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Question DetailsAsked on 7/13/2017

What can I do to prevent recurring mold at the highest point of my A-frame ceiling in my family room?

Because the house is an A-frame, there is no attic, and thus no ventilation. Is there a venting system that would work to remove the moisture and thus prevent the mold from recurring. Once we solve the problem that is causing the mold, we can repaint knowing the problem will not recur.

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1 Answer


If winter mold (most common), proper ventilation and insulation in any unconditioned space above the A-frame or cathedral ceiling. If a true A-frame, where the ceiling is the underside of the roof, then short of putting in a ventilated and insulated attic over it, your only solutions are (after making sure moisture is not coming through the roof sheathing from leakage) is ventilation - preferably with bare wood to maximize moisture evaporation to the house. If painted that promotes mold growth in that case, but after mold removal priming with Kilz or similar mold-resistant paint (I add additional mildewcide additive like Krud Kutter MC-2), then a finish coat also with mildewcide added.

If summer mold, your humid hot air is rising and forming a mold farm - so dehumidification, combined with ventilation to keep the humidity down at that area is needed.

In either case, ventilation to remove any moisture accumulating there (either coming through from the roof, or condensing on the cold ceiling) is the ultimate way to keep it from coming back - reversible ceiling fan so the fan is blowing the air against the ceiling in the cold weather works best unless the fan is quite close to the peak, in which case downcast airflow is preferred. Unfortunately, the fan has to run more or less continuously - so in peaks where condensation on cold surfaces is the case insulated attic construction, insulated roofing, or a continuous-run household fan with directed ports blowing air across that area is sometimes needed.

Note - normal ceiling fans (the $100-300 box store type) are NOT rated for continuous use - for this sort of case you need a commercial continuous run circulation fan like is used in convention centers and casinos, atriums, pool buildings, etc. Come in basic industrial plus a variety of artistic but commonly $250-300 on up for the fan unit itself.

Answered 3 years ago by LCD

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