Air Leakage Testing and Air Sealing of a House in Takoma Park

September 2008

This is the house where I have my home office in Takoma Park. It is a one and a half story brick house with an attached garage and front porch. On this and followng pages I will go through measuring and sealing the air leaks on this house.

House for Air Sealing Case Study

To measure air leakage, we use a piece of equipment called a blower door. The reading from the blower door is in a measurement called CFM@50 which is the number of cubic feet per minute of air that gets sucked in through the leaks when the house is depressurized to 50 pascals (a unit of air pressure). We close all windows and doors, turn off any heating or cooling equipment and fans and run the test. When my house was measured, it had a air leakage rate of 6400 CFM@50.

This is a very high leakage rate, over 5 times higher than the optimal rate of leakage for a house like this! Another way to look at this is by converting to natural air changes per hour (ACH). This house has an ACH of 0.92, that means that in one hour almost all the air in the house that we might have heated up in the winter with a gas furnace has leaked out.

This could translate to as much as $300 per year wasted for natural gas heating in the Takoma Park climate.

NEXT: Sealing the leaks (click for the next page in the series )...



Blower Door Testing

A blower door is a special piece or equipment used to measure how leaky a house is to air. It consists of a calibrated fan, an air tight frame and membrane that temporarily fits in an outside door frame, and a sensitive air pressure meter. When the fan is turned on the house is depressurized and air will come through any leaks in the house and exit through the fan.

Blower Door for Testing House Air Leakiness

Air Sealing

  • Air sealing is the name we call all efforts to reduce the leakyness of a home to air.
  • Air sealing makes use of high expansion foam, weatherstripping and other barriers to air flow.
  • A successful air sealing effort can in some cases reduce home heating energy use by 20-30%.
  • The most important place to air seal is the junction between the top floor and the attic!
  • The second most important air sealing is done in the basement.
  • Sealing windows and doors is the last place we work as it is, believe it or not, the least important.