Which type of blower door test result indicates better air-tightness of a home?

The result that indicates better air-tightness of a home is represented by a lower CFM50 value. CFM50 stands for "Cubic Feet per Minute at 50 Pascals" and measures the amount of air that leaks through the envelope of a building when a blower door test is performed at a pressure of 50 pascals.

In simpler terms, a lower CFM50 value means that less air is escaping from the building, which is a direct indication of improved air sealing and energy efficiency. This helps in reducing energy costs, enhancing indoor comfort, and minimizing potential issues related to humidity and pollutants entering the home. Conversely, higher CFM50 values signify greater leakage and poorer air-tightness, which can lead to energy loss and other challenges associated with uncontrolled air infiltration.

While ACH50 also deals with air changes per hour, a lower ACH50 value indicates better air-tightness just like lower CFM50, but in the context of the question asking for the test result as a direct measurement, CFM50 is the clearer indicator of leakage rates. Thus, among the choices, the emphasis on CFM50 provides a straightforward approach to assess a building's air-tightness visually and numerically.