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NBS TECHNICAL NOTE 946

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IF COMMERCE/ National Bureau of Standards
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards 1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and

technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the Office of Experimental Technology Incentives Program.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Center for Radiation Research — Laboratory Astrophysics 2 — Cryogenics 2 — Electromagnetics 2 — Time and Frequency3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational insti- tutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials, the Office of Air and Water Measurement, and the following divisions:

Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor Radiation — Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services developing and promoting the use of avail- able technology; cooperates with public and private organizations in developing technological standards, codes, and test methods; and provides technical advice services, and information to Government agencies and the public. The Institute consists of

the following divisions and centers: Standards Application and Analysis — Electronic Technology — Center for Consumer Product Technology: Product Systems Analysis; Product Engineering — Center for Building Technology: Structures, Materials, and Safety; Building

Environment; Technical Evaluation and Application — Center for Fire Research: Fire Science; Fire Safety Engineering.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus wthin the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer

languages. The Institute consist of the following divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE OF EXPERIMENTAL TECHNOLOGY INCENTIVES PROGRAM seeks to affect public policy and process

to facilitate technological change in the private sector by examining and experimenting with Government policies and practices in order to identify and remove Government-related barriers and to correct inherent market imperfections that impede

the innovation process. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS; promotes the development of the National Standard Reference Data System and a system of in- formation analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services

to ensure that the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following organizational units:

Office of Standard Reference Data — Office of Information Activities — Office of Technical Publications — Library —

Office of International Standards — Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

2 Located at Boulder, Colorado 80302.
Urea-Formaldehyde Based Foam Insulations:

An Assessment of Their Properties and Performance

Walter J. Rossiter, Jr., Robert G. Mathey,

Douglas M. Burch and E. Thomas Pierce

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

<)'# STANDARDS

l^BRABY

JUL . k

Sponsored by:

Office of Policy Development and Research

Division of Energy Building Technology and Standards Department of Housing and Urban Development

Washington, D.C. 20410 ^

0F oQl

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued July 1977
National Bureau of Standards Technical Note 946

Nat. Bur. Stand. (U.S.), Tech. Note 946, 92 pages (July 1977) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1977

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $2.30

Stock No. 0O3-OO3-O180t-5
TABLE OF CONTENTS

Page

1. INTRODUCTION 1

1 .

Background 1 1.2 Objectives of the Report 2 1.3 Scope of the Project 3 1.4 Sources of Information 3

2. SYNOPSIS OF THE MAJOR FINDINGS 4 2 . 1 Guidelines for Materials Properties 6

3

GENERATION OF UREA-FORMALDEHYDE BASED FOAM INSULATIONS 8

4. PROPERTIES OF UREA-FORMALDEHYDE BASED FOAMS. 9 4.1 The Literature 9 4 .

Test Reports 9

4 .The Properties 10

5

FOREIGN STANDARDS AND RELATED TECHNICAL DOCUMENTATION 22

6

BUILDING CODES 25

7. FACTORS AFFECTING THE PERFORMANCE OF UREA-FORMALDEHYDE BASED FOAM

INSULATIONS 26 7.1 Cell Structure 28

7.2 Density 28 7.3 Durability 29

7 .

Electrical Properties 29

7 .

Effect on Other Building Materials 30 7.5.1 Gypsum Plaster and Wallboard 30 7.5.2 Metals 31

7.5.3 Paints and Coatings 32 7.5.4 Wood 32

7 .Effect on Energy Conservation 33

7 .Flammability and Combustibility 33

7 .Freeze-Thaw Resistance 38

7 .

Mechanical Properties 39

7 . 10 Mold and Vermin Resistance 39

7 . 11 Odor 40

7 . 12 Photodegradation 40

7 . 13 Rain Penetration 40

7 . 14 Reactivity of the Foam Ingredients 41

7 . 15 Service Temperature Range and Decomposition Temperature 41

7 . 16 Shrinkage 42

7 . 17 Specific Heat 45

7 . 18 Sound Absorption and Acoustic Properties 45

7 . 19 Temperature and Humidity. 45

iii
TABLE OF CONTENTS (cont.)

Page

7 . 20 Thermal Conductivity 47

7 . 21 Toxicity 54

7 . 22 Water Absorption 55

7 . 23 Water Vapor Transmission (Permeability) 56

8. FORMALDEHYDE GAS 56

8 .

Health Hazard 57

8 .

Chemical Determination of Formaldehyde Concentration 58

8 .

3

The Incidence of Formaldehyde Odor Problems 58

8 .

Causes and Solutions of Formaldehyde Odor 59

9

ACOUSTIC PROPERTIES 60

10. GENERAL APPLICATION GUIDELINES 65

11. RECOMMENDATIONS. 68 12

REFERENCES 70

13. ACKNOWLEDGMENT 77 APPENDIX A. THE MAJOR U.S. MANUFACTURERS OF UREA-FORMALDEHYDE BASED FOAM

INSULATIONS 78 APPENDIX B. BUILDING RESEARCH INSTITUTES CONTACTED FOR INFORMATION ON UREAFORMALDEHYDE BASED FOAMS 79 APPENDIX C. ADDRESSES OF MODEL BUILDING CODE AND OTHER ORGANIZATIONS

REFERENCED IN SECTION 6 80 APPENDIX D. CALCULATIONS OF OVERALL THERMAL TRANSMITTANCE OF A WOOD-FRAME

CAVITY WALL DESCRIBED IN SECTION 7.20 81

IV
LIST OF TABLES

Table 1. Suggested Guidelines for Materials Properties.

Table 2. Properties of Urea-Formaldehyde Based Foams as Reported in the Literature and

Test Reports.

Table 3. Synopsis of the Material and Performance Properties of Urea-Formaldehyde

Based Foams Given in Foreign Standards and Related Technical Publications.

Table 4. Approximate Heats of Combustion of Some Thermal Insulations.

Table 5. Results of Fire Testing on Urea-Formaldehyde Based Foam Specimens as a Function of the Age of the Foam.

Table 6. Additional Results of Fire Testing on Urea-Formaldehyde Based Foam Specimens

as a Function of the Age of the Foam.

Table 7. Percent Linear Shrinkage of the Urea-Formaldehyde Based Foam in the National

Bureau of Standards Test House as a Function of Time.

Table 8. National Bureau of Standards Thermal Conductivity Measurement of UreaFormaldehyde Based Foam.

Table 9. The Thermal Conductivity of Urea-Formaldehyde Based Foams as a Function of

Density.

Table 10. Calculated Overall Thermal Transmittance Values for a Test Wall as a Function

of the Percent of the Hypothetical Shrinkage of a Urea-Formaldehyde Based

Foam.

Table 11. Sound Transmission Loss of Wood Stud Interior Partitions.

Table 12. Sound Transmission Class (STC) Ratings for Various Wood stud Partition Walls.

Table 13. Sound Transmission Loss of Metal Stud Interior Partitions.

Table 14. Sound Transmission Class (STC) Ratings for Various Metal Stud Partition Walls.
LIST OF FIGURES

Figure 1. Foam Specimens before Exposure to a Combination of High Temperature and High

Humidity.

Figure 2. Foam Specimens after Exposure to 122°F (50°C) and 92% rh for 7 Weeks. Control

Specimens 12, 22, 32 and 42 were not Exposed to High Temperature and Humidity.

Figure 3. Effect of Linear Shrinkage of the Foam on the Overall Thermal Transmittance

of a Wood-Frame Cavity Wall.

Disclaimer:

Certain trade names and company products are identified in order to adequately

specify the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Bureau of Standards, nor does it imply that

the products are necessarily the best available for the purpose.

VI
UREA-FORMALDEHYDE BASED FOAM INSULATIONS:

AN ASSESSMENT OF THEIR PROPERTIES AND PERFORMANCE

by

Walter J. Rossiter, Jr., Robert G. Mathey,

Douglas M. Burch, and E. Thomas Pierce

The properties and performance of urea-formaldehyde based foams

pertinent to their use as insulation in buildings were assessed based

essentially on existing information. Pertinent materials properties were

identified and guidelines prepared for the suggested values of these properties along with corresponding methods of test. For certain materials

properties information was not found to enable suggested values of these

properties. The factors affecting performance of urea-formaldehyde based

foam insulations were also identified and discussed. Some performance

factors could not be adequately evaluated because of insufficient or con- tradictory data in the literature. Methods of foam application were studied

and suggested general application guidelines were prepared.

The advantages and disadvantages of using urea-formaldehyde based foam

insulations were discussed and problem areas identified. Recommendations were made pertaining to the use and assessment of urea-formaldehyde based

foam insulations for residential construction.

Keywords: Cellular plastics; foam insulation; insulation; materials properties; performance; urea-formaldehyde.

1. INTRODUCTION

1 . 1 Background

The energy crisis has increased interest in the use of cellular plastics for insulation

because of their thermal insulation characteristics and their ability to be used on irregularly shaped surfaces or in spaces where access is difficult. There have been

problems associated with cellular plastics used in residential construction; however, it is

believed that by proper formulation, design, and application many of these problems can be

resolved.
Urea-formaldehyde based foam is one of the oldest of the cellular plastics, having

been known since 1933 [1]—. The principal application of urea-formaldehyde based foam is as thermal insulation in new and existing building construction. Although it has been

commercially available in the United States since the 1950' s [2], its use as an insulation

has not been extensive. It has been more widely used in Northern Europe for nearly 20 years [3], primarily in the cavities of masonry walls. However, with the energy crisis and

the need to conserve energy, the use of urea-formaldehyde based foam insulation in the

United States has been increasing. In recent years in the United States it has been applied

mostly as a thermal insulation for retrofitting walls of residences.

Although urea-formaldehyde based foam insulation has been considered a generic material,

there are differences in composition and properties of the various foams available in the

United States. Additives, fillers, extenders and plasticizers may be added to the foam to improve or alter some of its properties such as to increase the compressive strength of the

foam, to reduce brittleness, to mask odors and to discourage vermin. Different types of

apparatus are used to produce the foam and mechanically mix the component materials at the

job site, which may result in some differences in cell structure and cell size.

Guidelines are presently not available in the United States for the evaluation and use

of urea-formaldehyde based foam insulations. Much of the information available about the

foams in the literature is contradictory. There are no material, product or industry

standards. The American Society for Testing and Materials (ASTM) has appointed a task

group to initiate development of a standard for urea-formaldehyde based foam insulations.

Because of the potential benefits in energy conservation to be gained through its proper use and application, the U.S. Department of Housing and Urban Development (HUD) requested

the U.S. National Bureau of Standards (NBS) to assess the current state-of-the-art of urea- formaldehyde based foam technology. This study for HUD was intended to summarize existing

information on the properties and application of urea-formaldehyde based foams that are pertinent to their use as insulation in buildings, and to determine whether or not sufficient

experience and research data exist to serve as a basis for recommending guidelines for

their use and application.

1.2 Objectives of the Report

The objectives of this report are:

1) to present currently available information on which the assessment of ureaformaldehyde based foam insulations may be based;

2) to identify the properties of urea-formaldehyde based foams which affect

their performance as thermal insulation;

±7 Figures in brackets indicate references listed in Section 12.
3) to recommend guidelines for suggested materials properties and to identify

existing test methods for< measuring these properties ; and

4) to recommend general guidelines for the proper application of the foam.

1.3 Scope of the Project

The project was limited to an assessment of urea-formaldehyde based foams as thermal

and sound insulation for buildings. Other uses, such as the insulation of refrigerated

trucks, have not been considered.

There are three types of systems by which urea-formaldehyde based foams are generated.

In one, the urea-formaldehyde based resin is transported to the job site as an aqueous

solution. In another, the resin is brought to the job site as a powder and mixed with

water on-site. In the third, the resin is brought to the job site as a concentrated

solution where it is diluted with water prior to application. This report is limited to an assessment of the first type of system (aqueous solution) , since the powder-water

mixtures and concentrated solutions are not generally used in the United States at the

present time.

1.4 Sources of Information

As requested by HUD, the assessment of the properties and performance of urea-formaldehyde

based foam insulations was based essentially upon existing information and not NBS laboratory studies. NBS did conduct limited tests to observe the effect of the combination of

high temperature and humidity on urea-formaldehyde based foams. Shrinkage of a foam in a residential building at their facilities was also observed.

There were four major sources from which the information was gathered. The first source was the chemical and engineering literature. A second source was building research

organizations in foreign countries where the foams have had more use than in the United

States. Information was received from Canada, the United Kingdom, the Netherlands, France,

and West Germany that included research reports, material standards and application

standards. A third source was the four major United States producers of urea-formaldehyde

based foam insulations. Producers cooperated with NBS by supplying product information,

application guidelines and test reports on their products from independent testing laboratories. The final source was third parties who were familiar with urea-formaldehyde based

foams, including testing laboratories, researchers and building code officials. The

information was collated and assessed by a team of NBS researchers consisting of a chemist,

materials engineer, mechanical engineer, and a physicist.
2. SYNOPSIS OF THE MAJOR FINDINGS

This study involved a comprehensive survey to assess urea-formaldehyde based foams and

their performance as thermal insulation. The assessment was based on information and data

obtained from a review of the literature complemented by private communications and test

results. Detailed discussions of findings and data are presented in subsequent sections of

the report to substantiate the information and guidelines for materials properties given in

the synopsis.

There are a number of advantages associated with urea-formaldehyde based foam insulations.

First of all, the use of the foams as cavity wall insulation conserves energy through

reduced fuel consumption. It is unfortunate, however, that few studies evaluating energy

savings are available in the literature.

Secondly, urea-formaldehyde based foams are easy to install. Installation techniques

have been developed by the major resin producers who have also initiated training programs

for their applicators. Conscientious conformance to the installation guidelines by applicators should reduce the risk of faulty application to a minimum.

The component materials from which the foams are produced are easy to transport and

3 handle since they are available as aqueous solutions in 55 gallon (0.21 m ) drums. Because

they are aqueous solutions, clean-up of application equipment is easily accomplished with

water. In addition, it has been reported that the materials offer little risk of a health

hazard to the applicator provided contact of the materials with the eyes and skin is avoided.

A fourth advantage is that the properly installed foam offers no excessive safety

hazard to the occupants of the building. Based on a current method for evaluating the fire

resistance properties of foam plastics, urea-formaldehyde based foams present no excessive

risk of fire. It must be remembered that the foam is combustible as defined by ASTM E 176-73—'"

The fumes from burning foam have been shown to be no more toxic than burning plywood or northern white pine products when tested in the laboratory according to a current test

for determining smoke toxicity. The validity of the smoke toxicity test has not been

established. Based on the results of fire and toxicity tests, some proprietary foams have

been accepted for use by certain building code organizations.

Some proprietary foams have been subjected to inhalation toxicity tests and were

classified as being non-toxic.

YJ Combustible is defined as capable of undergoing combustion (any chemical process that

produces light and heat either as glow or flames) in air, at pressures and temperatures

that might occur during a fire in a building, or in a more severe environment when specified.
The foams present no attraction as a feed for vermin and are normally resistant to mold growth.

The foams are being used abroad to a greater extent than in the United States. As a consequence, certain European countries and Canada have or are in the process of developing

standards for the foams. These documents are referred to frequently in this report.

Finally, from the available information it appears that the likelihood of a formaldehyde

odor problem occurring in residences after foaming is slight. The evidence indicates that

there has only been a minor incidence of the problem. However, if an odor problem does

occur, it could be major, especially if the foam has to be removed to eliminate the odor.

A number of disadvantages associated with the foams have also been identified. First, some material and performance properties have not been determined. Those properties which

have been determined and agreed upon in the literature include density, mechanical strength,

and water absorption. A design value for the thermal conductivity of the foam has been

recommended in Section 7.20. For other performance properties, there are insufficient data

available from which performance may be adequately evaluated. Performance properties in

this category include the effect of the foams on other building materials, the resistance

of the foams to freezing and thawing, water vapor transmission, the effect of absorbed

water on the thermal conductivity of the foams, shrinkage of the foams, maximum service

temperature and the effect of high temperature and high humidity.

For some properties of the foams the data in the literature are contradictory . A

notable example is the maximum service temperature which is reported to range from 120 °F

(49°C) to 320°F (160°C) . It is difficult to assess any property from a literature survey

where the range of values are widespread.

The final disadvantage is that no standards or specifications exist in the United

States for urea-formaldehyde based foams. Standards are written to assure a minimum level

of quality in a material. At the present, no means of assuring a minimum level of quality

of urea-formaldehyde based foams are available. The ASTM has appointed a task group to initiate development of a standard for these foams.
In addition to determining advantages and disadvantages associated with urea-formaldehyde

based foams, two major problem areas have also been identified. The problem areas deal with

shrinkage of the foam and its resistance to high temperature and high humidity. Evidence

from preliminary tests conducted at the National Bureau of Standards supports information

from the literature that these aspects of the performance of the foams may be suspect. In considering shrinkage, the evidence has shown that one urea-formaldehyde based foam in a test house has continued to shrink 20 months after application without any indication of

stabilizing. The magnitude of the linear shrinkage after 20 months was observed to be 7.3

percent. With regard to the resistance of the foams to high temperature and high humidity,

the preliminary results have shown that 3 out of 4 different foam specimens disintegrated

after 7 weeks exposure to 122°F (50°C) and 92% rh. When comparable foam specimens were

exposed to 104°F (40°C) and 92% rh, the same 3 out of the 4 specimens disintegrated after

14 weeks. Prior to disintegration of the three specimens, all the specimens underwent

shrinkage, loss of weight and slight discoloration.

Both of these NBS preliminary observations raise serious questions concerning the

durability of the foams when used under certain conditions. Field data are not available

which demonstrate how long after application the shrinkage process continues or the amount

of the shrinkage of the foams which may be expected in building constructions. Field data are also not available to document the performance of the foams in areas of the United

States which are exposed to hot and humid weather conditions. Field surveys are needed to gather data that will show the in-service performance of the foams. Until such surveys are conducted, the question of durability will remain largely unanswered.

2.1 Guidelines for Materials Properties

The pertinent materials properties were identified and guidelines for the suggested

values of these properties are presented in table 1 along with methods of test. For certain

materials properties, information was not found to enable the suggestion of property values.

Values of the properties of urea-formaldehyde based foams as published in the literature are given in Sections 4 and 5 of this report. Factors affecting performance of the foams

which are in many cases related to materials properties are discussed in Section 7. The

information in these three sections was considered in preparing the suggested guidelines

for material properties given in table 1.
1/ Table 1. Suggested Guidelines for Materials Properties—

Material Property Suggested Value Method of Test

Cell consistency

Cell content (porosity)

Cell size

Decomposition temperature

Density, dry

Density, wet

Flammability

Freeze-thaw resistance

Mechanical properties

Compressive strength

Flexural strength

Friability

Tensile strength

Mold resistance

Shrinkage, linear during

curing

Shrinkage, linear longterm

Temperature and humidity

resistance

Thermal conductivity

Toxicity

Inhalation

Burning foam

Water absorption

Water vapor permeability

Vermin resistance

Uniform cell size without voids

Percent open cells not established

Range of cell size not established

392°F (200°C) , minimum

0.6 to 0.9 lb/ft3 (10 to 14 kg/m3

) 3 3 Approximately 2.5 lb/ft (40 kg/m )

Flame spread classification should

not exceed 25

Not established

Not established

Not established

Not established

Not established

No growth

4 percent maximum in 28 days

Not established

Not established

0.24 Btu in/h ft2 °F (0.035 W/m-K)

Classified as non-toxic

No more toxic than fumes from

burning wood

Not established; absorption through

capillarity is slight

Maximum value not established

Not a feed for vermin

Visual observation

ASTM D 2856-70

Microscopic examination

Oven test for one hour

ASTM D 1622-63 (1975)

Weigh a foam filled

plastic bag of known

volume

ASTM E 84-76a, test specimen

thickness comparable to

application thickness

Not established

ASTM D 1621-73

Not established

Not established

ASTM D 1623-72

ASTM G 21-70 (1975)

Sample size and test conditions not established

Not established

ASTM D 2126-76, maximum

temperature and humidity

not established

ASTM C 177-72, mean

temperature 75°F (24°C)

Federal Hazardous Substances Act, Section

191(f) (2)-1961

Not established

ASTM D 2842-69 (1975)

ASTM C 355-64 (1973)

Not established

1/ These guidelines were suggested by the authors based on an assessment of available

information.
3. GENERATION OF UKEA-PORMALDEHYDE BASED FOAM INSULATIONS

As a building insulation, urea-formaldehyde based foam is generated on-site using

portable equipment to foam a partially polymerized urea-formaldehyde based resin mechanically

which then reacts chemically (cures) in place. This process has been described in the

literature [1, 3, 4, 5].

Three major ingredients are used in the generation of the foam: urea-formaldehyde

based resin, a surfactant (generally called a foaming agent) which includes an acid catalyst or hardening agent, and air. The resin and foaming agent-catalyst mixture are transported

to the job site as aqueous solutions in two separate containers.

The equipment for generating the foam generally consists of a compressed air pump and

a mixing or foaming gun. In the United States the foaming agent-catalyst mixture is in

general pumped into the gun where compressed air mixes with it and mechanically expands it

into foam consisting of small bubbles. The bubbles are then coated in the nozzle of the gun

with the urea-formaldehyde based resin which has been pumped through a separate line into the

gun. The foam, consisting of resin coated bubbles, is forced out of the gun under pressure

at which time it contains about 75 percent water by weight.

After the urea-formaldehyde based resin mixes with the catalyst on the surface of the

foam bubbles, the resin immediately begins to cure. The resin coated bubbles exit from the

nozzle of the gun as a white, fully expanded lather which has a consistency typically

described as resembling a foam shaving cream. Normally, within less than a minute after

leaving the gun, the resin has partially cured into a stiff, self-supporting foam. Complete

chemical curing of the foam generally occurs within weeks after application. The rate of

chemical curing is dependent upon factors such as temperature and foam formulation. The

water, present initially during foaming, dries out at a rate which is dependent upon temperature

humidity and the type of construction to which the foam is applied.

The chemical formulations used in the production of urea-formaldehyde based foams are proprietary and are not reported in the literature. It is known that minor components are often added to the basic formulations in order to improve or alter the foam properties.

For example, components may be added to lessen the friability of the foam or to mask an

odor of formaldehyde. For purposes of this report, a knowledge of the chemical compositions

of the foam formulations is not necessary, since the performance of the foam insulation is

of primary importance. The foam is produced on the job by mechanical mixing and stabilized

by a chemical reaction. Therefore, proper foam producing ingredients, proper use of the

foaming equipment and proper application are critical in producing an acceptable product.

If basic principles governing chemical reactions, which are intrinsic to the foaming process, are violated, an unacceptable product may result. In this regard the quality of the foam

is dependent upon a number of application parameters such as:

8
° the quality of the ingredients

° the ratios of the ingredients

° the mixing of the ingredients

the viscosities of the ingredients

° the age or shelf-life of the ingredients

° the temperature at which the foaming takes place.

4. PROPERTIES OF UREA-FORMALDEHYDE BASED FOAMS

4.1 The Literature

As part of the assessment of the performance properties of urea-formaldehyde based

foam insulations, an extensive literature search was conducted. The primary sources examined

for literature citations were the chemical and engineering abstract services and the files

of the U.S. National Technical Information Service (NTIS) . A number of publications concerning urea-formaldehyde foam insulation were obtained from the literature survey. Many

articles were qualitative, describing the foaming process, and the advantages and disadvantages of using the foam. Other articles were quantitative, listing values of the mechanical,

chemical, and physical properties. These property values, as reported in the literature, were tabulated and are given in table 2. For many of these properties, neither the test

methods nor the test conditions were specified. It can be seen from table 2 that much of

the published data on the material properties of urea-formaldehyde based foams cover a wide

range and in some cases are contradictory. A possible explanation for this is that the

foams and test conditions may not have been identical. The foams may not be identical

because of differences in source and foaming equipment used to produce them.

4.2 Test Reports

The major manufacturers— of urea-formaldehyde based foam insulations cooperated with

the National Bureau of Standards by providing copies of reports of tests in which properties

of urea-formaldehyde based foams were measured. These tests were in general conducted by

independent testing laboratories under the sponsorship of the urea-formaldehyde based foam

manufacturers. Additional reports were obtained from other research and testing laboratories

which had conducted laboratory tests on urea-formaldehyde based foams. Values of properties

of urea-formaldehyde based foams as measured by independent testing and research laboratories are also presented in table 2 along with the property values obtained from the chemical and

engineering literature.

T/ The major manufacturers of urea-formaldehyde based foam insulations are listed in

Appendix A.
4.3 The Properties

Those properties of urea-formaldehyde based foams for which numerical values were

found in the literature or were given in test reports include:

° Cell size

Cell structure

Coefficient of linear expansion

° Compressive strength

° Density

° Flammability

° Flexural modulus

Freeze-thaw cycling resistance

° Shrinkage

° Thermal conductivity

° Thermal stability

° Water absorption

Water vapor transmission.

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21
5. FOREIGN STANDARDS AND RELATED TECHNICAL DOCUMENTATION

Since urea-formaldehyde based foams have been used as insulation more extensively in

Northern European countries and in Canada than in the United States, information was requested

from foreign building research institutes on the material and performance properties of the

foams. Building research institutes in Canada, the United Kingdom, France, West Germany

and the Netherlands were contacted. The addresses of these institutes are given in Appendix B. Information requested include the availability of foreign standards or specifications and

other technical publications, problems encountered with using the foams and steps taken to correct problems.

A number of documents were received in response to the NBS inquiries. These documents

include a Dutch standard as well as a proposed revision of the standard [51] , a proposed

West German standard [52] , a proposed application standard from Canada [53] , technical

guidelines from Sweden [54] , and Agrement Certificates from the United Kingdom. In addition,

it was learned that the Canadian Government is preparing a draft for a materials standard.

These foreign publications represent the most extensive published information presently

available concerning the material properties and application procedures for urea-formaldehyde

based foam insulations. A synopsis of the material and performance properties of ureaformaldehyde based foam, insulations given in foreign standards and related technical publications is presented in table 3. It can be seen from this table that certain properties of

the foams are not included in all of the documents.

The various foreign documents are not all of the same type. The Dutch and West German

documents are standards. As such, they specify values of the material and performance

properties required of the foams and in general give test methods by which these values are

measured. The Swedish document is not a standard. Rather it is a set of guidelines for

using the foams and a resume of the properties expected of the foams. In this document

there are no test methods described by which the material properties can be measured.

The British Agrement Certificate is a third type of document, which differs from the

Dutch, West German and Swedish documents. Under the Agrement system, a technical committee

examines the properties of the construction material produced by a specific company and

determines its suitability for the intended use. If the material is accepted as being

suitable, an Agrement Certificate is issued. Material and performance properties are normally described in the Agrement Certificate. Agrement Certificates have been issued to many companies for urea-formaldehyde based foam insulations. The foam properties described

in a typical Agrement Certificate are included in table 3 [55]

.

It is noted that urea-formaldehyde based foam insulations in Northern European countries are used primarily in, and often restricted to, masonry cavity wall construction. For

example, the Dutch standard and the British Agrement Certificates apply only to masonry walls.

22
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24
6. BUIIDING CODES

Information about the use of urea-formaldehyde based foam insulations in residential

construction was requested from officials representing model building code and other

organizations in the United States. The information received from these organizations is

presented in this Section of the report.

Specific requirements for plastic foams given in the Basic Building Code (Building

Officials and Code Administrators)—, Uniform Building Code (International Conference of

Building Officials) and the Standard Building Code (Southern Building Code Congress, Inc.)

deal primarily with fire safety. Approved foam plastics are to have a flame spread classification of seventy-five (75) or less and a smoke density no greater than four hundred fifty

(450) when tested in accordance with ASIM E 84. Other fire-resistance requirements are based on ignition temperature, wall and corner tests. When wall tests are required, testing

is to be carried out according to ASIM E 119.

The Basic, Uniform and Standard Building Codes require that foam plastics used on the

inside of buildings in walls or ceilings be fully protected by a thermal barrier of fireresistive materials having a finish rating of not less than fifteen (15) minutes.

The Basic Building Code (Building Officials and Code Administrators International,

Inc.) treats all plastic foams the same and applies the requirements of the Code to all

foams including urea-formaldehyde

.

Two producers of urea-formaldehyde based foam insulations have applied for recognition

of compliance with the Uniform Building Code. One of the foam insulations has been approved.

Briefly, the approval states that the foam is applied through a patented gun in which the

3 3 foaming takes place. The dry density of the foam is approximately 0.7 lb/ft (11 kg/m )

.

The foam may only be applied as a cavity fill and not exceed 3.5 in (89 mm) in thickness.

The material may be installed in fire-resistive wood stud walls without affecting the fire

resistance. When installed in steel stud walls, the assembly is to be considered as combustible, non-rated construction. All surfaces to receive the fill material must be clean,

dry and free from agents tending to reduce good bonding qualities. The insulation cannot

be located in areas where temperatures will exceed 210°F (99°C) . The approval further

states that application can be at any temperature provided that the components brought to the foaming apparatus are between 55 and 85°F (13 and 29°C) . The insulation is rated as a combustible material. It is assigned a Class I flame spread classification when the thickness does not exceed 2 in (51 mm) , For thicknesses over 2 in (51 mm) and not exceeding 3.5

in (89 mm) , it is assigned a Class III flame spread classification.

17 Addresses of the model building code and other organizations referred to in this section

of the report are given in Appendix C.

25
The International Conference of Building Officials noted that there were two reported

cases of odor problems in California. They stated that occupants were forced to leave

their buildings for a period of time due to odors associated with formaldehyde. In addition

the question was raised as to whether urea-formaldehyde foam might result in breakdown of

aluminum wiring. No evidence was presented to indicate that this problem existed. The

International Conference of Building Officials also noted that the question has been raised

concerning all foams as to what effects they may have on electrical wiring within wall

cavities where heat cannot be dissipated.

The New York City Housing and Development Administration granted acceptance to three

producers of urea-formaldehyde based foam insulation. For one acceptance, qualification was based on the ASTM E84-61 test with a maximum flame spread rating of 25, a smoke developed

rating not to exceed 50 and a toxicity test. The other two acceptances were based on the

ASTM E136-65 test and a toxicity test. In the toxicity test the products of combustion

produced by burning of the insulation were required to be no more toxic than comparable

concentrations given off by wood or paper when burned under comparable conditions.

These insulation materials were accepted by the New York City Housing and Development

Administration within the past three years. There has been no significant feedback concerning

performance or possible problems encountered during this time.

The Society of the Plastics Industry, Inc. was not aware of any companies among their

membership, with the exception of one subsidiary of a large corporation, who supply or

install urea-formaldehyde based foam insulation. The Society has not developed any objective

data for evaluating the foam.

Urea-formaldehyde based foam insulations are not referred to as a generic material by

the building codes. Rather, acceptance for the use of these types of insulation materials

by building code organizations has been granted only for materials considered proprietary.

7. FACTORS AFFECTING THE PERFORMANCE OF UREA-FORMALDEHYDE

BASED FOAM INSULATIONS

A list of the factors considered to affect the performance of urea-formaldehyde based

foam insulations was compiled from extensive information obtained from many sources. Each

factor is discussed based primarily on literature information, test reports, foreign standards

and preliminary National Bureau of Standards test results. For some factors there is a

lack of published information so that discussions of these aspects of performance are

limited. The discussions of the factors affecting performance provide the basis of the

assessment of urea-formaldehyde based foam insulations.

26
The factors considered to affect the performance of urea-formaldehyde based foam

insulations discussed in this section are:

° cell structure

consistency (discussed in Section 7.1, cell content)

° density

° dimensional stability (discussed in Section 7.16, shrinkage)

° durability

° electrical properties

° effect on energy conservation

° effect on other building materials

- gypsum plaster and wallbcard

- metals

- paints and coatings

- wood

° flammability and combustibility

° friability (discussed in Section 7.9, mechanical properties)

° freeze-thaw resistance

° mechanical properties

° mold and vermin resistance

° odor (due to formaldehyde gas)

photodegradation

reactivity of the foam ingredients

service temperature range and decomposition temperature

° shrinkage

specific heat

sound absorption and acoustic properties

temperature and humidity

thermal conductivity

° toxicity

water absorption

water vapor transmission (permeability)

.

Other factors were identified but not included in this list since they were not

considered to affect performance of the foam as a thermal insulation. Factors considered

not to affect performance include adhesion to other materials, resistance to chemicals and

coefficient of thermal expansion.

27
7.1 Cell Structure

It is the low density, cellular structure of urea-formaldehyde based foams that

accounts for their low thermal conductivity. The air content of the foams has been reported

as approximately 99% by volume [6, 8] . There is disagreement in the literature as to the

cell structure. The foams have been described as consisting of completely open cells [6, 8]

,

or as having closed cell contents of 60% [7] or 80% [9] . Reasons for these published

differences between closed and open cell content are not known. The cell structure can be

altered by changes in the foaming technique [56]. The cell structure will influence other

performance parameters such as air, water and water vapor transmission.

-4 -2 The size of the cells has been reported, as being within the range 8 x 10 to 2 x 10 in

(2 x 10" 2 to 5 x 10

-1

mm) [6] , or 4 x 10~5 to 1 x

10~3 in (1 x10~3 to 3 x 10~2 mm) [7]

.

Small cell size contributes to the low thermal conductivity of the foam, since small cells

result in less convectional currents within the foam [57] . Cell size has significance for

the foam applicator. He must maintain and regulate his foaming apparatus to assure small

cells. Large cells or voids will result in a less thermally efficient foam. Foam manufacturers generally instruct their applicators to check the appearance of the foam for cell

uniformity. In this respect, the proposed West German standard has a requirement for the

consistency of the cells [52]

.

7 . 2 Density

3 Urea-formaldehyde based foams are applied wet at a density of approximately 2.5 lb/ft

(40 kg/m ) [15] . After application, the wet foam dries at a rate which is dependent upon

temperature and humidity conditions, and also the composition and construction of the wall

cavity. Foam manufacturers instruct their applicators to check the wet density of the foam

immediately prior to application since the wet density generally is indicative of the dry

density.

The density of the dry foam has been reported in the literature to be normally in the

range of 0.5 to 0.7 lb/ft

3

(8 to 11 kg/m3

) [13-16]. The Dutch and West German standards

3 3 3 require that the dry foams have a minimum density of 0.5 lb/ft (8 kg/m ) and 0.6 lb/ft

3 (10 kg/m ), respectively [51, 52]. The major U.S. manufacturers' recommendations for dry

density range from 0.6 to 0.9 lb/ft3 (10 to 14 kg/m3

).

Table 2 shows that the density of dry urea-formaldehyde based foams has been reported

3 3 to vary within the range 0.4 to 10 lb/ft (6 to 160 kg/m ) . This wide range of densities

results from the various techniques available for foam production, and is not typical of

the density range of foamed-in-place insulation.

28
Dry density may be used as an easily measured indicator that the foam has been applied

according to the manufacturers' recommendations. Foams whose dry densities lie well beyond

the manufacturers recommended range may have been misapplied and, as a result, may not

perform adequately. Density by itself should not be used as a criterion for performance

since it is possible that a foam with a density within the recommended range may perform

poorly.

7.3 Durability

Durability may be defined as the capability of a material to resist deterioration so that its performance remains above a ininimum acceptable level for its intended service

life. The durability of a material may be ascertained through in-service performance or estimated by accelerated aging tests. In the survey of literature only one report was found— which considered foam durability [11] . In this German report, a proprietary foam in a pipe chase in one building was inspected 9 1/2 years after installation. The foam was

described as showing no signs of decomposition and it had shrunk away from the pipe chase

wall. At the present time, reliable information on the durability of urea-formaldehyde

foam, or its ability to perform over a long period of time as an efficient thermal insulation,

is not available.

From the literature, the reader may get the impression that once the foam is in place,

it remains there indefinitely without deteriorating. Such a suggestion has been made by

the British Agrement Board 155]. Once the foam is injected into walls, it is generally not

observed; thus, its in-service performance is not documented and remains unknown. A comprehensive survey is needed to determine the conditions of the foam in walls after a number of

years of service in various regions of the United States.

7.4 Electrical Properties

Urea-formaldehyde based foams may be injected into cavity walls which contain electrical

wiring and junction boxes. Evidence has not been found in this survey to show that a safety hazard exists. The dry foam is considered an electrical insulator.

~±f The authors received a report in Dutch from the Bouwcentrum, Holland too late for

inclusion in this NBS Technical Note. This report by E. K. H. Wulkan, entitled "Onderzoek van een 6 1/2 jaar oud monster UF-schuim, afkomstig uit een spouwmuur," describes tests on

a foam removed from a cavity 6 1/2 years after installation.

29
Because of the quantity of water in the foam during application, the wet foam may

conduct electricity. Freshly applied, wet foam may present a risk to the applicator if

recommended safety precautions are not followed. At least one of the major U.S. manufacturers

recommends that electrical lines of 220 volts or above be turned off during application. A

similar recommendation is included in the proposed Canadian application standard [53]

.

Power lines of 110 volts are normally not considered to present a hazard to the applicator,

and are not usually shut off during application. However, if the applicator is standing on wet ground during installation, a risk of shock may exist. Under these conditions, it is

advised to shut off 110 volt power lines.

Although the dry foam presents no safety hazard due to electrical conduction, the

installed foam should not come in contact with heat-dissipating objects such as light

fixtures, motors, fans, blowers, heaters, flues and chimneys [17]. Insulation of any type

in contact with heating-dissipating objects could hinder heat dissipation and cause heat

build-up, thus, creating a risk of fire.

7.5 Effect on Other Building Materials

The effect of installed urea-formaldehyde based foam on the performance of other

building materials in contact with or adjacent to the foam is not adequately documented in

the literature. Materials which may conceivably be adversely affected by the foam or its

installation include gypsum plaster and wallboard, metals, paints or coatings, and wood.

7.5.1 Gypsum Plaster and Wallboard

The effect of water in freshly applied urea-formaldehyde based foams on gypsum plaster

and wallboard has not been discussed in the literature. No evidence was found in this

survey to indicate that problems existed.

A problem may occur if water in the freshly applied foam accumulates in the bottom of

the cavity of a gypsum faced wall by drainage through the foam. This possibility was

recognized by the Canadian Government and a water drainage test was included in their

proposed application standard [53] . The test method consists of applying foam in a plastic

bag and two hours after application opening the bottom of the bag and examining for the

presence of water. The test requires that water should not be present, even as droplets,

although the surface of the bag and the foam may feel damp.

30
7.5.2 Metals

When injected into a wall cavity, it is conceivable that the foams may cause corrosion

of metal objects such as ties or electrical junction boxes due to the water and acid catalyst

in the foams. The problem of corrosion has been discussed in the literature, but the

results are inconclusive and contradictory. The foam has been described as non-corrosive

[8, 58] or as capable of causing corrosion in some cases [12] . This latter reference

further mentioned that improved foams are available that have reduced corrosive properties or none at all.

These references [8, 12, 58] did not describe any test method for measuring the

corrosive properties of the foam. No standard test method was found during this survey.

Baumann has described [44] briefly the corrosive action on various metals. His test method

consisted of placing the metals in contact with moist foam for various periods of time,

after which the metals were examined for evidence of corrosion. The extent of corrosion was compared to that occurring on metals stored without contact with the foam. From his

experiments Baumann concluded that the foam material itself does not cause corrosion on

metals used in buildings.

Baumann 's conclusion is consistent with the statements published by Swedish and British

Government Agencies. The Swedish State Planning Organization has stated that, when properly

formulated, foam will not cause corrosion of metals in buildings [54] . The British Agrement

Board Certificates have stated without qualification that foams have no detrimental effect on metals [55]. Contrary to these statements, some U.S. manufacturers of urea-formaldehyde

based foams recommend that foam inadvertently sprayed on aluminum building components

should immediately be removed by thoroughly rinsing with water.

The Dutch Government has considered the corrosion problem important enough to include

a requirement for corrosion testing in their standard [51] . It is required that a galvanized

steel rod embedded in fresh foam show no more effect of corrosion than a similar rod not

embedded in the foam. They have not, however, developed a satisfactory test method for

determining the potential corrosive action [51]

.

31
7.5.3 Paints and Coatings

The water present in the foam during application may increase the risk of blistering

and peeling of paints or coatings on wall surfaces. The amount of water contained in the

2 2 fresh foam is about 0.5 lb/ft (0.2 kg/m ) of wall surface area for a wall cavity approximately 3 1/2 in (88 mm) thick. As the foam dries, the water will normally migrate to the

exterior of the house in the winter and to the interior in the summer. In either case if

the paint on the surface of the wall is a good vapor barrier, the paint may blister. In cases where blistering of the paint may be a potential problem, adequate means should be

provided to allow the water in the foam to vent to the atmosphere. Such means may consist

of inserting properly designed vent plugs in the holes drilled in the walls during application, although the effectiveness of vent plugs has not been shown.

A study at the National Bureau of Standards conducted on a wood-frame house has shown

that water present in the foam during application migrated during the winter into the

exterior wood-fiber sheathing and wood siding as the foam dried [43] . Blistering of the exterior

paint was observed in this study.

7.5.4 Wood

There has been some concern expressed that water present in the foam during application

may cause rotting of wood members in wood frame housing. Data and in particular field

experience are lacking to evaluate the rate of drying of the foam and the effect of the wet

foam on wood. This topic has received little discussion in the literature. The Swedish

State Institute for Construction Research has stated that under conditions where the wall

would not dry out, the wood could conceivably rot 159] . They did not have sufficient

experience to evaluate the risk, and thus gave no guidelines.

In field tests of the wood-frame house at the National Bureau of Standards, it was

observed that a wall filled with foam during the winter remained partially wet during the

spring and dried out the following summer [43] . Examination of a wall section 16 months,

after foaming showed no evidence of wood rot at a location 3 ft (0.9 m) above ground level, even though the wall retained some moisture for four to five months. Additional data of

this type would be desirable.

32
7.6 Effect on Energy Conservation

There was little information available on the amount of energy conserved due to the

application of urea-formaldehyde based foam insulations in residential construction. One

study was sponsored by the U.S. Department of Housing and Urban Development on energy

conservation in public housing during the winter of 1975-1976 in Atlanta, Georgia [60] . In this study, a comparison of the amount of energy used in heating was made between five

buildings retrofitted with a urea-formaldehyde based foam insulation and five uninsulated

buildings in the same housing complex. The foam was applied in the 2 in (51 mm) cavity of

brick-block masonry walls. The preliminary analysis indicated that the amount of fuel

saved was about 30 percent in the retrofitted houses. Since the final results have not

been published, it is not known what other retrofit measures may have been included in the

study such as storm windows and doors, caulking and weather stripping.

A detailed study of energy conservation in one residence located in Hertfordshire,

England was conducted by the U.K. Building Research Establishment [61] . The average mean

temperature in Hertfordshire is 50°F (10°C) . The cavity of the brick-block masonry walls

in a three bedroom house were filled with urea-formaldehyde foam. Approximately 85 percent

2 2 of the 220 ft (21 m ) window area was double glazed one year before the walls were insulated.

The gas fuel consumption was measured for one year before and after application of the foam

and a reduction of 23 percent was reported. The savings in fuel consumption was also

reported as approximately 30 percent for periods when the mean external temperature was

between 32 and 54°F (0 and 12°C)

.

7.7 Flammability and Combustibility

Urea-formaldehyde based foam insulations are organic materials composed of nitrogen,

hydrogen, carbon and oxygen and are combustible as defined by ASTM E 176-73^ and release

heat when burned. The heat of combustion of one foam has been measured and is given in

table 4 along with the heats of combustion of other insulations [62] . It can be seen that

the urea-formaldehyde based foam has a lower heat of combustion per unit weight than polystyrene and polyurethane foams but a higher heat of combustion than mineral wool and glass

fiber insulations. In the case of insulation which may be used in different densities and

thicknesses, it is more appropriate to consider heat of combustion per unit area for the

thickness and density used. Misleading published statements have been made in the past

referring to urea-formaldehyde based foam insulations as "noncombustible , " " self-extinguishing,

and the like. These descriptions of the fire resistance of the foams are inaccurate and

should be disregarded.

17 The definition of combustible is given in Section 2 of this report.

33
Table 4. Approximate Heats of Combustion of Some Thermal Insulations [62]

Insulation Material Heat of Combustion

Btu/lb MJAg

Mineral Wool—

Fibrous Glass—

Urea-Formaldehyde

Based Foam

Polyurethane Foam

Polystyrene Foam

0-1,000

1,000-3,000

6,000

11,000

17,000

0-2.3

2.3-6.9

13

25

39

1/ The heat of combustion depends upon the amount of organic

binder in the insulation.

The flammability of the foams has been of great concern to the industry. It is often

through an examination of the flammability characteristics that a building code jurisdiction

will grant approval for use of the foam. As a consequence, many reports describing the

results of fire testing of foams were available.

The most commonly employed test method for urea-formaldehyde based foams has been the

ASTM E 84 flame spread test which is similar to UL 723. The test gives a numerical classification to a material as to its surface flame spread, smoke density and fuel contribution.

The test is a laboratory evaluation of the material and is not intended to show the hazard

presented by the material under actual fire conditions. In general, plastic foams are difficult to evaluate by. ASTM E 84 . Some hazards associated with plastic foams having

numerical flame spread classifications derived from this test method may be significantly

greater than those which would be expected of other products with the same numerical classification. This test has been recommended as one way to judge the fire performance of

insulations, since other test methods relating to primary safety properties such as ignitability and rate of heat release are not fully developed [17] . Information on the rate of

heat release of foam insulation and on the performance of foams in full-scale room fire

tests would be very useful. For fire safety validation of non-bearing walls and ceilings

containing plastic foam, at least one model building code refers to the use of full scale corner tests or room burnout tests [63]

.

It has been reoointiended that the flame spread classification for a foam plastic

insulation should not exceed 25 when tested according to ASTM E 84 [17] . The behavior of urea-formaldehyde based foams in the flame spread test, as described in the references

cited in this report, is favorable in that it is usually less than the recommended flame

spread classification of 25, as shown in table 2. In one instance the flame spread classification of a test specimen was 35, while in all other cases it was 25 or less. There was

some variation in the test results given in table 2 which may in part be attributed to differences in foam density, thickness and formulation.

34
The flanimability of a foam as demonstrated by ASTM E 84 test varies with the water

content at the time of testing. A freshly prepared specimen will show a lower flame spread

classification than an older specimen. Water in the fresh foam reduces its flame spread

classification. As the foam dries, the flame spread classification increases. The results

of two fire tests of foam specimens as a function of the age of the specimens are given in

tables 5 and 6 [64, 65]. In the tests, the flame spread classification increased with the

age of the foam for a period of two weeks in one test and eight weeks in the other. It is

noted that the classification did not exceed the recommended value of 25 in either test.

This recommended classification of 25 is more stringent than the requirement of the

model codes for flame spread (see Section 6) . The model codes require that foam plastics

have a flame spread classification of 75 or less, and also a smoke density no greater than

450. In addition, the model codes stipulate that a foam plastic must be covered by a thermal barrier of fire-resistive material having a finish rating of not less than 15

minutes. Since urea-formaldehyde based foam is designed for injecting into cavity walls,

unexposed urea-formaldehyde based foam in a residence would not, in normal circumstances,

be a problem. Although there are other technical reasons such as friability and light

sensitivity for not using urea-formaldehyde based foam in an exposed application, from a

fire safety point of view, it must always be covered as recommended by the model codes.

Based on this survey, flammability does not appear to be a major concern of the

Europeans. A flammability requirement has not been specified in the Dutch standard [51]

.

A British Agrement Certificate has stated that the foam which is only permitted in masonry

cavity walls does not reduce the fire properties of the wall [55] . The West German standard

has a requirement for flame spread classification [52]

.

This survey has not uncovered any evidence that shows urea-formaldehyde based foams

increase the fire hazard. These foams burn, but based on one current method of evaluation,

they in general meet the recommended flame spread of 25 [17]

.

A second hazard due to the flammability of urea-formaldehyde based foams is the toxicity

of gases released when the foam burns. There is no standard test method currently available

for determining the toxicity of combustion products. One test procedure exposes laboratory

rats for six hours to a given concentration of combustion products to determine the effects

of the products on the rats. After exposure, surviving rats are observed for fourteen days

for any ill effects. The reliability of this test procedure for determining the toxicity

of combustion products is not fully known. Nevertheless, the test has been used as an indication of the relative toxicity of the combustion products of various materials. It is

noted that the state-of-the-art of toxicity testing of combustion products is rapidly

developing and future developments may invalidate present test results.

35
Table 5. Results of Fire Testing on Urea-Formaldehyde Based Foam

Specimens as a Function of the Age of the Foam [64]

1,2/ Foam Age

. 3/ Foam Density—

lb/ft|

(kg/mJ

)

Test Resuits4/5,6^

Flame Spread Smoke Developed

0.25 h

0.25 h

1 h

1 h

4 h

4 h

8 h

24 h

2 wk

4 wk

0.93 0.83

(14.9) (13.3)

0.59 0.53

(9.4) (8.5)

0.59 0.52

(9.4) (8.3)

12.8

12.8

12.8

10.3

12.8

12.8

12.8

10.3

17.9

17.9

7.0

29.6

48.1

154.1

1/ Duplicate specimens were tested at specified time intervals.

2/ Aged specimens were stored at 70 ± 5°F (21 ± 3°C) and 35 to 40% rh.

3/ This is not the density of the fire test specimens. Additional

block samples of unidentified dimensions were prepared at the same time

as the fire test specimens. Density determinations were conducted on

the block samples. Density measurements were made on duplicate specimens.

4/ Test was conducted according to the procedure described in UL 723, "Test Method for Fire Classification of Building Materials."

5/ Test specimens were 3 in (76 mm) thick.

6/ All the test specimens displayed an apparent negative fuel contributed

classification, which was expressed as not determinable.

36
Table 6. Additional Results of Fire Testing on Urea-Formaldehyde Based Foam

Specimens as a Function of the Age of the Foam [65]

1.2/ Foam Age

• 3/ Foam Density—

lb/ft?

(kg/in )

Test Results4 ' 5,6^

Flame Spread Smoke Developed

Fresh 2.00

(32.0)

- -

24 h -

24 h

2 v* 0.61

(9.8)

12.8 88.6

2 wk 17.9 111.1

4 wk 0.55

(8.8)

12.8 92.2

4 wk 15.4 139.5

6 wk 0.52

(8.3)

17.9 110.0

6 wk 20.5 108.0

8 wk - 20.5 50.0

8 wk 23.1 91.2

12 wk - 20.5 100.8

12 wk 20.5 90.5

18 wk - 17.9 122.8

18 wk 20.5 66.5

24 wk - 17.9 69.1

24 wk 20.5 90.4

1/ Duplicate specimens were tested at each time period.

2/ Aged specimens were stored at 70 ± 5°F (21 ± 3°C) and 35 to 40% rh.

3/ This is not the density of the fire test specimens. Density

determinations were made on additional foam samples in such a manner

as to approximate the densities of the fire test specimens.

4/ Test was conducted according to the procedure described in UL 723, "Test Method for Fire Classification of Building Materials .

5/ Test specimens were 3 in (76 mm) thick.

6/ All the test specimens displayed an apparent negative fuel

contributed classification, which was expressed as not determinable.

37
This type of toxicity test has been conducted using urea-formaldehyde based foam

insulations in which laboratory rats were exposed to either the fumes of burning foam or of

burning wood or plywood. One test was carried out on each of three proprietary products.

Under the test conditions, the burning foams appeared no more toxic than the burning wood

or plywood. In one case, within 24 hours two of 10 rats exposed to foam fumes died while

four of 10 rats exposed to burning plywood fumes died [66] . In a second test, within 24 hours, two of 10 rats died when exposed to the fumes of burning foam, while four of 10 rats died from burning plywood fumes [67] . In another test, none of the 10 rats exposed to the

foam fumes died, while within one hour six of 10 rats exposed to the fumes of northern

white pine died [68]

.

7.8 Freeze-Thaw Resistance

The question has arisen as to whether or not freeze-thaw cycling can cause deterioration

of the foams, especially if the foams are wet. This question has been mainly ignored in

publications which discuss performance parameters. One report described a test in which a foam specimen saturated with water was cycled between 59 and 5°F (15 and -15°C) for 25

cycles [11] . No damage reportedly occurred to the foam during testing. This report did

not describe the conditions under which the foam was "saturated with water," and the results

may thus be open to question. No other reports describing freeze-thaw cycling were found

in the literature.

The U.S. /Army Cold Regions Research and Engineering Laboratory (CRREL) has been

applying foams, on an experimental basis, in buildings in Alaska. Freeze-thaw cycling

resistance has been considered an important parameter because of the weather in Alaska. At

present, CRREL has little data on the freeze-thaw resistance of urea-formaldehyde based

foams. In a study at Fort Greely, Alaska 135] , urea-formaldehyde based foam was injected

into 2x6 wood stud wall cavities which contained either 2 1/2 in (68 mm) foiled faced

fiberglass or expanded aluminum foil insulation. The foam was applied from the outside of

the buildings such that the existing insulations were pressed against the interior sides of

the walls. The walls were filled with foam in August, 1975 and were opened for visual

inspection of the foam insulation in April, 1976 after an extremely cold winter and numerous freeze-thaw cycles. No problems with the foam were detected. It was also observed that

the exterior sheathing and wind-paper (asphaltic kraft paper having low permeability) were

dry which was an indication that no significant amount of moisture had passed through the

urea-formaldehyde based foam and collected on the vapor resistant outer wall elements [35]

.

38
A field inspection was carried out by CRREL to observe a urea-formaldehyde based foam

in the walls of a chapel at Eielson Air Force Base near Fairbanks [69] . The foam was installed in late July of 1975 without addition of an interior vapor barrier. The following

March the foam was observed in some of the wall sections. At that time there was frost

present in the foam, but the foam appeared to have retained its structural integrity. It could not be determined whether the water observed in March resulted from the foam application or from condensation during the winter. The wall sections of the chapel were re- examined in August, 1976 at which time the foam was observed to be dry and in satisfactory

condition.

Freeze-thaw cycling appears important enough to warrant additional research and testing.

Foam applied in cold regions of the United States where condensation is likely to occur may

be subjected to stress caused by freezing and thawing. Although no evidence was found

which showed that freeze-thaw cycling is detrimental to the foams, evidence on this point

is incomplete. Additional data are needed.

7.9 Mechanical Properties

Within the density range employed for cavity wall insulation, the mechanical strength

of urea-formaldehyde based foams is low [2, 4, 6, 9, 12, 16]. In addition the foams are described as being friable and brittle [12, 16] . The mechanical properties have little

relationship to the performance of the foams as cavity wall insulations, except that the

foams must be strong enough to support their own weights in the cavity. The foams should

not collapse or crumble. Based on the available information there appears to be no problem

with regard to the foams' mechanical properties. The Agrement Board in England has examined

cavity wall fills of up to 2 stories high [14] . They found no evidence that the foams at

the properly specified densities would fail due to collapse under their own weight. The

Dutch standard allows the filling of a continuous cavity up to 6 stories high [51]

.

7.10 Mold and Vermin Resistance

There is agreement within the literature that urea-formaldehyde based foams are mold

resistant 13, 4, 8]. Nevertheless, both the Dutch and West German standards have specified

a mold resistance requirement [51, 52] . It is conceivable that changes in formulation

could result in a foam that is not mold resistant. No evidence was found in this survey

that indicates mold growth has been a problem in the United States. Also, no evidence has

been found to indicate that vermin attack is a problem. The Swedish State Planning Organization has reported that the foam does not constitute a feed for rats or insects [54]

.

39
7.11 Odor

There was concern that the application of urea-formaldehyde based foams in residential

construction may, under certain conditions, lead to odors of formaldehyde. This aspect of

performance was examined in detail and is reported in Section 8.

7 . 12 Photodegradation

Urea-formaldehyde resins are susceptible to photodegradation. It was observed that

foam samples exposed to natural and fluorescent lighting in the NBS laboratories for a few

months have shown yellowing and a tendency to crumble. Photodegradation presents no problem

for foams in cavity walls because the foams are not exposed to light. For new constructions,

where the foams may be applied to open stud spaces, the foams should be covered immediately

after installation. Covering not only assures that the foams do not dry too rapidly but

also assures that the foam are not exposed to light. At least two of the major producers

of urea-formaldehyde based foam insulations recommend that freshly applied foam in open

wall construction be covered immediately.

7.13 Rain Penetration

Rain penetration of masonry cavity walls filled with urea-formaldehyde based foams has

occasionally been a problem in Europe I 8 , 14] . These walls are designed such that rain may

penetrate the exterior wall of the cavity. In severe rains, free flowing water will run down the inside surface of the outer wall and drain away from the residence at the bottom

of the cavity. Filling a cavity with foam insulation may, under certain circumstances,

direct the water into the residence. Within the cavity, hydrostatic pressures are not

generally great enough to force water through the dry foam [14] . The water can penetrate

across the cavity by flowing through voids which may result from inadequate foaming or shrinkage cracks.

Measures to reduce rain penetration problems in Europe include water repellent treatment

of the outer surface of the exterior wall, or facing with stucco or siding. In the United

Kingdom the Agrement Board does not recommend the use of urea-formaldehyde based foams for

cavity walls in areas of the country which receive severe rain exposure unless the masonry

is protected with an outer facing 155]

.

In the United States, rain penetration due to cavity wall filling was not found to be

a problem. No complaints of rain penetration due to foam filling were uncovered during

this survey. The exterior walls of U.S. residences are generally designed to resist and

shed rain water. One caution, based on the European experience, is noted. A foam filled

masonry cavity wall may have an increased risk of rain penetration, especially if exposed

to severe rains.

40
7 . 14 Reactivity of the Foam Ingredients

The foam ingredients should react chemically at a rate that is slow enough to allow

complete filling of wall cavities and fast enough to allow an initial cure of the foam in

the cavity without collapsing. The reactivity is a function of proper formulation and

application. The West German standard has considered this parameter and specified that the

foam ingredients must sufficiently react within 60 seconds to leave a smooth surface when a conical specimen is sliced with a spatula [52] . The revised Dutch standard, the proposed

Canadian application standard and the British Agrement Board have made similar recommendations

[51, 53, 55].

Sixty seconds is also the maximum reactivity time recommended by the majority of major

U.S. manufacturers. One manufacturer recommended the maximum reactivity time to be

30 seconds. In a few typical foam applications observed by the authors, the foam reacted

(set up) within 60 seconds.

7.15 Service Temperature Range and Decomposition Temperature

There is wide disagreement among various literature sources as to the maximum service

temperature to which urea-formaldehyde based foams may be subjected. As can be seen in

table 2, the maximum service temperature has been reported to be as low as 120°F (49°C) or

as high as 320°F (160°C) . In addition, the service temperature range has been quoted as being -20 to 120°F (-29 to 49°C) [9] or -300 to 210°F (-180 to 99°C) [7]

.

It has not been possible during this survey to document the reasons why such disagreement

exists among the published values for the naximum service temperature. None of the publications cited in table 2 described the test method and conditions under which these values were measured. Possibly, the test conditions were different. The results of a heat

stability test of the foam may be dependent upon the relative humidity during testing, and

the water content in the foam, since it has been shown that the foam may degrade when

subjected to high temperature and humidity (see Section 7.19)

.

The Dutch standard requires heat testing of the foam [51] . The foam must be at least

4 weeks old and conditioned at 77°F (25°C) and 50% rh for 2 weeks before testing. The

Dutch requirement is that the foam should not show any change (with the exception of color) on heating to 158°F (70"C) and no decomposition on heating to 320°F (160°C)

.

41
Regarding the minimum service temperature, the U.S. Army Cold Regions Research and

Engineering Laboratory (CRREL) is conducting field experiments at Fort Greely, Alaska to evaluate urea-formaldehyde based foam insulation under conditions of intense, sustained

cold temperatures [35]. Minimum temperatures at Fort Greely often approach -60 °F (-51°C)

.

The preliminary results indicate that the foam insulation has a potential for use in very

cold regions.

The published values for the thermal decomposition temperature of urea-formaldehyde

foam were found to be in general agreement. They have been given as 415°F (212°C) [11] or 428°F (220°C) [44] . The Swedish State Planning Organization has listed the decomposition

temperature as 392°F (200°C) [54] . Decomposition temperature is not considered a performance

parameter for normal use as cavity wall insulation. It may be used as an indication of the

quality and the overall thermal stability of the foam.

7 . 16 Shrinkage

It is known that during the curing process urea-formaldehyde based foams undergo

linear shrinkage in all three dimensions. However, there is disagreement in the literature as to the magnitude of the shrinkage and time period over which it occurs. The linear

shrinkage during curing is most often quoted as being within the range of 1-3 percent [7,

11, 14, 15, 27, 28], but there are other reports stating that this shrinkage is higher.

The French Centre Scientifique et Technique du Batiment (CSTB) has reported a shrinkage of

6 percent which occurred over one month at 68°F (20°C) and 65% rh [46] . The Swedish State

Planning Organization has stated that the shrinkage may be as high as 8-10 percent and occurs over a period of a year [54] . The environmental conditions were not described.

The Dutch and West German standards both contain shrinkage requirements that foam

specimens must meet for acceptance, but their respective requirements differ [51, 52]

.

Under the conditions of testing, the Dutch standard requires that the freshly prepared foam

specimen not shrink more than 8 percent, while the West German standard requires not more

than 4 percent. The Dutch standard specifies that the shrinkage be measured after the foam

has dried, while the West German standard specifies that the shrinkage be measured after 28 days. It is not known how these requirements relate to the amount of shrinkage that occurs during the curing of the foam within a cavity wall.

42
Shrinkage of the foam during curing is an important performance parameter. As the

shrinkage occurs, the foam either pulls away from the wall studs or splits and cracks. The

resulting gaps and cracks are void spaces in which air may circulate and thus lower the

insulating properties of the foamed wall (as discussed in Section 7.20) . It is thus

desirable that additional data be gathered to understand in detail the shrinkage process

and the conditions, such as temperature, humidity and rate of drying of the foam, which

influence the magnitude of the shrinkage. It is generally reported that the slower the

rate of drying of the foam, the less is the shrinkage. However, there is even some disagreement

with this point. It has been reported that the final shrinkage of the foam in the free state does not seem to be much affected by rate of drying [14]

.

J* Most of the shrinkage data reported in the literature has been based on laboratory

experiments and not in-service evaluations. The amount of shrinkage and the time period

over which it occurs in building constructions has not been fully documented. Limited data

are available from the NBS retrofit study in which one urea-formaldehyde based foam had

been installed in a wall of a test house [43] . A section of the wall insulated with the

foam has been periodically inspected to document the amount of shrinkage. The average

linear shrinkage has been determined across the width of the foam within the 14.5 in (368 mm)

space between studs. The results of the inspections are given in table 7. It can be seen that after approximately 20 months, the foam had undergone an average linear shrinkage of

7.3 percent. A plot of the percent shrinkage versus time gives a straight line which

indicates that the foam has not yet, even after 20 months, shown a tendency to stabilize

dimensionally

.

Table 7. Percent Linear Shrinkage of the Urea-Formaldehyde Based Foam in the National

Bureau of Standards' Test House as a Function of Time [43]

Date of Measurement Time, Months Shrinkage , %

January 27, 1975

May 1, 1975

April 21, 1976

September 29, 1976

3.1

14.8

20.1

2.6

5.6

7.3

43
It is pointed out that the NBS data are preliminary. They should not be construed as conclusive evidence that urea-formaldehyde based foams undergo excessive shrinkage in all

applications • The NBS data represent the results of a single test which may have been

influenced by a number of factors such as the chemical compositon of the foam, the application and the climate. The shrinkage of 7.3 percent in the NBS test house is still lower

than the 8-10 percent reported by the Swedish State Planning Organization [54] . However,

their report that the shrinkage stops in about 1 year conflicts with the NBS results, since

the foam in the NBS test was still apparently shrinking after 20 months.

The observation from the NBS test house that the shrinkage is still occurring after 20

monthp also contradicts statements that the foams undergo only a short-term shrinkage as they dry out. Although the NBS data are limited, they suggest the possibility of a longterm shrinkage, and raise some questions regarding the shrinkage problem. For example, is

there more than one mechanism by which shrinkage can occur? If so, is it possible to differentiate between the mechanisms? What are the factors which influence the long-term

shrinkage? Perhaps the most important question is, at what point does the shrinkage stop?

The U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) has limited

data on the shrinkage of foam injected into walls of buildings at Fort Greely, Alaska [35]

.

The walls were insulated in August, 1975 and visually examined in April, 1976. The linear

shrinkage of the foam was observed to be less than 2 percent over the 8 month period. This

rate of shrinkage was much less than that observed at the NBS test house which showed a 2.6

percent shrinkage in a little more than 3 months [43] . The colder climate at Fort Greely

may be partially responsible for the lower shrinkage of the foam observed there. These

data suggest that the foam may undergo less shrinkage or shrink at a lower rate in cold

climates than in hot humid climates.

The small amount of field data concerning shrinkage is far from conclusive. Additional

data are needed. A comprehensive survey is recommended in order to evaluate the extent of

shrinkage occurring in foams in buildings. The performance of the foam in areas of the

United States which experience long periods of hot humid weather should be emphasized

during the survey.

44
7.17 Specific Heat

A value of the specific heat of urea-formaldehyde based foams was not found in the

literature.

7.18 Sound Absorption and Acoustic Properties

In cases where urea-formaldehyde based foams are applied in buildings as thermal

insulation, sound absorption is not considered to be a performance parameter. However,

since the foams have been applied both as thermal and acoustical insulations, information

for the assessment of the foams as acoustical insulation is given in Section 9.

7.19 Temperature and Humidity

During the course of this survey, it was pointed out that urea-formaldehyde resins may

be susceptible to hydrolysis. Hydrolysis is defined as the chemical reaction of the resin

with water. For the purposes of this report, hydrolysis should be considered as the degradation of the urea-formaldehyde based foam by water. Because of the potential consequences

of degrading the foams, this performance parameter was given much attention during the

survey. In particular, attempts were made to ascertain whether or not the combination of

high temperatures and high humidities will have a deleterious effect on the foams.

A review of the literature showed that the effect of high temperatures and high

humidities on the foams was a nearly neglected topic. In one publication, it was reported

that the foams do not hydrolyze [7], but no evidence was given supporting this conclusion.

On the contrary, it was learned that the National Research Council of Canada was conducting

tests on the effect of high temperature and humidity on foams [70] . The final results of

these tests are not yet available. In general, the preliminary results have shown that

foam specimens undergo shrinkage and weight loss when subjected to high temperatures and

humidities. The magnitude of the shrinkage and weight loss at a constant humidity were, in

general, dependent upon the temperature of the test as well as the composition of the foam.

In another test carried out in a commercial laboratory, cured foam specimens, 4 x 4 x 1 in

(102 x 102 x 25 mm) , were exposed for 10 days to 158°F (70°C) and 95 to 100% rh [29]

.

During the test period, it was observed that the specimens underwent a 9.6 percent weight

loss and a linear shrinkage of approximately 30 percent. It was also reported that the

specimens had warped severely, were very powdery and could not be handled.

45
Because of the implications of these test results [29, 70], and because other data

concerning hydrolysis were lacking, it was decided to conduct a preliminary experiment at

the National Bureau of Standards on the effect of high temperature and high humidity on foams.

The description and results of this test will be presented in a separate publication [71]

.

A synopsis is given herein.

Foam insulation specimens were obtained from four major manufacturers or their representatives. After curing for at least a month in the laboratory, the specimens, approximately 4.7 x 3.9 x 3.5 in (120 x 100 x 90 mm) , were exposed to 122°F (50°C) and 92% rh for a 7 week period. Figure 1 shows the specimens before their placement in the temperaturehumidity chamber. Once a week, the specimens were removed from the chamber and their

dimensions and weights were recorded.

Figure 1. Foam Specimens before Exposure

to a Combination of High Temperature

and High Humidity.

46
The results showed that the foam specimens were susceptible to degradation under the

test conditions. The specimens underwent shrinkage and weight loss, slightly discolored

and lost mechanical strength. After the 7 week period of testing, 3 of the 4 specimens had

disintegrated into small pieces. Figure 2 shows each of the exposed test specimens along

side similar unexposed specimens. After the first two weeks of testing, the average

linear shrinkage occurring in the chamber was 4 percent. The additional shrinkage during

the remaining 5 weeks of the test was small. Obviously, shrinkage could no longer be

determined after the specimens disintegrated. The average weight loss of the specimens

after 7 weeks was approximately 8 percent.

In a similar test conducted in NBS laboratories comparable foam specimens were exposed

to 104°F (40°C) and 92% rh [71] . The same 3 out of the 4 specimens disintegrated after

14 weeks as in the test carried out at 122°F (50°C)

.

The results from this experiment are preliminary. Nevertheless, they are considered

significant. They have pointed out that the durability of the foams under certain environmental conditions may be questionable. Further research is needed to establish the extremes

of temperature and humidity to which the foams may be exposed without a severe loss of

performance properties. These NBS results suggest that foams should not be applied in

areas subjected to high temperature and high humidity. Since high temperature and high humidity

may be encountered over prolonged periods of time in attics and ceilings, it is recommended

that foams not be applied in these areas until additional data are available.

7.20 Thermal Conductivity

The thermal conductivity value of urea-formaldehyde based foam insulations is a controversial subject. Thermal conductivity values cited in the literature range from 0.18

to 0.29 Btu in/h ft °F (0.026 to 0.042 W/m-K) , as is shown in table 2. The thermal conductivity of the foams is a function of test parameters such as the mean temperature of the

materials, their density and moisture content. For many of the values cited in the literature,

the test parameters are not given. Thus, it is difficult to compare the values given in

the literature or to recommend a design value from these data. When recommending a design

value, it is important that the properties of the test specimen used for thermal conductivity

measurements be approximately equivalent to those of cavity wall or in-service insulations.

47
Figure 2. Foam Specimens after Exposure to 122°F (50°C) and 92% rh for 7 Weeks

Control Specimens 12, 22, 32 and 42 were

not Exposed to High Temperature and Humidity.

48
Measurement of the thermal conductivity of a urea-formaldehyde based foam was recently

performed at the National Bureau of Standards [43] . The density of the foam was approximately

equal to that of cavity wall insulation. In lieu of oven drying, the foam was permitted to

reach moisture equilibrium with room air (similar to the case of cavity wall insulation) at

75°F (24°C) and 40% rh. The thermal conductivity measurement was performed according to ASTM C 177-71. The result and test parameters are given in table 8.

Table 8. National Bureau of Standards Thermal Conductivity Measurement

of Urea-Formaldehyde Based Foam [43]

Test Result Test Parameter

Thermal

Conductivity

Btu in/h ft2 °F (W/m.K)

R-Value

h ft2 °F/Btu in

(m.K/W)

Moisture Content

Mean

Temp.

°F

(°C)

Foam

Density

Ib/ft^

(kg/ni)

Before Test

% (wt)

After Test

% (wt)

0.246

(0.0354)

4.07

(28.2)

16.8 16.8 75.7

(24.3)

0.60 ! (9.6) j

The thermal conductivity value of 0.246 Btu in/h ft °F (0.0354 W/m.K) given in table 8 is within the range of values reported in the literature although it is higher than many, as shown in table 2. Because the foam in this NBS test was chosen to approximate that of urea-formaldehyde based foam in cavity walls, it is recommended that for design purposes

2 the thermal conductivity value for the foams be taken as 0.24 Btu in/h ft °F (0.035 W/m-K)

at 75°F (24°C) . Since only one foam was tested at NBS and comprehensive round robin tests by technical organizations such as ASTM and ASHRAE have not been conducted, a comprehensive

test program may result in a value of thermal conductivity which will supersede the value

recommended in this report.

The U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) has reported on

the thermal conductivity values of a urea-formaldehyde based foam measured at various

temperatures using the Dynatech Rapid K testing apparatus [35] . These values are given in

2 table 2. The CRREL thermal conductivity value of 0.26 Btu in/h ft °F (0.037 W/m-K) at

71°F (22°C) is slightly higher than the NBS recommended design value of 0.24 Btu in/h ft

2 °F (0.035 W/m-K) at 75°F (24°C)

.

49
The Institution of Heating and Ventilating Engineers (IHVE) Guide has recently published

thermal conductivity values for urea-formaldehyde based foam [72] as shown in table 9. The

data from the Institution of Heating and Ventilating Engineers Guide shows that at densities

3 3 slightly above the normal recommended application density of 0.7 lb/ft (11 kg/m ) , the

thermal conductivity of urea-formaldehyde based foam decreases. This decrease in thermal

conductivity with an increase in density, for the density range near the normally recommended

density, has also been shown in another report [39] , from which data are also given in

table 9. It is interesting to note that the data agree favorably with the thermal conductivity value determined at NBS.

The effective insulating properties of foamed walls may be lower than those calculated on the basis of the thermal conductivity of the foam as measured in the laboratory. Shrinkage may result in cracks in the foam, gaps between the wall studs and the foam, and gaps

between the wall surfaces and the foam. Shrinkage thus creates void spaces where the

thermal resistances are less than that of the foam. In addition, convection air currents

within the voids created by shrinkage may contribute to reducing the overall insulating

properties of the wall from the calculated values.

Recently, a laboratory test was conducted by a commercial laboratory on a full-scale

wall to evaluate the effect of shrinkage of the foam on the insulating properties of the

wall [73]. The wall specimen was 9 x 14 ft (2.7 x 3.7 m) , constructed with 2x4 studs

spaced 16 in (400 mm) on centers and insulated with a urea-formaldehyde based foam in

accordance with the supplier's recommendations. The exterior of the wall consisted of

redwood siding placed over wood-fiber sheathing. The interior was gypsum board. During

testing, the wall specimen was exposed to approximately -21°F (-29 °C) on the exterior and

74°F (23°C) on the interior.

The results of the study showed that the measured thermal transmittance (U-value) of

2 2 the wall specimen was 0.077 Btu/h ft °F (0.44 W/m -K) [73]. NBS calculated the thermal

transmittance of the test wall described above, using the thermal resistance method as outlined in Appendix D. Using a thermal conductivity value of 0.24 (0.035) for the urea- formaldehyde based foam, the calculated value of thermal transmittance of the test wall was

2 2 0.06 2 Btu/h ft °F (0.35 W/m -K) . The experimental thermal transmittance was thus found to

be 24 percent higher than that predicted from calculations. Although shrinkage of the foam

increased the observed thermal transmittance of the insulated wall above the expected

design value, the thermal transmittance of the insulated wall was observed to be 63 percent

lower than that calculated for the uninsulated wall. The calculated thermal transmittance

of the uninsulated wall was 0.21 Btu/h ft

2 °F (1.2 W/m2

-K)

.

50
Table 9. The Thermal Conductivity of Urea-Formaldehyde Based

Foams as a Function of Density

Thermal Conductivity

Btu in/h ft2 °F (W/m-K)

Density

lb/ft?

(kg/in )

Mean Temperature

°F

(°C) Reference

0.25

(0.036)

0.22

(0.032)

0.22

(0.032)

0.75

(12)

0.94

(15)

1.9

(30)

_

67

0.245

(0.0355)

0.235

(0.034)

0.225

(0.0325)

0.23

(0.033)

0.225

(0.0325)

0.48

(7.8)

0.64

(10)

0.86

(14)

1.05

(17)

1.07

(17)

72

(22)

72

(22)

72

(22)

72

(22)

72

C22)

34

51
The foam in the test wall was observed to shrink 3 percent across the stud space

width, which was considered to be partially responsible for reducing the effective insulating

properties of the wall [73]. Table 10 shows the reduction in the calculated thermal trans- mittance of the test wall as a function of the percent of the hypothetical shrinkage of the

foam insulation. The calculations by which the values in table 10 were obtained are given

in Appendix D. As can be seen from table 10, the increase in the thermal transmittance of

the wall corresponding to a 3 percent shrinkage of the foam was calculated to be 6.5 percent,

which is much less than the 22 percent increase observed experimentally. The calculation

only considers heat flow paths of high thermal conductance created by shrinkage of the foam

away from the studs. The calculation does not consider heat losses due to convection, nor any effect of moisture accumulation in the foam during testing.

The effect of shrinkage on the thermal insulating properties of a foamed wall has been

discussed in the literature. The Swedish State Planning Organization reported that the

effect of convection currents occurring in shrinkage cracks and moisture content in the

material reduces the thermal-insulating capacity of the foam to about one-half of that of

the dry uncracked foam [54] . They recommend that, for practical purposes, the "applicable

2 thermal conductivity" of the foam in walls can be assumed to be about 0.48 Btu in/h ft °F (0.069 W/m-K)

.

The Dutch standard does not specify the thermal conductivity of urea-formaldehyde

based foams. Rather it requires a thermal resistance test of a wall specimen in which foam

has been applied [51] . For the foam to conform to the Dutch standard, the effective thermal

2 conductivity of the foam in the test wall should not be greater than 0.35 Btu in/h ft °F (0.050 W/m-K)

.

It is difficult to correlate these literature data concerning relationships between

shrinkage and the effective thermal conductivity of urea-formaldehyde based foams. The

Swedish assumption that the effective thermal conductivity may be twice the value measured

in the laboratory [54] is not substantiated with test data. Two other reports have suggested

lower values of the effective thermal conductivity of the foams in walls [51, 73] . These

latter reports are based on laboratory tests which may or may not have a relationship to inservice performance. In particular, the shrinkage of the foam in the test specimens at the

time of testing may be less than that occurring in building constructions after a prolonged

period of aging. Additional data are needed to correlate the effects of shrinkage on the

insulating properties of foamed walls.

52
Table 10. Calculated Overall Thermal Transmittance Values for a Test Wall as a Function

of the Percent of the Hypothetical Shrinkage of a Urea-Formaldehyde Based Foam

Linear Shrinkage

in

(mm)

Linear Shrinkage

percent

Thermal Transmittance

Btu/h-ft2 °F (W/m -K) Thermal Transmittance

percent increase

0.0618

(0.351)

0.44

(11) 3 0.0663(0.376)

7.3

0.52

(13) 3.6 0.0672(0.382)

8.7

0.89

(23)

7.1 0.0710

(0.403)

14.9

2.07

(53)

14.3 0.0833

(0.473)

34.8

53
7 . 21 Toxicity

The question has arisen as to the toxicity of the foams and the components from which

the foams are produced. The foams are normally used in cavity walls; therefore, there is no direct contact with the building occupants. Danger to building occupants, if present,

would result from inhalation of or contact with gases released by the foam. The results of

two inhalation toxicity tests on proprietary foams were made available during the survey

[66, 67]. Both of these test reports indicated that the foam in question was classified as non-toxic according to the Federal Hazardous Substances Act, Section 191 (f) (2) -1961.

Urea-formaldehyde based foams may release formaldehyde gas under certain conditions.

Toxic effects of formaldehyde gas are discussed in Section 8.

Few data or guidelines are available which indicate whether or not a health hazard exists

during foam production at the job site. The available evidence shows that there is no hazard when proper application procedures are followed. No complaints that the foam production has caused health problems were uncovered during this survey. One brief report was made available on this subject [74] . It was reported that, after reviewing the components

used in preparing a proprietary foam, the foaming process should not pose a significant

health hazard if reasonable precautions are observed. It was recommended in this report

[74] that protective gloves or clothing be worn to eliminate or reduce to a minimum skin

contact with the foam ingredients. The Canadian Government has recommended that the applicator must exercise care in the handling of foam ingredients and the resulting foam because

they can cause severe eye and skin irritation [53] . It is noted that none of the major

U.S. manufacturers recommends the use of respirators by workmen during foam application.

Possible safety hazards presented by the application of foams to buildings which store foodstuffs in the open have not been addressed in this report. As a precautionary measure, foam should not be applied in warehouses or similar buildings where foodstuffs may be

stored in the open, unless it is determined prior to application that the foam application

presents no safety hazard. Some manufacturers of the foams have mentioned that their

products have been applied in warehouses where foodstuffs have been stored in the open. It is anticipated that these manufacturers have data concerning the health and safety aspects

regarding this type of application.

54
7.22 Water Absorption

Water absorption is a significant performance factor since the thermal conductivity of

the foams is dependent upon the amount of water in the foam. The Centre Scientifique et

Technique du Batiment (CSTB) has reported on the thermal transmittance of a test wall as a function of time and moisture content of the foam [46] . They showed that a decrease in the

moisture content of the foam was accompanied by a reduction in the thermal transmittance of

the test wall.

Moisture may be absorbed either in the form of water vapor or liquid water. In the case of water vapor, values of the equilibrium moisture content have been given in the

literature. NBS has reported a value of 16 percent by weight at 75°F (24°C) and 40% rh [43]

.

The Swedish State Planning Organization has reported 8 and 15 percent by weight at 35% and

85% rh, respectively [54] , but no corresponding temperature was given. The CSTB has stated

that the equilibrium moisture content is 0.2 percent by volume at 68°F (20°C) and 65% rh [46]

.

Two tenths of a percent (0.2%) by volume is approximately 18 percent by weight. The CSTB

has indicated the relative humidity of the air has little influence on the equilibrium

moisture content of the foam [46] . This observation supports an earlier report that a freshly applied wet foam will dry out at very high humidities [14]

.

The resistance of the foams to liquid water absorption is not clearly defined in the

literature. The amount of water absorbed during immersion of the foams has been reported

as being as low as 2 percent by volume or as high as 42 percent by volume. Reasons for

this wide range are not understood, although variations between the types of cells, cell

sizes and voids in the foams, as well as differences in test methods, may be responsible.

For cavity wall insulations, both the CSTB and the British Agrement Board have stated

that water absorption of the foams through capillarity is slight [46, 55]. The resistance

of the foams to water absorption through capillarity has been described in the literature [75]

However, under pressure the foams may absorb large quantities of water [54] . The Dutch and

West German standards have requirements for low capillary moisture absorption of the

foams [51, 52].

As previously mentioned, water absorption is important because of its adverse effect on the thermal conductivity of the foams. Little data are available which show this effect.

The Swedish State Institute for Construction Research has published a graph of the results

of a study performed in Denmark [59] . It is difficult to obtain precise values of the

thermal conductivity as a function of the water content from this graph. The graph indicates

that, as expected, the thermal conductivity increases with an increase in moisture content. Additional data on the effect of water absorption on thermal conductivity are needed from

laboratory research.

55
7.23 Water Vapor Transmission (Permeability)

There is a wide range of values in the literature for the water vapor permeability of

urea-formaldehyde based foams. As can be seen from table 2, values for the water vapor

-12

permeability are reported as low as 4.5 perm-in or as high as 100 perm-in (7 or 146 x 10

kg/Pa- s.m) . The water vapor permeability is significant in so far as water vapor migrating

through the foam may condense within it under certain temperature and relative humidity

conditions and thus increase its thermal conductivity. It is anticipated that water condensation problems may be reduced through the use of a properly designed vapor barrier. For a cavity wall retrofitted with an insulation, the vapor barrier would most likely be a paint or coating applied to the surface of the interior wall. Guidelines for such vapor barriers are presently not available.

In the previously mentioned study conducted at Fort Greely, Alaska, by the U.S. Army

Cold Regions Research and Engineering Laboratory (CRREL) , a section of a wall insulated

with a urea-formaldehyde based foam was visually examined in the spring after an extremely

cold winter [35]. It was observed that the exterior sheathing and wind-paper (asphaltic

kraft paper of low permeability) were dry, which indicated that no significant amount of

moisture had passed through the foam and collected on the low permeability outer wall

elements. It is noted that before application of the foam these walls contained insulations

having vapor barriers as previously described in Section 7.8. The foam was described as being tight against the inside of the sheathing, and shrinkage was less than 2 percent.

8. FORMALDEHYDE GAS

One of the questions that has been raised concerning the use of urea-formaldehyde

based foam insulations is whether or not the foams liberate formaldehyde gas within the

insulated structure. If formaldehyde gas is liberated, is its presence a health hazard to the occupants? These questions have been addressed in this review of the performance of urea-formaldehyde based foam insulations.

56
8.1 Health Hazard

Formaldehyde is a colorless gas which condenses to a liquid at -2°F (-19°C) and

freezes to a solid at -180°F (-118°C) [76] . The gas is denser than air, and has a pungent

and characteristic odor. The toxicity and health hazards of formaldehyde have been reviewed

[77-79] . Formaldehyde toxicity is evidenced on inhalation, contact with the mucous membranes

of the eyes, nose and throat and oral imbibition of solutions. The toxic effects of

formaldehyde have been determined by studies involving workers who have been exposed to formaldehyde gas in their occupations. Allowable concentrations of exposure are defined

according to the threshold limit value (TLV) . The threshold limit value represents the

concentration that would have no harmful effect on almost any worker on repeated exposure

throughout a normal work day (8 hours) [78]. For exposures longer than 8 hours, the

maximum concentration that may be tolerated by building occupants has not been defined.

The most recently recommended threshold limit value for formaldehyde gas is 2 parts

per million (ppm) by volume in air [77] . The symptoms of exposure to formaldehyde gas have

been described [78] . Exposure to small concentrations causes burning of the eyes, weeping,

and irritation of the upper respiratory passages. Stronger concentrations produce coughing,

constriction in the chest, and a sense of pressure in the head. Inhaling a large quantity

of formaldehyde may cause sleeplessness, a feeling of weakness and palpitation of the

heart. It has been reported that a threshold limit value of 5 ppm is low enough to prevent

respiratory injury but not necessarily low enough to prevent subjective evidence of irritation

[77]. With some individuals, irritation to the eyes, nose, and throat, as well as disturbed

sleep, may be possible at limits below 5 ppm. It is for these reasons that the threshold

limit value is recommended at 2 ppm.

Short-term exposure to 10-20 ppm produces immediate eye irritation and a sharp burning

sensation of the nose and throat which may be associated with sneezing, difficulty in

taking a deep breath, and coughing [79] . Recovery is reported to be prompt from these

transient effects after elimination of exposure. The atmospheric concentration of formaldehyde which is immediately hazardous to human life is not known [79]

.

It is interesting to note that the least concentration of formaldehyde gas which can be detected by its odor has been reported as 0.8 ppm [78] . This is below the recommended

threshold limit value of 2 ppm. Thus, formaldehyde gas may be present in the atmosphere in

concentrations that are detectable by the sense of smell but which may not in normal

circumstances cause irritation problems to a worker during an 8 hour day. Formaldehyde gas serves as its own warning agent and can be detected before it may cause irritation.

57
It may be speculated that the effects of exposure to 2 ppm for 8 hours a day nay be

less severe than the effects of exposure on a building occupant to the same or lower concen- trations for longer periods of time (possibly up to 24 hours a day) . Information regarding

the health hazard to such exposure was not found. In this regard, the Dutch standard has

specified the maximum allowable concentrations of formaldehyde gas which may be liberated

in the rooms of a building insulated with urea-formaldehyde based foams [51] . Two weeks

after foaming, the maximum allowable concentration of formaldehyde is specified as 0.5 ppm. After two months, the maximum allowable concentration is specified as 0.02 ppm.

8.2 Chemical Determination of Formaldehyde Concentration

Formaldehyde can be detected and determined quantitatively by a number of chemical

methods [78]. The chronotropic acid (l,8-dihydroxynaphthalene-3,6-disulfonic acid) method

used for determining formaldehyde at low concentrations in ambient air is reliable in the

concentration range of about 0.01 to 200 ppm. In brief, the method consists of sampling

the formaldehyde in a solution of chromotropic acid, and analyzing the resulting solution

in a laboratory. Upon heating, the chromotropic acid-formaldehyde solution develops a violet color. The intensity of the violet color is proportional to the concentration of

formaldehyde.

8.3 The Incidence of Formaldehyde Odor Problems

During the application of urea-formaldehyde based foam insulations, an odor of formaldehyde may occur because the foam contains formaldehyde. Under normal circumstances, any

odor occurring during application should dissipate rapidly and not linger longer than a few

days. One major manufacturer has stated that formaldehyde gas is emitted from the foam, in

the part per million range, during the drying and curing process which he states will be

over in two weeks. The severity of an odor problem depends upon the intensity of the odor

and the time period over which it lasts.

It was not possible to document the number of formaldehyde odor problems which have

occurred in the United States within residences insulated with urea-formaldehyde based foams.

Based on the results of this survey, the incidence of formaldehyde odor problems in the

United States appears to be minor. Three cases were noted, but the severity of the problem

in two of the three cases was not determined. In the third case, the odor problem was so severe that the urea-formaldehyde based foam was removed from the walls and replaced with

another insulation. This points out a disturbing aspect to the formaldehyde odor problem.

Although the incidence of occurrence may be minor, a problem, if it does occur, may be

major and in extreme cases, require an expensive solution such as removal and replacement

of the foam.

58
In support of the findings regarding the minor incidence of formaldehyde odor problems

in the United States, some documented figures were received from the Netherlands [80] . It was reported that in 60,000 Dutch dwellings insulated from the middle of 1974 to early

1977, 32 cases of formaldehyde odor problems were documented. The severity of the problems was not reported.

8.4 Causes and Solutions of Formaldehyde Cdor

Formaldehyde odors are caused by the presence of free formaldehyde gas. There are two

sources of the formaldehyde. First, formaldehyde is present in the urea-formaldehyde based

resin and may be liberated upon foaming. Secondly, formaldehyde is liberated during hydrolysis

of urea-formaldehyde based foams which may occur under conditions of high temperature and

high humidity.

Factors which would increase the likelihood of liberating formaldehyde from either

source will contribute to an odor problem. The major manufacturers of urea-formaldehyde

based foam insulations have outlined a number of these factors which are in general related

to improper manufacture or improper application of the resin. The relative significance of

these factors is not known. The factors contributing to formaldehyde odor problems as described by the manufacturers are:

° an excessive amount of formaldehyde in the resin

° an excessive amount of catalyst in the foaming agent an improper ratio of resin to foaming agent

excess foaming agent

° foaming at high humidities

foaming with cold chemicals

dry density of the foam exceeding manufacturers' specifications

application against recommended practice; e.g. in an air plenum or ceilings

improper use or lack of vapor barriers

improper venting on some constructions.

To ensure formaldehyde cdor problems will not occur, the foam producing materials must

be properly manufactured and the foam must be properly applied. In particular, excess formaldehyde in the resin must be kept to a minimum, and the foam should not be applied in areas subjected to high temperature and high humidity.

59
If prolonged formaldehyde odor problems occur, there are a number of procedures which

are recommended by manufacturers of urea-formaldehyde based foams for correcting the problems.

These corrective procedures include:

° ventilation (open doors and windows for 20-30 minutes twice a day)

° modification of air conditioning filters to contain impregnated activated

charcoal

evaporate household ammonia in closed and overheated rooms, then ventilate

° inject ammonia gas into the foam through holes in the walls

° spray air filters or floors with a specified odor absorbent (available from

the manufacturer)

° employ a "masking agent" (available from the manufacturer)

apply vinyl wall paper or a non-permeable paint to interior walls.

9. ACOUSTIC PROPERTIES

A quantitative measure of the air-borne sound insulation of a structure is referred to

as the sound transmission loss. The sound transmission loss is a measure of the reduction

in transmission of randomly incident sound energy, in decibels (dB) , through a partition.

The procedure for measuring the sound transmission loss in the laboratory is to place

a test wall specimen in an aperture between two rooms that are acoustically insulated from

each other. Only the wall under test transmits sound from the source room to the receiving

room. The sound transmitted through the test wall gives rise to a random sound field in

the receiving room. By measuring the sound level in the receiving room, it is possible to determine the sound transmission loss through the test wall.

The results of several sound transmission tests on wood stud partition walls performed

according to ASTM E 90 are given in table 11. These tests were performed on conventional

partition walls having nominal 2x4 wood studs spaced 16 and 24 in (106 and 610 mm) with

either 1/2 or 5/8 in (13 or 16 mm) gypsum board on both sides of the wall. Values of sound

transmission loss are provided for various frequencies for walls of this type containing

either urea-formaldehyde based foam, glass-fiber batts or no insulation in the cavities.

60
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61
The need to provide a single-number rating for comparing the sound transmission loss

of partitions for general building design purposes has led to the development of the Sound

Transmission Class, STC, which- is described in ASTM E 413-73. The procedure for obtaining

the STC rating is given in this ASTM standard. It involves fitting a contour, the STC

contour, to measured sound transmission loss data. The rating is designed to correlate

with subjective impressions of the sound insulation provided against the sounds of speech,

radio, television, music and similar sources of noise in offices and dwellings. In general,

a high STC rating corresponds to a high resistance to sound transmission.

Table 12 presents the STC ratings for the sound transmission loss data given in table 11. These data in table 12 show that installing urea-formaldehyde based foam or glass-fiber

batts in wood stud partition walls as acoustical insulation did not appreciably affect the

STC rating. From table 12 it can be seen that the difference in STC ratings ranged from

to 6 depending on which tests are compared. The relative ineffectiveness of the cavity

insulation is due to the transmission of sound by vibration through the rigid coupling of

both sides to the studs.

Table 12. Sound Transmission Class (STC) Ratings

for Various Wood Stud Partition Walls

Type of Cavity Insulation STC Rating-/

Urea-formaldehyde based foam 3941

40

Glass-fiber batts 40

No insulation 35

3640

37

1/ The STC ratings correspond to the transmission loss data presented

In table 11.

62
In a recent study 185] , it was confirmed that the effectiveness of cavity insulation

could be markedly improved by installing resilient channels between the studs and the

gypsum wall boards. Tests conducted in that study showed in general that with the inner

walls decoupled by the resilient channels, transmission took place largely through the air

cavity rather than through the studs. This allowed the sound absorbing action of the

cavity insulations to become more effective.

Sound transmission loss data and corresponding STC ratings for metal stud partition

walls are given in tables 13 and 14, respectively. A comparison of the STC ratings presented

in tables 12 and 14 shows that the metal stud walls were more resistant to sound transmission

than the wood stud walls. The higher resistance of the metal stud walls is attributed to the metal studs being more resilient than the wood studs. In addition it can be seen from

table 14 that the insulated metal stud walls had higher STC ratings than the uninsulated

walls and the STC ratings for metal stud walls insulated with urea-formaldehyde based foam

and glass-fiber batts were comparable.

In the previously mentioned study [85] it was shown that installing insulation in a conventional exterior frame wall, as is also true of an interior partition wall, was not

effective in providing significant reduction in sound transmission. As in the case of the

partition wall, the ineffectiveness was attributed to the transmission through the wood

studs rather than the cavity.

Measured data on the sound transmission loss of exterior frame walls insulated with

urea-formaldehyde based foams were not found in the literature. Although data are not

available, it is believed that urea-formaldehyde based foams or other insulations will not

provide significant reduction in the sound transmission of exterior walls when most of the

transmission is taking place through the studs.

63
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64
Table 14. Sound Transmission Class (STC) Ratings for

Various Metal Stud Partition Walls

Type of Cavity Insulation STC Rating-^

Urea-formaldehyde based foam 44

45

46

4443

Glass-fiber batts 43

No insulation 37

3941

1/ The STC ratings correspond to the transmission loss data

presented in table 13.

10. GENERAL APPLICATION GUIDELINES

The question of proper application of urea-formaldehyde based foam insulations was

addressed during this survey. It was found that application guidelines existed both in the

United States and in some foreign countries. The four major U.S. manufacturers have guidelines for applying their own materials. In addition, the Dutch standard for urea-formaldehyde

based foams contains a section on proper application procedures 151], and a di ift application

standard has been written by the Canadian Government 153]

.

These documents were reviewed and form the basis for the general guidelines presented

in this section. The authors believe that the major U.S. foam manufacturers have conscientiously attempted to assure that their products are properly applied. Application manuals

have been written and programs for training applicators have been initiated. Adherence to the manufacturers' guidelines by applicators should reduce the risk of problems due to improper application to a minimum.

65
Each manufacturer's recommended set of application instructions differs slightly from

those of the other manufacturers because of variations in foam formulation and differences

in design of the gun for applying the foam. It is not feasible to recommend a detailed set of application guidelines that would be universally applicable to each of the urea-formaldehyde

based foam systems which are currently available in the United States.

Therefore, this section presents a general set of guidelines to assist contractors,

inspectors, and users in ascertaining that proper application procedures and certain safety

precautions are being followed.

The general set of guidelines includes:

Foam installation should only be performed by an applicator who has been

trained or approved by the foam manufacturer. Installation by an inexperienced applicator may result in an unacceptable foam which may perform poorly.

Foams should not be applied in ceilings or attics. (Reasons for this recom- mendation are noted in Section 11 .

)

° Foams should not be applied in exposed applications. U.S. model building

codes require that all foam plastics used on the inside of buildings in

walls and ceilings be protected by a thermal barrier of fire-resistive

materials having a finish rating of not less than fifteen minutes. In addition exposed urea-formaldehyde based foams may be subject to photodegradation.

Prior to the application of foams in warehouses or similar buildings where

foodstuffs may be stored in the open, it should be determined if this type

of application presents a safety hazard. Possible safety hazards presented

by the application of foams to buildings which store foodstuffs in the open

have not been addressed in this report.

Foaming equipment should be kept clean and well-maintained. Manufacturers

have cleaning and maintenance recommendations for their equipment.

Dates after which the resins and foaming agents are not usable should be

clearly labeled on the resin and foaming-agent containers. These dates (or

shelf-lives) , as recommended by the manufacturers, should never be exceeded.

One U.S. manufacturer has stated that his resin whose shelf-life has not been

exceeded should have a milk-like consistency and be white to transparent.

The resins and foaming agents should be stored within the temperature range

recommended by the manufacturer. Some U.S. manufacturers have recommended

that 70'F (21°C) is the maximum storage temperature for their materials.

The Canadian Government Specification Board has proposed a storage temperature

range of 50 to 86°F (10 to 30 C C) . In general, as the storage temperature is

increased, the shelf-life is shortened.

66
The temperatures of the resins and teaming agents as they enter the foaming

gun should normally be within the range of 59 to 86°F (15 to 30°C) , unless

otherwise specified by the foam manufacturer. One U.S. manufacturer recommend

that his materials enter the gun at temperatures not less than 70°F (21°C)

.

The maximum temperature of 86°F (30°C) should never be exceeded. For cold

weather applications, the resins and foaming agents should be kept in a heated area (normally the applicator's van) during foam production, and the

supply-lines from the storage containers to the foaming gun may have to be

insulated.

The surface temperature of the cavity in which foams are to be applied

should be within the range of 23 to 86 GF (-5 to 30 °C) . It is recommended

that these temperature limits should not be exceeded for a period of four

days after application. This guideline concerning the temperature range of

the surface of the cavity is adopted from the Canadian Government Specificatio

Board's application guidelines [53] and all U.S. manufacturers do not agree

with it. For example, one manufacturer recommends that his product be

applied within cavities whose surface temperatures range from to 90 °F (-18

to 32°C)

.

The resins and foaming agents should be pumped to the foaming gun at pressures

recommended by the foam manufacturers.

Power lines in excess of 200 volts within cavities in which foams are applied

should be shut off until the foams have dried or until the cavities are

sealed.

Power lines in excess of 110 volts within cavities in which foams are applied

should be shut off during application if foaming is performed with the

applicator standing on wet ground or not electrically insulated from wet

ground.

The appearance of the foams should be checked immediately before application.

The foams should be white in color and fluffy with a warty surface. When

the foams are sliced, the cells should be uniform.

The setting time of the foams should be determined before application and

should be no less than 20 seconds and no longer than 60 seconds. The setting

time determined as follows:

A conical sample of foam, approximately 12 in (300 mm) in diameter at

the bottom and 12 in (300 mm) in height, is formed by spraying. Immediately after spraying, the foam sample is sliced repeatedly with a

spatula or trowel until it can no longer be sliced but shears off

leaving a smooth surface on the foam sample. The time interval between

spraying the foam sample and the initial shearing of the foam is the

setting time.

67
The wet density of the foams should be determined before application and

should lie within the manufacturer's specified range for the wet density.

3 3 The normal wet density of the foams is approximately 2.5 lb/ft (40 kg/m )

.

Wet density is measured by filling a cardboard box or plastic bag of known

weight and volume and then weighing the filled box or bag.

If the foams are inadvertently sprayed on aluminum building components such

as door frames, window frames, or awnings, the foams should be immediately

removed and the aluminum component should be rinsed thoroughly with water.

In cases where it is anticipated that an aluminum component may be sprayed

during application, the component should be protected before application

begins

.

° Foams which are sprayed on glass should be removed by rinsing with water.

Water present in the foams at application should be permitted to escape from

the wall as the foams dry in the cavity. In cases where the two wall surfaces

may restrict the water vapor transmission, provisions such as vent plugs should

be provided to allow the water in the wall to escape. The effectiveness of

vent plugs has not been demonstrated.

In applying the insulation in exterior walls of homes which are located in

geographic locations having long cold winters, consideration should be given

to applying a vapor barrier on the interior (warm side) surface of the wall.

The absence of the vapor barrier on the interior of the insulated wall may

cause condensation and the accumulation of excessive moisture within the

wall. This may lead to problems such as blistering and peeling of paint,

buckling of wood siding, or in extreme cases rotting of wood members within

the wall. A vapor barrier may be created by applying a low permeability

paint or vinyl wallpaper to the surface of the interior wall.

In retrofitting the walls of residences with any type of insulation, if the

need arises to verify the completeness of filling the wall cavities, one method which can be used is infrared thermography.

11. RECOVMENDATIONS

This study on urea-formaldehyde based foam insulations involved a comprehensive review

of the literature which was complemented by private communications and preliminary test

results. The intent of the study was to assess the performance of the foam insulations.

Guidelines are presently not available in the United States for their evaluation and use. The results of the study have shown that available information to establish guidelines is

in many cases lacking or contradictory. Therefore, based on this study the following

recommendations are made:

68
A voluntary national consensus standard be developed for urea-formaldehyde

based foam insulations. At the present time there are no U.S. material,

product or industry standards nor federal specifications available.

The design value for the thermal conductivity of the foams should be taken

as 0.24 Btu in/h ft

2 °F (0.035 W/m-K)

.

The foams should not be applied in attics and ceilings. This recommendation

is based on properties of the foams dealing with shrinkage, resistance to high temperature and high humidity, and odor. Excessive shrinkage may occur when the foams are applied to an open cavity and dried too rapidly. Preliminary

laboratory data indicate degradation of the foams when exposed to high

temperature and high humidity. If free formaldehyde gas is present, being

denser than air, it may tend to settle in inhabited areas.

Foams should not be applied in exposed applications. This recommendation is

made to comply with fire resistance requirements of the U.S. model building

codes and to avoid photodegradation of the foams.

The description of foams as "noncombustible" is improper and should be

disregarded. Additional information on the rate of heat release and on the

performance of the foams in full scale room fire tests should be developed.

Additional information should be developed through field surveys and laboratory research. Data are not available on long-term performance or durability

of the foams in typical wall constructions in the United States. Information

is needed from both field surveys and laboratory research on shrinkage,

resistance to a combination of high temperature and high humidity, freezethaw resistance and the effect of the foams on other construction materials.

Information is also needed from laboratory tests to determine the effects of

shrinkage, resistance to high temperature and high humidity, and moisture

content of the foam on the thermal transmittance of walls filled with ureaformaldehyde based foams.

69
12. REFERENCES

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Kautschuk , 18, 340-6 (1971)

.

2. Varney, Charles L. , "What the Cellular Plastics Industry Offers the Building Construction

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1963.

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(1968)

.

5. Pace, L.S., "Thermal Insulation by Cavity Wall Fill," Insulation , 26, 28, 29, September/

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.

7. Meyer, Werner T., "Urea-Formaldehyde Foam Insulation for the Construction Industry,"

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.

8. "UF Foam Cavity Fill," Part 1, Architects Journal Information Library, 311-17, August

(1971)

.

9. Bender, Rene J., "Handbook of Foamed Plastics," Lake Publishing Corporation, Libertyville

,

Illinois, 1965, p. 330.

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September 1964.

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Perlacherstrasse 125," Test Report 112/66, H. Knapp, Commercial Chemist, 5 Koln - Siebengebirgsalle 23, Fernsprecher 41 41 50, Sparkasse Der Stadt Koln 10 292 068,

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70
14. Parker, T.W. , "Performance in Use of Insulated Cavity Fill Walls," The Agrement Board,

Paper No. 6, July 1971.

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.

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Charles A., Ed., McGraw-Hill, New York, 1975, p. 7-61.

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edited by Rossiter, Walter J. and Mathey, Robert G., National Bureau of Standards

Report NBSIR 75-795, November 1975, pp. 6-9.

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Corporation, 1151 Boston-Providence Turnpike, Norwood, Mass., February 25, 1970.

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Foams," Project No. 3-207-359, Southwest Research Institute, 8500 Culebra Road, San

Antonio, Texas, June 10, 1970.

20. "Report in Fire Classification of Foamed Plastic," File R7572, Project 74NK8988,

Underwriters' Laboratories, Inc., Northbrook, 111., May 22, 1975.

21. "Flame Spread Classification, Smoke and Fuel Contribution," Test Report No. A13851,

United States Testing Company, Inc., 1415 Park Avenue, Hoboken, New Jersey, January 30, 1974.

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Testing Bureau, Inc., 44 Trinity Place, New York, N.Y., August 25, 1970.

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#102)," Serial No. 28215, Class No. 4820, Factory Mutual Research Corporation, 1151

Boston-Providence Turnpike, Norwood, Mass., June 17, 1976.

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United States Testing Company, Inc., 1415 Park Avenue, Hoboken, New Jersey, June 13,

1974.

25. "ASTM E 84(75) Fire Test Results for the Surface Burning Characteristics of Tripolymer

Foam Insulation (Puff #102) , Report 28343 (4820) , Factory Mutual Research Corporation,

1151 Boston-Providence Turnpike, Norwood, Mass., October 28, 1976.

26. "Evaluation of Isoschaum Urea Formaldehyde Foam Insulation," ESCI Test Report #68-7,

Electric Space Conditioning Institute, Madison Avenue, Morristown, N.J., August 26, 1968.

71
27. "Mold Shrinkage," Test Report A-40487, United States Testing Company, Inc., 1415 Park

Avenue, Hoboken, New Jersey, October 16, 1975.

28. "Linear Shrinkage of Samples of Urea Formaldehyde Foam," Dynatech, 99 Erie Street,

Cambridge, Mass., May 21, 1975.

29. "Urea Formaldehyde Foam," Report No. 39573, Owens-Corning Fiberglas Corporation,

Technical Center, Granville, Ohio, April 26, 1973.

30. Kleimann, H., et al., "Foamed Plastics from Reacting Individual Components," Kunststoff

e

, 61, 405-16 (1971).

31. Baumann, H., "Further Developments in the Study of Urea-Formaldehyde Foams," Kunststoffe ,

47_, 256-59 (1957) .

32. "Foamed Plastics Insulation, Part 1 - Cavity Filling Materials," Plast. Rubbers Tex. ,

1, 23-4 (1970)

.

33. Mittasch, H., "Dependence of the Thermal Conductivity of Foamed Plastics on Moisture

Content," Plaste und Kautschuk , 16_, 268-71 (1969).

34. Kuster, W. , "The Thermal Conductivity of Foamed Plastics," Kunststoffe , 60 , 249-55

(1970)

.

35. Tobiasson, Wayne N. and Flanders, Stephen N., "Reinsulating Old Wood Frame Buildings

with Urea-Formaldehyde Foam," Second International Symposium on Cold Regions Engineering,

University of Alaska, 1976.

36. Project No. 6071, Report No. 14157, American Standards Testing Bureau, Inc., 44 Trinity

Place, New York, N.Y., December 4, 1970.

37. "Report on K-Factor Test," Lab. No. B3611, Northwest Laboratories, 200 James Street,

Seattle, Washington, December 2, 1964.

38. "Thermal Conductivity," Test Report A20238, United States Testing Company, Inc., 1415

Park Avenue, Hoboken, New Jersey, June 4, 1974.

39. Report on "The Thermal Conductivity of Samples of Urea Formaldehyde Foam," Dynatech,

99 Erie Street, Cambridge, Mass., May 21, 1975.

72
40. "Thermal Insulation Properties of Urea-Formaldehyde Foam Insulation," National Research

Council, Canada, June 1972.

41. "Thermal Conductivity," Test Report A 20283, United States Testing Company, Inc., 1415

Park Avenue, Hoboken, New Jersey, June 4, 1974.

42. "Thermal Conductivity," Test Report 70513, United States Testing Company, Inc., 1415

Park Avenue, Hoboken, New Jersey, December 27, 1976.

43. Burch, D.M. and Hunt, CM., "Retrofitting an Existing Wood-Frame Residence for Energy

Conservation - An Experimental Study," NBS report in review.

44. Baumann, H., "Properties of Foamed Cold-Setting Urea Formaldehyde Resins," Part 1,

Kunststoffe , 48, 362-4 (1958)

.

45. Report on Foam Samples, Lab No. C5164, Northwest Laboratories, 200 James Street,

Seattle, Washington, July 3, 1968.

46. Noury, Jean-Paul, "Increase in the Thermal Insulation of Cavity Walls," The Activities

of the CSTB, Cahiers du Centre Scientifigue et Technique du Batiment, No. 170, 155-56

(1976) .

47. Project No. 6071, Report No. 14309, American Standards Testing Bureau, Inc., 44 Trinity

Place, New York, N.Y. , May 4, 1971.

48. Project No. 6071, Report No. 13982, American Standards Testing Bureau, Inc., 44 Trinity

Place, New York, N.Y. , June 3, 1970.

49. Report on "The Water Vapor Transmission of Urea Formaldehyde Foam," Dynatech, 99 Erie

Street, Cambridge, Mass., May 21, 1975.

50. "Water Vapor Transmission Rate," Report Number A-34501A-1, United States Testing

Company, Inc., 1415 Park Avenue, Hoboken, New Jersey, July 16, 1975.

51. Draft of the revision "Quality Specifications for UF Foam and Workmanship Standards

for Insulation of Hollow Walls With This Foam," obtained from the Bouwcentrum, Ratiobouw

Rotterdam-3, P.O. Box 299, 700 Weena, The Netherlands.

73
52. "Urea Formaldehyde Spray-in-Place Foam for Thermal Insulation; Method of Application;

Properties; Production Requirements; Testing," Proposed Standard, the German Institute

for Standard Specifications (DIN) , Fachnormenausschuss Bauwesen, 1 Berlin 30, Reichspietschufer 72-76 Germany.

53. "Procedure for the Installation of Foamed-in-Place Urea-Formaldehyde Foam Insulation,'

Second Draft, Canadian Government Specifications Board, May 1976.

54. "Insulation by Urea-Formaldehyde Foam Injection in Building Constructions," Report

SBN-U 33:23, State Planning Organization; Swedish Building Standard Specifications,

Sweden, 1968.

55. "Econoseal Urea Formaldehyde Cavity Wall Insulation," Certificate No. 75/316, The

Agrement Board, Lord Alexander House, Waterhouse Street, Hemel Hempstead, Herts- HPI

IDH, England.

56. Benning, Calvin J., "Plastic Foams: The Physics and Chemistry of Product Performance

and Process Technology," Vol. I, John Wiley and Sons, New York, 1969, pp. 461-62.

57. Levy, Marshall M. , "Moisture Vapor Transmission and Its Effect on Thermal Efficiency

of Foam Plastics," J. Cell. Plast. , 2, 37-45 (1966).

58. "The Encyclopedia of Basic Materials for Plastics," edited by Simonds, Herbert R.

,

and Church, James M. , Reinhold Publishing Corporation, New York, 1967, pp. 234-35.

59. State Institute for Construction Research, Classification UDK 699.86, Publication No. 1963:4, Sweden.

60. 0' Sullivan, Emmett J., Aero-Space Corporation, Personal communication.

61. Whiteside, D., "Cavity Insulation of Walls - A Case Study," The Building Services

Engineer , 42, 201-9, December (1974) .

62. Gross, Daniel, National Bureau of Standards, Personal communication.

63

.

ICBO Proposed Research Committee Acceptance Criteria for Foam Plastics Under Section

1717 of the 1976 Uniform Building Code, October 1975.

74
64. Report of "Steiner Tunnel and Smoke Density Chamber Fire Tests; Conducted on Foamedin-Place Plastic CERL-SB-R-119 , " Assignment 71NK5280, File USNC49, Underwriters'

Laboratory, Inc., Northbrook, Illinois, August 12, 1971.

65. Report of "Steiner Tunnel Tests Conducted on Foamed-in-Place Plastic CERL-MC-296,

DACA88-72-M-0793," Assignment 72NK2828, File USNC49, Underwriters' Laboratory, Inc.,

Northbrook, Illinois, November 27, 1972.

66. Project No. 6071, Report No. 14053, American Standards Testing Bureau, Inc., 44 Trinity

Place, New York, N.Y., August 10, 1970.

67. Report P. 7251; LR 16087B, American Standards Testing Bureau, Inc., 44 Trinity Place,

New York, N.Y., November 27, 1974.

68. Report of Test, Number 89483-1, United States Testing Company, Inc., 1415 Park Avenue,

Hoboken, New Jersey, April 4, 1974.

69. Flanders, Stephen N. , U.S. Army Cold Regions Research and Engineering Laboratory, Personal

communication

.

70. Shirtliffe, C.J., National Research Council of Canada, Personal communication.

71. Pierce, E.T. and Burch, D.M., NBS report in preparation.

72. IHVE Guide, The Institute of Heating and Ventilating Engineers, 49 Cadogan Square,

London, Table A3. 23, p. A3-27 (1975).

73. "Competitive Insulation, Large Scale Thermal Tests," Report No. 40132-1, Owens-Corning

Fiberglas Corporation, Technical Center, Granville, Ohio, January 19, 1973.

74. Memo of L. A. Hansen, Chief, Industrial Hygiene Section, Department of Labor and

Industries, Olympia, Washington, May 19, 1967.

75. Diamant, R.M.E., "Wall Insulation with Injected Urea-Formaldehyde Foam," Building

Materials , 296-99, September 1962.

76. "Encyclopedia of Industrial Chemical Analysis," edited by Snell, Foster Dee and Ettre,

Leslie S., Interscience Publishers, New York, N.Y., Vol. 13, 100-17 (1971).

77. "Documentation of TLV Substances in Workroom Air," American Conference of Government

Industrial Hygiene, 3rd edition, Cincinnati, Ohio, 1971.

75
78. Walker, J. Frederic, "Formaldehyde," American Chemical Society Monograph Series, 3rd

edition, Reinhold, New York, N.Y., 1964.

79. "Formaldehyde," Hygienic Guide Series, March-April 1965.

80. Wulkan, E.K.H., Bouwcentrum, The Netherlands, Personal communication.

81. Reports 68-134 and 68-135 of STL, Western Electro-Acoustic Lab., 11821 West Pico

Blvd., Los Angeles, California, April 1968.

82. Report NCI-68-7 of STL, Wilson, Ihrig and Associates, Inc., 2344 Sixth Street, Berkeley,

California 94710, October 1968.

83. Report 39853 of STL, Owens-Corning Fiberglas Co., Granville, Ohio 43023, January 1973.

84. "Technical Manual on Architectural Acoustics," U.S. Army TM 5-805-15 (1976), in

publication.

85. Sabine, H.J., Lacher, M.B., Flynn, D.R. and Quindry, T.L., "Acoustical and Thermal

Performance of Exterior Residential Walls, Doors, and Windows," Nat. Bur. Stand.

(U.S.), Bldg. Sci. Ser. 77, 170 pages (November 1975).

86. Report NCI-68-8 of STL, Wilson, Ihrig and Associates, Inc., 2344 Sixth Street, Berkeley,

California 94710, October 1968.

87. Report NCI-68-9 of STL, Wilson, Ihrig and Associates, Inc., 2344 Sixth Street, Berkeley,

California 94710, October 1968.

88. Report of Sound Transmission Loss Test, Test No. KAL-1010-1-70, Kodaras Acoustical

Laboratories, 75-02 51st Avenue/Elmhurst, New York, N.Y. 11373, October 1970.

89. Report of Sound Transmission Loss Test, Report No. 434031, KAL Reference 1904-75,

Kodaras Acoustical Laboratories, 75-02 51st Avenue/Elmhurst, New York, N.Y. 11373,

November 26, 1975.

90. Report of Sound Transmission Loss Test, Test No. KAL-405-2-67, Kodaras Acoustical

Laboratories, 75-02 51st Avenue/Elmhurst, New York, N.Y. 11373, January 3, 1967.

76
13. ACKNOWLEDGMENT

This study was sponsored by the U.S. Department of Housing and Urban Development

(HUD) . The authors acknowledge with thanks the many individuals and organizations who

responded to NBS requests for information on urea-formaldehyde based foam insulations. The

assistance of Mr. C.J. Shirtliffe, National Research Council, Canada, Mr. E.K.H. Wulkan,

Bouwcentrum, The Netherlands, Mr. S.N. Flanders, U.S. Arms/ Cold Regions Research and

Engineering Laboratory, and Dr. M. Widmann, Borden Chemical Company, Canada, in providing

NBS with research and test results and standards, is worthy of special mention and is

sincerely appreciated. Thanks are also extended to the major U.S. manufacturers of urea- formaldehyde based foams and their representatives for their cooperation in providing NBS

with product information and test results.

77
APPENDIX A

THE MAJOR U.S. IYMCIFACTURERS OF

UREA-FORMALDEHYDE BASED FOAM INSULATIONS

Borden Chemical

Division of Borden, Inc. 50 West Broad Street

Columbus, Ohio 43215

Brekke Enterprises, Inc. 1320 Tidehaven Road East

Tacoma, Washington 98424

C.P. Chemical Company, Inc. 25 Home Street

White Plains, New York 10606

Rapperswill Corporation

305 East 40th Street

New York, New York 10016

78
APPENDIX B

BUILDING RESEARCH INSTITUTES

CONTACTED FOR INFORMATION ON

UREA-FORMALDEHYDE BASED FOAMS

Country

Canada

Institute

National Research Council

Division of Building Research

Ottawa, Ontario

K1A OR6

France Centre Scientifique et Technique du Batiment

Establishment de Grenoble

24, Rue Joseph Fourier BP 55 38401 Saint Martin D ' Heres-Isere

Netherlands Bouwcentrum

Ratiobouw Rotterdam3

P.O. Box 299

700 Weena

United Kingdom Building Research Establishment

Building Research Station

Garston, Watford

WD2 7JR

The Agrement Board

Lord Alexander House

Waterhouse Street

Hemel Hempstead, Hertfordshire

HP1 1DH

West Germany Bundesanstalt fur Materialprufung

1000 Berlin 45

Unter den Eichen 87

79
APPENDIX C

ADDRESSES OF MODEL BUILDING CODE AND OTHER

ORGANIZATIONS REFERENCED IN SECTION 6

BOCA Basic Building Code, 1975

Building Officials and Code Administrators International, Inc. 1313 East 60th Street

Chicago, Illinois 60637

Uniform Building Code, 1976

International Conference of Building Officials

5360 South Workman Mill Road

Whittier, California 90601

Standard Building Code, 1976

Southern Building Code Congress, International

3617 Eighth Avenue, South

Birmingham, Alabama 35222

The City of New York

Housing and Development Administration

Department of Buildings

100 Gold Street

New York, New York 10038

The Society of the Plastics Industry, Inc. 355 Lexington Avenue

New York, New York 10017

80
APPENDIX D

CALCULATIONS OF OVERALL THERMAL TRANSMITTANCE OF

A WOOD-FRAME CAVITY WALL DESCRIBED IN SECTION 7.20

1. Background

The purpose of this appendix is to calculate the effect of linear shrinkage of ureaformaldehyde based foam on the overall thermal transmittance of a conventional wood-frame

cavity wall. When the installed foam shrinks, void spaces adjoining the studs are normally

created which extend the height of the wall cavities. Void spaces are also created at the

top and possibly bottom of the wall cavity. These void or air spaces create high con- ductance heat flow paths through a portion of the wall. The foam also normally shrinks in

the thickness direction, creating thin air spaces between the foam and the inside and the

outside wall surfaces. A continuous air space completely encompassing the foam

may exist, and thereby make it possible for air exchange between the front and back sides

of the foam to occur. This analysis includes only the effect of the creation of highconductance heat flow paths adjacent to the studs. The effects of shrinkage at the top or bottom of the wall cavity and of air exchange between the front and backsides of the foam

are not included.

2. Wall Construction Details and Heat-Transfer Properties

The wall construction details are given in the following:

Inside to Outside

1/2 in (13 mm) gypsum board

2x4 studs, 16 in (400 mm) on center

1/2 in (13 mm) wood-fiber sheathing

3/4 in (19 mm) redwood siding.

The thermal conductivity values used in the analysis are given as follows:

Gypsum board

Wood-fiber sheathing

Redwood siding

Urea-formaldehyde based foam

Wood stud

Btu in/h ft2 °F W/m-K

1.13 0.16

0.38 0.055

0.84 0.12

0.24 0.035

0.82 0.12

81
Btu/h ft °F

2 W/m -K

1.5 8.5

4.0 23

1.0 5.7

The coefficient of heat transfer and the thermal conductance of the air space were

taken to be the following values:

Inside surface heat-transfer coefficient

Outside surface heat-transfer coefficient

Air space

3. Calculation Procedure

The portions of the wall having studs, insulation, and air spaces sandwiched between

other wall components were treated as separate parallel heat-flow paths. The heat transfer

through these separate heat transfer paths was treated as one-dimensional; lateral heat

transfer between adjacent elements was neglected. The thermal transmittance , U, through the

separate heat-flow paths was calculated using the steady-state equation:

u = N

(1) V + E ( LA) + '/h

i n =l n c where h . , h = overall heat-transfer coefficient at the inside surface and outside surfaces

,

l* o

respectively

(L/k) = thermal resistance of the n-th layer.

The overall thermal transmittance for the wall is given by the relation:

U

°Verall

= A^' U

s + ^

U

a

+ ^

U

I

(2)

where A denotes surface area. The subscripts s, t, a, I denote stud, total, air, and

insulation property, respectively.

4. Results

Using the foregoing procedure the effect of linear shrinkage on the thermal transmittance

of a wood-frame cavity wall was calculated. The percent increases in the overall thermal

transmittance for various percents of linear shrinkage are given in table 10 (see Section 7.20)

These values, as calculated herein, show that the overall thermal transmittance of the

described wood-frame cavity wall insulated with urea-formaldehyde based foam increases by

approximately twice the percentage of linear shrinkage of the foam. The values given in

table 10 are plotted in figure 3. As previously noted, the calculated values were based on

shrinkage of the foam adjacent to the studs and the effects of shrinkage at the top and

bottom of the wall cavity were not included.

82
6 8 10 12 14

LINEAR SHRINKAGE, %

16 18 20

FIGURE 3. EFFECT OF LINEAR SHRINKAGE OF THE FOAM ON THE OVERALL

THERMAL TRANSMITTANCE OF A WOOD-FRAME CAVITY WALL.

<r U. S. GOVERNMENT PRINTING OFFICE : 1977 —240-848/221

83
THBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN %6

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Urea-Formaldehyde Based Foam Insulations: An Assessment of

Their Properties and Performance

5. Publication Date July 1977

6. Performing Organization Code ,

7. author(S) waiter J. Rossiter, Jr., Robert G. Mathey,

Douglas M. Burch r F.. Thomas Piprnp

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Office of Policy Development and Research

Division of Energy Building Technology and Standards

Department of Housing and Urban Development

Washington, 20410

13. Type of Report & Period Covered

Final Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTPvACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) The properties and performance of urea-formaldehyde based foams pertinent to their use as insulation in buildings were assessed based essentially on existing information.

Pertinent materials properties were identified and guidelines prepared for the suggeste

values of these properties along with corresponding methods of test. For certain

materials properties information was not found to enable suggested values of these

properties. The factors affecting performance of urea-formaldehyde based foam insulati were also identified and discussed. Sane performance factors could not be adequately

evaluated because of insufficient or contradictory data in the literature. Methods of

foam application were studied and suggested general application guidelines were prepare

The advantages and disadvantages of using urea-formaldehyde based foam insulations were discussed and problem areas identified. Recommendations were made pertaining to the

use and assessment of urea-formaldehyde based foam insulations for residential

construction.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Cellular plastics; foam insulation; insulation; materials properties; performance; urea-formaldehyde

18. AVAILABILITY ^J Unlimited

~2 For Official Distribution. Do Not Release to NTIS

[XJ Order From Sup. of Doc, U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. C13»46:940

2] Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

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21. NO. OF PAGES

92

22. Price $2.30

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A typical plant can save about 20 percent of its fuel—just by installing waste heat recovery equipment. But with so much equipment on the market,

how do you decide what's right for you?

Find the answers to your problems in the Waste

Heat Management Guidebook, a new handbook

from the Commerce Department's National Bureau

of Standards and the Federal Energy Administration.

The Waste Heat Management Guidebook is designed to help you, the cost-conscious engineer or manager, learn how to capture and recycle heat

that is normally lost to the environment during in- dustrial and commercial processes.

The heart of the guidebook is 14 case studies of companies that have recently installed waste heat

recovery systems and profited. One of these applications may be right for you, but even if it doesn't

fit exactly, you'll find helpful approaches to solving

many waste heat recovery problems.

sources and uses of waste heat

determining waste heat requirements

economics of waste heat recovery

commercial options in waste heat

equipment

instrumentation

engineering data for waste heat recovery

assistance for designing and installing waste

heat systems

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Guidebook, send $2.75 per copy (check or money

order) to Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

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The Waste Heat Management Guidebook is part of the EPIC industrial energy management program

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PERIODICALS JOURNAL OF RESEARCH reports National Bureau

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DIMENSIONS/NBS (formerly Technical News Bulletin) —This monthly magazine is published to inform

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NONPERIODICALS

Monographs—Major contributions to the technical liter- ature on various subjects related to the Bureau's scientific and technical activities. Handbooks—Recommended codes of engineering and

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Applied Mathematics Series—Mathematical tables, manuals, and studies of special interest to physicists, engineers, chemists, biologists, mathematicians, computer programmers, and others engaged in scientific and technical work.

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quantitative data on the physical and chemical properties of materials, compiled from the world's literature and critically evaluated. Developed under a world-wide

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BIBLIOGRAPHIC SUBSCRIPTION SERVICES

The following current-awareness and literature-survey

bibliographies are issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service. A

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Superconducting Devices and Materials. A literature survey issued quarterly. Annual subscription: $30.00 . Send subscription orders and remittances for the pre- ceding bibliographic services to National Bureau of Standards, Cryogenic Data Center (275.02) Boulder,

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