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Large Building Air Leakage Test Calculator.

Online calculator analyzes the air
flows required to pressure test
the airtightness of a large
building with calibrated fans.

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See *NEW* for latest page updates.

This page includes a online calculator that analyzes the air flows required to test the airtightness of a large building by pressurization or depressurization with one or more calibrated fans. The calculator uses javascript, and it will not work if your web browser does not support javascript, or if you do not have javascript enabled.

The calculations default to recent UK airtightness recommendations for "Normal Practice" and "Best Practice" for office buildings with mixed mode ventilation from the UK Air Tightness Testing and Measurement Association (ATTMA) test standard Technical Standard 1: Measuring the Air Permeability of Building Envelopes (TS1). The full list of ATTMA building air leakage recommendations in Metric and US units is shown in Table 1 below:

*NEW*

Table 1: ATTMA Air Leakage Index (m3/hr/m2 [cfm/ft2] @ 50Pa)
Building Type Best Practice Leakage Index Normal Practice Leakage Index
Offices (naturally ventilated) 3.0 [0.1641] 7.0 [0.3828]
Offices (mixed mode ventilation) 2.5 [0.1367] 5.0 [0.2735]
Offices (air conditioned/low energy) 2.0 [0.1094] 5.0 [0.2735]
Factories/Warehouses 2.0 [0.1094] 6.0 [0.3281]
Superstores 1.0 [0.0547] 5.0 [0.2735]
Schools 3.0 [0.1641] 9.0 [0.4922]
Hospitals 5.0 [0.2735] 9.0 [0.4922]
Museums and Archival Stores 1.0 [0.0547] 1.5 [0.0828]
Cold Stores 0.2 [0.0109] 0.35 [0.0191]
Dwellings (naturally ventilated) 3.0 [0.1641] 9.0 [0.4922]
Dwellings (mechanically ventilated) 3.0 [0.1641] 5.0 [0.2735]

An "Old Practice Leakage Index" has been included in the calculator below that defaults to twice the UK "Normal Practice Leakage Index" in order to expand the range of the calculations to include older buildings.

These leakage index recommendations are based on leakage per surface area and not the commonly used air changes per hour (ACH) comparison used for smaller residential buildings. When the buildings of different size are compared, ACH does not provide a good comparison between buildings, and leakage per surface area comparisons provide a better measure of envelope construction quality. The online calculator below is provided as an introduction to large building air leakage testing, and it should not be used for actual testing.

One problem with large building tests is determining the type and quantity of fans necessary to perform a test. The online calculator estimates the number of fans required, both for blower door fans (e.g. the Infiltec E3 stacked blower door fan with up to 3 fans in each doorway and each fan capable of flows of 100-5450 cfm @ 50 Pa) and for large mobile fans (e.g. the Infiltec G54 mobile fan with flows of 15,000-55,000 cfm @ 50 Pa). Experience has shown that is undesirable to arrive at a test with either too much fan capacity or too little fan capacity.

For more information on large building air leakage testing, see the Infiltec Large Building Envelope Airtightness page. Click here to see pictures of a test of a 9,000,000 ft3 (256,000 m3) food distribution warehouse in Manchester, UK.

ONLINE BUILDING LEAKAGE CALCULATOR IN US UNITS:
(click here for Metric Units Calculator*NEW*)

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Instructions: you can type your building dimension
INPUT DATA into the boxes below, and the building leakage
CALCULATED DATA will be updated for your entries:
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INPUT DATA:

Building Dimensions: (type your building data into each box to replace the defaults)
Total Building Floor Area: square feet.
Height of 1 Story: feet.
Number of Stories: .
Ratio of Length to Width (input 1 when Length=Width, 2 when Length=2xWidth, etc.)
US Army Corps of Engineers (ACE) .25cfm/ft2@75Pa Leakage Index: cfm/ft2 (default 0.25 cfm/ft2 [4.57 m3/hr/m2] @ 75 Pa). *NEW*
UK Old Practice Leakage Index: cfm/ft2 (default 0.5469 cfm/ft2 [10 m3/hr/m2] @ 50 Pa). *NEW*
UK Normal Practice Leakage Index: cfm/ft2 (default 0.2735 cfm/ft2 [5 m3/hr/m2] @ 50 Pa for office building).*NEW*
UK Best Practice Leakage Index: cfm/ft2 (default 0.1367 cfm/ft2 [2.5 m3/hr/m2] @ 50 Pa for office building).*NEW*

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Calculations: all of the building leakage data below
is calculated from the building dimension INPUT DATA above that
you have entered or from the default values. Do not enter data
in the CALCULATED DATA boxes below. To update all of the
calculations below, click on any of the CALCULATED DATA boxes.
To return to the default values, press your browser refresh button.
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CALCULATED DATA:


BUILDING DIMENSIONS: (click on any box to recalculate all boxes)
Building Width: feet.
Building Length: feet.
Building Surface Area: square feet (includes envelope floor, wall and ceiling).
Building Volume: cubic feet.

MAXIMUM ALLOWABLE LEAK FLOW IF BUILDING JUST MEETS LEAKAGE INDEX: (click on any box to recalculate all boxes)
US ACE .25 Leakage Index flow: cfm @ 75 Pa.
UK Old Practice Leakage Index flow: cfm @ 50 Pa.
UK Normal Practice Leakage Index flow: cfm @ 50 Pa.
UK Best Practice Leakage Index flow: cfm @ 50 Pa.
** Note: the default normal and best practice for office building leakage are from the ATTMA March 2006 standard ***.

MAXIMUM ALLOWABLE LEAK AREA IF BUILDING JUST MEETS LEAKAGE INDEX: (click on any box to recalculate all boxes)
US ACE .25 Leakage Index equivalent area: square feet.
UK Old Practice Leakage Index equivalent area: square feet.
UK Normal Practice Leakage Index equivalent area: square feet.
UK Best Practice Leakage Index equivalent area: square feet.
** Note: Assumes 0.65 exponent. One square foot of leakage will pass about 1000 cfm @ 50 Pa pressure. **

NUMBER OF E3 STACKED BLOWER DOOR FANS REQUIRED FOR TEST: (click on any box to recalculate all boxes)
US ACE .25 Leakage Index: E3 fans.
UK Old Practice Leakage Index: E3 fans.
UK Normal Practice Leakage Index: E3 fans.
UK Best Practice Leakage Index: E3 fans.
** Note: the E3 fan flow is 100-5450 cfm @ 50 Pa, or 100-5000 cfm @ 75 Pa, and 3 fans can be stacked in each doorway. **

NUMBER OF G54 MOBILE FANS REQUIRED FOR TEST: (click on any box to recalculate all boxes)
US ACE .25 Leakage Index: G54 mobile fans.
UK Old Practice Leakage Index: G54 mobile fans.
UK Normal Practice Leakage Index: G54 mobile fans.
UK Best Practice Leakage Index: G54 mobile fans.
** Note: the G54 fan flow is 15-55 kcfm @ 50 Pa, or 15-50 kcfm @ 75 Pa, and predicted flows below 40% of maximum may not permit a full multi-point test covering 20-60 Pa. **

AIR CHANGES PER HOUR: (click on any box to recalculate all boxes)
US ACE .25 Index: ACH75.
UK Old Practice Index: ACH50.
UK Normal Practice Leakage Index: ACH50.
UK Best Practice Leakage Index: ACH50.
** NOTE: Compare to a 1 story, 1500 f2 house, where default leakage index values for Old Practice = 10 ACH50, Normal Practice = 5 ACH50, and Best Practice = 2.5 ACH50. **

Please send calculator problem reports and comments to .

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ONLINE BUILDING STACK PRESSURE CALCULATOR IN US UNITS:

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Instructions: you can type your stack pressure
INPUT DATA into the boxes below, and the stack pressure
CALCULATED DATA will be updated for your entries:
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INPUT DATA:

STACK PRESSURE INPUTS: (type your stack pressure data into each box to replace the defaults) .*NEW*

Barometric Pressure: PSI (default 14.7 PSI is sea level pressure).
Height difference: feet.
Indoor Temperature: degrees Fahrenheit.
Outdoor Temperature: degrees Fahrenheit.

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Calculations: all of the stack pressure data below
is calculated from the stack pressure INPUT DATA above that
you have entered or from the default values. Do not enter data
in the CALCULATED DATA boxes below. To update all of the
calculations below, click on any of the CALCULATED DATA boxes.
To return to the default values, press your browser refresh button.
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CALCULATED DATA:


STACK PRESSURE CALCULATION: (Click on any box to recalculate all boxes)
Change in Inside/Outside Pressure with height Pascals or Inches of Water Column.
** Note: When the outside air temperature is lower than inside, there will be an upward pressure at the top of the building, similar the lift of a hot air balloon. During temperature extremes, stack pressure variations with height may limit air leakage testing in tall buildings because of the requirement for nearly equal pressures on all surfaces of the building during the test. **

Please send calculator problem reports and comments to .

For further assistance, call Infiltec toll free at (888) 349-7236.
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This page copyright © 1996-2013 by , all rights reserved. Please send comments to the author, . The last update was May 28. 2013

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