The infiltration and exfiltration of air in buildings is the primary reason to install an air barrier system. When installing an air barrier system it is critical to understand the building pressures that cause infiltration and exfiltration. Here are the three major stressors:
- Wind Pressure
- Stack Pressure
- HVAC Fan Pressure
For the next several posts, we’ll discuss how each of these pressures affects building air leakage.
Wind is the first consideration that comes to mind when discussing air leakage from buildings. Wind pressure pressurizes a building positively on the façade it is hitting. As it blows around a building corner, it speeds up considerably creating strong negative pressure on those corners while less pressure is exerted on walls and the roof. Wind pressure on buildings is a significant factor when calculating energy or moisture–related air leakage. In fact, over the course of a year average wind pressure measures 10-15 mph in most locations in North America
(Hutcheon and Handegord, 1983). Left unchecked, wind pressure can create substantial air leakage and higher energy costs.
Up next post: stack pressure sometimes referred to as the “chimney effect.”