NBSIR 76-1178

Air Leakage and Thermal

Performance of a Mark III

Relocatable Lewis Building

C. W. Phillips

B. A. Peavy

and M. E. Kuklewicz

Building Environment Division

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

December, 1976

Final Report

Prepared for U.S. Naval Facilities Engineering Command

Naval Civil Engineering Laboratory

Port Hueneme, California 93041

NBSIR 76-1178

AIR LEAKAGE AND THERMAL

PERFORMANCE OF A MARK III RELOCATABLE LEWIS BUILDING

C. W. Phillips

B. A. Peavy

and M. E. Kuklewicz

Building Environment Division

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

December, 1 976

Final Report

Prepared for U.S. Naval Facilities Engineering Command

Naval Civil Engineering Laboratory

Port Hueneme, California 93041

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson. Secretary

Edward O. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Acting Director
,

.
Air Leakage and Thermal Performance of

a Mark III Relocatable Lewis Building

by

C.W. Phillips, B. A. Peavy, and M.E. Kuklewicz

Building Environment Division

National Bureau of Standards

Washington, D.C. 20234

ABSTRACT

This report presents the findings of air leakage and heat transfer tests

of a Mark III relocatable building at the National Bureau of Standards,

Building Environment Division, for the U.S. Department of the Navy.

Quantitative and qualitative (smoke trace) air leakage tests with the

building pressurized, and the heat transfer test, were performed with the

building erected in an environmental laboratory. The quantitative air

leakage tests were performed in two phases. One was with the building

racked to simulate a wind load and the other was without racking. The

building was of prefabricated honeycomb panel construction using

aluminum skins. Included are photographs of the building and test

equipment and tables and charts showing the magnitude of air leaks at

the windows and doors. Racking had negligible effect on the air

leakage rate.

Key Words: Air leakage of buildings; building heat transfer;

honeycomb panel construction; relocatable buildings;

wind load racking.

i
Table of Contents

Page

Abstract

1. Xntrodution. . ^

2. Test Specimen Description 2

3. Smoke Tests 8

4. Air Leakage Tests 14

5. Air Leakage During Racking 21

6. Heat Transfer Test 25

7. Thermal Performance Evaluation 27

8. Discussion and Conclusions 33

9. References 35

ii
Page

t List of Figures

Figure 1 . Partially Constructed Building 4

Figure 2. Wall Panel Detail 5

Figure 3. Typical Door Installation 6

Figure 4. Typical Window Installation 7

Figure 5. Smoke Leaks at Rear Door 9

Figure 6 . Smoke Leaks at Front Door 10

Figure 7. Method Used to Seal Windows on Internal Surfaces 11

Figure 8. Method Used for Sealing Doors 12

Figure 9. Wall Joint Leaks with Windows Sealed and Building

Interior Pressurized. (No Racking During this Test). 13

Figure 10. Air Flow Measurement Apparatus 15

Figure 11. Air Leakage vs House Air AP 18

Figure 12. Method of Applying Racking Load 20

Figure 13. Racking Test Air Leakage vs House Air AP

with Windows Sealed 24

Figure 14. Heat Transfer Test Floor Diagram of a Mark III Relocatable House 26

Figure 15. Temperature of Interior Window and Extrusion

Surfaces with 75°F Inside Air Temperature 32

iii
.

'

,

'

. '
Air Leakage and Thermal Performance of

a Mark III Relocatable Lewis Building

by

C.W. Phillips, B.A. Peavy and M.E. Kuklewicz

Building Environment Division

National Bureau of Standards

Washington, D.C. 20234

1. Introduction

This report presents data from the first part of a series of tests

to develop information to be used to improve the properties of a redesign of the relocatable Lewis building. The purpose of this report is

to present results of air leakage rate and thermal performance tests

of a Mark III relocatable Lewis building.

The thermal performance tests of a Navy relocatable building were

sponsored by the Naval Facilities Engineering Command and coordinated

by the Naval Civil Engineering Laboratory at Port Hueneme, California.

The tests reported within this report were conducted in the environmental

chamber of the Building Environment Division at the National Bureau of

Standards

The data was obtained from tests of a specimen consisting of two

bays of a normal three-bay building erected in an environmental chamber

at the National Bureau of Standards. The erection of the two bays of

the Mark III building was on a concrete foundation simulating the

recommended field installation.

The tests were to determine the rate of air leakage from the

building with and without a racking load, and to determine the paths

of air-leakage by using smoke tests. Section 7, discusses possible

material changes to reduce the Mark III building's thermal conductance

properties

1
The smoke test procedures and results are discussed, and some photographs of the smoke tests are included. The same format is used to

present the procedures and results of a heat transfer test of the

building.

The air leakage data has been summarized in table form, and photographs of the equipment used are included. The calculations of all

the air leakage rates found in Tables A and E were partially accomplished

with the aid of OMNITAB, a computer program for routine calculations.

Air leakage data were obtained by measuring the air flow rate required

to maintain a small pressure difference between the inside and outside

of the building. The air leakage information provided can be used

as a comparison with test results of future and past building designs.

2. Test Specimen Description

2.1 General

The test specimen was a Mark III relocatable Lewis building of

honeycomb sandwich panel construction with aluminum skins and aluminum

extrusion frame members.

2.2 Foundation and Floor

The building was erected on a concrete foundation supporting the

building at nine points, i.e., each corner, mid-point of the exterior

walls, and one in the center for the floor area. The floor area of the

two-bays-test-specimen erected in the 3-story, 2100 square foot environmental chamber was approximately 671 square feet^ The dimensions of

the base were 31 ft. 11 1/2 inches by 19 ft. 8 inches. The foundation

was made so that it simulated the proposed nine pier support system to

be used in the field. Special sections of the concrete foundation were

used to mount apparatus to apply the roof loads and simulated wind load.

This equipment was used by the group studying the 'mechanical properties of

the structure covered in other reports [1] and [2]. These extra foundation areas did not interfere with the building properties covered in this

report. Figure 1 shows the foundation and partially constructed building.

Conversion factors to International System of Units (SI) are given at

the end of this report.

2
The base of the building was constructed of aluminum I-beams

connected to the concrete at the nine support points . These beams

supported the flooring panels. The floor panels were not further

sealed against air leakage beyond the tongue and groove joints provided

at the top and bottom surfaces of the mating edges of the panels.

2.3 Wall and Roof

Each building end contained a panel with a door and a panel with a window. One side of the building was assembled using three window panels

and the opposite side was assembled using only plain wall panels. Figure

2 is an end view of a section of a wall panel. Aluminum channel ex- trusions were affixed to the flat floor with the open ends facing up.

The side panels rested in the channels and screws were used to anchor

the aluminum-skinned side panels. The vertical joints between the

side panels were mechanically connected and partially sealed with a plastic extrusion.

Aluminum extrusions were screwed on top of the wall panels to form

the mechanical connection between the building sides, eaves, and roof.

The roof was supported by the sides, eaves, and two beams that ran logitudinally down the middle of the building. The roof panels were

joined together in the same manner as the side panels.

Certain of the wall panels, as they were supplied, came with builtin windows and doors. Figures 3 and 4, respectively, show a typical

door and window assembly. A vinyl latex caulk was applied to all the

horizontal joints between panel skins and aluminum extrusions, but no sealer was used where vertical panel to panel joints were made with the

plastic connector strips. The seams between adjacent wall and roof panels

had no sealer applied after assembly.

3
4

Figure

1

Partially

Constructed

Building
t

*

Figure 2. Wall Panel Detail

5
Figure 3. Typical Door Installation

b
Figure 4. Typical Window Installation

7
3. Smoke Tests

3.1 General

The purpose of the smoke tests was to indicate the major sources

of air leaks by visual means. For five of the smoke tests the building

was pressurized by forcing air in; and for two there was no pressure

other than that created by the smoke generators themselves. When the

tests were performed a fan was always directed at the smoke generators

to distribute the smoke throughout the building interior. For these

tests pyrotechnic white smoke generators were used. The white smoke

completely filled the building within a minute after ignition for both

types of smoke tests.

Preliminary tests were used to determine the suitable techniques

to photographically record the leaks. Sixteen-millimeter color motion

pictures, color slides, and black-and-white and color negatives were

used in attempts to record the more significant air leaks. Figure 5 shows white smoke leaking around the rear door.

3.2 Smoke Leaks

The most obvious air leaks were around the doors and around the

sliding windows. Figure 6 shows smoke coming out under the front

door. Smoke leakage can also be seen in figures 3 and 4. The vertical

seams between side panels and the seams between the roof panels were

the next most obvious leaks. They were particularly noticeable when

the doors and windows were covered on the inside with a sheet of polyethylene film. See figures 7 and 8 for photographs of the method of

sealing the windows and doors. Figure 9 shows smoke leakage with windows sealed and with .01 inches W.G. pressure differential.

8
(

Figure 5. Smoke Leaks at Rear Door

9
10

Figure

6.

Smoke

Leaks

at

Front

Door
Figure 7 Method Used to Seal Windows on Internal Surfaces

11
4. Air Leakage Tests

4.1 Instrumentation

During the initial building air leakage tests the windows were

pushed closed as tightly as possible and latched. The fit was such

that the windows could move about 1/8 inch in their slides. There

were fans located in the building and around the outside area, but none of them were turned on during the air leakage tests. They were

used only during the smoke tests and immediately after the smoke tests

to hasten the clearing of the smoke from the environmental chamber.

The building was pressurized by forcing air in through a measuring

orifice. The orifice pipe assembly used to measure air flow was introduced into the building through a hole cut in the center of a window

glass so that the least change in building properties would be made by

the test apparatus. The tape visible on the glass in figure 10 is an air-tight duct tape that was applied to the glass area for safety or. the weakened window pane and as a flexible sealer between the glass and

the air pipe.

The manometer, connecting tubes, and their joints were tested by

applying near maximum pressure allowed by each manometer and clamping

the tube shut. The tubing held the applied pressures for an extended

time period, indicating no significant leak was present. During the

preliminary smoke tests no leakage was observed in the area around

the hole in the glass. The air supplied to the building was taken from

the laboratory compressed air supply.

The instruments used to measure air flow are shown in figure 10.

The air flow measuring device used was a flat plate orifice flow meter

with 2" ID stainless steel meter tube and an ASHE standard circular

[ 31 plate orifice of 8 = .60 size The pressures across the flat plate

orifice were measured by using two "U" tube manometers with each

referenced to atmosphere. The up-stream pressure was measured by a mercury manometer with 1 mm increment scale. The downstream manometer

had a range of zero to 50 inches W.G. in .1" increments.

14
Figure 10. Air Flow Measurement Apparatus

15
Static pressure differences across the building wall were measured

using two pressure taps of similar construction placed at the same absolute elevation with one insfde the building and one outside the

building. The height of the static pressure bulbs was 41 inches above

the building floor. The manometer used for this measurement was a micromanometer with a range of zero to 1.25 inches W.G. in .01 inch

increments

.

The air temperature in the orifice tube was measured with a thermometer placed on the air line 22 inches ahead of the orifice pipe.

The decorative ceiling trim pieces which are supported between

the longitudinal roof beams in the building and which are optionally

removable, were both in place for the air leakage tests with and

without racking.

4.2 Air Leakage Test Results

The air leakage tests were performed in three stages. The

first series of building air pressures was on the building as erected.

The second and third series of air leakage versus air pressure runs were performed with the building altered respectively by sealing all

the windows and then windows and doors with a polyethylene film as shown in figures 7 and 8.

For the air leakage tf:str. the .M f r

r rential pressures used were

.04, .06, .08, .10, and .12 inches W.G. The air leakage corrected

to standard cubic feet per minute is presented in Table A, with the

pressure differences and corresponding degrees of building sealing listed.

Figure 11 is a graph of the air leakage with different polyethylene film

sealing. When comparison of this building data with other buildings of the same type is done in the future, the care and degree of caulking both

structures must be duplicated as nearly as possible.

16
BUILDING AIR LEAKAGE

TABLE A

i

House Sealing

Plastic Film

Application

House Air Pressure Difference

Inches W.G.

Air Flow

Standard cfm

No Sealing .04 103

.06 135

.08 172

.10 196

.06 133

Windows Sealed .04 97

With Polyethylene .06 122

Film .08 148

.10 171

.06 126

Windows and Doors .08 92

Sealed with Poly- .10 108

ethylene Film .12 121

.08 93

17
AIR

LEAKAGE—

STANDARD

CFM

AIR LEAKAGE vs HOUSE AIR aP

HOUSE AIR PRESSURE DIFFERENCE— INCHES W.G.

Figure 1 1

.

18
4.3 Discussion of Results

Previous unpublished studies at the National Bureau of Standards

have developed a suggested upper limit for air penetration rates for a wall system of the aluminum skin type. The suggested upper limit was

2 0.9 CFH/ft for a wall AP of 0.10 inches of water at isothermal conditions.

To compare this suggested upper limit based on walls only with the

observed leakage of the total building structure of the Lewis building

requires an assumption that the total roof, wall, and floor areas approximate an equivalent area of wall only. The area of the floor,

roof, ends, and sides including the doors and windows is approximately

2240 square feet. The suggested upper limit air penetration rate

times this equivalent wall area gives a suggested upper limit of 2016

CFH for the test building assembled in the NBS laboratories.

Comparing the data from the test of the Lewis building (with the

windows and doors sealed with polyethylene to approximate an all-wall

condition) at a wall AP of 0.10 inches of water and isothermal conditions

with the suggested upper limit indicates an air leakage rate of 3.2

times the suggested value for this type of wall construction. It should

be noted that some walls of aluminum skin with paper honeycomb core construction previously tested at the National Bureau of Standards

have had air penetration rates equivalent to six times the suggested

value.

19
2 r

Method

of

Applying

Racking

Load
5. Air Leakage During Racking

f 5.1 Building Preparation

A series of air leakage tests were performed during racking of the

building to simulate wind deflection effect. Prior to the racking test

and after the air leakage tests previously described, four holes were

cut in the walls of the house near the roof joint to attach the loadapplying equipment to the building wall. A fifth hole was cut through

a wall panel to pass strain gage indicator wires to the outside of the

building. These openings were carefully caulked. During the racking

test the windows remained sealed with polyethylene film left in place

from the previous air leakage tests, but the doors were unsealed.

The windows were left sealed because their design was to be changed

on later model buildings and their leakage effect was not desired in the data.

This will allow valid air leakage comparisons with later buildings.

The racking forces were applied to the building by four hydraulic

devices connected to the building by cables, wood 2 x 4's and eye bolts

as shown in figure 12 and described in detail in another report [2] .

5.2 Air Leakage During Racking Test Results

For comparison with the previous air leakage tests, air flows were

measured at four pressure differences, 0.04, .06, .08, and .10 inch W.G.

without racking. Then, for ten cycles, the building was racked to .629

of the design load and returned to a no-load condition. The definition of

2 the design wind pressure is a wind-loading equivalent to 25 lb/ft on the

side of the building as described in another report [2]

An air pressure

difference of 0.10 inches W.G. was then held constant for the remainder

of the test. The air leakage, in standard cfm versus the degree of racking

is presented in Table B. Figure 13 is a graph of air leakage versus pressure

difference prior to and during racking, after installation of the racking

apparatus

21
Two small air flow excursions occurred at 0.377 and .755 rack

ratios. The differences from the air flow at the start of the test of

6 and 1 standard CFM are not too large when the capabilities of the air

flow metering system are analyzed. The measuring system has a tolerance

of 2% of the total flow considering the conditions during the tests

and the limits' of the tables used for calculation.

22
/

I

TABLE B

RACKING TEST BUILDING AIR LEAKAGE

WITH WINDOWS SEALED

House Air Air Flow Racking Time of

Pressure Loads* Reading

Difference Air Flow

Inches W.G. Standard cfm Ratio Hour Min

.04 94 0.000 0 00 (start of test ) .06 118 0.000 0 03

.08 153 0.000 0 05

.10 176 0.000

**

0 29

.10 176 0.000 0 45

.10 176 0.126 0 51

.10 176 0.252 0 55

.10 182 0.377 0 58

.10 176 0.503 1 00

.10 176 0.629 1 . 03

.10 175 0.755 1 06

.10 176 0.881 1 10

.10 176 1.005 1 16

.10 176 1.131 1 21

.10 176 1.26 1 26

.10 176 1.26 1 30

.10 176 0.76 1 34

.10 176 0.50 1 36

.10 176 0.00 1 41

.10 176 0.00 1 46 (end of test )

Racking Loads and Ratio of (Load)/ (Design Load).

Building cycled to 0.629 of design loa^ ten times.

Design load is a wind load of 25 lb/ft on the

side of the building.

23
RACKING

TEST

AIR

LEAKAGE—

STANDARD

CFM

RACKING TEST AIR LEAKAGE vs HOUSE AIR aP

WITH WINDOWS SEALED

HOUSE AIR PRESSURE DIFFERENCE— INCHES W.G.

Figure 13 Racking Test Air Leakage vs House Air AP

with Windows Sealed

24
6. Heat Transfer Test

6.1

The purpose of this test was to measure the heat transfer rate for

this building. Because the window design was to be changed on later model

buildings the windows were left sealed with the polyethylene film so that their infiltration effect would not be present in the results.

This will allow comparisons with later model building tests by sealing the

windows in the same manner. The closed doors were left unsealed.

Exterior air temperature was held at about 5°F and was measured with a four-in-one averaging thermocouple. The interior air temperatue leveled

out at about 65°F as measured by a two-in-one air thermocouple. This

measurement was made on the air return side of two fans which circulated

air around an electric resistance heater located in the center of the

building. The heat input was recorded on two 240-volt single phase watthour meters. Power to the fans was included in the measurement. The

watthour meters were calibrated under load conditions. The steady-state

heat input at the above temperature condition was 30,540 Btu per hour.

The air-flow orifice assembly was left in place in the window during

the test, however, it was insulated on the section outside of the

building

Several thermocouples were positioned at various locations for

future compaiison with other constructions. The location 6f thermocouples and other arrangements are shown schematically in figure 14.

The temperature and heat input were held steady for 63 hours before

the data used for computations were taken. After the basic heat loss

test data had been collected, an additional test with the interior

air thermocouples moved to a better averaging location was run. The

interior air thermocouples were moved from the air inlet side of the

floor fans to a location approximately five feet above the floor and

along the canter line of the building about one-third of the building

length from each end. The new locations gave an average temperature

2°F lower than the temperature indicated by the thermocouples when

25
HEAT TRANSFER TEST FLOOR DIAGRAM

OF A MARK III RELOCATABLE HOUSE

1 -- Locations of four in one outside air thermocouples,

held by wire halfway up the outside wall on a sixinch diagonal from the corner.

2 -- Two-in-one inside air thermocouples on fans.

3 -- Thermocouples on center of panel surface inside

and outside.

4 -- Thermocouples on corner and eave extrusions

Figure 14.

26
they were on the fan inlets. An adjustment to account for this difference was included in the building heat loss calculations.

6.2 Heat Transfer Test Results

Total building heat transfer rate for the Lewis building as it was assembled in the environmental lab using two of a possible three

bay construction and under the conditions outlined above was 527 Btu/hr

(°F) with the windows sealed with polyethylene film.

6.3 Discussion of Results

The heat transfer rate for this building expressed in accordance with

FHA minimum property standards was 57 Btu/hr per square foot of floor

area, as assembled and tested in the environmental lab. This value was

arrived at by referring to the FHA Minimum Property Standards Handbook

for One and Two Living Units in the section for buildings heated by other

than electricity [4]. These standards refer to living spaces heated to

70°F and for total floor area measured to the outside of the exterior

walls, and recommend a maximum of 50 Btu/ft“. The 57 Btu/hr ft value

for the Lewis building is slightly higher than the FHA suggested maximum

2 of 50 Btu/hr ft . It should also be noted that the Lewis building’s

heat transfer coefficient would have been higher if the windows had not

been covered with polyethylene film as noted earlier in this section.

The temperature observed on the inside surfaces of the aluminum

frame extrusions indicated that moisture condensation could be a problem at temperature conditions similar to those in the test. The

inside surface temperature of one extrusion, for example, was below

40°F, with an adjacent interior air temperature of about 65°F.

7. Thermal Performance Evaluation

7.1 Evaluation Objective

The purposes of this series of tests was to evaluate the probability

of condensation occuring on the interior of aluminum members of the

building and relating the thermal performance to the heat losses from

the structure under winter climatic conditions of the temperate

27
regions of the United States. Of special concern is moisture con- densation on the surfaces of aluminum extrusions used as structural

members. These extrusions form a preferred heat flow path from the inside

to the outside by means of highly conductive aluminum and give a very small

temperature difference from inside to outside whereby the temperature

on the inside surface may be lower than the desired dew-point temperature

in the structure. A discussion of alternate extrusions such as plastics

is included.

7.2 Thermal Performance of Prototype Building

7.2.1 General

The prototype building tested at the National Bureau of Standards has an inside effective area of approximately 2252 square feet for which 60 square

feet was in five single pane windows. The projected inside area of

aluminum through members was 103 square feet. This area is based on the

flange area assuming that the flange forms a highly conductive heat flow

path to the web of the extrusipn. The outside projected area (about

160 square feet) is considerably greater when considering that the flange

areas for the wall-corner, wall-floor and roof peak are two to three times

greater. In addition the floor rests on four inch aluminum I-beams over

a considerable area. These I-beams will act like fins promoting heat

losses from the structure.

7.2.2 Assumed Conditions

The assumed conditions for this study are taken from the Handbook

of Fundamentals of the American Spceity of Heating, Refrigerating and

Air-Conditioning Engineers. For a 15 mph wind outside the surface con-

-1 -2 _

1 ductance is 6 Btu hr ft F and a value for the inside surface is

-1 -2 -1

1.46 Btu hr ft F For these conditions U, = 1.13 for single

-1 -2 -1 1 pane windows and 0.6 Btu hr ft F for double pane windows. From

tests performed on a material similar to the three inch thick

sandwich honeycomb panel construction, a value for the conductance is

0.22 Btu hr” 1 ft”

2 F

_1

, giving = .185 Btu hr” 1 ft

2 F1

. The heat

loss through the panels and single pane windows for a degree temperature

difference between inside and outside is then,

28
.185 x 2089 + 1.13 x 60 = 454.27 Btu hr 1 F

1

7.2.3 Heat Transfer in Extrusions

The calculation for heat losses through the aluminum extrusion has no amenable solution and is further complicated by the fact that the flanges

of the extrusions have a thermal contact with the inside and outside

surfaces of the aluminum skin of the honeycomb panels. The linking of the

highly conductive aluminum skin with the preferred heat flow path of the

extrusions indicates a complex heat flow problem for which intuitive

approximations are necessary for the purposes of this report.

The aluminum alloy has a thermal conductivity of about 100 Btu hr

ft

1 F \ and if the heat flow from the aluminum skins of the panels is

neglected the transmission coefficient for the extrusions is approximated

by:

1 103 .125 103x3 103x , 125

1.46 6x160 12x100 5x12x100 12x160x100

= 1.18 Btu hr -*-ft 2 F

1

where the thickness of the web and flange is .125", the length of the web

is 3" and crossection area of web is 5 square feet. Under the above

assumptions, the heat flow through the extrusions for one degree temperature

drop is 1.18 x 103 = 121.54 Btu hr" 1!" 1

.

7.2.4 Heat Losses Due to Air Change

Here it is assumed that the number of air changes taking place per hour

is 1.5. For a structure volume of 5400 cubic feet, the heat loss for one degree temperature difference between inside and outside is 1.08 x 1.5 x 5400/60 = 145.8 Btu hr" 1 F

-1

.

29
7.2.5 Total Heat Loss

The sum of the calculated heat losses is 454.27 + 121.54 + 145.8

= 721.6 Btu hr ^F ^ . For a 75°F inside air temperature and a 5°F

outside temperature the heat loss from the structure is 50,513 Btu hr""'*' or about 79 Btu hr ^ per square foot of floor area.

The structure with double pane windows gives a calculated heat loss

of 689.8 Btu hr ^F ^ and for the conditions cited above the heat loss

is 48,286 Btu hr ^ or about 75 Btu hr ^ per square foot of floor area.

The calculated heat transfer rates of 79 Btu hr and 75 Btu hr""*

-

per square foot of floor area are higher than the actual laboratory

-1 2 test value of 57 Btu hr per ft reported in Section 6.3. The

assumption of 1.5 air changes per hour in calculating heat losses

could be one reason for the calculated and test value discrepancy.

The actual building was not pressurized during the heat transfer test

and had polyethelene film on all windows. Assuming an air leakage

rate of 0.5 air changes per hour instead of 1.5 results in a heat

-1 2 transfer rate of 63.4 Btu hr per ft which is in closer agreement

-1 2 with the 57 Btu hr per ft test value.

7.3 Plastic Extrusions

Assuming that it is feasible to replace the aluminum extrusions by

using plastic extrusions, the thermal conductivity of plastics is about

.333 Btu hr ^ ft ^F ^ The transmission coefficient becomes .253 Btu

-1 -1

hr F and the heat loss for one degree temperature difference is

26 Btu hr ^F *" which is a reduction of 95 Btu hr ^F ^ from the use of

aluminum. The total calculated heat loss for the building is then

626.1 Btu hr ^F ^ (68.5 Btu hr ^ per square foot of floor area with a 70°F temperature drop) .

30
7.4 Interior Condensation

Moisture in air will condense on surfaces it comes in contact with

if the dew point temperature of the air is greater than the temperature

of the surface. Interior surfaces that will be subjected to possible

condensation are windows and the flanges of the aluminum extrusions.

Based on the interior surfaces temperatures and an ins'ide temperature

of 75°F, figure 15 is a plot of the dew point temperature at which

condensation will take place versus the outside air temperature for the

aluminum extrusion and single and double window. The plastic extrusion

is not considered as a possible surface for condensation.

7.5 Conclusions and Recommendations

For comfort conditions in living spaces during the winter a dry bulb

temperature of 75°F and relative humidity of 30 percent or less is

acceptable

Figure 15 shows that it is not possible to maintain 30 percent

relative humidity in the building for outside air temperature below

34°F because at lower outdoor temperatures condensation will form on the inside surfaces of the aluminum extrusions and will continue to

form until an equilibrium relative humidity is attained somewhere

below 30 percent. This problem will not exist for the plastic extrusions

because condensation will form on the single or double pane windows in

preference. Double pane windows would allow a 30% indoor relative

humidity to be maintained for outdoor temperatures down to about -5°F.

The calculated heat losses for the Mark III building are believed

to be conservative values in that some of the possible sources of heat

loss were neglected such as the heat losses by the aluminum I-beams

supporting the building in thermal contact with extrusions and aluminum

skin of the floor and the heat flow paths of the aluminum skins on the

inside and outside of the panels which are in thermal contact with the

extrusions

31
Figure 15. Temperature of Interior Window and Extrusion Surfaces

with 75°F Inside Air Temperature

32
To relate the thermal performance of this building to winter climatic

conditions of the temperature regions of the United States, the minimum

property standards for similar types of housing ha\)e been set forth by

[A]

the Federal Housing Administration. Citing from paragraph 71A-31,

"The total calculated heat loss of the living unit shall not exceed

50 Btu hr ^ per square foot of the total floor area of the space to be

heated to 70°F measured to the outside of exterior walls." Using this

criterion, a floor area of 640 square feet and the calculated heat

loss, the recommended outside design temperature is

T = 70 - *- 50

= 25 . 6 °F

o 721.61

On this basis, the building is suitable only for the southern regions

of the United States. If it could be assumed that the building were

constructed with double pane windows and plastic extrusions, the

calculated heat loss is 584.2 Btu hr ^F ^ and the outside design

temperature T^ = 16°F. This extends the suitable range for this

building

.

8. Discussion and Conclusions

Observations during the smoke tests revealed the doors and windows

as the areas of major air leaks. These observations are supported by

the reductions in air flow shown in Table A and Figure 11 when the doors

and windows were sealed. There were no other single large leakage points.

One or two places where the edges of a panel had been damaged in handling

or assembly showed slightly higher smoke leakage than undamaged sections.

There was no change in the basic building leakage characteristics

due to installation of the racking equipment to apply the simulated

wind load force. This can be seen by comparing the standard air flows

shown in figures 11 and 13 for the tests with only the windows sealed.

From Table B which lists air flow while the racking loads are

applied to the building, it is significant that at a constant air

pressure difference there was no appreciable increase in the total

air leakage for a building racked to 1.13 times the original scheduled

2

design load of 25 lb per ft .

33
Air leakage rates at 0.10 inches W.G. before installation of the

racking apparatus ranged from 196 cfm with doors and windows unsealed

to 108 cfm when they were sealed. When only the windows were sealed,

the leakage rate was 171 cfm. After installation of the racking

apparatus, with the windows sealed, the leakage rate at 0.10 inches

W.G. was 176 cfm before the house was racked. During the racking tests

with the windows sealed, the air leakage at 0.10 inches W.G. ranged

from 175 to 182 cfm. The careful caulking of the panel-to-frame joints

both inside and out is believed to be a factor in this performance.

The heat loss of this test building 527 Btu/hr (°F) was no doubt

influenced by the heat conduction Of the aluminum extrusion members.

By testing a similar-size building with the windows sealed as they

were in this test, the comparative effect of using extrusions with

improved heat transfer characteristics can be determined.

All of the measurements in this report are primarily useful for

such comparison purposes where improved structures are similarly tested.

34
9. References

1. Reichard, T.W. and Leyendecker, E.V., "Test and Evaluation of the

Prefabricated Lewis Building and its Components, Phase I Part 1,

Evaluation of Sandwich Panel Components," National Bureau of

Standards, Report 10163, March 1970.

2. Reichard, T.W. and Leyendecker, E.V., "Test and Evaluation of the

Prefabricated Lewis Building and its Components, Phase I Part 2,

Full-Scale Building Tests," National Bureau of Standards Report

10164, February 1970.

3. The American Society of Mechanical Engineers, Flow Measurement,

Power Test Codes (PTC 19.5; 4-1959), Chapter 4 (1959).

4. Federal Housing Adminstration Minimum Property Standards for

One and Two Living Units, (FHA No. 300-1965) Paragraph 714-3.1

printed by the U.S. Government Printing Office, 1966.

35
The policy of the National Bureau of Standards is to encourage and lead

in national use of the metric system, formally called the International

System of Units (SI)

.

These tests were performed and the report was prepared prior to the

National Bureau of Standards commitment to the SI presentation of data.

This publication uses customary English units, so the reader interested

in conversion to SI units is referred to:

(1) NBS SP 330, 1972 Edition, "The International System of Units"

(2) E380-74 ASTM Metric Practice Guide (American National Standard

Z210.1)

The following table shows conversion factors for the units used in this

report

.

Quantity To convert from To Multiply by

Length inch meter (m) 2.540 x 10

2 foot m 3.048 x 10

1

Area sq.ft. m^ 9.290 x

10

2

Volume cu. ft

.

m^ 2.832 x 10

"2

Temperature F Celsius (C) tc=(t f-32) /1.8

Pressure inch of water

(60F)

N/m^ (Pa) 2.488 x 102

lb/ft 2 N/mz (Pa) 4.788 x 10

Velocity mph(US Statute) m/s 4.470 xl0

_1

Power Btu/h W 2.931 x 10" 1

Time minute second (s) 60.0

Conductivity Btu/ (hr . ft . °F) w/ (m.K) 1.730

Heat Flux Btu/ (hr . ft

2

) w/m2 3.155

36
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUHI.K ATION OR REPORT NO. NBSIR 76-1178

2. Gov’t Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SURTITLE

AIR LEAKAGE AND THERMAL PERFORMANCE OF A MARK III

RELOCATABLE LEWIS BUILDING

5. Publication Date January 1977

6 . Performing Organization Code

7. AUTHO Phillips , B.A.Peavy, and Mark E. Kuklewicz 8 . Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

U.S. Naval Facilities Engineering Command

Naval Civil Engineering Laboratory

Port Hueneme, California 93041

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) This report presents the findings of air leakage and heat transfer tests of a Mark III relocatable building at the National Bureau of Standards, Building

Environment Division, for the U.S .Department of the Navy. Quantitative and

qualitative (smoke trace) air leakage tests with the building pressurized, and

the heat transfer test, were performed with the building erected in an environmental laboratory. The quantitative1 ^ leakage tests were performed in two

phases. One was with the building racked to simulate a wind load and the other was without racking. The building was of prefabricated honeycomb panel con- struction using aluminum skins. Included are photographs of the building and

test equipment and tables and charts showing the magnitude of air leaks at the

windows and doors. Racking had negligible effect on the air leakage rate.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize <mly the first letter of the first key word unless a proper name; separated by semicolons

)

Air leakage of buildings; building heat transfer; honeycomb panel construction;

relocatable buildings; wind-load racking.

18. AVAILABILITY [^ ] Unlimited

1 For Official Distribution. Do Not Release to NTIS

Order !• rom Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20d()2, SI) Cat. No. CM

[y 1 Order From National Technical Information Service (NTIS)

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21. NO. OF PAGES

41

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