NATL INST OF STAND & TECH

A111D7 ElDfl3M

'is

DATE DUE

JUL 5 1985

CAVLORD PNINTCD IN U S A.





ireau of ^Standards

SEP 3 1940
National Bureau of Standards

JUL 16 1943

The program of research on building materials and structures, carried on by the

National Bureau of Standards, was undertaken with the assistance of the Central

Housing Committee, an informal organization of Government agencies concerned with

housing construction and finance, which is cooperating in the investigations through a subcommittee of principal technical assistants.

CENTKAL HOUSING COMMITTEE

SUBCOMMITTEE ON TECHNICAL RESEARCH

Walter Junge, Chairman. A. C. Shire, Vice Chairman.

, Federal Housing Administration. United States Housing Authority.

Sterling R. March, Secretary.

Albert G. Bear,

Veterans' Administration.

Pierre Blouke,

Federal Home Loan Bank Board (Federal Loan Agency).

Carroll W. Chamberlain,

Public Buildings Administration (Federal Works Agency).

Joseph M. DallaValle,

Public Health Service (Federal Security

Agency)

.

John Donovan,

Farm Security Administration (Agriculture).

George E. Knox,

Yards and Docks (Navy).

Vincent B. Phelan,

National Bureau of Standards (Commerce).

Edward A. Poynton,

Office of Indian Affairs (Interior).

George W. Trayer,

Forest Service (Agriculture).

Elsmere J. Walters,

Construction Division (War).

CHAIRMEN OF SECTIONS

Specifications Maintenance Mechanical Equipment

Carroll W. Chamberlain Charles Peters Robert K. Thulman

NATIONAL BUREAU OF STANDARDS

STAFF COMMITTEE ON ADMINISTRATION AND COORDINATION

Hugh L. Dryden, Chairman.

Mechanics and Sound.

Phaon H. Bates, Gustav E. F. Lundell,

Clay and Silicate Products. Chemistry.

HoBART C. Dickinson, Addams S. McAllister,

Heat and Power. Codes and Specifications.

Warren E. Emley, Henry S. Rawdon,

Organic and Fibrous Materials. Metallurgy.

The Forest Products Laboratory of the United States Department of Agriculture is cooperating with both committees on investigations of wood constructions.

[For list of BMS publications and how to purchase, see cover page III.]
UNITED STATES DEPARTMENT OF COMMERCE • Harry L. Hopkins, Secretary

NATIONAL BUREAU OF STANDARDS - Lyman J. Briggs, Director

BUILDING MATERIALS

and STRUCTURES

REPORT BMS52

Effect oi Ceiling Insulation Upon Summer Comfort

by THOMAS D. PHILLIPS

ISSUED JULY 1, 1940

The National Bureau of Standards is a fact-finding organization;

it does not "approve" any particular material or method of construction. The technical findings in this series of reports are to be construed accordingly.

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON • I94O

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, WASHINGTON, D. C. • PRICE lO CENTS
Foreword

This paper is one of a number planned fo]- the Building Materials and Structures

series, dealing with the general prohlem of making houses comfortable both in summer

and winter. Other subjects to be treated will be heating systems and appliances, heat

transmission and insulation, the latter serving both for conserving heat and making a house more comfortable in winter and for keeping it cooler during the hot days in summer.

This is a report of an investigation showing that even comparatively small amounts

of insulation, applied over a previously unprotected ceiling, may make the upper

floor of a house or apartment more comfortable in the summer.

Lyman J. Briggs, Director.

[11]
Effect of Ceiling Insulation

by THOMAS D.

Upon Summer

PHILLIPS ^

Comfort

C O N T E N T S

Foreword

I. Introduction 1 II. Method 1 III. Temperature of the unhisulated ceiling 2

Page IV. Temperature of the ceiHng under an attic

floor 4

V. Comparison of types of insulation 6

VI. Conclusions 9

VII. Summary 10

ABSTRACT

This investigation deals with the effect of insulation

in limiting the temperature rise of the rooms in the upper story of a building with a flat roof. For test purposes a structure was built on the roof of one of the

buildings at the National Bureau of Standards. This

structure has a "flat" (slightly sloping) roof, below

which is a low attic separated from the room below

by a ceiling of plasterboard. Various types of insula- tion were installed just above this ceiling to insulate it from the attic space. The temperature of the ceiling

in the room below was measured, and the effect of the

insulation in limiting the rise in the temperature of the

ceiling was determined.

The re.sults show that a lath and plaster or equivalent

ceiling exposed directly to the heat of the attic will be

so hot on warm summer days as to add materially to the discomfort of persons in the room below. Even a moderate amount of insulation will make the room much

more comfortable.

I. INTRODUCTION

Although there are abundant data on heat

transfer through building structures and in- sulating materials under winter conditions,

there is a scarcity of information on the eft'ective- ness of roof or ceiling insulation in helping to keep a building comfortable during hot weather.

The rooms in the upper story of a building

become warmer on a summer day than those on lower floors because the ceilings of such rooms become warmer, owing to roof exposure, than

do the ceilings of rooms lower down. In other

respects, the exposure of the top story is, in many cases, substantially the same as that of the lower stories. The ceiling temperatures

observed in similar rooms on the top floor in a

1 Dr. Phillips, professor of physics at Marietta College, Marietta, Ohio, conducted experimental work at the National Bureau of Standards during the summers of 1938 and 1939

typical building with various kinds of ceiling

insulation would therefore afford a direct index

to the effectiveness of the insulations used

The identical conditions for the insulations to be tested can be most readily attained by

dividing the ceiling of a single room into panels

and applying the various insulations to the

dift'erent spaces. In this way the air temperatures both above and below the ceiling would

be very nearly the same for all the spaces, and a measurement of the temperature under each

space would yield the desired information.

This method of comparing insulations was

used in the experiments to be described.

II. METHOD

Figure 1 is a view, from south-southeast, of the test structure built on the roof of one of the

buildings at the National Bureau of Standards.

The west end is exactly like the east end, except

that in the former the lower door is omitted.

The structure measures 20 feet by 8 feet and is divided into an attic and a room below by a

ceiling consisting of K-inch plasterboard nailed

to the lower sides of 2 by 4 joists. Figure 2 shows the plan of this ceiling separated into 10

spaces by the joists placed 2 feet apart, center

to center. The distance between ceiling and

roof is about 40 inches at the front and about

1 6 inches at the back. The height of the room

is about 7 feet. The roof consists of %-inch

sheathing covered with Ke-inch asphalt felt roofing.

The east and west walls were insulated from

roof to floor with 2 inches of fibrous insulating

material placed between the studs and covered on the inside with plasterboard. In the attic

229033°-40 [1]
Figure 1.—Test structure.

space the north and south walls were also covered with 2 inches of insulation. All

cracks where the roof joined the wall were packed with loose-fill insulation. Except in the

case of observations on September 1, 1939, the

north and south walls of the room below were

uninsulated. The doors are of double-thickness

%-inch board, fitted snugly in tlioir frames.

L I I

I I 1

I 2 3 4 5 6 7 8 9 10

F f r r \ r r r Figure 2.

Plan of ceiling showing numbering of spaces between joists. A multiple-point recorder was used to measure temperatures at the following points by means of resistance thermometers:

1. Outdoor an- on the north side of the

structure at the 4}2-foot level.

2. Room ah temperature within the struc- ture 8 inches below the middle of the ceiling.

3. Attic ah temperature 8 inches below the

middle of the roof.

4. Surface temperature under the roof boards.

This resistance thermometer was made of wire

about 0.5 mm in diameter and about 5 feet long.

It was placed in contact with the lower surface

of the roof boards and ran north and south at

the middle of the roof. Thermocouples were

used to measure surface temperatures on the

lower side of the plasterboard ceiling. These

thermocouples were located at the midpoints

of the joist spaces shown in the plan, figure 2. The 10 spaces between the joists in the ceiling were numbered from 1 to 10, with space number

1 at the west and space number 10 at the east end of the structure. Throughout all the tests the two end spaces (1 and 10) were insulated

with full-thick (3^8 in.) rock-wool bats. These

two spaces were not considered in the tests; they served only as a guard against uncertain

temperature conditions at the ends of the

buikling.

III. TEMPERATURE OF THE

UNINSULATED CEILING

During the observations made on August 3, 1939, the condition of spaces 2 to 9, inclusive, was as listed below:

Numbers 2, 6, and 9. —Uninsulated. The

space between the joists was left open at the

top, so that there was nothing but air between

the plasterboard ceiling of the room and the

roof of the building.

Number 3.—Insulated with 2-inch blanket

of wood fiber enclosed in strong paper. The

flanges of the blanket were tacked to the tops

of the 2-by-4 joists, so tliat there was an an- space between the blanket and the plasterboard ceiling of the room below.

[2]
Number 4. —Insulated with 2-inch rock-wool

bats laid on the plasterboard.

Number 5.—Insulated with a single layer of

aluminum foil tacked over the tops of the

joists, thus introducing two reflecting surfaces. Number 7.—Insulated with two layers of aluminimi foil, one tacked between the joists

and the other over the tops of the joists, so as to divide the joist space into two horizontal aii' spaces, each about 1% inches thick. Both

surfaces of each layer were reflecting.

Number 8.—Insulated with full-thick (/g-in.)

rock-wool bats laid directly on the plasterboard ceiling of the room below.

The insulating materials compared in this investigation were selected as being typical of those ordinarily used.

Figure 3 represents graphically the temperatures observed in the attic, in the room at a distance 8 inches below the ceiling, and of the

outdoor air. These curves simply represei; t the

conditions to which the ceiling was subjected.

It is interesting to note that at about 4:00 p. m.

the temperature of the attic roof fell below that

of the attic air. This represents the time when

the attic began to cool by transfer of heat out- ward through the roof. This shift happened at

about the same time on each of the days on

which observations were made.

Table 1 shows the temperatures of the lower

surfaces of the plaster-board ceiling under the

ujiinsulated joist spaces (2, 6, and 9) and idso

under insulated joist space 7. In addition,

column X gives the liighest temperature

measured under any of the insulated spaces,

3, 4, 5, and 8. Figure 4 shows temperature differences obtained by subtracting the temperature of the

ceiling imder space 7 from the other temperatures taken at the same time and given in table

1. Space 7 was selected for this pm'pose, as it was the coolest throughout the tests. Table 1 shows that under the uninsulated spaces the

ceiling temperature was 13 or 14 degrees F,

higher than that under the coolest of the in- sulated spaces, and about 12 degrees F higher

than that under the warmest of the insulated

spaces. The large amount of heat coming in through the uninsulated spaces made impracticable any comparison of the relative values of the different kinds of insulation used. The

insulated spaces are therefore represented in figure 4 by the shaded area. This shaded area

is so drawn that the difference between the

150

140

130

cnui 120

iro

UJQ iin

100

UI

on1-<

5 90

a.

S.UJH 80

70

A

/B

/

/

V

f /

-jV\

/

f V

/

D

8AM

10 12 1 EASTERN

2 3 STANDARD4 TIME

8

PM

FiGUHE 3.—Temperature-time carves jrom observations of August 3, 1939.

A, under surface of root; B, attic air; C, air, 8 inches below ceiling; D, air, outdoors.

[3]
V)

liJ oco

UJo

oz

UJ

18

16

12

it 8

ui

q:<

a.UJ

Q.2

UJ

—

/•

1

f •

7AM

Figure 4.

8 10 II 12 I 2 3 4 5 6 7 EASTERN STANDARD TIME PM

Temperature-dijferenc€-ti7ne curves fro7n observations of Augnsl S, 1939.

Curves 2, 6, and 9 for ceiling under uninsulated spaces. Curves 3, 4, 5, and 8 for ceiling below insulated spaces fall within the shaded area. Curve

7. for ceiling insulated with two sheets of aluminum foil, is the base line. Table 1. —Temperatures measured on ceiling several spaces

[Observations of August 3, 1939.]

under

Time

7:15_ 7:25-

7:33_

7:45,

8:00.

8:33. 8:43_

9:08. 9:18_ 9:35,

9:45..

10:08. 10:18.

10:35. 10:45.

ll:in

11:19.

12:18. 12:45. 1:45..

2:37. 3:20.

3:36.

3:45.

5:12.

5:30. 5:48.

6:05.

6:30.

6:48.

7:12.

Space numbers2 6 9 7 X

op op op op op

78.6 79.3 79.0 78.6 78.6

79. 2 79.7 79. 7 79.4 78.9

79.9 80. 5 80. 6 79.4 97.4

80.6 81. 2 81. 1 79. 7 79.7 81.7 82. 7 82. 2 79.9 79.9

84.7 85.8 85.7 81.6 82.0

85. 7 86. 9 86.8 82.4 82. 7 88.3 89.7 89. 7 84.0

89.9 90.8 90.8 84.0

91. 7 93. 2 93.4 84. 9 8.5.6

92.8 94.3 94.2 86. 1 86.2

95.6 96.9 97.1 87.6 88.0 96.8 98.2 98. 1 88. 1 88.4 98.3 99.9 98.8 89. 2 89. 7 99.0 100.9 100. 7 89.7 90. 1

100.9 102.2 102.

1

89. 9 90.6

102. 7 100.2 104.

1

91.7 92. 6

106. 2 107.3 107.7 94.4 95.5 108.5 109.5 109.3 95.8 96.9

110.2 111.2 110.3 97.2 98.7

110.8 111.8 111.0 97.8 99.3

110. 8 111. 2 110.5 97.9 99. 5

110. 9 111.0 110.3 98.4 99.8

111. 1 111. 1 110.7 99.1 100. 2

104. 2 103.9 103.4 96.6 98.0

101.9 101. 6 101.0 96.0 97.4

100.0 99.3 99. 2 95.5 96.3 98.0 97.5 97.6 94.6 95.2

95.9 95. 3 95. 1 93.2 94. 2 94.3 93.7 93.7 92. 5 93.0

92.6

j 91.8 91.8 90.9

j 91.6

temperature of the ceiling under any insulated

space and the temperature of the ceiling under

space 7 falls within the area.

IV. TEMPERATURE OF THE CEILING

UNDER AN ATTIC FLOOR

During the observations made on August 7, 1939, the condition of the joist spaces was the same as on August 3, except that space 6 was

insulated with full-thick {3% in.) glass-wool

strip, and space 2 was covered with }^-inch

insulating board nailed over the tops of the

joists. This space, 2, may be considered, for

all practical purposes, as equivalent to one

with a floored attic. As in figure 3, figure 5 gives the general temperature distribution.

Table 2 gives the temperatures of the ceiling

under the various spaces, and figure 6 shows

the amount that the respective ceiling temperatures exceeded that under space 7 at the times

noted. Column A' shows the highest temperature measured under any of the insulated

spaces, 3, 4, 5, 6, and 8. Here the uninsulated

spaced allowed a ceiling temperature 16 degrees

higher than the temperature of the coolest

insulated ceiling. The fact that the dift'erence in temperature between the roof and the room

[4]
150

70

AM

89 10 II 12 I 2345678

EASTERN STANDARD TIME PM

Figure 5. —Temperatiire-tirne—curves from observations of August 7, 1939.

A, under surface of roof; B, attic air; C, air, 8 inches below ceiling; D, air .outdoors.
air was 45° instead of 35° F, as on August

3, probably accounts for the fact that the uninsulated space was relatively hotter than on August 3.

Table 2.—Temperatures measured on ceiling under

several spaces

[Observations of August 7, 1939.]

Time

a.m.

8:10

8:45

9:03 9:40

10:11 10:37

11:38

p. m.

12:38

1:14

1:48 2:40

3:15

4:08

5:35 6:00

6:30

7:10

Space numbers

op

74.8

77.6

77.7

80. 6 84.3

86.8 92.6

94.8

97. 7 97.3

98.8

98.9

9fi. 2 95.1 92.9

90.7

78.0

81. 9 84.8

89.4

95.

1

97. 6 103.2

106.2

107. 3 107.4 107.5

106.9

105. 1 98.9

96. 2

93. 2

90. 1

°F

74. 5

77. 1 77. 7

79.

1

82. 2 84.0

88. 5

90.0

92.3

92.2 93.0

93.9

93.6

92. 2 91.3

90. 1 89.0

74.9

77, 1 77. 7 79.8 83.3

85.0

90. 5

91. 7 94.0

94. 1 95. 1 95.4

95.3

93. 2

92. 3

90. 6

89. 5

The data here reveal particularly the effects of /2-inch insulating board or an equivalent attic

floor laid over the joists. The result is a ceiling over 10 degrees cooler than was obtained without this protection, as shown by the difference

between space 9 (uninsulated) and space 2

(K-in. insulating board), but still 4 or 5 degrees warmer than a well-insulated ceiling.

V. COMPARISON OF TYPES OF

INSULATION

In the preceding discussion, no attempt has

been made to distinguish between the effects of the various insulations used. Before making

the observations of August 23 and September 1 presented below, two changes were made.

Space 9 was insulated with 2-inch rock-wool

bats. The insulating board was removed from

space 2, and the space was insulated with full- thick (3% in.) rock wool. The insulation of the spaces was then as follows:

Spaces 2 and 8—full-thick rockwool bats.

Spaces 4 and 9—2-inch rockwool bats. Space 3—2-inch wood-fiber

blanket.

Space 5—one layer of aluminum

foil. Space 6—full-thick glass wool

strip.

Space 7—two layers of aluminum

foil.

In spite of the fact that the east and west

walls of the structure were insulated and the

joist spaces at the two ends were left out of consideration, there was some differential in

temperature due to location. In order to decrease this effect screens of aluminum foil were placed outside the structure so as to shade

its east and west walls. Figures 7 and 8 give the temperature conditions to which the insulation was subjected on August 23 and September 1, 1939, respectively.

Tables 3 and 4 give the ceiling temperatures observed under each of the spaces and the means for the similarly insulated spaces 2 and 8 and 4 and

9. Temperature differences were obtained by

subtracting the ceiling temperature of space 7, the coolest, from the corresponding ceiling

temperatiires under each of the other insulations. In order to prevent confusion, these

data are presented in two graphs. Figures 9, 10, 11, and 12 show graphically the amounts by

which the various ceiling temperatures exceeded

that under space 7 (insulated with two layers

of aluminum foil). The numbers on the curves

refer to the space numbers previously listed. Curve 2,8 is drawn from the data for the mean

of the ceiling temperatures of the two spaces

insulated with full-thick rock wool and curve

4,9 for the mean of the two spaces insulated

with 2 inches of rock wool. Curve 4 (2 in. of rock wool) is also drawn in figures 9 and 10,

because this space was adjacent to space 3

(2 in. of wood-fiber blanket), and is therefore more reliable for the comparison of these two

types of insulation than would be the mean

curve, 4,9.

[6]
[7]
J it

J /

iIA\\

r•

Yl

\-

\

1

2,8 \A. i

H

^ ! —

\

V-

• i

1 1-

78 9 10 II 12 I 2 3 456 7 AM EASTERN STANDARD TIME PM

Figure 9. —Teni pi ralurc-il iffcn ncc-li im curvca from

observations of August 23, 1939.

Curve 2,8, average for ceiling under two spaces insulated with 3^-^ inches

of rock wool; Curve 3, for ceiling under 2 inches wood-fiber blankel: Curve 4, for ceiling under 2 inches of rock wool; Curve 4,9, average for ceiling under two spaces insulated with 2 inches of rock wool; Curve

7, for a ceiUng under two sheets of aluminum foil, is the base line.

UJ

o:o

UJa

UJ

UJ

cc

I-<

q:UJ

Q.2 „ UJ 0

6

T —\ c M

V- rf \ 1

/ V

789 10 II 12 I 234567

AM EASTERN STANDARD TIME PM

Figure II. —Tcinperature-differetice'-liinc curves from

observations of August 23, 1939.

Curve 5, for ceiling insulated with one sheet of aluininuni foil; Curve 6, for ceiling insulated with 3''8 inches of glass wool; Curve 7, for ceiling insulated with two sheets of aluminum foil, is the base line.

4A —

?

§

f

\

r

//

f

\

/8

e—

789I0III2 12.345 67

AM EASTERN STANDARD TIME PM

Figure 10. —Ton peral u re-dijfenuce—time curve.'i from

observations of Seytemher 1, 1939.

Curve 2,8, average for ceiling under two spaces insulated with 3?8 inches

of rock wool; Curve 3, for ceiling under 2 inches of wood-fiber blanket; Curve 4, for ceiling under 2 inches of rock wool; Curve 4,9, average for ceiling under two spaces insulated with 2 inches of rock wool; Curve 8. for ceiling insulated with 35s inches of rock wool; Curve 7, for ceiling under two sheets of aluminum foil, is the base line.

UJo

UJo

2

UJ

q:UJ

UJ 0

T

\ 5

%

^ \ i

—

1

t%

%

\—

/

>

7AM

9 10 II 12 I 2 3 4 5 EASTERN STANDARD TIME

7PM

Figure 12. —Tcmperalure-iliffcrcncc—lime curves from

observations of September 1, 1939.

Curve 5, for ceiling insulated with one sheet of aluminum foli ; Curve 6, for ceiling insulated with 3"s inches of glass wool; Curve 7, for ceiling insulated with two sheets of aluminum foil, is the base line.

[8]
Table 3.—Temperatures measured on ceiling under insulated spaces

[Observations of August 23, 1939

Space number and insulation

Time

(4

in.

of

rock

wool)

(2

in.

of

wood

fiber)

(2

in.

of

rock

wool)

(1

layer

of

Al

foil)

(4

in.

of

glass

wool)

(2

layers

of

Al

foil)

(4

in.

of

rock

wool)

(2

in.

of

rock

wool)

!ean

of2

and 8

(4

in.

of

rock

wool)

[ean

of4

and 9

(2

in.

of

rock

wool)

eo to 00 a>

a. m.

9:18._.

9:54.

10:28..

11:02 11:35".

" F.

77.1

79. j 81.8

84. 6 86.5

o p

77.3

79.8 82,7

85.3

87. 6

" F.

SO. 2 82.9

85. 5 87.8

o p

77. i 79.6

82.0 84,4

86. 6

o p_

77.6 80.2

82.9 85.5

87. 5

o p

77.4

79.4

82.0

84.2 86.0

o p_

77.4

79.8

82.0 84.6 86.5

o p_

77. i 80.3

83.

1

85. 7 87.6

" F.

77. 3 79.5 81.9

84. 6 86.5

0 p

77.6 80.2

83.0

85. 6 87.7

p. TO. 12:38-.

1:10-.. 1:47--- 2:20...

90.1 91.9

93. 2 94.2

91.3

93.2

94.3

95.

1

91.5

93.3 94.6

95.3

90.2

91. 8 93.2

94.0

91.0

92.6 93.8

94.3

89.5

91.5 92,3

93.2

90.0

91.7

92.8

93.5

91.2

92.9

94.0 94.7

90.

1

91. 8 93.0 93.9

91.4

93. 1 94.3 95.0

2:55..-

3:30...

3:55---

4:30.-.

94.2

94.9

94.7

94.2

95.3

95.8

95. 5 95.0

95.4

95.9

95. 6 94.9

94.2

94.9

94.6 93.9

94.4

94.8

94. 6 93.8

93.1

93.7

93. 5 92.9

93.5

94. 1 93.7

93.

1

94.6

95.

1

94.7 93.9

93.9

94.5

94 2 93.7

95.0

95. 5

95. 2 94.4

6:07...

6:38.-- 6:15...

92.7 91.9

90.

1

93.3

92.2

90.3

93.2

92.2

90.3

92.6

91.9

90.2

92.2

91.6

89.8

91.7

90.9

89.5

91.9

90.9

89. 5

92.4

91.6

89.8

92.3

91.4

89.8

92.8

91.9

90. 1

Table 4.—Temperatures measured on ceiling under

spaces

[Observations of September 1, 1939]

Space number and Insulation

Time

in.

of

rock

wool)

in.

of

wood

fiber)

in.

of

rock

wool)

layer

of

A!

foil)

in.

of

glass

wool)

layers

of

Al

foil)

in.

of

rock

wool) o

&

o

1^ *oa

m

of2

and

8

(4

in.

of

rock

wool)

m

of4

and 9

(2

in.

of

rock

wool)

cq CO CO oc Oi a 1

a. m. o p o p " F. o p 0 p o p ° F. o p o p_

O p

9:00-.. 71.7 71.7 72.0 71.7 71.8 71.6 71.7 71.6 71.7 71.8

10:00-. 74.0 74.2 74.2 74.0 74.3 73.8 73.8 74. 5 73.9 74. 4 10:30.- 75. 6 76.0 76.2 75. 6 76.2 75.5 7.i. 6 76.4 75.6 76.3

11:00.- 77. 4 78.

1

78.2 77.3 78. 1 77.

1

77.4 78. 4 77.4 78.3

11:30-. 79.3 79.9 80.2 79. 1 80.0 78.6 79.0 80.3 79.2 80.3

p. m.

12:30.. 82.8 83.6 83.9 82.6 83.3 81.8 82.4 83.7 82.6 83.8

1:00-.. 84.3 85.4 86.6

85.4 84.1 83.5 83.9 85.3 84. 1 85.4

1:30... 85.7 86.8 85.7 86.1 84.7 85. 3 86.6 85. 5 86.7

2:00... 86.3 87.4 87.5 86. 5 86. 7 85.3 86.0 87.2 86.2 87.4

2:30---

3:00.--

87.2 88.3 88.1 87.

1

86.

1

86.6 88.

1

86.9 88.

1

87.8 88.9 89. 88.9

1

87.8 88.0 86.9 87.2 88.6 87.5

3:30... 87.9 89.0 88.8 87.8 87.8 86.7 87.3 88.4 87. 6 88.6

4:00... 87.8 88.9 88.7 87.8 88.0 86.9 87.2 88.2 87. 5 88.6

6:30... 84.

1

84.4 84.4 84. 7 84.

1

84.

1

84.2 84.4 84.2 84.4

7:00... 83.4 83. 6 83. 6 ,84.0 83.6 83.4 83.3 83. 6 83.4 83.6

Between the observations of August 23 and

those of September 1, the south wall of the

structure was insulated with a single layer of aluminum foil tacked to the inner edges of the

studs. This was done in order to decrease the

entrance of heat to the room by paths other

than through the ceiling.

A comparison of the curves for these 2 days

shows that this addition produced no material

change either in relationship or relative magnitude of the temperatures observed. The data

for September 1 will be discussed in detail. Those for August 23 are presented only for

confirming the results. Figure 10 shows that 2 inches of rock wool, curve 4, corresponded very closely to 2 inches

of wood-fiber blanket (curve 3), and that either

of these insulations gave a ceiling temperature

about 2 degrees higher at the maximum than

that under space 7, insidated with two layers of

aluminum foil. A comparison of curve 4,

9

with curve 2, 8 shows that at 2:00 p. m., when

the dift'erence was a maxiinmn, the temperature of the ceiling under the spaces insulated

with 3/8 inches of rock wool was 1.2 degrees F

lower than mider the spaces insidated with only

2 inches of rock wool. Curve 8 provides a comparison between two layers of aluminmn

foil and 3% inches of rock wool in adjacent

spaces (7 and 8). The temperature of the

ceiling under the rock-wool section was slightly

higher, the maximum difference being 0.7 degrees F at 2:00 p. m. The corresponding

curves for a single layer of akuninum foil (in

space 5) and 3% inches of glass wool (in space 6) are shown in figure 12. At the maximum, the

ceiling under the smgle layer of aluminmn foil was 1 .2 degrees F warmer than the ceiling under

the double aluminum foil. Accordingly, 3%

inches of glass wool and the single layer of

aluminum foil are placed, as concerns eft'ective- ness, between 2 inches and 3% inches of rock

wool, by the results of these tests. Attempts were made to compare the rates of

coolmg at night. If difl^erences in this respect

exist between the insulations, the experunental

method was not adequate to evaluate them.

VI. CONCLUSIONS

On sunny days the temperatures of an un- shaded roof and of an unventilated attic air space beneath it rise very high, as much as 40 to 50 degrees F higher than the outdoor air temperature. This higher temperature produces, in the room below, ceiling temperatures which are

[9]
also liigli enough to be a source of discomfort. A

half-inch insulating board nailed over the ceil- ing joists, produced a marked improvement in

the comfort condition, lowering the ceiling

temperature by about 10 degrees. A tight wood

floor ui the attic would produce about the same

effect. Even with this, however, the ceiling was

about 5 degi'ees F warmer than the ceiling that

had the maxmium protection.

With the exception of the above, no great

differences exist between the performance of the

various insulations tested. It is questionable

whether these differences, about 2 degrees F at the greatest, are large enough to make a sensible

difference in comfort secured under sxmnner

conditions. With respect to such differences as do occur, however, the insiilations tested may

be listed in order of decreasing effectiveness in protecting the ceiling against summer heat, as follows

1. Two layers of aluminum foil (both sides of each layer reflecting).

2. Full-thick (3^!^ in.) rock wool

3. One layer of aluminum foil (both sides

reflecting)

.

4. Full-thick (3^^ in.) glass wool.

5. Two inclies of rock wool or 2 inches of

wood-fiber bl^mket.

The above listing refers only to limiting the

rise of temperature of the ceiling in summer. It does not apply to the escape of heat through the

ceiling in winter.

The effectiveness of reflective types of insulation under summer conditions was to be ex- pected, since, in a horizontal position, this type

of insulation gives its best performance when

resisting the flow of heat downward. The comparatively small differences between the ef- fectiveness of one layer and two layers of such

insulation, under summer conditions, would not

be found under winter conditions, since two

layers of reflective insulation would be nearly

twice as effective as a single layer for restricting

the flow of heat upward.

The building used was of relatively low heat

capacity. It is due to this fact, that in spite of the insidation of walls and ceilings (during the

observations on September 1) the temperature

of tlie air inside the building was definitely

higher after 2:00 p. m. than the temperature of the air outside. In buildings of more massive

construction, this condition does not arise untU

considerably later in the day.

These data apply to a slightly sloping roof,

with an unventilated attic space between the

roof and ceiling. Substitution of a pitched

roof or ventilated attic or both, would decrease

the amount of heat coming through the celling

and might therefore be expected to make the

differences between the various kinds of insulation still smaller.

The results show only the relative effective- ness of the various ceilings tested. They do

not answer the question, "How many degrees

cooler will a room be if the ceiling is insulated,

than it would be if the ceiling were uninsulated?"

The answer to this question depends not only on the insulation used, but also on the type of building, the extent to which it is shaded, and

other factors, so that no general answer which

would be applicable to all kinds of structures is possible. VII. SUMMARY

A room that has nothing but a plastered

celling between the occupants and the roof

boards will not be comfortable on hot summer

days, especially if the attic is not ventilated.

If there is no attic floor, a couple of inches of blanket or fill insulation put on top of the ceil- ing or a smgle layer of alummum foil tacked over

the tops of the joists, will greatly improve conditions. More than 2 inches of insulation will produce only slightly better results.

If the attic has a floor, about two-thirds of the improvement that woidd result from using

msulation has already been attained. Placing

additional insulation under such a floor may be

rather expensive, and although the room may

be perceptibly more comfortable with the insulation, there may be doubt as to whether the gain was sufficient to warrant the trouble and ex- pense.

Some of the work of preparing tliis manuscript for publication was undertaken by E. F. Mueller and H. V. Cottony.

Washington, February 27, 1940.

[10]
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BMSl Research on Building Materials and Structures for Use in Low-Cost Housing lOjS BMS2 Methods of Determining the Structural Properties of Low-Cost House Constructions 10^ BMS3 Suitability of Fiber Insulating Lath as a Plaster Base 10(i BMS4 Accelerated Aging of Fiber Building Boards lOji BMS5 Structural Properties of Six Masonry Wall Constructions 15(4 BMS6 Survey of Roofing Materials in the Southeastern States 15^ BMS7 Water Permeability of Masonry Walls 10^ BMS8 Methods of Investigation of Surface Treatment for Corrosion Protection of Steel 10^ BMS9 Structural Properties of the Insulated Steel Construction Co.'s "Frameless-Steel"

Constructions for Walls, Partitions, Floors, and Roofs 100 BMSIO Structural Properties of One of the "Keystone Beam Steel Floor" Constructions Sponsored by the H. H. Robertson Co lOji BMSll Structural Properties of the Curren Fabrihome Corporation's "Fabrihome" Constructions for Walls and Partitions 10^ BMS12 Structural Properties of "Steelox" Constructions for Walls, Partitions, Floors, and Roofs

Sponsored by Steel Buildings, Inc 15(4 BMS13 Properties of Some Fiber Building Boards of Current Manufacture 100 BMS14 Indentation and Recovery of Low-Cost Floor Coverings 100 BMS15 Structural Properties of "Wheeling Long-Span Steel Floor" Construction Sponsored by

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Sponsored by the Nelson Cement Stone Co., Inc 100

[List continued on cover page IV]
BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page III]

BMS27 Structural Properties of "Bender Steel Home" Wall Construction Sponsored bv The

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"Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co 10^ BMS37 Structural Properties of "Palisade Homes" Constructions for Walls, Partitions, and

Floors, Sponsored by Palisade Homes 10^ BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Dunn Manufacturing Co 10(4 BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin Units Co 100 BMS40 Structural Properties of a Wall Construction of "Knap Concrete Wall Units" Sponsored

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Insulating Boards Sponsored by the Celotex Corporation 100 BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 10(4 BMS44 Surface Treatment of Steel Prior to Painting 10(4 BMS45 Air Infiltration Through Windows 100 BMS46 Structural Properties of "Scot-Bilt" Prefabricated Sheet-Steel Constructions for Walls,

Floors, and Roofs Sponsored by the Globe Wernicke Co 100 BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for Walls, Partitions,

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Sponsored by the Homasote Co 100 BMS49 Metallic Roofing for Low-Cost House Construction 100 BMS50 Stability of Fiber Building Boards as Determined by Accelerated Aging 100 BMS51 Structural Properties of "Tilecrete Type A" Floor Construction Sponsored by the

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