Because the building shell represents the first line of defense against heat loss in winter and heat entry in summer, blower door air-tightness tests are important and informative steps in a residential energy inspection.
Thermal imager + blower door for a “one-two punch”
A blower door is a powerful, variable-speed fan mounted in a frame that forms an air-tight seal in a doorway. Blower doors are expensive, ranging in price from $2,500 to $5,000, but are available to rent.
They can be used both to pressurize the house under inspection so that air blows out of it or to create a low-level vacuum in the house, which draws air in. By creating a low-level vacuum in the house, a blower door serves two functions: First, it tells you how “tight” or “leaky” the house is overall. Then, by drawing outside air through all the leak points, it makes air leaks in the house and other problem areas easy to spot with a building diagnostics imager like the Fluke TiR32. Conversely, pressurizing a home with a blower door helps you to see leaks as the air “exfiltrates” from the house.
Blower doors usually have instrumentation that measures how much air the fan must move to produce a certain pressure differential between the inside and the outside of the house. By comparing the volume of air that the fan is moving per hour to the volume of the building interior, you can calculate the number of air changes that are occurring per hour. Older, leaky houses may have five or more times as many air changes per hour than a modern, Energy Star-rated dwelling, leaving lots of room for improvement.
Find it, fix it, bill it
A good first step to fixing an energy-inefficient house is to see exactly where the energy is going. A thermal conduction test can reveal problem areas such as wall areas where there’s no insulation, or cold spots where old metal window frames are conducting heat into or out of the house.
Next, using a thermal imager and blower door, you can quickly scan the building interior and exterior to pick out the spots that reveal where air is entering or leaving the building. With a thermal imager, you can capture images that document the problem spots, which you can then report to the homeowner, use when writing your estimate, and use again as a guide when you return to fix the problems.
Armed with the evidence you’ve captured with your blower door and thermal imager, you’ve got key information to turn your energy audit into an open door to more work: fixing the problems you’ve discovered.