Our Client’s Question: Should crawlspace vents be closed in winter

Dear Inspector John,

The other day I heard a tip that the crawlspace vents should be closed during the winter. Since I never had a vented crawl space before, I did not know this. If it is true (and it sounds true) maybe you could mention it occasionally, i.e. open your vents in summer and close your vents in winter.

Wondering in Winter

Dear Wondering in Winter,

Thanks for your question.
The old adage about closing the foundation vents in the winter and opening them in the summer was useful when the homes were not insulated as well as they are today. When they started to insulate the floors, the need to close the foundation vents became a mute point.  So no, since your home was built in 1990 I would advise you to keep your foundation vents open in the wintertime.
I recommend that in any crawlspace where the floors are insulated that the vents be open at all times for air circulation.  When the vents are closed, moisture can build up in the crawlspace and lead to moisture-related issues, such as fungal growth and deterioration which no homeowner wants.

Hope this helps,
John Hill
Starmark Home Inspections

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