After all the air sealing work is done, the building's leakage rate can be measured by doing a blower door test. A blower door test (shown below) pressurizes a house and measures the amount of air that escapes to the outside.
Tight houses lose less heating and cooling to the outside...and therefore use less energy. The leakage rate is therefore a crucial input in the energy model that determines how well the house will perform.
Leakage is measured in Air Changes per Hour (ACH) when a house is pressurized to 50 Pascals (50). So 7 ACH50 is 7 air changes of the entire volume of the air in a house in one hour. 7 ACH50 is the typical rate of infiltration for newly constructed homes today.
To put leakage rates into perspective...
New construction, to current code: 7 ACH50.
Energy Star qualified home: 5 to 6 ACH50
Passive House certified home: 0.6 ACH50
Our last project 411 Varnum NW: 3.5 ACH50
4310 4th TARGET AIR LEAKAGE RATE: 2.5 ACH50 OR LOWER
This is not new construction. We don't have control of many of the details of the home original construction. We are constantly improving our construction strategies and techniques, but we are also realistic on what we can achieve.
However, we will be performing a preliminary blower door test prior to drywall to allow us time to find air leaks prior to drywall so we can correct them. This should be a big step forward in achieving, or being below our target leakage rate.