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How to stop a cathedral roof from sweating?

I have good venting but it still sweats ........

Asked by Gary Bleedorn
Posted Sat, 02/08/2014 - 19:14
Edited Sun, 02/09/2014 - 06:48

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Gary,
The reason that condensation is accumulating in your cathedral ceiling assembly is that your ceiling is leaky. Warm, humid interior air is escaping through holes and cracks in your ceiling. When the humid air contacts a cold surface (usually, the underside of the roof sheathing), the moisture condenses (or, more accurately, is adsorbed by the sheathing, or in some cases accumulates as frost).

Ventilation can't solve this problem. In fact, ventilation can make this problem worse (by accelerating the flow of air through your ceiling cracks).

The solution is to include a ceiling-side air barrier (or to seal all of your ceiling leaks). For more information on these issues, see these two articles:

How to Build an Insulated Cathedral Ceiling

All About Attic Venting

Answered by Martin Holladay, GBA Advisor
Posted Sun, 02/09/2014 - 06:47
Edited Sun, 02/09/2014 - 15:53.

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