly. I don't think that it would change

it very much in any significant way except in

speed.

Mr. Robinson : If I could add a few points to

that, I agree that that would be one way to staff the Round-Robin, which is important. Another

is that the statistical planning and interpretation of the results might be advantageously car- ried out with some of the assistance easily available at the Bureau. Further, I think that if this were done, the research associate would be learning things from the field that he should know

about in his experimental work for you.

Mr. McKinley : He might serve as the technical

secretary for the ASTM committee.

Dr. Gordon : I might throw in the idea too that

any work that goes on here is completely out in

the open, the results are open to everybody, any- one who wants to can come in and look at them;

if they are publishable, they'll be published. It's a way that some other standards-making organizations have found useful to avoid built-in biases

that sometimes interfere with the standards-making process. And I might repeat, because I repeat

and repeat and still it sometimes isn't understood, we are here only to furnish technical back-up, to give what technical help we can, and not to in- fluence the making, the acceptance, of an actual

standard.

Mr. Robinson : Thank you very much. Dr. Gordon.

I think Ave have come to a certain juncture.

This has been a Seminar of people with interests

and concerns and problems who represent a broad cross-section of the sealed insulating glass

unit industry and its customers. You are all interested . . . you have been a most satisfactory au- dience and have been very responsive but I see here at present no motor by which to effect action on the part of this Seminar or this industry ex- cept possibly through the agency of the association which you have—The Sealed Insulating

Glass Manufacturing Association. There may be

69
other ways. It's not for me to organize them, it is for me to try to call them forth for whatever

action can be effected at this meeting. I call upon

those of you who have views as to what this

Seminar might do and how it might do it to come

forward now and generate some of the action or

set up the nuclei for action. As regards what NBS

can do, we plan to publish in some form the proceedings and the papers of this Seminar, and

make the publication available to each of you

who are attending and to the wider population of

your industry. This we can do and Avill do but it

is now up to the members of this Seminar and

this industry to pull themselves up by their own

bootstraps.

I call for your suggestions or comments in this

regard.

Sir?_

_ Participant : I'm speaking as a very small manufacturer and until the man from Andersen spoke

today I was wondering Avhether it would continue. I'm sure that there is no manufacturer here

who wants to make defective units. There is no

architectural acceptance of units that are going

to be defective. When the man from Andersen

said their failures in field operation amounted to 1/10 of 1 percent of their dollar value and then

when I hear the different manufacturers who have

testing laboratories speak, the opinion I get

and it may be wrong—is that they designed their

tests to show how the other man's product won't

work rather than what is good about it. I'm say- ing that if the FHA feels a need to work with

the industry to upgrade insulating glass units

then they should work with SIGMA and go over

the standards they have set for the betterment of

the products ... I don't know how else to do it. Mr. Robinson: I see the point you are refer- ring to. I will say that one of the great advantages of having access to highly objective and well

respected laboratories, such as those our neighbors in Canada have and those they have been

developing in Norway, is for protection against

such a situation as you have foreshadowed. Thank

you for your comments.

Mr. O'Shaughnessy ? Mr. O'Shaughnessy: I think, in talking with

the other SIGMA members, that we feel that the

adoption of the SIGMA specification with its new revisions is a realistic move. The next steps are a bit obscure to us ; however. I think they will come out. I do think the ASTM proposal for

a round-robin is a good one and I think it should

definitely be enacted. And I do feel I have to speak personally now, that the research associateship is an extremely good move to speed things

along which is obviously necessary. However,

there's a certain reluctance on the part of the

SIGMA organization and it does not stem from

lack of desire by any means. We have, should I

say, expended our budget every year in the past

in the Avork we have done and I cannot make a

commitment for the organization because there

just are not funds available for the moment.

However, in view of FHA's acceptance for an

interim type thing, conceivably a new membership program would generate some funds which

would definitely be contributable to the research

associateship. Here again I can't propose this and

then not be able to back it up. So we're faced with

somewhat of a dilemma here and I'd like some

discussion from the group to see if they have any

proposals.

Mr. Snell : Now, Bob, I'm going to try to open

this thing up a little bit for discussion. Do you

feel that your group, the SIGMA group, at this

time with what they have, do you feel that you've

moved as far ahead as you can? In other words

I'm asking do you feel that you have a specification that would give us the protection that we

need?

Mr. O'Shaughnessy : The specifications that we

are proposing are undoubtedly far ahead of what we had before. However, in the committee meetings on Wednesday, a lot of proposals were pushed out or thrown out to the members of the

committee and I by no means think that our proposals as now on the board are going to be the

end of what SIGMA can do independently. I think we can take it a long way from there. However, there are certain areas which we cannot

contribute to substantially and one is additional

methods of testing or variations of the present

methods.

Joe, over here, wants to say something.

J. Amstock : Actually SIGMA was formed to get the specification done. We've worked for the

past couple of years and moved right along. No,

we're not at the end, Lyn, and if ASTM or this

Seminar had not come up we would still continue.

We have the same interest that Bob mentioned

earlier, we have the faithfulness' to the companies that pay us as individuals. But secondly, we

have a certain relationship with SIGMA to keep

the industry thriving for the betterment of each one of us because this is where we're going to make our money in the end and I think this ties in with your comments. Bob, with ASTM.

We're going to continue work, definitely. It's not because of the equipment. Many of the pri- vate organizations do have substantial funds and

are willing to pass on their data to other members. SIGMA definitely would cooperate in a Round Robin program. I am sure there would be an overlap of many of these people in the

SIGMA organization who would continue the

upgrading of the existing specification. We had

a rather extensive meeting Wednesday whicK is going beyond what Roger has on the board. As

private companies we're going to add research

and I think it's not at an end, definitely not. We're staying with the organization and it's going to grow. I think we've added a half dozen new members in the past few days because of the

70
iproceedings here and what they've seen has been

ihappening.

All we need is FHA, GSA to give us this basic

] • sanction of O.K., we're going to go further with

" you, and I think the industry is going to jump

j in and get on the bandwagon.

' Mr. Robinson : Thank you, Joe. Sir ? Participant: I felt this group would be interT jested in knowing just what one specification

writer thinks of groups such as SIGMA and the

use of this specification for groups of this type

and the comparison of the use of such specifications by ASTM. The one thing that all specification writers have to bear in mind in the use of

these specifications is that these specifications are

I formed by single interest groups. They do not

incorporate the broad interest of the entire spec- trum of the manufacturer of the product parts,

the manufacturer of the sealed unit, the installer,

I the contractor, the user and the specifier, as ASTM generally incorporates them.

Participant : I would have to take exception to

that. As a general basic rule, excuse me, I also included the present specifications too. The diffi- culty that you have here really in using just a

single specification is fabulous. Yes, it may ex- clude a great many dogs but, on the other hand,

it's interesting to me to note that the great mai jority of members of SIGMA are indeed comj ponent manufacturers and not installation glass

manufacturers. It's also interesting to me to note

] that the major glass manufacturers in this counjj try do not belong.

I Participant: There is a very good reason why

they do not belong.

Participant: I'm sure that there is. My point

is this, that these are the things we have to consider as specifiers. Yes, I think you have a treS mendous organization in SIGMA. I think that

|l you've made tremendous strides and I'm most

interested in getting a copy of this specification.

In fact, I asked for one, 3 or 4 weeks ago before I got here but something got mixed up and it

i never got to me. I would like to study it thoroughly but by golly don't think for a minute that

because a single interest group has drawn up a

specification and may not have had this thoroughly checked by the user and by the contractors, that we're just going to buy it hook, line,

and sinker. What you're asking us architects to do is to buy something on face value and when it fails you know they don't come back to you, they come back to us. We're No. 1 on the list, we're the ones that made the mistake.

Mr. Robinson : Thank you for expressing that

point of view sir. Mr. MacLeod.

W. MacLeod : I do Avant to speak, Mr. Chairman and gentlemen, on this point that was made

here. It is true that in developing standards in

any group that I know of, and like many of you

I have been associated with such developments

for several years, that the greatest input of technology generally comes from the producing areas. This is true of any standard that I know of, in- cluding federal specifications with which I'm

very familiar. Now if you look at the procedures

under which these national standards are developed, what you fibnd is a means by which the

least of us can make known our position, through

the consensus principle that is applied.

Now I have had the very fortunate experience

of sitting two years actively on the Standards

Committee of ASTM and I've read every negative ballot that was written by any of you during

that period and considered it objectively and in- dependently from the viewpoint of your position.

And I have the privilege of saying that I stopped

one standard when one negative ballot was pres- ent . . . and this was from a user . . . this was

from a typical man like this. We stopped the

quorum. I would not vote "yes" on that standard.

And it was a technical question that the man

raised. Now under these procedures, for example,

if SIGMA should transmit, and I want you to know this, its standard to the USA Standards

Institute, it will not measure up to a consensus.

It would not be cast as a USA Standard at this

writing and your Seminar has demonstrated this, so try it for size if you wish . . . this is an action

you should take. Submit all of your specifications, all of your support, all of your endorsement

of your standard to the USA Standards Institute,

and I have an idea it Avould go before the Miscellaneous Standards Board.

This Seminar has demonstrated that you do

not have any national consensus on your standard. You have but one segment of a very good

consensus but you haven't gone this distance. Now

in consequence what procedure do you use?

In answer, I point out that the consensus principle is the best solution we have in our kind of

system of production, distribution and utiliza- tion of parts. But something has to be done to achieve an effective coordinating process of all the experience available.

In conclusion I repeat what I said yesterday.

The American Society for Testing Materials

stands ready to serve in this field. You are the

groups that will decide in what degree the professionals in our organization can be utilized to serve you. Thank you very much.

Mr. Robinson : I would like to add to Mr. MacLeod's answer to the gentlemen who raised the

point, that at present the SIGMA specification

could be charged with being a limited-field producers' document. It is my feeling that this can- not be said about the Canadian document. It is also true that the SIGMA specification at present

does not have direct correlation with field durability. However, if this were supplied it would

probably satisfy you even though it was still a

limited producer's document. If it also were modified in accordance Avith the evolution of testing

71
methods which might come about through these

actions, I think you would be satisfied. I hope

this is so. Participant: I would like to say that in my

opinion the sensible course for us is to go ahead

and take something. I believe that the only way

we're going to get this off the ground is to accept

the best that we have available now, in hopes that

people gathered here today will assume their

proper positions relative to this working out of a

better developed standard that perhaps can be

nationally recognized.

Mr. Robinson : Thank you.

As moderator I would like now to refer to a

different matter which has previously been mentioned at this Seminar, namely, the question of

a specification for sealants for insulating units. I imderstand that a superior specification can now

be drafted or perhaps has already been drafted. I would like to ask Mr. Box and Mr. Amstock

and others who may be familiar with the subject—How would such a document be instituted ? Would it be done in a normal course through an ASTM group like B-20?

I would like any expression of opinion on this

somewhat more limited subject which is nevertheless important. Is Mr. Box here?

J. Box : To be perfectly honest we at Tremco

haven't considered it too seriously so any com- ments I make are my own comments which I might regret later on. I personally look to what

you're actually trying to accomplish and that is to prove or guarantee performance of the insux

lating unit itself, and you are testing the unit

itself, which is what the owner of a building is interested in, and what the architect is interested

in. I'm not sure how much we advance ourselves

by having a specification for one individual component. It's true that the sealant itself is in- volved, and that it needs equally close attention,

considering the properties it must have.

So there might be a very good reason for having an individual specification for the sealant

itself to assure users of this material, that is, the

manufacturers, that they are working with a

satisfactory material. However, you also have to look at the fact that very few manufacturers make

the units the same Avay. Each one has his own

methods of production, possibly affected by economies. And so what is good for one unit in one

set of manufacturing procedures certainly isn't necessarily good for all manufacturers. And then,

assuming that we decided that we are going to have a sealant specification, I think it would have

to be universally accepted. In that case, a certain

organization would have to exist, and if that were

the case then obviously you should start with

SIGMA. But we haven't agreed yet upon what we are going to do with SIGMA so far as the

insulating imit itself is concerned, so it's difficult to say what we are going to do as regards individual SIGMA specifications.

J. A. Box: Tremco, for whom I can speak,!

really hasn't made up its mind on that point. ' Mr. Robinson: Would you also be willing to follow the ASTM route?

J. A. Box : Yes, I should have said that. Either

way which will effect universal acceptance most

readily is the way we should go. i Participant : Would a specification of the type we are discussing be a material specification or a performance specification? Performance specifications may be ideally suited to this area. Mr. Pritsker: I am on some ASTM committees. At a regular committee meeting I have been

told that ASTM does not allow performance

specifications.

Mr. MacLeod : I would like to correct a possible

misconception here. It depends on the scope writ- ten to allow performance specifications. In other

words, it depends upon the motion of the committee itself. Mr. Robinson: Thank you very much. I think

Joe Amstock wanted to speak.

J. Amstock: As producers of individual components, each of us has to have specifications for our own quality standards. Unit manufacturers

can use some of these in their own quality control. The desiccant people I am sure are in a similar position. I think we're stepping out of our bounds at this particular time to consider all these other outside specifications and to forget

about the main one we intend to discuss, that is, the specification for testing the insulating unit

itself, the thing that you people are really interested in. Let's continue with the growth of the

insulating unit specification as we know it. Participant : I suppose most of you know about

the old chestnut that's been bouncing arovmd

SIGMA for so long—to the effect that if a manufacturer made his unit out of bubble gum and it passed a rigorous performance test, well then it should be accepted. If enough manufacturers of

insulating glass units want some kind of test method for sealants, you should test the sealant in

the same way as you use it. Then maybe through

SIGMA they could get together and request

ASTM to develop the test method for the sealants

for insulating glass.

Mr. Robinson : Thank you.

Participant : I'd like to divorce myself from

SIGMA for a second and speak as a fabricator

of units. Now, undoubtedly in our plant we have

sealant materials, and certainly we would like to

see some sort of uniformity regarding their qualities, but I feel that this is a matter between me

and my supplier whoever he may be. I could con- ceivably take that same product out^of the same

drum, and one dav build a really fine unit, and

then simply by losing my in-plant quality control

or changing my machinery a bit, build a unit

that would fail joerformance tests in half the time.

So I think that rather than specifying sealants

you almost have to approve manufacturers and

72
! then keep some type of a check on his workmanj ship. Because that's really what a vmit is all about . . . selection first of materials and then

using them properly for your construction.

Mr. Robinson: Thank you.

Participant: I just wanted to say that we are manufacturers, and I suppose there are many of

us in SIGMA, who have been manufacturers for over ten years now. I can assure you that we are very grateful to the manufacturers of sealants for

their having upgraded their sealants because I know they have. With the help of the sealant

manufacturers and their standard quality control, and SIGMA, and the testing that we have

done, units today are much better than they

could possibly have been ten years ago. It only

stands to reason that in-plant quality control

must be taken care of. Mr. Robinson : Well, here's a question that we've

discussed at some length and with many views

expressed, so unless someone feels very strongly

I would suggest we retire that particular question for this meeting. I see a hand.

Participant: Could we hear from Mr. Stout

about his feelings as a consumer of insulating

glass? He's one of the few here . . . what his

feelings are on specifications and what he's going

to look for. Mr. Robinson : Mr. Stout, do you care to com- ment on this? C. C. Stout : The manufacturing of high quality

insulating glass units, as we have seen it, depends on the combination of materials, the combination

of design, the combination of production techniques, and of in-plant quality control and test- ing. I brought that out earlier. It seems to me

that perhaps you're looking for the government

or some Joe Smoe or someone to solve your problems, and I think a lot of them have to be solved

by yourselves. There is one thing that I would

like to impress upon you. I go back to that little analysis I made on the board concerning value vs. price. May I read something to you—It comes out

of Webster's Dictionary. The word is value and

one way they define it is this . . . "the quantity

of money which an article is likely to command in

the long run, as distinct from its price in an individual instance."

Participant : I think Mr. Stout and the preceding manufacturer who spoke are both correct in

what they said. Mr. Stout and I think the problem is that of manufacturers here today. We can

learn a good deal from manufacturers, and I think it will be interesting to learn what I do as

specifier, how I go about specifying material to be used in the buildings we design. There are hundreds of materials that go into a building and

I couldn't possibly become conversant with "all of

them. Now for each of these hundred materials

that are manufactured, there are at least two

dozen manufacturers of that material. So I would

have to be conversant with 25,000 manufacturers

in this country, and I couldn't possibly expect to have knowledge about every material.

What do I do if I don't have a suitable standard, and apparently we don't have the standard

today that I would use. I go to the most eligible manufacturers that I know and use their material because I don't have

the time to look into and investigate all of the

materials that are made. And so, I have to limit

myself to those people that I think can do the job

based on their own research, their own know-how,

and their capability. I don't want those specifications by the cus- tomer. I like to have competition. I don't want my

clients job-priced out of the market if I have

choice of specifications. Specifically, there are individual manufacturers' specifications, that are used in the absence of the manufacturer's name.

If I don't like that particular specification I am

not obliged to use it directly if I can find a manufacturer who can meet the qualifications.

And so for your own welfare, if you want to get

the right specifications, you had better adopt a standard because I don't have the time to look

into your own material when I have hundreds of

other materials to look into. I couldn't possibly

begin to have time to investigate all these materials and so we must abide by or rely on a standard that is acceptable to the manufacturer, the

consumer, and to all of the general interest that

made that standard.

Mr. Robinson: Gentlemen: I am sorry to say

that there are only 18 minutes before lunch. I think as moderator I should attempt here to summarize matters at least as they look to me.

It appears first, in regard to standards for

sealed insulating units, that there is one possible course of action somewhat independent of your

industry directly. The needs of Governmental

agencies in procurement and investment for this

advantageous product may require them to adopt some present specification, or something else, depending on what it was thought would provide

the best results, to assure their procurement of

high-quality units. Such unilateral action might

not be the best way—it would seem preferable

that there be joint action by industry and Government, to assure that the similar needs of both

the private and the public purchasers of insulating units are recognized and met. If the industry has developed, is developing, or will develop,

a standard that can be generally accepted, and

that can be implemented feasibly, then the immediate need would be met, and a necessary progressive step accomplished.

At the same time, in the report given yesterday,

I was not able to tell you that meeting the specifications now existing provides assurance, at present, as to the prospective satisfactory life of units

in service. Inversely, there is a better case for the

conclusion that units that fail present specifications have weak prospects for long satisfactory

service. It is of interest that one of our panel

73
members, having the consumer point of view, has

reported to us that in the experience of his com- pany if failures occur in service they tend to occur in the first year or two.

It seems to me important to emphasize the longterm need of the industry—correlation of data on

field performance and accelerated laboratory test performance. Much work and considerable time

are required to develop reliable correlations. Nevertheless, the acceptance and growing use of in- sulating glass products depends on satisfactory

performance in the field, and on predictable durability from laboratory testing. I interject here the

comment that the immediate need of the industry

for a good standard or specification is related

directly with the need for correlations. Field ex- perience with units that would not have passed

the laboratory tests would not assist in developing

reliable correlations; on the contrary, it would

obscure the effort. The laboratory techniques that are selected or developed to conduct accelerated laboratory tests on units for determination of compliance with

specifications are quite important for another

reason. A good deal of expenditure, and a large

testing capacity for determining compliance of

the units of the various manufacturers in a rea- sonable time, will be required. For this reason

and in addition to the need that the selected test methods be realistically meaningful and reasonable—there is need for selection or development

of testing apparatus that is well standardized so that it can be duplicated in several places at not

too much cost, and can handle a large number of

units, preferably of various sizes, at one time

under uniform and controlled conditions. There is also a need for assurance that the testing equipment and procedures at one testing-facility yield

test results satisfactorily comparable or equivalent

to those of another, if there is more than one. The round-robin that Mr. McKinley suggested,

to be undertaken under the auspices of ASTM

Committee E-6, is aimed at an evaluation of exist- ing test methods and procedures for laboratory

testing of insulating glass units. It would appear,

from the discussion that took place, that many in

your industry would like to participate in it. Let

us take a sounding. How many here would be

interested in cooperating with the Task Group in

conducting this round-robin? I see 15 hands.

Now, can we ascertain what percentage these rep- resent of all the unit manufacturers that are here ? Will all such manufacturers present make a show

of hands ? It looks to me that, in round numbers,

about 75 percent are interested, and willing to participate. That is very promising. If we can

elicit a similar response from others who are not

present, the round-robin will have a fine potential.

May I suggest that each of you who has indicated an interest in participating drop a line to Bob McKinley so that he can keep you informed

and keep in touch with you. I think we can as- sume that Bob would equally like to hear from

any others of similar mind who may not have

been represented here this morning.

Before we conclude, does anyone here wish to make a further comment or statement? . . . Mr.

Pearl.

Mr. J. Pearl: I would like to summarize here

the position and attitude of SIGMA. We are going to continue working on our present and

prospective association programs. We want to co- operate in every way as regards establishing a standard, and to cooperate in the round-robin

with Mr. McKinley of ASTM. At this time I can- not state that SIGMA can involve itself in something like the Research Associateship. However, it will be taken under consideration. That

is essentially what I have to say. Mr. Robinson : Thank you very much . . . Mr.

Stout. Mr. Stout : Just a comment. We obviously

would heartily support a good performance improvement beginning in the industry. We think

it is essential, and I am sure there are many

others who recognize the need for a good standard. I think that most people in this industry are trying to improve their products and I am sympathetic with them. We go to the people that have

the talent to produce a good performing part that

will last for the life of the structure. And don't

get frightened about this "life of the structure"

thing. I think you have to take a step. We stuck our neck out 11 years ago. We're glad we did, we

didn't go broke, and we did make some progress. The day of recognition came when we started to depend on the capabilities of good producers.

But standards are important. I have worked on

a few committees and I am familiar with, and I encourage that you work with, the Canadians;

and because I am a Swede, I would add a few

Swedes too. Finally I want to say that there is an

awful lot of insulating glass business in the world

and the future. Tremendous.

Mr. Robinson : Thank you, Mr. Stout. That has

a good sound. Gentlemen, the future beckons and

what will happen depends on what you do now

and tomorrow. I want to thank you as an audience, and as a most participative fifth element of

this panel, and I now turn the meeting back to Chairman Bob McKinley.

Mr. McKinley: Thank you very much, Henry.

I really believe that most of you have had almost

as good a time as I have had and we have learned

a great deal. It has been pleasant to be with you.

The National Bureau of Standards' hospitality

certainly has been wonderful.

I think Dr. Wright can report to Dr. Astin that

you all deserve credit for personal hospitality.

All Americans can be proud of our NBS facilities and I suspect that all of our foreign visitors are pleased that we have set a good standard. The

number of people here from the Construction

Specifications Institute makes it apparent that

their interest is active. The Building Research

Institute, another one of the sponsors, helped also

74
to build attendance. Mr. MacLeod's active pariticipation, representing the ASTM Board, has

[been a major contribution.

' Mr. McKinley: We are going to adjourn immediately. Luncheon is scheduled. The joint semi- nar committee will be meeting around the luncheon table to wind up their assignments. Among

the things we will do is prepare a brief formal

report to our sponsors. We will arrive at some

decision on publication of the papers and material

presented here, which, I believe, each of those who

registered will receive. I thank you all.

75

7. Biographies of Speakers

H. J. Rosen

H. J. Rosen, Chief Specifications Writer, Skidmore, Owings, & Merrill, Architects,

New York, New York, received a Bachelor of Chemical Engineering degree from the College of the City of New York. Since then he has accumulated over 25 years of experience

in specification writing and materials research.

A registered Professional Engineer in the State of New York, Mr. Rosen is a Fellow of

The Construction Specifications Institute and a member of the American Society for Test- ing and Materials and the American Concrete Institute. He is a Lecturer at Pratt Institute on specification writing, is author of Progressive Architecture''s monthly column, "Specifications Clinic," and recently authored a book. Principles of Specification Writing.

Mr. Rosen has also served on several Building Research Advisory Board task forces in the

development of reports on the use of materials in construction and is a member of the Commerce Industry Board. He was chairman of the committee that developed standards on architectural concrete. He is also a member of theNational Council of Architectural Registration

Board's Committee on Examinations.

W. E. Bryant

W. E. Bryant is currently Assistant Director of Technical Services for the National

Association of Home Builders.

Prior to being employed by NAHB in 1966, Mr. Bryant worked for the Bureau of

Public Roads in Washington, D.C., as an area engineer, where he was engaged in planning,

design, and construction of Federal-aid highways. He has worked extensively on building,

plumbing, electrical, and housing codes, and is a recognized expert in the field of underground

wiring. He is a member or alternate on numerous USASI and ASTM committees.

Mr. Bryant received a B.S.C.E. degree from the University of Michigan in 1868, and an

L.L.B. degree from George Washington University. He is currently a member of the Virginia Bar Association.

A. G. Wilson

A. G. Wilson graduated from the University of Saskatchewan with a B.E. degree in

1946. He received his M.S.C. degree from the University of Illinois in 1949. He has been

employed by the Division of Building Research, National Research Council of Ottawa since

1949. He is a member of ASHRAE and ASTM Committees E6 and Cl6.

K. R. Solvason

K. R. Solvason received his B.E. degree from the University of Saskatchewan in 1944.

This was followed in 1953 by an M.S.C. degree from the same university. Mr. Solvason has

been employed by the Division of Building Research, National Research Council of Ottawa

since 1949. He is a member of ASHRAE.

T. Gjelsvik

T. Gjelsvik is Senior Research Officer at the Laboratory of the Norwegian Building Research Institute, Trondheim, Norway. He joined the Norwegian Building Research Insti- tute in 1959, where his main fields of work include sealants and other types of jointing materials, sealed glazing units, and related subjects.

He received a degree in technical physics at the Norwegian Technical University, Trondheim, Norway, in 1954.

Mr. Gjelsvik has authored numerous papers and is a member of "Den Norske Ingenirforening" and "Norsk Fysisk Selskap."

77
J. S. Amstock

J. S. Amstock presently holds the position of Technical Manager, Eastern Division, Products Research and Chemical Corporation. He attended Drexel Institute of Technology

where he majored in chemical engineering.

Mr. Amstock holds Chairmanships in

:

A. Sealed Insulating Glass Manufacturers Assoc.

(1) Quality Standards Committee

(2) Certification Committee

B. Building Research Institute

(1) Sealants Committee

He also represents Products Research and Chemical Corporation in the following organizations : A. ASTM (American Society for Testing and Materials) C-24 Committee

B. The Construction Specifications Institute (CSI)

C. Joint Sealant Coordination Conference

J. D. Gwyn

J. D. Gwyn is presently the Assistant Director of Research at Libbey-Owens-Ford Glass

Company. He has also held the position of Chief of the Products Section during his tenure

at this company since 1934. He is also a member of the L.O.F. Policy Committee.

Mr. Gwyn graduated from the University of Michigan with a B.S. degree in chemistry.

R. J. Mazzoni

R. J. Mazzoni received his B.S. degree in mechanical engineering at the University of

Pittsburgh in 1949. Following this he spent 3 years in the Engineering Division of Kopper's

Company.

He has been engaged in double-glazing and glazing-sealant development at the Glass Research Center of Pittsburgh Plate Glass Industries since 1952. Since 1960 he has been

Head of the Building Materials Department at PPG.

J. A. Box

J. A. Box is Manager, Industrial Product Development, Tremco Manufacturing Company.

In this capacity he manages the research and development effort for new products in various

fields such as insulated glass sealants, automotive sealants and glazing tapes, metal building sealants, and anti-corrosive mastics.

Mr. Box received his B.A. degree in chemistry from the Hiram College in 1951.

Mr. Box is active in Technical Committee support work for the Sigma, NRC 12GP8 specification and the younger. Insulated Glass Manufacturers Association of Canada (IGMAC).

H. E. Robinson

H. E. Robinson is currently Chief, Environmental Engineering Section, NBS Building

Research Division. Prior to holding this position, he was Chief of the Heat Transfer

Section.

Mr. Robinson has been a Bureau employee for 31 years, during which time he has done

extensive work in the fields of heat transfer and thermal conductivity.

Mr. Robinson received his B.S. and M.E. degrees from the College of the City of New

York.

78
R. D. O'Shaughnessy

R. D. O'Shaughnessy is currently President of the Cardinal Insulated Glass Company in

Minneapolis, Minnesota. Previous to holding this position, he was Director of Quality Control, Director of In Plant Cost Control, and Vice President of the same company.

Mr. O'Shaughnessy attended the University of Minnesota where he majored in business

administration.

He is Secretary of the Sealed Insulating Glass Manufacturers Association and is also

Chairman of the Glazing Specification Committee SIGMA.

R. W. McKinley

R. W. McKinley is presently Manager, Technical Services, Glass Division, Pittsburgh Plate

Glass Industries. He received his degree in electrical engineering and architecture from the

Massachusetts Institute of Technology in 1940.

Mr. McKinley's professional experience includes the following positions : Application Engineer, Sylvania, Lighting Division and Westinghouse, Lamp Division; Electrical Engineer,

U.S. Navy, where he served under Admiral Rickover; Editor Lighting Handbook, Illuminating Engineering Society; and Development Engineer (Research) Pittsburgh Corning

Corporation.

Mr. McKinley is active in numerous professional organizations including the following:

American Society for Testing and Materials, American Society of Heating and Refrigerating

Engineers, Illuminating Engineering Society, Optical Society of America, and the Building Research Institute.

C. C. stout

C. C. Stout is Treasurer and Product Development Manager for the Andersen Corporation, Bayport, Minnesota. He received his B.C.E. degree from the University of Minnesota

in 1933.

From 1935 to 1936 Mr. Stout was employed by the Wood Conversion Company where he was engaged in research. In 1936 he began his career with the Andersen Corporation as a

sales representative in New York State. He was transferred to Bayport in 1953 as Assistant Sales Manager. He was appointed Sales Manager in 1961 and Marketing Manager in

1964. He has held his present position since 1967.

Mr. Stout is a member of the Board of Directors of the Andersen Corporation. He is also a member of the Forest Products Research Society and American Marketing Association.

L. K. Snell, Jr.

L. K. Snell, Jr., received the degree of Bachelor of Architectural Engineering from Washington State College, Pullman, Washington, 1953. He is a licensed architect in the State

of Washington and has previous experience in building contracting, construction supervision for Washington State College, and the ITniversity of Idaho.

Mr. Snell is presently the Deputy Coordinator of the Methods and Materials Section,

Architectural Division, Office of Technical Standards, Federal Housing Administration. He

is also a member of ASTM.

79

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