AlllOb

IMBSIR 78-1475

A111D1 72LL33

Air Leakage Measurements in

Three Apartment Houses in the

Chicago Area

Charles M. Hunt

Building Thermal and Service Systems Division

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D C. 20234

John M. Porterfield

Energy Resources Center

University of Illinois at Chicago Circle

Paul Ondris

University of Illinois at Chicago Circle

Chicago, Illinois 60680

June 1978

DEPARTMENT OF COMMERCE

QC

100

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“)NAL BUREAU OF STANDARDS

78-1475

Bureau of Standards APR 17 w%

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NBSIR 78-1475

• <4 AIR LEAKAGE MEASUREMENTS IN

THREE APARTMENT HOUSES IN THE

CHICAGO AREA

Charles M. Hunt

Building Thermal and Service Systems Division

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D C. 20234

John M. Porterfield

Energy Resources Center

University of Illinois at Chicago Circle

Paul Ondris

University of Illinois at Chicago Circle

Chicago, Illinois 60680

June 1978

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1 §

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman. Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Director

AIR LEAKAGE MEASUREMENTS IN THREE APARTMENT

HOUSES IN THE CHICAGO AREA

by

1 9 Charles M. Hunt , John Porterfield , and

Paul Ondris^

Abstract

Air infiltration measurements were made in three apartment houses in the Chicago

area using SF^ as a tracer gas. Ttoo were in tenement districts and one was suburban. Data were collected in selected apartments in each building, and

these data were used to estimate the infiltration rate for the entire building.

Whole building estimates of 0.94 and 1.2 air changes per hour were obtained

under the conditions of tests in the tenement apartments, and 0.82 air changes

per hour in the suburban apartment.

Comparisons of the tightness of individual dwelling units by fan pressurizationdepressurization techniques were also made. The suburban apartment was found

to be much tighter than the other two apartments. The difference was much greater

than predicted by the tracer tests.

An analysis of the ASHRAE Crack Method is also made.

Key Words: Air infiltration, air leakage, sulfur hexafluoride tracer, low income

housing

.

1 Thermal Engineering Section

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

9 Energy Resources Center

University of Illinois at Chicago Circle

3 University of Illinois at Chicago Circle
\

C

I
1.

INTRODUCTION

Work has been undertaken on behalf of the Weatherization Program of the Community

Services Administration to assess the effectiveness of various retrofit options

aimed at reducing energy losses in housing for lower income people. A number

of buildings have been selected for this study. The present report deals

with air leakage measurement in three apartments of this group which were initially selected to represent tight, intermediate, and leaky buildings.

This study is a joint effort of the National Bureau of Standards and the

Energy Resources Center at the University of Illinois at Chicago Circle.

While the measurements do not cover a wide range of weather conditions, and

in this respect are limited in scope, they do provide information on types

of housing for which little if any previous data are available. They provide

a starting point for computer modeling of the infiltration component of

energy consumption of the buildings.

2. DESCRIPTION OF BUILDINGS

For purposes of identification the three apartment houses will be designated

as Windsor, Kenmore , and Custer, these being the names of the streets on which they are located. Front views of the buildings are shown in

Figures 1, 2, and 3. Floor plans of the dwelling units in which measurements were made are shown in Figures 4, 5 and 6.

Windsor and Kenmore are in sections of the city which might be considered

tenement areas while Custer is more suburban in location. Windsor was undergoing renovation when the tests were carried out, so that different apartments

were in different degrees of repair, and many of them were unoccupied. This

afforded an opportunity for experimentation which would be more difficult

to achieve in occupied dwellings. Kenmore is comparable in size with Windsor,

but it was fully occupied. It had also received earlier weatherstripping

treatment, and doors into the hallways were better fitted. One of the reasons

for including it in the measurements was to see if these improvements made

a significant difference in air leakage characteristics. Presumably it was

a tight building in comparison with Windsor.

Custer was a newer structure. It had swinging steel frame casement windows,

while the other two apartments had double hung wooden sash windows. Custer also

had concrete in its floor construction.

3. INFILTRATION TESTS

Infiltration tests were made by the tracer gas dilution method using sulfur hexafluoride (SF^) as the tracer gas. The particular apparatus used in these tests is

similar to that described elsewhere [1,2], except that a chromatograph with a 6-port

rotary sampling valve was used in place of one with a plunger-type valve. Also, the

instrument response was linear instead of logarithmic as in the one previously

described

1
Tracer gas was distributed throughout the dwelling space and its concentration

measured as a function of time. Infiltration rate was calculated from the rate of

disappearance of tracer gas by the relationship

dc _ v

dt V

( 1 )

and ( 2 )

where c = initial concentration of SF/- o o c = concentration of SF^ at time t v = rate of which air enters and leaves the ventilated space

V = volume of ventilated space

I = infiltration rate

The natural logarithm of c/c

q was plotted as a function of time, and by proper

selection of units the slope of the line was equal to-I, where I=inf iltration

rate in air changes per hour.

4. FAN PRESSURIZATION-DEPRESSURIZATION TESTS

These tests were a modified and scaled down version of tests originally described

by Cover [3], but recently improved and described more extensively by Tamura [4]

and Strieker [5]. An assembly consisting of an axial fan connected downstream

from a commercial multi-port pitot-static flow measuring device was sealed into

one of the doorways at each apartment under test. Fan speed was controlled by means of a variable transformer, and air was exhausted from the apartment. By

reinstalling the assembly in the opposite direction the apartment could be

pressurized. Differential pressure measurements were made between the inside and

outside of selected dwelling units by means of a variable capacitance pressure

gage with tubes leading inside and outside of the test-space. The same device

was used to measure differential pressures across the pitot-static flow measuring

device.

5. INFILTRATION TESTS AT WINDSOR

Before going into the tests themselves some problems involved in making tracer

tests in buildings without central ducted ventilating systems should be mentioned.

Without such a system in a multi-room, multi-story building there is no simple

way to measure infiltration rate of the apartment house as a whole, so measurements were made in individual apartments, and projections as to what the infiltration rate should be for the entire building were made from these data. (A

theoretical analysis of air movements in a multi-room building is given by

Sinden [ 6 ] .

)

The first set of measurements at Windsor was made in the third floor north apartment. The floor plan and location of sampling points and fan is shown in Figure 4.

Sufficient tracer gas was distributed throughout the space to produce a concentration of about 10-15 parts per billion (ppb). A fan with a delivery rate of about

800 cfm was operated in the apartment to maintain mixing throughout each test.

It was directed away from outside windows or doors so that air flow was not

directed towards identified cracks. A fan was similarly used on the top floor

2
but not on the second floor apartment because only two fans were available.

Initially tracer gas was introduced only in this one apartment and concentration

measurements made in this apartment. The apartments directly above and below

were also checked for leakage of tracer into those areas, but none was found.

Infiltration rates of 0.75 and 0.81 air changes per hour were obtained and are presented as the first two runs in Table 1.

Tracer gas was then distributed in the apartment above. This was a top-floor

apartment. Higher infiltration rates were obtained than on the lower floor, as shown in Table 1.

In the remaining experiments tracer gas decay measurements were made with tracer

gas in all three apartments, and finally in all three apartments plus the stairwell. If significant air leakage occurred from apartment to apartment, apparent

infiltration rates would be correspondingly lower or higher depending on whether

air entering from the rest of the building contained tracer gas or not. In this

series of measurements, there was very little difference in infiltration rates

on the third floor if the apartments below or above and the stairwell contained

tracer gas. Even though there may have been some reduction in the calculated

infiltration rate for the top floor when tracer gas was present in the apartment

below and in the stairwell, these data suggest that the leakage paths were such

that most of the air exchange was with the out-of-doors. If it is assumed that

0.83 air changes per hour is representative of the infiltration rates of the

lower three floors and 1.25 represents the top floor, then the weighted average

air exchange rate for Windsor is 0.94 air changes per hour.

Wind data from O'Hare and Midway Airports indicated gusts as high as 15 to

20 knots at the time of the infiltration measurements. Some evidence of wind

activity at the Windsor site was evident from the movement of tree branches

and blowing of occasional bits of paper and light objects. However, the apartment building itself was surrounded by other buildings of comparable height which

would alter wind patterns considerably. Wind data are presented here for descriptive purposes' only.

Temperature was measured by a single alcohol-in-glass thermometer outside on a shaded

window ledge and another one centrally located indoors in the third floor apartment.

Initial outside temperature was 50°F and inside 60°F, and a temperature difference

of approximately 10°F was maintained throughout the day as inside and outside

temperatures increased. The low AT would suggest that a less than normal stack effect

was operating during the tests.

It was observed that tracer gas disappeared faster from the stairwell than from

the dwelling units. This suggests there is significant air movement up the stairwell and out of the vent which is part of the skylight assembly. However, it is not

certain how much this air leakage contributed to the leakage rates in the individual

apartments. Tighter fitting of the doors leading into the stairwell might produce

some reduction in air leakage. However, it might be noted that there are studies

of houses which showed that leakage around windows and doors accounted for only a fraction of the total air leakage [4,7].

3
TABLE 1. INFILTRATION RATES AT WINDSOR, KENMORE, AND CUSTER

Air Changes per Hour

WINDSOR*

Run 2nd Floor 3rd Floor 4th Floor (top)

1 0.75 S!6 added to 3rd

2 0.81 tf M

3 1.38 s!e added to 4th

4 1.56 M if ii

5 0.70 0.77 0.99 sf

6 added to each

6

7 1.12

1.08

0.73

1.33

0.97

S !6 added to each

Average 0.83 1.25 3 x .83 + 1.25 = Standard 0.14 0.25 4

Deviation (SD)

KENMORE

Run 1st Floor 2nd Floor 3rd Floor (top)

1 1.5

2 1.7

1 6 1 6 * -94 -12

1.25

CUSTER

Run 2nd Floor 4th Floor (top)

1 0.72 1.05

2 0.77 1.05

3 0.78 0.86

Average 0.76 0.99 3 x 0.76 + 0.99 _ (SD) 0.03 0.11 4

*The floor entered nearest to ground level is designated as the 1st floor.

6. INFILTRATION TESTS AT KENMORE

Tracer gas measurements were made in a top floor northside apartment at Kenmore.

The floor plan is shown in Figure 5. Infiltration rates of 1.5 and 1.7 air

change per hour were obtained. The results are included in Table 1. Kenmore is

presented in Table 1 as a three-floor apartment house. However it had a halfexposed basement and is treated as a four-story building like Windsor. Assuming

an average rate of 1.6 air changes per hour and further assuming that the average

air exchange rate for the apartment house was 75% of the rate for the top floor

as at Windsor, a projected estimate of 1.2 air change per hour for the building

is obtained.

As previously mentioned , Kenmore was selected as a tighter structure than Windsor

because of caulking and weatherstripping. This prediction was not borne out by

4
the infiltration measurement. However, no preretrofit data are available on the same building. Without such data it is difficult to accurately assess the effects

of caulking and weatherstripping.

Fewer data were collected at Kenmore than originally intended because of greater

problems encountered in working in occupied apartments than in vacant apartments.

These include such things as occupants not home to permit access, invasion of privacy,

doors or windows left open, certain rooms not accessible, etc.

Wind data indicated velocities of 10 knots at both Midway and O'Hara airports. Kenmore

was also in a somewhat protected location. An outside temperature of 58 °F and inside

temperatures of 68 to 71°F were observed, so AT was comparable with that observed

at Windsor.

7. INFILTRATION MEASUREMENTS AT CUSTER

Two apartments were measured at Custer. Both were in the south wing of the building.

One was on the second floor. It was an interior apartment with exposures on the

north and south. The other was an end apartment on the fourth floor with exposures

on the north, south, and west. It appears on Figure 3 on the top floor at the

right. Floor plans of the two apartments are also shown side-by-side in Figure 6.

The average infiltration rate of the second floor apartment was 0.76 air changes

per hour, and on the fourth floor 0.99 air changes per hour with a weighted average

for the entire building of 0.82 air changes per hour, assuming that all but the top

floor had an air exchange rate of 0.76 air changes per hour.

Wind velocities of 17 knots at Midway and 19 to 23 knots at O'Hare were reported.

An initial outside temperature of 72°F was observed, but this dropped to 52°F during

tests indicating that a front passed through. Indoor temperatures were 80 to 82°F

as measured in the second floor apartment.

The air infiltration rate was higher than anticipated from the comparative results

of fan tests at Custer and Windsor which are to be described in a subsequent section

of this report. A significant tracer gas concentration was always found in the

stairwell, although none was added there, indicating a leakage under the front door

and up the stairwell, as at Windsor. However, this leakage path was also present

during the subsequent fan tests. No entirely satisfactory explanation is offered

as to why this infiltration rate was higher than expected from the fan tests, but

it is noted that Custer was in a more exposed location and the average insideoutside temperature difference was greater.

8. PRESSURIZATION-DEPRESSURIZATION TESTS AT WINDSOR

8.1 COMPARISON OF DIFFERENT APARTMENTS

Depressurization measurements were made in the second, third, and fourth floor

apartments of Windsor. The purpose of this set of tests was to compare tightness

of the second and third floor apartments, which had undergone renovations, with

that of the fourth floor which was essentially in the run down state in which

the owner had acquired it. In each measurement the low pressure lead was a 1/4-inch (id) polyethylene tube leading into the apartment. The outside lead

ended in the stairwell far enough from the fan to avoid turbulence effects produced

by the fan. The data are presented in a log-log graph in Figure 7. Very little

difference is shown between the second and third floor apartments. The fourth

5
floor does not fit the correlation for the other two floors, although most of

the divergence lies in one point which is below the line. Since tracer gas

measurements indicated the fourth floor to have a higher leakage rate than the

other two floors, this is treated as an outlying point. While esthetically

and functionally the renovated apartments were very different from the top floor

apartment, they were not less permeable in the fan tests.

A fairly good argument could be made for the case that the higher infiltration

rate of the fourth floor in tracer gas tests was due more to unrepaired leaks

in the envelope structure than to its more exposed position. However, fan

depressurization suggests that the top floor apartment was not more leaky than

the others. This would favor the theory that the higher infiltration rate was

primarily due to greater area of weather exposure on the top floor.

8.2 EFFECT OF SEALING WINDOWS, DOORS, AND FIREPLACE

A set of measurements were made in the third floor apartment with polyethylene

film taped over each window and door frame so as to block the entire window

or door except for leakages where the frames fit into the walls. The fireplace

was also sealed. Pressurization was used on this set of measurements to reinforce the action of the tape rather than pull the film away from any openings

as might occur with depressurization. The film and tape were than removed and

the pressurization experiment repeated. The results are shown in Figure 8.

The doors, windows, and fireplace did not account for more than 12 to 18% of

the fan pressurization leakage. Since the measurements were made on an individual apartment rather than the building as a whole, the leakage through floors,

ceilings and internal walls could represent a greater fraction of the total

leakage than occurs in normal infiltration. If this were the case, leakage

through windows and doors could account for more than 12 to 18% of the leakage

through the external walls. However, Teitsma and Peavy [7] estimated that

sealing off jalousie windows of a mobile home led to about an 18% decrease in

leakage rate. In this case, pathways for internal leakages between different

compartments of the building were minimal. Tamura [4] measured six houses and

estimated that windows and doors represented about 15 to 24% of the total leakage

paths. However, this data was obtained with storm windows and storm doors

installed. Other tests indicated that leakage through the primary windows and

doors was greater than 15 to 24%.

It should also be noted that flow rates under conditions of pressurization were

less than under depressurization. This may be seen by comparing Figures 7 and 8.

9. DEPRESSURIZATION MEASUREMENTS AT KENMORE

Depressurization measurements at Kenmore were made in the second floor apartment on the north side of the building. The results are shown in Figure 9. They show

air leakage rates slightly higher than those found at Windsor. This suggests that

other parts of the apartment besides the weatherstripped windows and doors contributed to air leakage.

Measurements were not made on the top floor apartment where the tracer measurements were made, because the residents were out, and the apartment was not

available when these tests were being made.

6
10. DEPRESSURIZATION MEASUREMENTS AT CUSTER

Measurements were made in the second floor and the fourth floor apartments at

Custer. In these tests the fan assembly was sealed to the rear door, and the

outside pressure lead was conducted into the back stairwell. In addition, another

type of test was made in the second floor apartment at Custer in which the windows

were opened^ so that about 1/4-inch of daylight was visible between the window

and the frame as illustrated in Figure 10. The purpose of this latter experiment

was to see how much windows which leaked badly might contribute to the total leakage. The results are presented graphically in Figure 11. This slight opening of

the windows nearly doubled the air leakage rate. Also the top floor apartment

was slightly more leaky than the one in the second floor. This is qualitatively

consistent with the results of the tracer measurements, unlike the results at

Windsor.

It is also of interest to note that the Custer apartment with the windows cracked

open offered more resistance to air flow than the Windsor apartment with the windows

and doors sealed. This large difference in building tightness was not fully reflected

in the tracer measurements, but infiltration rates were slightly lower at Custer.

Also, the Custer apartment was smaller so that for a given pressure difference

about half the volume of air was flowing through the envelope as at Windsor.

It might be further noted that in fan tests pressures are applied symmetrically

to all surfaces, and all flows are in or out depending on fan orientation. When

single dwelling units are tested instead of the building as a whole, pressure

differences across internal walls may be as great as across external walls. In

normal infiltration pressure differences develop asymmetrically, and their magnitudes are typically less than those in fan tests. In any case, further analysis

would be required to quantitatively account for the differences between Custer

and Windsor in the tracer and fan tests.

11. COMPARISON OF FAN AND TRACER GAS TESTS

The results of selected fan tests are plotted in Figure 12. These include data

from Windsor, Kenmore, and Custer as well as data from one other study [7]. The

flow rates have been converted from cfm to air changes per hour in order to compare them with tracer infiltration values. The solid squares in the figure represent infiltration rates by tracer measurements normalized to wind velocity of

10 mi/hr and inside-outside temperature difference of 10°F. These are plotted

against extrapolated estimates of the pressures which would be required to achieve

the same air leakage rates by fan pressurization or depressurization. These pressures

range from about 0.0003 to 0.002 in W.G.

This analysis assumes that the extrapolation is valid, and there is evidence

that such log-log plots can be linear over a fairly wide range. It also assumes

that under conditions of low wind perturbation integrated time-averaged pressure

differences due to wind are negligible compared to fan-induced pressure differences.

Two of the seven windows were left closed, because they were difficult to operate.

7
If these assumptions are correct, the results suggest that pressure differences required to induce natural infiltration may be much less 0.1 inches

of water which is the lowest value for pressure induced air leakage through

window cracks listed in the ASHRAE Book of Fundamentals [9], In addition, the

results in Figure 12 suggest that there is no simple extrapolation which will

permit prediction of natural ventilation rates from fan pressurization measurements, which can be applied across the board to all kinds of housing.

There are some differences between fan induced and natural air leakage which

should be pointed out. In fan tests presumably all of the air is flowing into or out of the structure depending on fan orientation. If natural infiltration

is treated as a simple "flow through" process, air may be considered to enter

through half of the openings and leave through the other half. As evidenced

by the straight line plots in Figure 12 as well many other examples, flow may

be expressed by the relationship

Q

= kApn

(3)

where Q

= flow rate through crack

k = flow constant

A = area of cracks

p = pressure difference across cracks

n = a parameter having a typical value of about 0.6 in the present

measur ements.

If the same flow rate is maintained, but through only half the area, the pressure

differential would have to be about three times as large.

That is to say, if A^ = 0.5A2*

and

Ql

= kA^ p^

Q2 = kA2P2U

Ql = Q 2

n =0.6

1 / 0.6

= ( 2 ) = 3.17 .

(3a)

(3b)

Moreover, since air is assumed to enter through half of the cracks and exit

through the other half, the two halves are in series, and the pressure difference

is doubled. Therefore, it should be approximately six times as large, and instead

of values 0.0003 to 0.002, the simple "flow-through" model would call for pressures

on the order of 0.002 to 0.012 in. W.G. The thermal head for a 10 degree temperature difference over a 10 ft. height would be of the order of 0.003 in. W.G.

The calculated impact pressure of a 10 mi/hr wind is about 0.04 in. W.G.

8
In addition to the question of how large the pressure difference is between the inside

and outside of the building, a paper by Hill and Kusuda [8] introduces additional con- siderations. They measured infiltration rates in a closed room with a special window

crack whose dimensions could be measured and controlled at will. They obtained experimental infiltration rates less than those calculated from measured average wind speed,

particularly at velocities greater than 5 mi/hr. They also measured pressure difference across the crack and showed that it had a strong pulsating component. This

indicates that it is a great over-simplification to treat wind pressure as a simple

steady state function. In their words, "the infiltration process that actually occurs

in and around window cracks is an extremely complex one". The results in Figure 12

and in the subsequent analysis suggest that infiltration rates correspond to lower

pressure differences than would be calculated from simple impact wind pressures.

12. FLOW RATES PER UNIT AREA

The lines in Figure 12 were extrapolated to a pressure difference of 0.3 in. W.G. , converted to cfm and divided by the estimated area of the respective dwelling

units. In this way the following estimates were obtained of flow rates expressed

in cfm/ft^ at 0.3 in. W.G. or in m /s at 75 Pa

Windsor 1.6 Vv?~ Windsor 0.7^ ^[AIO ' Kenmore 1.7 Kenmore 0 .n(6

Custer .6, Custer 0/27^

These are estimates for individual dwelling units and not the building envelope.

Most of the surface areas were interior walls, floors and ceilings.

13. CALCULATION OF INFILTRATION AT WINDSOR BY THE CRACK METHOD

Although fan pressurization tests indicated that the exposed cracks around

windows and doors which would be included in a crack length survey do not account

for all of the leakage paths in the apartment, an analysis of the crack method 19]

for estimating infiltration is presented here. The lengths of cracks in the

Windsor third floor apartment are itemized in Table 2.

TABLE 2. CRACK SURVEY AT WINDSOR THIRD-FLOOR APARTMENT

Multiple Footage

Crack at joints omitting windows "painted in"

at top sash.

1.0 X 137.7

Bed of frame at bottom or top where applicable

(see above).

1.0 X 84.43

Cross strip (meeting of upper and lower sash). 1.0 X 35.51

Threshold of doors. 2.0 X 5.66

Putty loose or missing (includes leaded glass

panes in upper sash).

1.0 X 156.85

TOTAL CRACK LENGTH 425.81 ft.

9
If, for example, the value of 77 ft J per hour per foot of crack length is assumed,

a total leakage of 32,800 ft^/h is obtained, which corresponds to 3.7 air changes

per hour in the Windsor apartment, which has a volume of about 8,900 ft . This

does not include leakage where the window frame is mounted in the wall. The

value of 3.7 air changes per hour is more than four times the rate of 0.83

obtained by the tracer method. The flow rate of 77 ft^ per foot of crack

length comes from Table 2 in the ASHRAE Handbook [9] for double-hung windows,

non-weatherstripped , loose fit. It corresponds to a pressure difference of 0.1

inch of water, the lowest pressure difference listed in the table. Actually,

this use of the leakage rate corresponding to 0.1 inch of water is not specified

in the ASHRAE Handbook, but it serves to point out that infiltration rates higher

than the true rate can be obtained by assuming too high a pressure difference

across windows and doors, even though these elements do not account for all of the

leakage. The significantly higher air leakage determined by the crack method

calculation in comparison with the measured value in the Windsor apartment could

be due to erroneous assumptions of pressure difference, crack length, crack width,

or a combination of these factors. The 1977 ASHRAE Handbook states, "Accuracy

of the crack method for design load calculations is restricted by the limited

data on air leakage characteristics and by the difficulty of estimating pressure

differences under appropriate design conditions of temperature and wind." The

results of these measurements would support this statement.

14. SUMMARY

The following average air leakage rates have been estimated from SF^ tracer

measurements at three apartment buildings:

Average Air Changes per Hour

Top Floor

Apt.

Lower Floor

Apt.

We ighted

Average for

Entire Apt.

House

Windsor 1.25 0.83 0.94

Kenmore 1.6 1.2 (assumed 75% of value

for top floor.)

Custer 0.99 0.76 0.82

At Windsor and Kenmore inside-outside temperature difference was about 10°F. At

Custer it started at about 4°F and increased to about 30°F during the tests.

Fan pressurization-depressurization measurements indicated Kenmore to have a very

slightly higher leakage rate than Windsor, while Custer was indicated to be

much tighter than either of the other two.

Sealing all of the exposed areas of the windows, one door, and one fireplace

at Windsor with polyethylene film produced at most a 20% reduction in air leakage

rate measured by fan pressurization. However, the total leakage may have included

pathways through internal walls plus floor and ceiling, as well as through outside

10
walls. Custer offered more resistance to air flow, with windows cracked open

slightly, than Windsor with windows and doors sealed. These results, plus the

observations of others, indicate that leakage around windows and doors represents

only part of the total air leakage paths in most buildings.

An analysis was made which suggests that experimental infiltration rates are intrinsically less than would be predicted from the simple impact pressure due

to wind.

Analysis of the ASHRAE crack method suggests that it underestimates the number

of leakage paths, but in applying the method results may be obtained which are plausible or even too high, if pressure difference across the cracks is over- estimated .

15. SI CONVERSIONS

Familiar English units have been used in this report. To convert to units the

following conversion factors are provided:

(cfm) X 4.719 x 10~4 = (m /sec)

(mi/hr) X 0.44704 = (m/sec)

knots X 0.51444 = (m/sec)

W. G.) X 249.1 = (Pa)

in. X 0.025400 = m

5 (°F-32)g = °C

16. REFERENCES

1. D. T. Harrje, C. M. Hunt, S. J. Treado, and N. J. Malek. Automated

Instrumentation for Air Infiltration Measurements in Buildings, Center

for Environmental Studies Report No. 13, April 1975. (Princeton U.).

2. C. M. Hunt and S. J. Treado, A Prototype Semi -Automated System for

Measuring Air Infiltration in Buildings Using Sulfur Hexafluoride as

a Tracer, National Bureau of Standards Technical Note 898, March 1976.

3. L. E. Cover, Modern Insulation Methods. IVo papers presented before the

Institute of American Meat Packers, Copyright 1929.

4. G, T. Tamura, Measurement of Air Leakage Characteristics of House

Enclosures, ASHRAE Trans. 81 (1), 202-211 (1975).

11
5. S. Strieker, Measurement of Air-Tightness of Houses, ASHRAE Trans. 81. (1), 148-167 (1975).

6. F. W. Sinden, Multi-Chamber Theory of Air Infiltration. To be published

in Vol. 12 of Buildings and Environment (1978), Pergamon Press.

7. G. J. Teitsma and B. A. Peavy, The Thermal Performance of a Two-Bedroom

Mobile Home. National Bureau of Standards, Building Science Series 102

(1978).

8. J. E. Hill and T. Kusuda, Dynamic Characteristics of Air Infiltration,

ASHRAE Transactions 81 (1), 168-185 (1975).

9.

ASHRAE Handbook of Fundamentals, American Society of Heating, Refrigerating

and Air-Conditioning Engineers (1977), Chapter 21.

12
Figure

1.

Front

view

of

Windsor

apartment

(left

of

center).
Figure 2. Front view of Kenmore apartment
Figure

3.

View

of

Custer

apartment
Figure 4. Floor plan of third-floor apartment at Windsor. Units on second and fourth floors have essentially the same floor plan.

Location of circulating fan is shown, and circled crosses

show locations of air-sampling points. "A" denotes location

of high-speed fan used in pressurization-depressurization tests.
i d D d

o r—o

rl u •H U u U

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5.

Floor

plan

of

top-floor

apartment

at

Kenmore

showing

1<

of

circulating

fan

and

air-sampling

sites

indicated

by

crosses.

Unit

below

had

essentially

the

same

floor

pi,

"A"

denotes

location

of

high-speed

fan

used

in

pressur

depressurization

tests.
Figure

6.

Floor

plans

for

second-floor

inside

unit

and

fourth-floor

end

unit,

drawn

side

by

side.

Circled

crosses

indicate

sampling

sites.

"A"

denotes

location

of

high-speed

fan

in

pressurizationdepressurization

tests.
—

•

3rd

FLOOR

(RENOVATED)

8000

—

4

4th

FLOOR

(UNRENOVATED)

—

B

2nd

FLOOR

(RENOVATED)

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PRESSURE

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(CFM)

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8000

6000

4000

3000

2000

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Figure 8. Comparison of fan pressurization tests at Windsor with

windows, doors, and fireplace sealed and unsealed.
FLOW

RATE

(

CFM)

Figure 9. Fan depressurization tests at Kenmore.
I

Figure 10. Illustration of a window opened slightly to

intentionally produce a leak.
FLOW

RATE

(

CFM

)

Figure 11. Fan depressurization tests at Custer comparing

second-floor interior apartment and fourth-floor

end apartment, and also showing the effect of

slightly opened windows.
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NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLIC ATION OR RLPORT NO. NBSIR 78-1475

2. Gov’t Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Air Leakage Measurements in Three Apartment Houses

in the Chicago Area

5. Publication Date June 1978

6. Performing Organization Code

7. AUTHOR(S)

C. M. Hunt, J. Porterfield and P. Ondris

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)

Research work on this project was done for the Weatherization

Program of the Community Services Administration, as a joint

effort of NBS and the Energy Resources Center for the University

of Illinois at Chicago Circle

13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

This NBS-funded report will make the results generally available.

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

bibliography or literature survey, mention it here.) Air infiltration measurements were made in three apartment houses in the Chicago

area using SF^ as a tracer gas. Two were in tenement districts and one was

suburban. Data were collected in selected apartments in each building, and these

data were used to estimate the infiltration rate for the entire building. Whole

building estimates of 0.94 and 1.2 air changes per hour were obtained under the

conditions of tests in the tenement apartments, and 0.82 air changes per hour

in the suburban apartment.

Comparisons of the tightness of individual dwelling units by fan pressurizationdepressurization techniques were also made. The suburban apartment was found

to be much tighter than the other two apartments. The difference was much

greater than predicted by the tracer tests.

An analysis of the ASHRAE Crack Method is also made.

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

Air infiltration; air leakage; sulfur hexafluoride tracer, low income housing.

19. SECURITY CLASS 21. NO. OF PAGES

(THIS REPORT)

27

UNCL ASSIFIED

20. SECURITY CLASS 22. Price (THIS PAGE)

UNCLASSIFIED $4.50

18. AVAILABILITY fX Unlimited c For Official Distribution. Do Not Release to NTIS

Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. Cl 3

[~X1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 USCOMM-DC 2904 2- P74


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