How It Works: The Stack Effect

Three forces move air through a house: HVAC equipment, wind, and the stack effect.

Three forces move air through a house: HVAC equipment, wind, and the stack effect. Associate editor Rob Yagid explores how the stack effect works in both winter and summer. In the winter, cracks and openings throughout the building shell allow the pressure difference between indoor and outdoor spaces to drive air out of the top floor and to suck air in through the first floor. In the summer, when indoor air is cooled, the reverse occurs; however, because the temperature difference between inside and outside typically isn't as great as it is in winter, the stack effect isn't as great either. Whatever the season, the best way to remedy the stack effect in most houses is by air-sealing the house to minimize gaps between indoor and outdoor spaces.