It is impossible to determine the actual air exchange rate of a house without measuring it. More importantly, it is difficult to find and plug air leaks when the weather is nice enough to be doing the work. A blower door is a tool used to determine air exchange rates for precise energy calculations, and to make it easier to discover and repair sources of air leaks – even on a nice summer day.
The house is first sealed of as many known air leaks as possible – such as fireplace chimneys, furnace flues and ventilation fans (by stuffing them full of insulation, rags, etc.). All windows and doors are closed and the blower door is installed in one exterior door. The blower door is turned on to suck air out of the house and create a negative pressure inside. This causes an artificial ‘worst case’ scenario for air infiltration that rushes into the house to equalize the pressure.
The house is then checked for infiltration using smoke sticks, tracer gas, thermal camera or something similar, to make the air leaks and their sources more visible. Each leak is plugged (where possible) and the house is tightened up. Before and after measurements can estimate savings from the work completed.
Some variations will occur with seasonal changes – such as building materials expanding and contracting, which will influence results, but the blower door is the most accurate method developed to date for dealing with air infiltration on a measurement basis.
Infiltec (Main Office)
5613 Leesburg Pike, Suite 53
Bailey’s Crossroads, VA 22041
Go to their web site at www.infiltec.com
The Energy Conservatory
2801 21st Ave. South
Minneapolis, MN 55407
Go to their web site at www.energyconservatory.com
Source: Text Bob Fegan 12/2008; Photos by Bob Fegan