Stack Effect
- camden Dionne
- Jan 29
- 2 min read
The weather is calling for -6 degrees Saturday in Central Maine. The temperature difference (delta T) between inside and outside will be in excess of 70 degrees in most homes. This has an affect on the “stack effect”
If your home has poor air sealing and a temperature difference (ΔT), the stack effect can cause conditioned air to escape. Just like heat, air moves from areas of higher pressure to lower pressure, meaning that for every cubic foot of air
leaving the home, an equal amount must enter to maintain balance.
Stack effect happens as warm air naturally rises inside a home, creating positive pressure at the ceiling. If the ceiling is not properly sealed, this air escapes into the attic or outside. To replace the lost air, cold air is drawn in at the lower levels, which then gets heated and rises, repeating the cycle throughout the winter. The greater the ΔT and the taller the structure, the stronger this effect becomes.
In addition to energy loss, stack effect can lead to moisture issues. Escaping warm air carries humidity, which condenses when it meets a cold surface. As you lose conditioned air, the air being replaced from outside and is dry in winter and once warmed the humidity drops even lower.
There is also reverse stack effect, which I will hold off on writing about until summer when it is applicable.
The picture posted was from a home we visited this week. There has been roof alterations made and when this happened, the attic space became much cooler. There was a significant amount of air leakage into the attic space that is condensing and freezing on the bottom of the roof sheathing.
Is there a Solution to Mitigate the Stack Effect?
The most effective solution to avoid the stack effect is to air seal and insulate key areas, including the basement and attic. (Also the lowest leaks and the highest leaks) If you invest in getting your home air sealed and insulated, you can benefit from utility bill savings, greater indoor air quality and comfort. Lakewood Home Energy offers standalone air sealing as a service, with rebates from efficiency maine.
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