When performing a blower door test, what is being measured?

When performing a blower door test, the primary measurement involves the air tightness of the building envelope. This test is crucial in assessing how much air is escaping or intruding through the various leakage points within a structure. The blower door creates a pressure difference between the inside and outside of the building, allowing technicians to quantify the amount of air leakage that occurs, usually expressed as air changes per hour (ACH) at a specific pressure differential (often 50 Pascals).

Understanding the air tightness of a building envelope is essential for several reasons. It not only affects energy efficiency—because air leaks can lead to higher heating and cooling costs—but also impacts indoor air quality, moisture control, and overall comfort. A tight building envelope typically leads to improved energy performance, fewer drafts, and a more consistent internal environment.

The other choices relate to important aspects of building performance but do not directly pertain to the measurement taken during a blower door test. For instance, while the energy efficiency of HVAC systems can be influenced by air tightness, it is not a direct measurement gained from a blower door test. Similarly, insulation quality and resident comfort levels are also critical factors in building performance, yet they are assessed through different methods and criteria, rather than through the specific process