Blower Door Building Envelope Air Leakage Test

In order to determine the “air tightness” measured in amount of cubic feet per minute (cfm) is leaked through the “Building Envelope” the energy auditor performs what is commonly known as a Blower Door Test. These are some reasons for establishing the proper building tightness:

• Reducing energy consumption due to  air leakage
• Avoiding uncomfortable drafts caused by cold air leaking in from the outdoors
• Making sure that the home's air quality is not too contaminated by indoor air pollution.
• Air leakage can increase heating and cooling costs over 30% and contribute to comfort, health and safety problems.
• Finding hidden air leakage sites, called bypasses, can be difficult without the use of a blower door.

Equipment Used in Test

The reason why the test is known as a “Blower Door Test” is because the equipment used in the testing procedure is in fact called a “Blower Door.”

The Blower Door is a powerful fan that mounts into 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. To determine the amount of leakage  the blower door creates a pressure difference of 50 Pascals between inside and outside. (50-Pascals is approximately equivalent to a 20 m.p.h. wind blowing against all surfaces of a building). The leakier the house, the harder the fan must work to maintain the pressure. The amount of air the fan blows, measured in cubic feet per minute (CFM), is used to determine air changes per hour (ACH). 

In order to properly measure the pressure differences and air flow a specialized manometer is attached to the Blower Door while the fan is operating. Measuring the amount of air leakage can be determined in either air changes per hour (ACH), or, cubic feet per minute (CFM). Higher the ACH and CFM  means higher heating and cooling costs, and greater potential for moisture, comfort, and health issues.

                       Preparing for a Blower Door Test

The following steps to prepare your home for a blower door test will be taken:

·         Close windows and open interior doors

·         Turn down the thermostats on heaters and water heaters

·         Cover ashes in wood stoves and fireplaces with damp newspapers

·         Shut fireplace dampers, fireplace doors, and wood stove air intakes.