Home Energy

How Air Moves Through Your House according to: https://smarterhouse.org/home-systems-energy/ventilation-and-air-distribution

Virtually all houses, even yours, exchange indoor air with the outdoors. There are two reasons for this: First, a house will always have some leaks (air passages), however small, that connect the inside with the outside. These might include larger gaps around pipes, vents, and chimneys, and smaller cracks at places such as the join between the window frame and the wall. The second reason for air exchange is that there are temperature and pressure differences between inside and outside — air works hard to move from regions of high air pressure to ones with lower air pressure.

Consider a two-story house with a basement during winter. We all know that the warmest air tends to rise to the top floor, and that it can be several degrees warmer near the ceiling than in the basement. The warm, buoyant air is at a higher pressure than the cold air outside, and will want to move up and out, through windows, ventilation openings, and leaks in the walls, ceiling, and roof. Downstairs and in the basement, low-pressure cool air rushes in to replace the rising air in an attempt to maintain pressure balance.  In most houses, the amount of air that enters the house increases when it’s windy and cold. When it’s warm outside, the stack effect is much weaker or reverses.

If air movement between inside and outside is accidental, we call it infiltration.