NATIONAL BUREAU OF STANDARDS REPORT

kk72

WATER VAPOR TRANSMISSION THROUGH JOINTS AND

BREAKER STRIPS OF INSULATED PANELS FOR REFRIGERATED

WAREHOUSE, PANEL NO. 1

Eeport to

Hea-dquapt ©rs , Quart ermas ter Research. & Development Command

Natick, Mass.

P. R. Achenbach

0. N. McDorman

U. S. DEPARTMENT OF COMMERCE.

NATIONAL BOREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003-20-14832 January 9 , 1956 I4I472

WATER VAPOR TRANSMISSION THROUGH JOINTS AND

BREAKER STRIPS OF INSULATED PANELS FOR REFRIGERATED

WAREHOUSE, PANEL NO. 1

by

P, R, Achenbach

Oc N. McDorman

Heating and Air Conditioning Section

Building Technology Division

To

Headquarters, Quart erraas ter Research & Development Command

Natick, Mass*

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, ApprOVCd for pubHc release by the or in part, is prohibited

unless permissio Direetor of the National Institute of Standards,Washington

25 .D.C. Such, Standards and Teehnology (NIST) report has been specifically prepared !• Oetober 9 20 1

S
1
V/ATER VAPOR TRANSMISSION THROUGH JOINTS A^ID

BREAKER STRIPS OF INSULATED PANELS FOR REFRIGERATED

WAxREEIOUSES, PANEL NO. 1

by

P. R, Acheribacli and 0. N, McDorman

Abstract

adjacent panels,

specimen panel,

with only a cold

basic need for a

At the request of the Quartermaster Research and

Development Laboratories Natick, Mass,, several

tests were made of a special Insulated warehouse

panel representative of the construction currently in use for demountable refrigerated warePioiises by the Armed Services. This was the first

of several panels constructed for the investigation using different Insulating materials and

different methods of protecting the wood breaker

strips and panel, fasteners at the joints between

Four tests were made of the

The first two tests were made

edge gasket to evaluate the

gasket at the warm edge for

limiting vapor transmission into the panel joint

and to study the effect of above-freezing and

below-freezing temperatures on the cold side of

the panel on the moisture and ice deposition in

the panel joints. The third and fourth tests

employed warm and cold edge gaskets with the cold

edge gasket being slotted for the fourth test to

provide ventilation of the joint space with cold

air from the refrigerated space. The tests revealed tb.at vapor transfer into the panel joint

and into the Insulation space was rapid without

a gasket at the x^jarm edge of the panel indicating the basic need for such a gasket. The

double-gasketed panel operated under a vaporpressure difference of 1,23 Hg and an air-toair temperature difference of 113°F for 73 days

without moisture or frost being formed in the

insulation space although some ice formed and

some wetting occurred in the panel joint. Slotting the cold side gasket to the ejxtent of

of its length tripled the rats of vapor tr:

2

irito and out of the panel joint for equivalent

vapor pressure and temperature differences,

caused considerable frost to be formed in the

insulation space during 23 days of exposure,

and produced a noticeable increase in the

amount of ice deposited in the panel jolnto

This latter test brings into question the value

of ventilating the joint space with air from

the refrigerated space, but does not answer the

question conclusively.

1, INTRODUCTION

Four tests were made of the first of several specimens of

insulated panels for refrigerated warehouses to study the mechanism and magnitude of water vapor transmission through gasketed

joints between adjacent panels and through the breaker strips

at the gasketed joints ^ Since the test panels were faced on

both sides with sheet metal. Impervious to water vapor, moisture

ingress into the panels could occur only through the gasketed

joints and thence through the breaker strip or the panel fasteners in the breaker strips.

The tests were made with a temperature of about 110°F on

the xiiarm side of the panel and a nominal temperature of either

35 °F or 0°F on the cold side of the panel. The relative humidities on each side were selected to provide a suitable

vapor pressure gradient across the panelo The tests were made

in a special apparatus designed for the purpose as Illustrated

in Fig, 1, The apparatus is described in National Bureau of

Standards Report No, 2914? entitled ”An Apparatus for Measurement of Simultaneous Heat and Water Vapor Plox^ through Ijx8

foot Insulated Panels'*

2 c DESCRIPTION OF TEST SPEC MEN

The specimen panel was constructed in accordance with

sketch No, N-78 prepared by the Office of the Quartermaster

General, It consisted of a center section approximately

78 inches hi^, 3 ^ inches x>jlde, and five Inches thick and

foTur border sections to form a test section about four feet

wide and ei^t feet hi^. Fig, 2 is a photograph of the

assembled panel. The top and bottom pieces were approximately

nine Inches vjide, whei^aas «the side pieces were .approximately

Irich'.u; wide. The center section was framed of 3 /^ inch





plywood with 3/8 inch plywood stiffeners spaced 12 inches apart

horizontally and 26 inches apart vertically„ The edges of the

vertical stiffeners were reinforced with metal channels. The

panel was insulated with Palco i-^ool fibers. Three panel fasteners were used on each of the vertical edges of the center

section and two panel fasteners were used on each horizontal

edge of the center section to attach the border pieces to it.

Five inspection holes three inches in diameter were cut

through the metal skin of the center panel on the cold side.

One opening was located in the center of the center section

with two other openings located at the sam.e height and at

distances of approximately six inches and. seven inches

from the edges respectively, '.lwO , .Ox ^ open... ivw.Ln i' : de

directly above the two outer openings and at a distance of

approximately 12 Inches from the top of the panel. During

the test these openings were covered with four inch squares

of Plexiglas 1/8 inch thick. The edges of the Plexiglas

we:,' ., sealed with a mastic material

„

Humidity sensing elements and pieces of bare iron wix-e

were placed in small recesses made in the fibrous insulationback of these inspection ports and adjacent to the cold skin

of the panel. Mastic material was also placed at the four

corners of the panel where the border panels met, to eliminate

the horizontal travel of moisture at these points which were

not considered a part of the joint under test,

3 , TEST PROCEDURE

Four tests were made on the specimen panel with different

temperature and vapor pressure gradients across the panel or

with different conditions of gasketing at the edges of the

center section. The conditions for the four tests are summarized in Table 1,

TABLE 1

Bummary of Test Conditions

Test No. 1 2 3 4

Gaskets Used Cold Side Cold Side Both Sides Both Sides

only only V entilation

Slots in

Cold Side

Gasket

Nominal Ml' Temp

Adjacent to Panel

harm Side 110 110 no no

Cold Side 35 0 0 0

Relative Humidity

Adjacent to Pan el,

%

Warm Side 70 62: i|8 53

Cold Side 20 71 55 3-5..

The test specimen was installed in the apparatus and sealed

at the edges to prevent air and water vapor transfer at these

extremities. '"he entire apparatus was tested for air exchange

to and fro: / o laboratory space after fastening the two parts

of the box co^ ether. The temperature and humidity of the warn

and cold sides of the apparatus were brought to the desired

values as quickly as possible by operation of the heater and

humidifier on the warm side and the refrigerating system and

desiccant chamber on the cold side. Temperatures and humidities

were kept constant by means of automatic thermostats and humidity controllers for the duration of the test,

Ob servations were made at regular intervals of the heat

input to the warm side, air and panel surface temperatures, relatlve,.;humldl ties of air adjacent to test panel, water evaporation

from the humidifier, water adsorption of the desiccant, and

the temperature differential between laboratory and warm box.

About one week was required to use all of the water (about

3 lb) in the humidifier during Tests 1 and 2, made with a gasket

on the cold edge of the panel only. The d.uratlon of Test 3 with

both gaskets on the panel was 73 days whereas 23 days were required to use all of the water In the humidifier during Test l\

“ 5

“

with both gaskets in place^ but x^iith six two=-lnch slots in the

gasket on the cold edge of the panel. Three of these slots were

made in the horizontal gasket at the bottom of the center section

and thrss were made in the corresponding positions at the top of

the center section. The slotted gasket can be seen in Fig, 3 on

the right hand border panel ,

At the end of each test the apparatus was opened as quickly

as possible. The test panel was removed^ the Plexiglas covers

on the inspection ports were examined for condensation or frost,

the Plexiglas covers were removed and the Insulation and sheet

metal skin examined for moisture, the gasketed joints and

breaker strips were examined for moisture or frost, and the panel

fasteners were examined for moisture and corrosion. The test

panel was I^7ei^ed for comparison ^^Jlth the original weight.

1|, TEST RESULTS

The visual observations made on the panel after each test

by a group of five observers are summarized belows

Test 1.

1, Condensation was observed only on the top right Plexiglas window as observed from the cold side,

2, The warm side of the apparatus was opened 10 minutes

after opening the cold side.

3, The wood breaker strips were wetted on the upper half

of the panel from the warm side through to the cold side at

the panel fastener locations and almost the full width of the

breaker strip between the fasteners.

I|, Free water was observed in the hook openings of the

top and middle panel fasteners.

5, The bottom panel fasteners were dry.

6, The top hooks were badly rusted.

7, The insulation back of the Inspection ports felt dry,

8, The cold side metal skin x-jas dry on the side adjacent

to the Insulation.
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9. There vjas a puddle of water on the floor of the warm

side bo.x (2oll lb were sponged up during the inspection of the

panel )

.

Test 2,

1, There was frost on the insulation side of all five

Plexiglas windows. The frost was more prominent on the two

^ppcr windows and there was frost on the insulation back of

rhese two inspection ports.

2, The cold side skin was wet adjacent to the Insulation^

with more water being present at midheight than at the top,

3, There was ice in the top and center panel fastener

recesses causing some difficulty in manipulating the fastener-

.

The top right panel fastener was especially difficult to disengage,

JLi, Ice was observed between the mating wooden members

at the panel joint on the upper half of the panel. The ice

was observed in a strip about l/2 inch wide reaching for one

foot down the left side from the top of the center section, and

in a strip about one inch wide reaching from the top of the

center panel down to midheight on the right side. The ice

appeared to be thick enou^ to fill the entire space between

breaker strips at these locations and it was in contact with

the cold side metal skin where it overlapped the breaker strip,

5 , The breaker strips were dry on the right side of the

center panel from midheight to the bottom and on the left side

from between the middle and top panel fastener to the bottom,

6, The hooks and the screw heads of the upper panel

fasteners were badly rusted,

7 , There was no condensation on the warm side metal

skin of the panel facing the warm box,

8, Some water was found on the floor of the warm side

box, ( 0.62 lb of water was sponged up during the inspection

of the panel )

,

Test 3 .

1, All five of the Plexiglas windows were dry and clear,

2, The Insulation adjacent to the cold skin felt dry.

- 7

-

3. Tiiei’e was no evidence of rust on the pieces of bare

iron wire that had been placed inside the Plexiglas windows,

L:, The humidity indicators installed inside the Plexiglas

windows indicated that condensation was not imminent on the cold

side skin.

5 . There was ice in the joint at the right side of the

center section reaching down about one foot from the top. The

strip of ice was about 1/2 inch in width and was attached to

the cold side metal skin where it overlapped the breaker strip,

6. Tiiere was ice on the top edge of the center section

reaching about two inches from the same corner that revealed

ice in the vertical joints

7 . The wood breaker strips were damp on the left side of

the center section covering an area of about two sq. in. near

the junction of the center section and the top and left border

pieces,

8. The pa.nel fasteners functioned satisfactorily,

9 . A small amount of water (0,13 T^) sponged up from

the floor of the warm side box during inspection of the panel.

Test I4 .

1. All five of the Plexiglas windows were covered with

frost on the Insulation side. See Fig. L'. Fig. 5 is a closeup view of two of the Plexiglas windows showing the frost

accumulation

,

2. There was considerable condensation in the insulation

behind the Plexiglas windows.

3. The six two-inch slots in the cold side gasket were

clear of frost or condensation.

I4

. There was ice in the hook recesses of the two panel

fasteners at the top of the center section. This ice is

visible in Fig, 3,

5 . There was a strip of ice from l/2 inch to one inch

3ad.de for the full length of the joint at the top of the centersection, This strip of ice was near tl-.e cold edge of the joint

and can be seen clearly in Fig. 3.


aI

k
- 8 -

6 . There was a wet streak on the wood breaker strip of

the left side border section located about l /2 inch from the

overlapping metal skin on the cold side (the left edge of the

joint shown in Fig. 6 ,

7. There was condensation on the warm skin of all the

border sections on the side facing the warm box, but there

was none on the warm skin of the center section ( 0.15 I'd of

water was wiped from warm side of border panels and 0.26 lb

of water was mopped up from the floor of the warm box during

the inspection of the panel).

The test conditions and observed results for the four

tests of the first panel are summarized in Table 2. Fig.

7 and 8 show the amount of water evaporated on the warm side

and the amount of moisture adsorbed in the desiccant on the

cold side on a cumulative basis for a period of several days

during Tests 3 and [|, respectively.

The inspections of the panel at the end of the tests

showed that some free water had drained down into the warm

box during each test. This drainage was a maximum in Test 1

during which the warm humid air had access to the joints between the center section and the border sections because the

warm side gasket was not present and the temperatures in these

joints were above freezing. During' Test 2 the gasketing conditions were the same as for Test 1, but some of the moisture

entering the joints was frozen and, therefore, did not drain

into the warm box. The drainage in Test 3 was equivalent to

an average of about 0.5 grain per hour for the duration of the

test and about five grains per hour in Test li. This drainage

water probably did not enter the panel joints at all in Tests

3 and Ije

Fros't or moisture was observed in the Insulation space

of the center section in Tests 1, 2, and l\. This condition

developed in a week’s time in Tests -1 and 2 with a gasket

on the cold side of the panel only. This type of gasketing

is not found in practice, but the tests reveal the speed

with which water vapor passes through the breaker strips and

panel fasteners under unfavorable gasketing conditions and

shows the need for gaskets on the warm side of the panel

joints.

A comparison of the results in Tests 3 and I4 indicates

that slotting the cold side gasket to provide ventilation of

the panel joints did not have the desired effect in reducing

Fi, . 6
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i
TABLE 2

SUMMARY OF RESULTS

WATER VAPOR TRANSMISSION TESTS OF FIRST SPECIM-EN PANEL

Test No. 1 2 3 4

G-askets Used

Average Conditions in

Warm Box

Cold Side

only

Cold Side

only

Both

Sides

Both Sides

V entilation

Slots in

Sold Side

Gasket

Temperature °F 110c2 109 «

9

110.6 107.7

Relative Humidity % 70 62 48 53

Dew Point Temp °F 98.5 93 c 8 86 87

Vapor Pressure

Average Conditions in

Cold Box

In Hg 1.85 1.60 1.25 1.29

Temperature °F 36»6 - 0.1 - 3.0 -1,6

Relative Humidity io 20 71 55 35

Dew Point Temp °F 3 -7 -14 -20

Vapor Pressure

Vapor Press .Differenc

In Hg

e

OoOlj O 0 O 3 0,02 1—

1

0 • 0

Across Panel In Hg lo 81 l»57 1.23 1.28

Duration of Test

Rate of Water

days 7 6 73 23

Evaporation ,

45- Rate of Moisture

gr/hr 369 481 16.8 49.3

Adsorption

Rate of Moisture

Transfer from

gr/hr 6.8 20.5

Humidifier ,-?5- gr/hr(s qft)(lnHg) 6e6 9.9 0.4 1,2

gr /hr (ft) (in Hg) 10 „

7

Thermal Conductance

16.1 0.7 2.1

of Panel-::- Btu/lir ( sqf t ) ( °F ) Weight Gain of0.189 0.193 0.146 0.153

Center Panel, lb 0.75 1.75 0 0.38

{J-The moisture evaporation, moisture transfer and thenrial conductance

values reported do not app7j.y to the entire test, but during periods

of Several days when conditions were steady.

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vapor transmission into the insulation space. Frost was found

at all five points of observation in the insulation after 23

days in Test h whereas condensation was not imminent after 73

days during Test 3« The vapor pressure on the warm side and

the vapor pressure difference across the panel were comparable

for the two tests, but the water evaporation rate required to

maintain the vapor pressure on the warm side during Test I4 was

about three times as high as for Test 3* The moisture £>c? sorption rate on the cold side during Test I4 was also about three

times as higli as for Test 3 , These results Indicate that

slotting the cold side gasket permitted higher overall moisture

transfer through the panel joints, and also suggests that the

vapor pressure in the joint itself adjacent to the wood breaker

strips and panel fasteners was probably higher in Test Lj. than

in Test 3 . The moisture content of the air in the panel joints

was not measured during these tests.

More frost and ice was found in the joint spaces at the

end of Test 4 than at the end of Test 3 even though the joint

space was ventilated to the cold space in Test ii. The difference between the total evaporation on the warm side and the

total pc’ sorption by the desiccant on the cold side during these

two tests indicates that more moisture was accumulated in the

panel during Test 3» These results Indicate that the ventilation provided by the slots in the cold side gasket did not

effectively prevent ice formation in the panel joints.

The rate of moisture transfer from the humidifier is

expressed in Table 2 in terms of grain^^hour per square foot

of panel area per unit vapor pressure difference and also in

terms of grain q/hour per linear foot of gasketed joint per

unit vapor pi-essure difference. For a panel with vapor impervious faces the panel area is of little significance in

expressing permeance. It would be expected that the moisture

transfer would be more directly related to the length of the

panel joints. The figures recorded in Table 2 for moisture

transfer per foot of length in Tests 1 and 2 represent the

rates at which vapor was entering the joint space from the

ungasketed side, some of which drained back out into the warm

box as water. The corresponding values for Tests 3 and 4 represent the approximate rates at which vapor was moving past

the gasket on the warm side of the panel. In these two tests

the rate of vapor transfer past the cold side gasket was only

about 40^ oT that passing the warm side gasket. Presumably,

the difference in these two rates represents the rate of

accumulation of moisture in the joints and in the panel.

- 10

Water or frost was observed ir the panel joints at the

end of all four tests. Even though the double gasket apparently

prevented condensation or frost formation in the insulation space

for 73 days under rather severe e:cposure conditions in Test 3,

the wood breaker strips were wetted in some areas and there x>jas

some frost or ice formed in the joints. The presence of water

In the panel joints would probably cause rusting of the panel

fasteners and hasten deterioration of the wood breaker strips,

and the accumulation of ice might cause mechanical damage in

the joint. However, the tests do not provide quantitative

evaluation of these processes.

Pig. 7 shows the rate of water evaporation on the warm

side of the panel and the rate of moisture adsorption on the

cold side of the panel on a cumiulatlve basis for fifteen days

during Test 3 when these rates were nearly steady. Conditions

\<iere not as steady for the entire 73 days as those shown in

Fig, 7 because of difficulties in obtaining steady vapor generation in the humidifier. The rates of moisture transfer reported in Table 2 for Test 3 correspond to those plotted in

Pig. 7» Fig* 8 shows corresponding water evaporation and

moisture adsorption data for the entire duration of Test Li,

This figure shows some change in water vapor transmits si on

rates after the first eight days of the test, but nvsarly constant rates thereafter. The rates of moistiure transfer reported in Table 2 for Test li correspond to those shown for uhe

last eight days in Fig, 8 , Table 2 shows that the thermal conductance of the whole

panel averaged about 0,19 Btu/hr ( ft^ )

( °F) with only a cold side

gasket in use whereas it averaged about 0.15 Btu/hr ( f t^ )

( °F)

'With both gaskets in use. The higher conductance observed in

Tests 1 and 2 was due almost entirely to the entry of x^Jarm

humid air into the joint space from the warm side because all

other test conditions remained essentially the sarae for Tests

3 and Li, The condensation of I|8l grains of moisture per hour

in the joint space in Test 2 corresponds to a latent heat transfer of about 0o02 Btu/hr (ft^')(°F) for the entire panel area,

thus representing approximately half the difference in the

thermal conductances observed for the single-gasketed and doublegasketed conditions of the panel.

The test results on this specimen did not shox\r any measurable change in thermal conductance during the course of the tests

the accumulation of msoisture or frost

of the thermal conductance measurethat could be attributed to

in the panel. The accursioy

ments is probably no better than two significant figures unde
I

I
-lithe conditions of operation that prevailed during the four

tests made of this first panel. Wlien the evaporation of moisture in the humidifier can be more precisely controlled from

hour to hour and day to day more accurate thermal conductance

measurements may be possible. Presumably, the drainage of

condensed water down the warm side of the panel could cause

deviations in the relative huraidlty in the warm box and affect

the demand for water from the humidifier.

5. DISCUSSION AND CONCLUSIONS

The results observed during the four tests of the first

specimen of several insulated warehouse panels for the Quartermaster Research and Development Laboratories indicate the following conclusions:

1. A gasket on the warm edge of the panel is necessary.

Without such a gasket moisture or frost was observed in the

insulation space after a week's exposure to hot humid conditions

on the outside while normal refrigerator temperatures were maintained on the inside. Extensive wetting of the wood breaker

strips and corrosion of the panel fasteners were also observed

under these conditions. The overall heat transmission of the

panel was increased about 25 percent as a result of leaving

off the warm side gasket.

2, A double-gasketed panel operated for 73 days with a vapor pressure difference of 1.23 in. Hg across the panel and

an air-to-air temperature difference of 113 °F without moisture

or frost being formed in the insulation space. The rate of

water vapor entry into the panel joint was about 0,7 graln/hr

per foot of joint length per inch Hg of vapor pressure difference across the panel, and the rate of water vapor transfer

from the panel joint to the refrigerated side of the panel was

about liO^ of this value in the same units. Some ice was formed

and some wetting occurred in the panel joint under these conditions.

3.

Removing about 5^ of the cold side gasket in the form ' of slots at the top and bottom edges of the panel to increase

air exchange between the panel joint and the refrigerated space

tripled the overall vapor transfer into and through the panel

joint. This modification resulted in considerable formation

of frost in the Insulation space and a noticeable Increase in

the amount of ice deposited in the panel joint during 23 days

of exposure under conditions otherwise comparable to the test

with full gaskets on warm and cold edges. Slotting the cold

12 -

edge gasket did not significantly increase the overall heat

transmission of the panel. This test does not establish

categorioally_^„that ventilating the panel joint to the refrigerated space is undesirable, but it does indicate that the amount

of ventilation provided for this test in relation to the leakage of the warm side gasket resulted in more overall moisture

transfer, more moisture entry into the insulated space, and

more ice formation in the panel point. Possibly the use of a

tighter x^jarm side gasket x-jould have shown that joint space

ventilation to the refrigerated space was advantageous,

l|c Water or ice was deposited in the panel joint during

every one of the four tests made. This suggests that the possible deterioration of wood breaker strips, the corrosion of

panel fasteners, the possible mechanical damage from operating

the panel fasteners when filled with ice or the physical damage

to the panel joint by the growth of ice formations are problems

that need consideration as well as the condensation of moisture

or frost in the Insulation spaces.

Experience with the water vapor transmission apparatus

during these tests indicates the need for some modification

to the testing procedures and for some additional instrumentation, Condensation of water vapor on the warm side of a test

specimen should be avoided to afford better control of the

water vapor demand from the humidifier and better control of

the warm side humidity.

Methods should be devised, if possible, to determine the

moisture content of the air in the insulated spaces of the

panel near the cold face of the panel. The electric hygrometer elements now used in the insulation space provide an

average value for a layer of air l/2 inch thick or more,

adjacent to but not extremely close to the cold face of the

panel. It is not possible "und-er present conditions to analyze

with much precision the disposition of the water or ice in

the panel joint or the framework of the panel. Determination

of the amount of air exchange between the warm and cold boxes

througlL the panel joints would also be halpful in studying the

performance of insulated panels and their gasketed joints.

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematies

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.