Blower Door - Air Density Corrections

Air Density Corrections

In order to increase the accuracy of blower door test results, air density corrections should be applied to all airflow data. This must be done prior to the derivation of building air leakage coefficients and pressure exponents . The following methods are used to correct blower door data to standard conditions.

For depressurization testing, the following equation should be used:

= Airflow corrected to actual air density

= Airflow derived using and

= Air density inside the building, during testing

= Air density outside the building, during testing

For pressurization testing, the following equation should be used:

The values and are referred to as air density correction factors in product literature. They are often tabulated in easy to use tables in product literature, where a factor can be determined from outside and inside temperatures. If such tables are not used, the following equations will be required to calculate air densities.

can be calculated in IP units using the following equation:

= Air density inside the building, during testing

= Elevation above sea level (ft)

= Indoor Temperature (F)

can be calculated in IP units using the following equation:

= Air density outside the building, during testing

= Elevation above sea level (ft)

= Outdoor Temperature (F)

In order to translate the airflow values derived using and from the blower door manufacturer to the actual volumetric airflow through the fan, use the following:

= Actual volumetric airflow through the fan

= Volumetric airflow calculated using manufacturer's coefficients or software

= Reference air density (typically 1.204 for Kg/m3 or 0.075 for lb/ft3)

= Actual density of air going through the fan for depressurization and for pressurization