CONDENSATION AND MOLD

CONDENSATION AND MOLD IN A BATHROOM

Question


I have mold along the outside wall of my bathroom. It is mostly above the shower and the top of the outside wall. There is adequate insulation in the attic and the vent is connected and discharging outside. I think this might be cased by warm moist air from the shower meeting a cold spot on the wall and ceiling. If I remove the shower and replace it with a full tub and shower and replace the gyprock with cement board and seal the vapor barrier on the outside wall, will this stop the problem?

Answer


No. You will have done very little to change the surface temperature of the walls and ceilings. The moisture laden air from the shower in the bathtub will be virtually the same as the moisture laden air from the shower stall. When humidity levels are very high, it takes very little drop in temperature to form condensation. Any cool surface will do.



It sounds like you are about to do some bathroom renovations. Your best bet is to install a high quality bathroom exhaust fan. These fans cost three or four times what a typical bathroom exhaust fan costs. They move considerably more air and are quieter. Most have dual squirrel cage blowers (similar to the design of your furnace fan).

I installed one in my bathroom a few years ago. It is ceiling mounted immediately outside the shower stall -- no condensation on the walls, mirrors, anywhere. If you leave the bathroom after showering, and return one minute later, you have no sense that someone has just showered. The humidity in the bathroom is the same as the humidity in the rest of the house.

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