The purpose of a blower door test is to check for air leaks–all homes have them–and then measure the extent of those leaks.
Blower doors consist of
Frame and flexible panel that expand to fit in a doorway.
Pressure gauge to measure the pressure differences inside and outside the home.
Airflow manometer and hoses for measuring airflow.
A powerful fan mounts within the frame of an exterior door. The fan pulls air out of the house, lowering the air pressure inside. The higher outside air pressure then flows in through all unsealed cracks and openings. These tests determine the air infiltration rate (air leakage) of a building. You want a calibrated test rather than an non-calibrated one
These tests were originally used to make certain a new home was tight enough to achieve the Energy Star certification. For a while they were used by professional energy auditors to seek air leaks.
However, all houses leak–even those that are Energy Star certified. Where those leaks occur is well-known to anyone in the business:. Basically they are:
Weather stripping around doors.
Wall- or window-mounted air conditioners.
In any good weatherization program, whether you do-it-yourself or hire someone to do it, leaks should be anticipated at the above locations and stopped.
Therefore, it is sometimes best to do the blower door test after the home has been caulked and weatherized. This test, although it looks impressive to a homeowner, is still best as a tool for certification of new homes.
In all the existing homes I have seen tested with a blower door, this test did find only one leak in a place we would not have looked to caulk or weatherize anyway. This was probably a fluke–it was a hole through an exterior wall, behind a water heater inside (not visible) and behind a hedge outside (not visible). So, if you have the money to spend, have a blower door test, but wait until after the caulking and weatherization process is finished. The test will check how tight your house is now and for the future.
Before you sign on the dotted line to buy an existing home or sign the contract to build a hew home, there is a good use for a blower door test. Click here.
For further information about Energy Audits or Renewable Energy inthis area of Texas contact