During heavy rain at my Seattle house, mold starts growing on the inside of walls that are outside walls. Would central heating help?

Asked by Meg Sablinsky
Seattle, WA

I have a central gas wall furnace that heats the entire 720 sq foot house from the center main room. I have a dehumidifier that has helped. My tenants tend to put their couch and bookcases right up against the wall, which I think is the problem because no air is able to flow and therefore mold grows. There is a pristine vapor barrier under the house. Any other ideas that would help with the problem?


Scott Grieves, CPM, CEA

Answered by Scott Grieves, CPM, CEA

Kissimmee, FL

Kissimmee Utility Authority

April 18, 2013

This sounds like a tough one, however it's simple.

We first need to know how mold grows--- mold requires water, dirt, and oxygen to grow.

I recommend you find the source of the water leak and seal it. If you have any water penetration into the thermal envelope of a home this could be the leading cause. Material like drywall can hold all three--- water, dirt, and oxygen.

Other possible questions:

  • Is it near a bathroom or behind a tub or shower?
  • Re-check the vapor barrier?

I can't tell you how many times I have not checked something when somebody told me it was perfect, and later we find is was the problem or not installed correctly. I hope this helps.

Regards, Scott

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