NOT FOR PUBLICATION OR FOR REFERENCE

FOR GOVERNMENT USE ONLY Copy No.

NATIONAL BUREAU OF STANDARDS REPORT

8052

PROPOSED SPECIFICATION OF REQUIREMENTS FOR INSULATIONS

AND SELF-DRYING FLAT-ROOF CONSTRUCTIONS AT NORMAL OCCUPANCY

by

F. J. Powell and H. E, Robinson

Heat Transfer Section

Building Research Division

Final Report

to

Office of the Chief of Engineers

Bureau of Yards and Docks

Department of the Air Force

Washington 25, D» C a

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

^ 27- 0 o

'ilU

MdT-FOR PuffETCATTON 0R F0R REFERENCE
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Documents, Government Printing Office, Washington 25, D.C.
NOT FOR PUBLICATION OR FOR REFERENCE

FOR GOVERNMENT USE ONLY

NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1006-12-10462 129 Jmly 1963 8052

PROPOSED SPECIFICATION OF REQUIREMENTS FOR INSULATIONS

AND SELF-DRYING FLAT-ROOF CONSTRUCTIONS AT NORMAL OCCUPANCY

by

F a J. Powell and H, E„ Robinson

Heat Transfer Section

Building Research Division

Final Report

to

Office of the Chief of Engineers

Bureau of Yards and Docks

Department of the Air Force

Washington 25 , D„ C*

IMPORTANT NOTICE NATIONAL BUREAU OF S

for use within the Government

and review. For this reason, 1 whole or in part, is not auth Bureau of Standards, Washinj

the Report has been specifical

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

ress accounting documents intended

s subjected to additional evaluation

re listing of this Report, either in he Office of the Director, National

jy the Government agency for which

copies for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NOT FOR PUBLICATION OR FOR REFERENCE

FOR GOVERNMENT USE ONLY

PROPOSED SPECIFICATION

of

Requirements for Insulations

and

Self-Drying Flat-Roof Constructions

at

Normal Occupancy

Table of Contents

1. Introduction -. 1

2. The Specification

Section L Scope 3

Section II. Applicable Publications 4

Section III. Performance Requirements 5

3. Discussion 14

4. Examples of Constructions Found Acceptable 19

5. References 21

Figure 1 23

Proposed Specification of Requirements

for

Insulations and Self-Drying Flat-Roof Constructions

at

Normal Occupancy

by

F. J. Powell and H. E. Robinson

1. INTRODUCTION

In this report, a draft of a proposed specification is given

for complete insulated flat-roof designs having the property of selfdrying, if wet, through their undersurfaces, as a result of summer seasonal exposure with daily solar heating of the roofing. In short, a roof design to be admitted by this specification should be capable of

self-drying in place, if wetted, to a degree which allows the construction to function with fair insulating value.

To ascertain such performance, it is necessary to consider the

entire insulated roof assembly, or ensemble of components, excluding here

only the built-up roofing which is common to all flat roofs, and which

can be regarded as simply a practically vapor- impermeable membrane subject to temperature changes due to climatic variations.

Present typical designs for insulated flat roofs generally

provide a selected arrangement, possibly with options, of a supporting

deck (concrete slab or plank, steel, or wood, or formboard) , with a

suitable thickness of insulation (factory-made board or slab form, or cast-in-place insulating concrete) placed over it, this being covered

by the roofing. The associated specification generally concerns the
- 2 -

required properties, and method of application, of the individual com- ponent materials, and often requires a selected vapor barrier placed

between the deck and the insulation. The vapor barrier is usually included in an effort to prevent ingress of vapor from the building,

with possible condensation and wetting of the insulation. However,

what happens to the performance of the construction if the roofing or flashing leaks accidentally, or if the insulating materials were wet

or damp when placed, or when roofed over? In such case, the vapor

barrier effectively prevents or slows the drying of the wetted insulation, and the insulating effect of the construction is seriously

impaired [see References 1, 2 and

The solution to such almost inevitable accidental wetting of

a construction is to provide a roof design that will dry out in place

and under service conditions, once the roof leak or source of accidental moisture entry is corrected. It has not proven feasible to

evaluate the self-drying ability of a proposed construction simply from

data on the properties of the components. It seems necessary, at the

present time, to conduct a suitable test of the performance of a proposed construction. This specification refers to a test method and

procedure developed for this purpose, and gives quantitative criteria

for acceptability based on current experimental data. This report presents also a discussion of the specification requirements and lists,

for guidance, several insulated flat-roof constructions which tests

have indicated have adequate self-drying characteristics.
- 3 -

The test method and procedure on which this specification is

based are described in detail in Reference 4 (Method 2). Figure 1

illustrates in a general way the possible behavior of an acceptable

construction under test, in response to the schedule of conditions or

events indicated. It will be noted that the criteria for acceptability

given later concern both the moisture content of the construction and

its insulating effect (thermal resistance).

2. THE SPECIFICATION

The following specification gives minimum requirements . The

use of equivalents or better is permitted.

Section I_. Scope

This specification covers the insulating and self-drying performance requirements of insulated flat-roof constructions intended for

normal occupancy buildings. Normal occupancy spaces in buildings are defined here as those in which the dew-point temperature does not exceed 60° F, which corresponds to a relative humidity of 50 percent at

80° F dry bulb. Laboratory tests are specified for simultaneously

determining insulating value and moisture content. The testing procedure requires exposure of a sample of the proposed construction to

repeated daily cycles of simulated in-service environmental conditions

of temperature and relative humidity, starting with the specimen containing normal construction moisture. The tests required cover the

determination of: (a) The time required for the specimen to expel initial construction moisture by a process of self-drying to an approximate
- 4 -

moisture content equilibrium when exposed to a simulated summer exposure condition; (b) rate of moisture gain during an immediately following winter exposure condition; (c) duration of a second summer exposure condition required to expel the winter-gained moisture; (d) selfdrying performance of the specimen during a summer exposure condition

after it was wetted with water in simulation of a roof leak. The tests

include simultaneous measurement of insulating effect during these

exposures. Adjunct laboratory tests to determine particular physical

properties of the component materials are also specified.

The specification sets limits for the performance of an ac- ceptable construction. These are illustrated in Figure 1.

Section II . Applicable Publications -

The publications listed here or their latest revisions form

a part of this specification to the extent indicated by reference

thereto.

a. American Society For Testing And Materials

(1) Measurement of Effect of Moisture on Heat Transfer

Through Insulated Flat-Roof Constructions, ASTM

Special Technical Publication No. 312, Symposium

on Testing Building Constructions, pp. 35-66, 1962.

(2) Standard Method of Test For Thermal Conductivity of

Materials By Means of the Guarded Hot-Plate: ASTM

Designation C 177.

(3) Tentative Methods of Test for Water-Vapor Transmission of Materials in Sheet Form: ASTM Designation E96-55T (Method A).

(4) Tentative Methods of Test for Water-Vapor Transmission of Materials Used in Building Construction:

ASTM Designation C355-59T (Desiccant Method).
5

Section III . Performance Requirements

The construction shall have performance characteristics as specified below when evaluated in accordance with the methods referenced

or described.

a. Thermal Insulating Value

The criterion of insulating performance of the construction

shall be a thermal resistance ratio, Rt /R^. Rt is the average thermal

resistance of the specimen over the total test period, evaluated as described below. Rd is the dry thermal resistance as calculated on the

basis of test results for the thermal conductivity of the dry components. The minimum acceptable value of Rt /R^ shall be 0.6. The thermal

resistance of the construction shall be reckoned from its underside

(indoor) surface to the top surface of the construction underneath the

roofing.

The thermal resistance of the construction as tested, Rt , shall

be determined daily (usually 5 days per week) by using the National

Bureau of Standards Calorimeter Plate Method (Method 2) of test described in ASTM STP No. J>\2. [applicable publication a(l)]. The individual daily measured values of thermal resistance of the construction

shall be averaged for each week. The average of the weekly averages,

over a period totalling J7 weeks (the 29th week is excluded from this

average) constitutes the thermal resistance, Rt, of the construction

as tested. The total test time specified is calendar weeks. (See

attached Figure 1.)
- 6 -

The thermal conductivity of the dry materials used in the

specimen shall be determined at 75° F mean temperature using the method

of test ASTM C 177. The thermal resistance, Rn , of each component

shall be calculated using the formula Rjj — Xn/kn , where is the thick

ness of the component in inches and is its thermal conductivity in

Btu/hr ft2 (deg F/in.). The thermal resistances of the tandem components shall be summed (R^ + R^, . . . etc.) to determine the total . calculated dry thermal resistance, R^, of the construction.

b. Self-Drying Time for Initial Construction Moisture

and Equilibrium Moisture Content

The maximum testing time under the first summer exposure con- dition for the construction to expel initial construction moisture by

self-drying to a moisture content equilibrium shall be 16 calendar

weeks. Specimen weight loss shall be determined from daily weighings,

using scales sensitive to 0.01 lb., made simultaneously with the daily

thermal resistance measurements. The average of the daily weight observations for each week constitutes the average gross specimen weight

Gt for that calendar week. The gross weight, Gt, is the sum of the

actual net specimen weight Nt end a tare.

Weight measurements and thermal exposure and testing shall

begin immediately upon fabrication and installation of the test specimen. The start shall in no case be later than one week after castin-place components are poured. When installed, component materials

shall be in a moisture condition similar to that to be expected when

roll roofing would be applied over such a construction in the field
7

that is, materials shall be not more than air-dry, and cast-in-place

components shall not have been subjected to air-drying for longer than

one week after pouring.

The specimen shall be considered to be at an approximate

moisture content equilibrium during exposure testing when its change

A

of weight, Wt , does not exceed 0.05 lb/ ft 2 (week) for 2 consecutive

weeks

.

c. Equilibrium Moisture Content

The value of the approximate equilibrium moisture content of

the construction achieved as a result of self-drying at the conclusion

of the first summer exposure period shall be evaluated by means of the

ratio Mt/Mc> where M^. is the average specimen moisture content at the

end of the first 16-week summer exposure period. Mt is evaluated as

(i/^[(Gt

- Gf) + (Nf - N^) ] where A is the plan area of the specimen,

Gt is defined above, Gf is the gross specimen weight after week 38 and

just before determining (Nf - N<j) , which is the loss of total weight

of the net specimen on oven-drying its components to constant weight.

M^, is the calculated moisture content based on equilibrium hygroscopic

moisture content determinations of the component materials, and is defined below. The maximum acceptable value for the ratio Mfc/Mc shall

be 2.0.

The equilibrium hygroscopic moisture absorption of each component material shall be determined by exposing a conveniently- sized

sample having a thickness of at least 1 inch and an exposed surface

area of about 1/2 ft2 to a uniform temperature of 75® F + 2* and a
8

relative humidity of 90 percent + 3 percent until the sample shows no

further change of weight. The dry weight of the sample shall then be

determined by oven-drying it to constant weight at a temperature commensurate with the use limit of the material. For drying most building mate

rials an oven temperature of 215° F can be used but for some materials

the softening point temperature or other factors must be observed. The

equilibrium hygroscopic moisture content, Me, in lb/ft2

is calculated

as follows:

x = thickness of each component material, in. = constant weight of each component specimen at 75* F

+ 2* and 90% -f 3% relative humidity

W^ = constant weight of each component specimen after ovendrying

d. Regain of Moisture- -Winter Exposure Conditions

The maximum permissible average rate of moisture regain under

winter test exposure conditions shall be 0.05 lb/ft2 (week) . The time of

exposure to determine the average rate shall be the six calendar weeks

immediately following the first summer exposure period at the conclusion

of which an approximate moisture content equilibrium was established.

e. Summer Self-Drying Time for Winter Regain Moisture

The maximum permissible testing time under the second summer

exposure period for expulsion by self-drying of moisture gained under

where p = dry density of each component material, lb/ft3
9

the first winter exposure period (d. above) shall be six calendar weeks.

The second summer exposure test shall immediately follow the first winter

exposure period. The specimen shall dry to a moisture content not greater

than that at the end of the first summer exposure period.

f. Summer Self-Drying Time for a Simulated Roofing Leak

During the second summer exposure period and following e.

,

above, a roof leak shall be simulated by adding water to the center of

the upper surface of the top component material of the specimen in an

amount equal to 10 percent of the total specimen volume.

In order to facilitate water admission and its lateral distribution, a small well 1/8-inch deep and 1 inch in diameter shall be made

if necessary in the upper surface of the top component of the specimen,

directly under the water feed tube through the calorimeter plate, and

one layer of well-washed cotton muslin 1 inch less in size than the specimen shall be interposed without folds between the upper surface and the

calorimeter undersurface. For admission, the head of water over the ca- lorimeter plate shall not be more than 6 inches. The maximum time allowable for admission of water shall be one week. If the full 10 percent

by volume cannot be introduced in this time, the amount actually introduced shall be noted. If dripping of water from the undersurface of the

specimen occurs, the rate of admission shall be slowed to prevent dripping,

if possible. Thermal resistance values obtained during this week shall

not be used when averaging to determine the test thermal resistance, Rt

.

The maximum allowable exposure time for expulsion of added

water by self-drying during the second summer exposure period to a
10

moisture content equilibrium shall not exceed 9 calendar weeks. During

this time period (9 weeks) the insulating value of the specimen shall

return to approximately the same value as that observed before water was

added.

After the test is completed the amount of moisture in each com

ponent shall be determined by oven-drying to constant weight.

g. Water Vapor Permeance and Hygroscopic Moisture Capacity

The ability of the construction to self-dry in service shall

be evaluated by the ratio Pt /Me, where Pt is the overall water vapor permeance in perms (grains/hr ft2 in,Hg) of the construction (exclusive of

roofing) calculated from water vapor permeability determinations and Me

is the calculated moisture content in lb/ft2 of the construction based

on equilibrium hygroscopic moisture content determinations of the component materials. The calculated value of the ratio Pt/Mc shall be numerically between 2 and 50.

The over-all water vapor permeance, Pt , shall be calculated

from values of water vapor permeability and thickness of each component

of the construction as follows:

where u is the water vapor permeability in perm-inch units [grains/hr ft2

(in. Hg/in^] determined by either ASTM E-96-53T, Procedure A, or ASTM C

355-59T, Desiccant Method.

The hygroscopic moisture capacity. Me, shall be calculated

and determined as described in Section IIIc, Equilibrium Moisture Content
11

ho Exposure Conditions

During exposure the atmosphere beneath the specimen shall be

maintained constant at 90° F and 30% relative humidity.

The temperature of the calorimeter covering the upper surface

of the top specimen component material shall be programmed to repeat

daily the following (24-hour) cycle:

Clock Time

10 a.m.

10 a.m. to 12:30 p.m.

12:30 p.m. to 4:30 p.m.

4:30 p.m. to 7:30 p.m.

7 :30 p.m. to 10 a.m.

Calorimeter Plate Temperature. °F

Winter

38

75 «- in transition to

75 (Steady)

38 «- in transition to

38 (Steady)

Summer

75

138

I38 (Steady)

75

75 (Steady)

Measurements of the heat flux and temperatures at the surfaces

of all materials and the specimen moisture content shall be made each

working day between the hours of 7:00 and 10:00 a. m. For convenience when testing, instead of using clock time as shown above, the temperature of the calorimeter may be programmed as

(A + x) hours, where A is any chosen clock time and (0 < x < 24). For

example, if A = 10 a.m. then 12:30 p.m. = A + 2.5 hours. If the time of

day for making measurements is more suitable as 2 to 5 p.m. , the clock

time schedule may be adjusted accordingly.

ing:

i. Report

A report of the results of all tests shall include the follow-

(1) Exposure Tests (STP 3^2)
12 -

(a) The name and any other pertinent identification of the

test construction,

(b) A description of the test specimen, including the thicknesses of each component material, the technique used

to seal and prepare the specimen, and the time required

for preparation, A description of the test apparatus

used including the procedures and specimens used for

calibration. A description of the water addition procedure including observations of wetting, if any, of the

exposed (indoor) surface of the test specimen.

(c) The daily values of the test data shall be numerically

averaged for each week of testing (usually five values

per working week) and a tabulation of the following

items prepared:

[1] Test week number in consecutive order

[2] Simulated exposure condition (summer or winter)

[ 3 ] Weekly test thermal resistance, Rt, for the construe

tion. deg F/ Btu

hr ft2

[4] Weekly test thermal resistance, R, of each component

material, deg F/ Btu

hr fts

[5] The specimen moisture content, lb/ft2

(d) Calculated thermal resistance, R^j, based on thermal conductivity determinations of the dry component materials

and their thicknesses, deg F/ Btu “ft-2"
- 13 -

(e) The numerical average of the values of specimen thermal

resistance, R^., for thirty-seven 07) weeks of testing,

deg F/ Btu

hr ft2

(f) The numerical value of the ratio R^/R^.

(S) The change of specimen moisture content, lb/f

t

2 (week)

,

during each of the last two weeks of the first summer

exposure period during or after which a specimen moisture content equilibrium was achieved.

(h) The numerical value of the ratio Mt /Mc for the last week

of the first summer exposure period after a moisture

content equilibrium was achieved.

(i) The average rate of moisture regain during 6 weeks of

exposure of the specimen to the first simulated winter

test period, lb/ft2 (week)

.

(j) The self-drying time in weeks required for the specimen

to achieve an equilibrium moisture content during the

second summer exposure period starting immediately following the first winter exposure period.

(k) The maximum value of £he specimen moisture content in

lb/ ft2

, obtained after adding water in the amount of

10 percent by specimen volume, and the week number during

which water was added.

(l) The self-drying time, in weeks, required, after water was

added during the second summer exposure period, for the

specimen to reach a moisture content equilibrium.
14

(m) The dry weight per square foot of the specimen and of each

of the component materials, lb/ft 2

.

(n) A graphical representation of the results. This shall consist of plots of pertinent data obtained versus the corresponding test week number, plotted as ordinates and abscissas, respectively. Figure 1 is a sample plot.

(o) A sample plot of the calorimeter plate temperature for a

daily cycle of a winter and summer test condition.

(2) Thermal Conductivity Tests.

(a) A report as required in ASTM Designation C 177.

( 3 ) Equilibrium Hygroscopic Moisture Content Tests.

(a) For each component material of the specimen, give name and

any other pertinent identification.

(b) A description of the size of the test specimen.

(c) The equilibrium water content in percent of dry weight,

at 75 ± 2° F and 90 ± 3% relative humidity.

(4) Water Vapor Permeance Tests.

(a) A report as required in ASTM designation E-96-53T or

C 355-59T.

3. DISCUSSION

The main feature of this specification is the requirement that

a laboratory test demonstrate that a particular design of an insulated

flat roof will give reliable long-term insulating value and remain free

of serious moisture problems that have been and are being experienced in
15

the field. Laboratory testing of designs selected is considered necessary

because it is impossible to accurately predict long-term insulating and

moisture performance on the basis of the more quickly and easily measured

physical properties of the component materials. Such factors as variable

moisture contents of materials when installed in the roof, difficulties

in obtaining consistent and high-quality workmanship on the job, and the

ever-present possibility of roofing leaks being accidentally created

preclude predicting field performance. The requirement of testing the

design by laboratory exposure offers assurance before the construction

of large-area roofs that the design is such that the construction is capable of drying out in place if wetted from roofing leaks during and subsequent to construction. Thus the costly replacement of large areas of

roofing and insulation is prevented and maintenance would consist of simply patching and sealing roofing. Further, the test procedure allows

several designs to be tested simultaneously for comparison and selection

of the best, most economical construction to suit the needs for a specific

building use. A critical discussion of the requirements listed under Section

III of the Specification follows.

Thermal Insulating Value

For any component material the value of its thermal resistance,

Rq, can be firmly fixed because the thermal conductivity of a dry specimen is determined by a standardized method —ASTM C 177. The value of

the test thermal resistance of a specimen or a component varies with time,

moisture content, arrangement of the components of the specimen, and

exposure conditions. The requirement that the average test specimen
16

resistance achieve a minimum of 60 percent of its dry value may at first

appear to be easily accomplished. However, the procedure for calculating

Rj. consists of numerically averaging values that are obtained by exposure

under moist conditions during simulated summer and winter seasons. For

some specimens that are wet the weekly value of Rt may be as little as

25 percent of the dry value. Also, limits of time of exposure are specified. Thus, the average value Rt includes values obtained with the

specimen both dry and moist, as well as values for two seasonal exposures.

From laboratory data obtained on specimens that demonstrated good ability

to dry in place the value of 0.6 for the ratio Rt/R^ was selected as a minimum to assure a reasonably efficiently-insulated construction year

round. For many constructions that are installed with only normal hygroscopic moisture in them, the weekly value of the ratio R^/R^ will be

mostly in the range from 0.8 to 1.0. Further, some constructions that

have decks that are relatively quite permeable to water vapor will indicate high values of R^ when covered with a wet material of high water

absorptive capacity. This occurs because the heat entering the bottom

face of the specimen during measurement is largely used as latent heat

of evaporation and the quantity of heat remaining to be absorbed by the

calorimeter is small. The apparent thermal resistance of the specimen

thus indicated may exceed the dry value and in such cases the maximum

value that should be used to obtain Rt is the dry value R^. Such exceptional results were obtained only with rapidly-drying specimens having

quite permeable decks, so the procedure of allowing dry values for obviously wet specimens occurs for only a small fraction of the total time

of averaging.
17

Self - Drying Time for Initial Construction Moisture and Kquilibrium

Moisture Content

The quantity of moisture present initially will vary widely

with various types of constructions. Manufactured insulation normally

will contain only hygroscopic moisture. Green concrete will contain a relatively high percentage of free moisture by weight.

Those constructions that are placed in the field with all materials nearly dry will under laboratory exposure conditions for the first

summer exposure condition reach a moisture content equilibrium rapidly

and the values of Rt should be high and stable. For these cases it may

be permissible to reduce the time of testing to less than the maximum

of 16 weeks specified. However, when averaging weekly values of Rt over

the aggregate of 37 weeks the appropriate values of R^ should be included

for the full time period of 16 weeks.

For those specimens containing relatively much moisture, the

maximum of 16 weeks for the first summer exposure condition will probably be needed to establish a moisture content equilibrium. It is important that the weight and heat transfer measurements begin within one

week after concrete is poured because prolonged laboratory air drying can

reduce the moisture content considerably and this would not be compatible

with field installation where roofing is usually applied as soon as possible to prevent rain-wetting.

Equilibrium Moisture Content

Evaluation of the approximate equilibrium moisture content at

the conclusion of the first summer exposure condition ia specified to

assure that the quantity of moisture present is not excessive.
18

Laboratory results on specimens have shown that for two-component constructions, after several weeks of the summer exposure condition, the evaporable moisture present in the construction is widely distributed throughout it. To set a limit on the amount of evaporable

moisture an allowable construction may contain after 16 weeks of summer

condition exposure, a maximum value of 2 for the ratio Mf-/^ was selected, where Mt is the average evaporable moisture content of the specimen at that time, and Mc is the hygroscopic moisture content of the total

specimen if each of its components has the moisture content corresponding to its hygroscopic equilibrium at a condition of 75° F and 90 percent

relative humidity. It has been found that for most constructions the

latter quantity of moisture does not markedly affect the insulating value

under the winter exposure conditions.

The value of M^ differs considerably among constructions of

different kinds, depending both on their weight and on the hygroscopicity

of their materials. Information on hygroscopicity at this condition

available in the literature is sparse, and what is available indicates

considerable variation for ostensibly the same material, and also with

specimen size. Hence it appears necessary to require test measurements

to ascertain Mc for a construction. The quantity of hygroscopic data

obtained thus far as an adjunct to the NBS tests on roof constructions

is small. It is felt that as more information becomes available it may

be possible in some cases to omit specific measurements to obtain Me.

It may also be desirable in the future to change the present limiting

value of the ratio Mt/Mc.
19

Water Vapor Permeance and Hygroscopic Moisture Capacity

The ratio Pt/Mc is included in the specification to assure that

the specimen and especially its deck component is permeable enough to

permit adequate self-drying. Permeability measurements to determine Pt are sometimes variable on the same type of material. The value of the

ratio Pt/Mc i s also subject to variations of Mc as discussed above. Therefore the specified interval of 2 to 50 should be subject to future adjustment as more data become available.

4. EXAMPLES OF CONSTRUCTIONS FOUND ACCEPTABLE

The following constructions have demonstrated in laboratory

tests satisfactory insulating value and a capability for self-drying,

when moist from initial construction moisture or when wetted later

a simulated roofing leak, when they were subjected to simulated inservice exposure conditions of temperature and relative humidity. They

constitute a guide to which other constructions may be added upon approval

of laboratory tests that show similar acceptable performance. Pertinent

materials specifications and tests are included in the listing.

Sheet or mastic type vapor barriers were not used between the

deck material and the top cover material of any specimen listed, and

light spray-painting of the under- sur face , sufficient to change its color

but not to set as a continuous film, did not seriously affect the performance characteristics.
20

Construction

Number

I

II

III

IV

V

VI

VII

VIII

Formboard or Deck Material

Thickness and Dry Density

1 in., 11.4 pcf, glass fiber

formboard; (HH-I-526a; CS131-46; ASTM C 378; ASTM E96-53T; ASTM C 555-59T)

1 in., 11.4 pcf, glass fiber

formboard; (HH-I-526a; CS131-46; ASTM C 378; ASTM

E-96-53T; ASTM C 355-59T)

1-1/2 in., 11.6 pcf, glass

fiber formboard; (HH-I-526a;

CS-131-46; ASTM C 378; ASTM

E-96-53T; ASTM C 355-59T)

1-1/2 in., 11.6 pcf, glass

fiber formboard; (HH-I-526a;

CS-131-46; ASTM C 378; ASTM

E-96-53T; ASTM C 355-59T)

1-1/2 in., 18.9 pcf, woodfiber formboard- -upper

inch with asphalt binder;

(LLL-I-535 Class C; CS

42-49; SPR R 179-56; ASTM

E-96-53T; ASTM C 355-59T)

1-1/2 in., 18.9 pcf, woodfiber formboard- -upper inch

with asphalt binder; (LLLI-535 Class C; CS 42-49;

SPR R 179-56; ASTM C 208;

ASTM E-96-53T; ASTM C 355-

59T)

3 in., 24 pcf, wood-fiber

cementious binder formboard; (ASTM E 96-53T; ASTM

C 355-59T)

2 in. , 56.7 pcf gypsum concrete tile; (CE 219.02; ASA

A59. 1-1954; ASTM E 96-53T;

ASTM C 355-59T)

Top Cover Material

Thickness and Dry Density

3 in., 34*2 pcf, perlite

aggregate concrete; (CE

219.03; ASTM E-96-53T; ASTM

C 355-59T)

3 in., 39.6 pcf, vermiculite

aggregate concrete; (CE

219.04; ASTM. E96 - 53T; ASTM

C 355-59T)

3 in. , 30 pcf perlite

aggregate concrete; (CE

219.03; ASTM E-96-53T;

ASTM C 355-59T)

2 in., 56.7 pcf, gypsum

concrete; (CE 219.02; ASA

A59. 1-1954; ASTM E-96-53T;

ASTM C 355-59T)

3 in., 31*6 pcf, perlite

aggregate concrete; (CE

219.03; ASTM E-96-53T;

ASTM C 355-59T)

3 in., 41.1 pcf, vermiculite aggregate concrete;

(CE 219.04)

2 in., 56.7 pcf, gypsum

concrete; (CE 219.02; ASA

A 59.1-1954; ASTM E 96-53T;

ASTM C 355-59T)

1-3/4 in., 12.6 pcf, glass

fiber insulation board; (HHI-526a; CS 131-46; ASTM C

378; ASTM E 96-53T; ASTM C

355-59T)
21

Construction Formboard or Deck Material

Number Thickness and Dry Density

IX 2 in., 56.7 pcf gypsum concrete tile; (CE 219.02; ASA

A 59.1-1954; ASTM E 96-53T;

ASTM C 355-59T)

X 2 in., 56.7 pcf gypsum concrete tile; (CE 219.02; ASA

A 59.1-1954; ASTM E 96-53T;

ASTM C 355- 59T)

XI 3 in* , 30 pcf , perlite aggregate concrete, plank or

tile; (CE 219.03)

XII 3 in., 30 pcf, perlite aggregate concrete, plank or

tile; (CE 219.03)

XIII 3 in., 30 pcf, perlite aggregate concrete, plank or

tile; (CE 219.03)

Top Cover Material

Thickness and Dry Density

pH*

2-1/2 in., 16. 3^

mineral

wool board with asphalt

binder; (HH-I-526a; CS

136-46; ASTM C 378; ASTM.

E-96-53T; ASTM C 355-59T)

2-1/2 in., 14.2 pcf, woodfiber insulation board; LLL

1-535 Class C; CS 42-49;

SPR R 179-56; ASTM C 208)

1-1/2 in., 11.6 pcf, glass

fiber insulation board; (HH

I -526a; CS 131-46; ASTM C

378)

1-1/2 in., 18.9 pcf, woodfiber board —lower inch

with asphalt binder; (LLL1-535 Class C; CS 42-49;

SPR R 179-56; ASTM C 208)

1 in., 2 pcf, expanded poly

styrene insulation board;

(HH-I-524)

XIV 3 in., 30 pcf, perlite aggre- None

gate concrete, plank or

tile; (CE 219.03)

XV 2-1/4 in., 12.3 pcf, wood- None

fiber insulation board;

(LLL-I-535 Class C; CS

42-49; SPR R 179-56; ASTM

C 208)

XVI 1-3/4 in., 8.1 pcf, cork None

insulation board; (HHC-561b)

5. REFERENCES

1. NBS Report 6283 , The Effect of Moisture on Heat Transfer Through Insulated Flat Roof Constructions, January 15, 1959.
22

2. NBS Report 7347, Heat Transfer and Self-Drying Characteristics of

Insulated Flat Roof Constructions, October 3> 1961.

3* NBS Report 7817, Heat Transfer and Self-Drying Characteristics of

Formboard-Type Insulated Flat-Roof Constructions, March 15, 1963.

4. F. J. Powell and H. E. Robinson, Measurement of Effect of Moisture

on Heat Transfer Through Insulated Flat-Roof Constructions, Special

Technical Publication No. 312, Symposium on Methods of Testing Build

ing Constructions, Am. Soc. for Testing and Materials, pp. 35-66,

(1962).
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U. S. DEPARTMENT OP' COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C.,and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the

front cover. WASHINGTON, D. C.

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Dielectrics. High Voltage. Absolute Electrical Measurements.

Metrology. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering Metrology.

Mass and Volume.

Heat. Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Pure Substances. Spectrochemistry. Solution Chemistry. Standard Refer- ence Materials. Applied Analytical Research. Crystal Chemistry.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls.

Polymers. Macromolecules: Synthesis and Structure. Polymer Chemistry. Polymer Physics. Polymer Characterization. Polymer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research.

Metallurgy. Engineering Metallurgy. Metal Reactions. Metal Physics. Electrolysis and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Glass. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials.

Codes and Safety Standards. Heat Transfer. Inorganic Building Materials. Metallic Building Materials.

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Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Far Ultraviolet Physics. Solid State Physics. Electron

Physics. Atomic Physics. Plasma Spectroscopy.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instru- ments. Basic Instrumentation.

Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Ele- mentary Processes. Mass Spectrometry. Photochemistry and Radiation Chemistry.

Office of Weights and Measures. BOULDER, COLO.

CRYOGENIC ENGINEERING LABORATORY

Cryogenic Processes. Cryogenic Properties of Solids. Cryogenic Technical Services. Properties of Cryogenic

Fluids.

CENTRAL RADIO PROPAGATION LABORATORY

Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Research. Prediction Services. Sun- Earth Relationships. Field Engineering. Radio Warning Services. Vertical

Soundings Research.

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Measurements. Tropospheric Analysis. Spectrum Utilization Research. Radio-Meteorology . Lower Atmosphere

Physics.

Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency Research. Fre- quency Utilization. Modulation Research. Antenna Research. Radiodetermination.

Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. High Latitude Ionosphere

Physics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Standards Physics. Frequency and Time Disseminations. Radio and Microwave Materials. Atomic Fre- quency and Time-Interval Standards. Radio Plasma. Microwave Physics.

Radio Standards Engineering. High Frequency Electrical Standards. High Frequency Calibration Services. High

Frequency Impedance Standards. Microwave Calibration Services. Microwave Circuit Standards. Low Frequency

Calibration Services.

Joint Institute for Laboratory Astrophysics -NBS Group (Univ. of Colo.).