True or False: All pressure taps used to measure building pressure should cross the air barrier at or about ground level.

The statement that all pressure taps used to measure building pressure should cross the air barrier at or about ground level is true. This is important because pressure taps function by allowing for accurate readings of the differential pressure between the inside and outside of the building. When these taps are located at or about ground level, it ensures that they can effectively measure the pressures acting on the building without being influenced by the effects of thermal stratification or other factors associated with height in the building.

Positioning pressure taps at ground level minimizes potential inaccuracies that could arise from variations in pressure due to elevation changes within the building. It also helps ensure that the readings obtained are reflective of the overall building envelope performance, which is essential for assessing the effectiveness of the air barrier and identifying areas of leakage or infiltration.

This understanding is crucial in the context of whole-building airtightness testing, where precise measurements are necessary to evaluate and improve building performance in terms of energy efficiency and indoor environmental quality. The other options suggest scenarios or conditions where different locations for pressure taps might be valid, but the standard practice aligns with using ground-level pressure taps for consistency and reliability in measurements.