MS report has been prepared

for information and record SSi*- *• ««

NATIONAL BUREAU OF STANDARDS REPORT

<y

9412

PERFORMANCE CHARACTERISTICS OF EXTERIOR WALLS

Progress Report for Period Edding June 30, 1966

Edited by

J . V . Ryan

to

Federal Housing Administration

U.S. Department of Housing and Urban Development

Washington, D.C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assur- ing maximum application of the physical and engineering sciences to the advancement of technology

in industry and commerce. Its responsibilities include development and maintenance of the national

standards of measurement, and the provisions of means for making measurements consistent with

those standards; determination of physical constants and properties of materials; development of methods for testing materials, mechanisms, and structures, and making such tests as may be necessary, particularly for government agencies; cooperation in the establishment of standard practices

for incorporation in codes and specifications; advisory service to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Govern- ment; assistance to industry, business, and consumers in the development and acceptance of commercial standards and simplified trade practice recommendations; administration of programs in cooperation with United States business groups and standards organizations for the development

of international standards of practice; and maintenance of a clearinghouse for the collection and

dissemination of scientific, technical, and engineering information. The scope of the Bureau’s

activities is suggested in the following listing of its three Institutes and their organizational units. Institute for Basic Standards. Applied Mathematics. Electricity. Metrology. Mechanics. Heat. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radiation Physics. Radio Standards

Laboratory:* Radio Standards Physics; Radio Standards Engineering. Office of Standard Reference

Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.* Materials Evaluation Laboratory. Office of Standard Refer- ence Materials. Institute for Applied Technology. Building Research. Information Technology. Performance

Test Development. Electronic Instrumentation. Textile and Apparel Technology Center. Technical

Analysis. Office of Weights and Measures. Office of Engineering Standards. Office of Invention and

Innovation. Office of Technical Resources. Clearinghouse for Federal Scientific and Technical

Information.**

•Located at Boulder, Colorado, 80301. ••Located at 5285 Port Royal Road, Springfield, Virginia, 22171.
NATIONAL BUREAU OF STANDARDS REPORT

MBS PROJECT

4-21-2405 September 9, 1966

MBS REPORT

9412

PERFORMANCE CHARACTERISTICS OF EXTERIOR WALLS

Progress Report for Period Ending June 30, 1966

Edited by

J . V . Ryan

to

Federal Housing Administration

U.S„ Department of Housing and Urban Development

Washington, D. Co

NATIONAL BUREAU OF STAI

for use within the Government. B

and review. For this reason, the j whole or in part, is not authorizi Bureau of Standards, Washington,

the Report has been specifically p

IMPORTANT NOTICE

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

accounting documents intended

ibjected to additional evaluation

isting of this Report, either in Office of the Director, National

the Government agency for which

lies for its own use.

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PERFORMANCE CHARACTERISTICS OF EXTERIOR WALLS

Progress Report for Period Ending June 30, 1966

Edited by

J . V . Ryan

Building Research Division

1. INTRODUCTION

The objectives of this project are to adapt or develop test methods and

techniques for the measurement of the performance characteristics of

exterior walls, and to provide values obtained by such tests when applied

to representative walls. This project was designed to bring under con- sideration all the characteristics of exterior walls and to determine which

are of importance. For the latter, means of measurement are sought and

values obtained. These are expected to form the basis for decisions as to

the levels of performance against which to judge walls of various types.

2. PROJECT PLAN

The plan of the project called for (1) an analysis of the functions of

exterior walls in order to develop a list of all characteristics and the

selection of those subject to physical measurement, (2) review of existing

test methods having potential applicability, (3) testing of representative

samples by these methods, (4) development of additional test methods and

apparatus as needed, (5) measurement of the performance characteristics of

samples of representative wall systems by all the various methods, and

(6) where possible, suggest limiting values for each of the significant

wall performance characteristics subject to physical measurement.

3.

ACTIVITIES

The item number (1) under Project Plan was completed in an earlier period,

except as review may be required in the light of progress under the other

items. Work has continued under items (2), (3), and (4). However, the

principal effort over the past six months has been under item 5. This work

is being carried out in all but one of the Sections of the Building Research Division.

As a result of conferences among the Division staff engaged in the project,

and with staff of the Federal Housing Agency, a set of six wall constructions

were agreed upon for submission to tests, per item (5) of the Project Plan.

Since the original selection of basic types, some modifications have become

necessary among the prefabricated walls due to changes in what has been

available on the market. A seventh wall was added at the request of the

sponsor. The present types are:

1. Framing : 2x4's, common pine or fir, 16 in. o.c. with firestops near midheight.
Exterior ; 1/2 in. insulating fiber sheathing nailed to studs;

1 in. air space; single wythe 4 in. common face brick, with ties

nailed to framing (through sheathing)

,

Interior; single layer of 1/2 in. aluminum foil backed gypsum

wallboard, nailed to studs with joints vertical, joints taped

and cemented, nailheads cemented; two coats of self-sealing

latex base paint.

2. F raising ; same as 1 above.

Exterior ; 1/2 in. insulating fiber sheathing nailed to studs;

1x6 air-dried select wood drop siding nailed through sheathing

to studs; painted per MPS.

Interior s same as 1 above.

3. Exterior ; 4 in. common face brick backed with 4 in. cinder

aggregate concrete block (3 oval hollow cores); each set

in mortar.

Interior : 1x2 wood furring, nailed vertically, at 16 in. o.c.,

with horizontal strips at top, bottom, and midheight; drywall

and paint as 1 above.

4. Sandwich wall ; (prefabricated) consisting of aluminum skins and

paper honeycomb core. Surface coatings (paint) as per normal

production of the manufacturer.

5. Sandwich wall : same as 4 except plywood skin on both faces.

6. Prefabricated : 18 ga galvanized steel Z-studs 24 in. o.c.; 18 ga

top and bottom channels; 2 in, of glass fiber insulation; interior

facing 1/2 in. foil-backed gypsum wallboard cemented on; exterior

facing 3/8 in. exterior grade plywood siding held by barbs integral to Z“Studs„

7. Framing : 2x4 's, common pine or fir, about 16 in. o.c., with let

in 1x4 diagonal brace.

Exterior : horizontal aluminum siding applied directly to the

studs, per FHA UM-27.

Interior s 1/2 in. gypsum wallboard applied with adhesive and

reduced nailing per manufacturers specifications.

For each of the above, enough material, or samples of prefabricated walls

will be obtained in a single order to provide specimens for all tests to

be carried out

.

- 2 -
3.1 Structural and Water Permeability - T. W. Reichard

3.1.1 Racking test

Four different wall constructions have been tested using the diagonal racking equipment

.

Six specimens of type 2 were tested; two each at three different edge loads.

Three specimens of type 7 were tested: one at each of the three different

edge loads. The results of these racking tests are given in table 1. It can be seen that if the edge-loading had any effect on the stiffness, or strength, of these panels it was obscured by the inhomogeneity of the

specimens. It should be pointed out that the type 7 specimens were tested

with the load applied parallel to the let-in brace; and that the strength

of the brace appeared to be the controlling factor in the strength of the

wall

.

Table 1. Racking Test Resul ts

Wall

type

Edge

Load

Horizontal Racking Load

at 0.2-in. Horizontal

Maximum movement in 8-ft. Length

lb/ft. lb/ft

.

lb/ft

.

c\i'| 04 0 1200 710

2- 630 1190 850

2~ 1250 1280 810

1 0 1010 620

1 630 710 390

7 1250 890 640

1 / Horizontal Racking Load = 0.707 Diagonal Racking Load

2 / Average of two specimens.

The results from the tests on wall types 4 and 6 have cast some doubt on the

suitability of any existing standard racking test. The controlling factor

in the strength, and rigidity, of wall systems constructed from individual

panels is in the strength of the connections and to a certain extent the

restraint provided by the floor and roof.

For instance the equivalent horizontal racking strength of a single 4 ft x

8ft type 4 panel was found to be approximately 425 lb/ft. Using 2 - 4 ft x 8ft panels connected as per manufacturer's recommendations the strength was only 180 Ib/ft for the 8ft x 8ft assembly. There is no doubt that the con- nections specified are inadequate, however there is also no doubt that, with

the restraint provided by the floor and roof, the wall system would come closer to utilizing the full racking strength of the individual panels.

- 3

-
3.1.2

Wind Load and Water Permeability Test

Wall types 4 and 7 were tested for both wind load and rain penetration.

Both types were very permeable to air; in fact so permeable that the air

supply was insufficient to provide the 50 psf wind load without special

sealing of the joints. Both walls were fairly elastic in their reaction

to the simulated wind load, but were not as stiff as the more-conventional

type walls (Type 2).

The through-wall water leakage of both walls, with 10 psf wind pressure, was considerable. Wall type 4 which was poorly sealed at all edges except

the floor joint started to leak immediately at a rate of about 160 lb/hr.

Wall type 7 started to leak in about 20 min. at about 2 Ib/hr.

3.1.3

Compressive and Transverse Load Tests

The testing of the walls, using the ASTM E-72 procedures is continuing.

The transverse- load test results will be correlated with the results from

the tests in the wind and rain test chamber. This will be done in order to

check the effect of the edge restraint (in the chamber) on deflection.

The compressive strength of types 4 and 6 was 3100 lb/ft., type 7 was 5600

lb/ft. while type 2 was 10,200 lb/ft. Wall type 7, which failed due to

buckling, exhibited no sign of any type of permanent distress after removal

of load. All other walls tested exhibited some form of structural damage

after testing.

3.2 Smoke Production - D. Gross

A detailed report on the smoke measurement apparatus was appended to the

report for the period ending December 31, 1965. The information contained

therein was prepared for presentation as part of a symposium on smoke

held during the Annual Meetings of the American Society for Testing and

Materials. The manuscript had been given appropriate review and approval

by the National Bureau of Standards and the Federal Housing Administration

prior to being offered for presentation at the symposium. It is expected

that ASTM will publish the symposium papers, probably as one of their

Special Technical Publications.

Specimens from the typical walls (in Section 3) will be tested as they are

obtained. In some cases extra materials are to be ordered: in others

samples will be cut from large panels after the latter have been subjected

to racking or other tests. The specimens will be subjected to three fire

test methods: 1J the smoke production test, the details of which were

reported with the last report; 2) the surface flammability test of ASTM E162

and 3) a flame penetration test using the apparatus of Federal Specification SSA-118b.

3.3 Air and Water Vapor Transfer - T. K. Faison

Because of mechanical failures in the refrigeration system, progress on the

testing of the six typical wall specimens for performance characteristics

has been minimal. The contractor having the responsibility to furnish
the refrigeration system according to specifications, has had great difficulty in getting the system operational and maintaining the required control

of conditions. Much of the delay has been caused by the mechanical failure

of a number of compressors and the break-down of the refrigerant pump.

Once the refrigeration system seems to be functional, a short period of

operation will be required to check cut the entire system to determine if

all phases of control necessary for the test (temperature, humidity, and

pressure control, air flow rate measurement, physical deflection, etc.) can be achieved. The control features not directly related to the refrigeration

system have been tested individually and seem to be adequate for their

specific function. The chambers, both warm and cold, have performed very

satisfactorily during the periods when the cold side temperature was at

0 F and the warm side temperature was at 70 F » The trial wall of 1/2-in.

plywood has provided the barrier between the two spaces and control of

temperature and humidity on the warm side has posed no problem.

Upon satisfactory control of the cold side temperature, the activity on the

program will be increased to achieve maximum results prior to the move to

Gaithersburg

.

3.4 Weathering. Discoloration. Abrasion, etc. - W. C. Wolfe

Additional tests were performed on siding materials by the same methods

described in previous reports and by different methods. Steel siding is

being introduced for uses similar to aluminum siding and it was considered

important to compare both products. The effects, on performance, of the

advantages and disadvantages of each product need to be investigated. Steel

is harder and stiffen than aluminum and would be expected to have greater

dent resistance; there should be less damage during installation from bending

or distrotion in handling; and there should be less "oil canning" or wavi- ness after installation. However, steel is harder to cut than aluminum.

Aluminum can be cut with ordinary tinsnips or scored with a knife, while

steel requires special airplane shears. Also steel will rust if the coating

is scratched through.

Weatherometer Tests

In order to determine whether steel siding presents a corrosion problem, as compared to aluminum siding, weatherometer tests were run on specimens cut

from both types. The aluminum siding came finished with a thin, smooth coat

of acrylic enamel. The steel siding came in two finishes, one a thin, smooth

coating and the other a thicker, textured coating called "Plasticol ", Exposure to a xenon arc in a dry atmosphere for 1172 hours had no effect on any of the three specimens tested, one of each type of siding. Another set

of three specimens was exposed for 1100 hours in a carbon arc weatherometer

with a cycle of 3 minutes tap water spray and 17 minutes dry. The aluminum

and the smooth finish steel specimen were unaffected but the Plasticol

coated steel specimen was stained yellow, indicating rust.

- 5

-
3.5 Impact Resistance W. C. Wolfe

While no tests have been performed with a simulated hail gun, a desk study

of the subject was continued. According to early investigators, a 2 1/2-in.

diameter hailstone has a terminal velocity of about 120 ft/sec, while a 3-in. diameter hailstone has a terminal velocity of about 130 ft/sec.

J. A. P. Laurie (1) reported the design and construction of an air gun which

would fire an ice sphere 2 1/2 in. in diameter, weighing 110-150 grams, up

to 150 ft/sec, with an air pressure of 180 psi. Complete drawings have

been obtained which would enable construction of this air gun. A gravity

system would require too high a drop to be practicable. For low velocities

of this order, air resistance can be neglected. From the classic formulas,

it can be seen readily that a 224 foot drop is required for a terminal velocity of 120 ft/sec.

The method of preparing the ice spheres or artificial hailstones is important.

Laurie (1) drilled cores from a block of ice and molded them into a roughly

spherical shape. Ice spheres made by pouring water into a mold and then

freezing are reported not to give the same results in impact tests. Natural

hailstones are formed from the inside out in layers, an onion type structure. This might be simulated by freezing spheres in layers by successive

dipping in ice water and freezing.

Private communication with Mr. Boardman, who was acquainted with Laurie and

his work, indicated that Laurie and others found that the steel ball drop

test did not simulate hail damage. Some tests were performed with a pendulum

and impact tup at a drop height of 12 in. The tup was chisel shaped, the

chisel being at a 10-degree angle. This did not break ceramic materials,

as asbestos cement shingle, as readily as a ball or rounded plunger, which

gives a point impact, but dents soft material, as aluminum or wood, more

readily than a round tup or ball.

We considered the possibility of constructing our own pendulum impact machine. The tup would be a 1-3/4-in. diameter steel ball and the pendulum

would be an aluminum bar 60 in. long. The drop height could be varied up

to 120 in.

A high speed impact test machine was designed and constructed by United

Engineers, Inc. of Boston, Mass, and Fabric Research Laboratories, Inc. (2)

The machine was designed to test parachute materials, such as nylon webbing.

It employs a gas gun with 2 1/2-in. bore, which fires missiles up to 10 lbs

with velocities from 200 to 750 ft/sec.

There is also the possibility of transferring momentum from a projectile to an ice sphere. The ice, to be molded in a refrigerator, would be 2 1/2 to

3 in. in diameter and held in place on the siding with some type of special

holder or clamp. A projectile could be fired at the ice sphere from an ex- isting air gun used for textile testing at the Bureau. This gun fires a projectile 5/8-in. in diameter, weighing 50 grams. In order to transfer

momentum without rebound and avoid blast, it would be necessary to place

the specimen at least 12 in. from the muzzle.

6

-
Another possibility is a sling-shot type machine (3), for which complete

drawings have been obtained. The machine uses heavy rubber bands about

1/2 in. in cross section and 1 ft in diameter.

Probably the best and certainly the most convenient possibility is the

commercial Avalauncher, Mark 14, manufactured by Diamond King, Inc., 220

Standard Street, El Segundo, California and purchased by Mr. Sidney Greenfeld of the Asphalt Roofing Industry Bureau (ARIB) . Mr. Greenfeld is

located physically at the Bureau and the equipment will be available. It

consists of a compressed air or gas operated gun, readily portable, with a barrel 3 1/4 in. ID and 46 in. long, producing muzzle velocity of 300 ft/sec

with normal working pressure. Ice spheres would be made by Mr. Greenfeld

at the Bureau, using a special mold.

A commercial machine, the Gardner Variable Impact Tester, was purchased from

Gardner Laboratory, Inc. of Bethesda, Maryland. This machine consists of

a cast aluminum base plate, a 2 lb steel rod impact weight, a hardened steel

round-nosed punch, a removable punch die and punch holder, and a slotted,

plated brass tube having graduation marks in which the selected impact rod

is lifted and dropped, and a bracket to hold the tube in a vertical position.

A pivot arm with hand knob aligns the punch and die and allows removal of

the punch so that other punch shapes and sizes can be inserted if desired.

The instrument is furnished with a 5/8- in. punch. Direct or reverse impact

resistance is determined by subjecting either side of a panel to an impact

of 2 in. -lb up to 80 in. -lb, in interval steps of 2 in. -lb. The range of

the device may be doubled by substituting a 4- lb impact weight for the

2-lb weight. The panel is place over a 5/8- in. hole in the base plate. The

steel rod is raised by lifting the pin, which extends from the rod through

the slot in the tube. The rod is raised until the pin coincides with the

desired graduation mark on the slotted tube, and then dropped. The test

panel is then examined for flaking, cracking or deformation. Another method

of operation is to place a steel ball in the tube so as to rest upon the

test panel. The rod is then raised and dropped on the ball and the test

panel examined as before.

For one series of tests (Tables 1 and 2) a plywood frame was built similar

to but smaller than the one specified in ASTM 1037-64, "Standard Methods of

Evaluating the Properties of Wood-Base Fiber and Particle Panel Materials".

Two pieces of plywood frame were made, each 8- by 8- in. by 1/2 in. thick,

with a square hole in the center, 3- by 3- in. A third piece of plywood

was cut 8- by 8- in. by 1/2 in. thick. Each of the three pieces had

corresponding 1/4-in. diameter holes to enable specimens to be clamped between two pieces. For "unsupported" impact tests, the specimens were clamped

between the two plywood pieces with the square holes. For "supported"

impact tests, specimens were placed on the solid piece of plywood (without

hole) and one of the pieces of plywood with a square hole placed on top,

then the two pieces clamped together with the specimen in between. Test

specimens were cut 4 in. square and positioned so that the border around

the square hole was as even as possible.

- 7-
In another series of tests, 4-in. square specimens of materials were tested

using the Gardner Variable Impact Tester already described. The 2-lb

plunger was used and force was expressed in in. -lb, the value being twice

the drop height in inches

.

In a third series of tests (Tables 4 and 5), specimens were mounted in the

manner actually used in houses, on a frame, 18- by 27- in., and tests performed as on page 12, NBS Report 9056, the progress report for this project

for the period ending December 31, 1965.

- 8

-
Table 1. Drop-Impact Tests, at 90-degree angle, on 4- by 4- in. pieces of

house siding, fully supported on plywood. Visible damage from 3-ft. drop

(28 in-lb) of 1 3/4-in. steel ball, weighing 0.79 lb.

Siding Material Visible Damage

Aluminum (Brands A, B, C), 22 mils

thick

Deep dent in each specimen

Cement asbestos shingle (Brands A

and B); 3/16 in. thick

Slight dent in each specimen

Cement asbestos board containing

wood fibers, factory primed and

factory painted; 3/8 in thick

Dent in each specimen

Hardboard coated with polyester;

1/2 in. thick

No effect

Plywood coated with Tedlar;

1/2 in. thick

Dent

Steel; 19 mils thick Deep dent

Wood - Douglas fir; 3/4 in. thick Deep dent

- 9-
Table 2. Drop-Impact Tests^ at 90 degree angle., on 4- by 4- in. pieces of

house siding using a 1 3/4 in, diameter steel ball, weighing 0.79 lb.

Siding Material Ht. of Impact

Drop. Force.

ft. in a -lb

Aluminum, 22 mils

thick

Brand A 1/2 4.7

1 9 .

5

3 28

Brand B 1/2 4.7

3 28

Brand C 1/2 4.7

3 28

Cement asbestos^ 3/16

in. thick

Brand A 1 9.5

2 19

3 28

Brand B 1 9.5

2 19

3 28

Cement ashes tos^ Containing Wood Fibers,,

3/8 in. thick

Factory primed spe- 1 9.5

cimen 2 19

3 28

Factory painted 1/2 4.7

specimen 1 9.5

3 28

Hardboard Coated with 3 28

Polyester,, 1/2 in. 6 57

thick

10 95

Plywood coated with 1/2 4.7

Tadlar, 1/2 in. 3 28

thick

Visible Damage Depth

of Dent,

mils

Dent; some distortion 49

Deeper dent; more distortion

Deep dent; deformation

73

Dent; deformation

Deep dent; deformation

50

Dent; slight deformation

Deep dent; deformation

32

No effect

Radiating cracks on underside

Radiating cracks all the way

No effect

Crack underneach

through

Rad dating cracks all the way through

Slight dent 3

Slight dent 10

Deep dent; break in coating;

slight cracking underneath 25

Slight dent 6

Dent 7 Deeper dent 26

No effect

Dent; circular mar; cracking

on underside 9

Dent; more pronounced circular

mar; break in material on underside 10

Very slight dent 2 Dent 12

- 10 -
Table 2 (con't)

Siding Material Ht. of Impact Visible Damage Depth

Dr °P. F orce. of Dent

ft. in. -lb mils

Steel, 19 mils thick 1/2 4.7 Dent; no deformation 10

1 9.5 Dent; no deformation 35

Wood - Douglas fir,

3/4 in. thick 1/2 Mar 13

1 9.5 Dent

- 11 -
Table 3. Drop-Impact Tests, at 90 degree angle, on pieces of house siding

using a Gardner Variable Impact Tester.

Siding Material

Aluminum, 22 mils thick

Brand A

Brand B

Brand G

Cement asbestos, 3/16 in.

thick

Brand A

Brand B

Cement asbestos containing

wood fibers, 3/8 in.

thick

Factory primed

Impact

F orce

in . - lb

Visible Damage Depth of

Dent

mils

2 Dent 30

4 Dent 50

6 Dent 67

12 Dent 89

24 Dent 130

36 Dent 147

2 Dent 35

4 Dent 50

6 Dent 74

12 Dent 96

24 Dent 125

36 Dent 147

2 Dent 23

4 Dent 44

6 Dent 52

12 Dent 84

24 Dent 113

36

4

Dent

Slight mar

134

6 Dent; slight bulge in back of material

12 Dent; bulge and crack in back of material

24

36

6

Deeper dent; sheet nearly punctured

Sheet punctured

Practically no effect

12 Dent; bulge and crack in back of material

24 Deeper dent; material nearly punctured

36 Material crushed all ithe way through

4 Dent 4

6 Dent 11

12 Dent 26

24 Dent 43

36 Dent 78

- 12 -
Table 3 (con't)

Siding Material Impact Visible Damage Depth of

F orce Dent

in. -lb mils

Cement asbestos containing

wood fibers, 3/8 in.

thick

Factory painted 4 Dent 7 6 Dent 14

12 Dent 20

24 Dent 40

36 Dent 63

Hardboard coated with 6 Dent 2 Polyester, 1/2 in. thick 12 Dent 3 24 Dent 7 36 Dent 8

Plywood coated with Tedlar, 4 Dent 3 1/2 in. thick 6 Dent 5 12 Dent 7 24 Dent 17

36 Dent 31

Steel, 19 mils thick 4 Dent 35

6 Dent 43

12 Dent 60

24 Dent 82

36 Dent 95

Vinyl, 1/16 in. thick 12 None

24 Dent 43

36 Dent 91

Wood ~ Douglas fir. 4 Dent 12

3/4 in. thick 6 Dent 17

12 Dent 17

24 Dent 33

36 Dent 47
Table 4. Drop-Impact Tests, at 90 degree angle, on sections of house siding

mounted on an 18- by 27- in. wooden frame, using a 1 3/4-in.

diameter steel ball. Weight of ball 0.79 lb.

Siding Material

Aluminum siding backed

with plastic foam (aluminum, 21 mils thick;

backing 3/8 in. thick)

Height of

drop, ft

Aluminum- corrugated

paper sandwich

10

1

3

6

Visible Damage Resulting from Drop- Impact'

on Flat Surface on Butt or Edge

Dent about 3/8 in. diam. Slight bulge, 3/8 in.

diam.

Noticeable dent, 3/4 in. Dent, marked deformation, 5/8 in.

Dent, 5/8 in. diam.

Large, deep dent, 1 in.

Dent, marked deform.,

7/8 in.

Marked dent, deform.,

1 1/8 in.

Dent approx. 40 mils deep and 3/4 in. diameter

Dent approx. 100 mils deep and 1 in. diameter

Dent approx. 160 mils deep and 1 1/4 in. diam.

10

Steel, smooth coating, 1 22 mils thick

3

6

10

Steel, heavy textured 1 coating, 22 mils thick

3

Dent approx. 210 mils deep; aluminum sheet bent

and deformed; damaged area about 2- by 2- in.

Very slight dent, 3/16 in. Very slight dent,

Shallow dent, 1/4 in.

Dent, 3/8 in. diameter

Dent, 1/2 in. diameter

No damage

Dent, 1/4 in. diameter

3/16 in.

Shallow dent, crease;

very slight bulge;

damaged area 1/2 in.

diameter

Dent, deform., 3/4 in.

Dent, deformation,

bulge; damaged area

7/8 in. diameter

Very' slight dent

Dent; deform.; 1/2

in.

- 14 -
Table 4 (con't)

Siding Material 1

Steely hea-^ry textured

coating, 22 mils thick

Height of Visible Damage Resulting from Drop-Impact

drop, ft. on Flat Surface on Butt or Edge

6 Dent, 3/8 in. diameter Dent; deform.; 3/4

in.

10 Dent, 9/16 in. diameter Dent; deformation;

pronounced bulge;

13/16 in. damaged

area

NOTES:

1. Size of dents or damaged areas in inches maximum diameter.

2. This product consisted of two sheets of painted aluminum with three in.

of corrugated paper inside. The specimens were tested by placing on the

floor and were not mounted on a frame as were the other specimens.

- 15 -
Table 5. Drop-Impact Tests, at 45 degree angle, on sections of house siding

mounted on an 18- by 37 - in. wooden frame, using a 1 3/4-in. diameter steel

ball. Weight of ball 0.79 lb.

Siding Material Height of Visible Damage Resulting from Drop-Impact

drop, ft on Flat Surface on Butt or Edge

Aluminum siding backed

with plastic foam (aluminum, 21 mils thick;

backing 3/8 in. thick)

1

3

6

Slight dent about

3/8 in.

Dent about 1/2 in,

diameter

Dent and scuffing;

damaged area 1/2 in.

wide and 7/8 in. long

in direction of impact

Crease; damaged

area 3/8 in.

Dent and deformation;

damaged area about

1/2 in. diameter

Dent; deformation;

scuffing; damaged

area 7/8 in. wide

Steel-smooth coating,

22 mils thick

Steel, heavy textured

coating, 22 mils thick

10

13

6

1

3

Large, deep dent, 1 in, wide

No test run No test run

Dent; scuffing; damaged area 5/16 in.

wide; 1/2 in. long

No damage

Shallow dent, 3/8

in

.

Marked dent; deformation; damaged area

1 1/8 in.

No damage

Dent; crease; scuffing; damaged area

3/8 in. wide

Dent; crease; scuffing; small piece of

finish removed to bare

metal; damaged area

7/8 in. wide.

Very slight dent

Dent; crease; 1/2 in.

wide

6 Dent; scuffing; Dent; deformation;

damaged area 5/16 7/8 in. wide

in, wide by 1/2

in. long

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Tests on specimens supported by plywood (Table 1) did not show up weaknesses

in the materials as observed in practice or in tests on simulated house sec- tions (Tables 4 and 5). Aluminum and steel gave nearly the same results,

whereas Tables 4 and 5 show that aluminum is bent and deformed on impact

more readily than steel, even though both might show about the same size

dents with a given impact.

Tests on 4- by 4- in. specimens clamped over a 3-in. square opening were

more realistic. Aluminum dented much more than steel and showed deformation.

Cement asbestos cracked on impact. Hard board cracked on severe impact,

which might indicate behavior of lapped boards on unsupported areas.

The Gardner Variable Impact Tester failed to show differences between

aluminum and steel.

The tests showed that hardboard is definitely more impact resistant than

other materials tested. Aluminum, cement asbestos board containing wood

fibers, plywood, steel, and wood are dented on impact and aluminum is deformed, especially if struck on the butt or edge. However, the serviceability of the above materials is not affected. Cement asbestos shingle

is cracked by moderate impact, which leaves an opening for entry of moisture and affects serviceability. Materials might be classified as:

1. Impact resistant: Not affected by moderate impact; severe impact

damages appearance and serviceability. (For example, hardboard)

2. Marred by impact: This indicates that the appearance of the

material is affected by moderate impact, but not the serviceability. (Moderate impact dents aluminum, cement asbestos board

containing wood fibers, plywood, wood, and steel. Severe impact

might puncture aluminum, will crack cement asbestos board con- taining wood fibers, and splinter plywood and wood.)

3. Non-resistant to impact: Serviceability is destroyed by moderate

impact. (Cement asbestos shingle).

3.6 Dynamic Thermal Performance of Exterior Walls - B. A. Heavy

NBS Report No. 9410 "Dynamic Thermal Performance of Exterior Walls" has been

prepared and, after reproduction, copies will be furnished as an addendum to

this progress report.

The report concerns the development of a laboratory test method whereby the

characteristics of a composite non-homogeneous exterior wall construction, in

regard to thermal behavior under conditions of periodically-varying exterior

insolation and air temperatures, can be effectively measured. A test method

for such measurements is not now available, although the importance of such

information is increased by current trends to light-weight wall construction.

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A schematic model for a test apparatus and method was devised, and mathematically analysed to provide a rigorous basis for two thermal parameters - an "effective thermal conductivity" and an "effective dif f usivity " for a composite

nonhomogeneous wall to characterize it as a homogeneous wall of equal overall thickness and thermal performance under sinusoidally-varying exterior

conditions. To do so, however, it is necessary to fix upon a definite period

for the sinewave; a 24-hr period is satisfactory and comports reasonably with

actual exterior variations. These matters are presented in the report. It

will be of interest that in mathematically examining two two-layer composite

walls, identical except that in one the outdoor face is the indoor face of

the other, large differences in effective conductivity and effective

dif f usivity were found, for a 24-hr period.

A chief conclusion of the report is that it is experimentally feasible, and

it is believed practically feasible, to build and operate an apparatus for

the determination of the effective thermal parameters of composite walls.

The parameters determined would serve to characterize different walls and to

indicate significant differences between them in regard to periodic heat flow.

By testing various walls, of types that are conventional or considered generally satisfactory in service as regards periodic thermal performance, the

ranges of values of the parameters that represent usual or satisfactory performance can be developed, against which to compare values for new or different kinds of wall. Thus, the construction and operation of the apparatus

would enable a step forward in assessing the qualities of wall constructions

from the point of view of realistic thermal performance.

There is a further possibility of potential importance. The parameters

obtained refer to those of a homogeneous wall of thickness and thermal re- sponse equal to that of the tested composite wall. It is feasible, therefore,

with these parameters to calculate mathematically the thermal response at

any time of the indoor side of the wall to periodic outdoor variations of

conditions. To do so, as a practical matter, would require use of a digital

computer program, which could readily be furnished, and used at low cost.

However, an essential input for this computation is a statement of the ex- terior variable climatic condition appropriate for a given case as a design

condition. At present, such design conditions, for periodic exterior exposures, are not available, and undoubtedly their development would be a major

undertaking. Such information is not needed for the more limited task of

intercomparing one wall with another, but is necessary to enable designers

to calculate heating or cooling loads realistically under periodicallyvarying outdoor climatic conditions.

Since a test method is feasible, and is essential for developing information

needed for characterizing composite wall constructions in regard to periodic

heat flow performance, it is recommended that a wall-testing apparatus be

built for the purpose. A start in the direction of developing testing facilities and information for taking account of the variable periodic heat

transfer performance of walls is of growing importance at this time, in view

of the increasing use of air conditioning in buildings and dwellings, and

of trends toward the use of light-weight and panel constructions.

- 18-
References

(1) J. A, P. Laurie, "Hail and Its Effect on Buildings", C.S.I.R. Research

Report No. 176, National Building Research Institute Bulletin 21 . Pretoria, South Africa, August, 1960, pp . 1-12.

(2) Chauncey C. Chu, Robert J. Coskren, and Henry M. Morgan, "Investigation

of the High Speed Impact Behavior of Fibrous Materials", WADD Technical

Report 60-511, Part I. Design and Apparatus, Fabric Research Laboratories, Inc., September, 1960, Wright Air Development Division, Air

Research and Development Command, USAF, Wright-Patterson AFB, Ohio.

(3) Malcolm N. Pilsworth, Jr., "Tensile Impact on Rubber and Nylon",

Technical Report PR-3, Thermodynamics Laboratory, May, 1962, QM

Research and Engineering Command, U.S. Army, Pioneering Research Division, Natick, Massachusetts.

- 19 -

USCOMM-NBS-DC