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Last Updated: , Created: Sunday, June 24th, 2001

West Coast crawl spaces and high humidity.

Gills writes from South Surrey, B.C.:

Problem: High humidity in a crawl space. What do you suggest to reduce this problem.
Info: Rancher style home (single level), 1800 sq.ft.
Crawl space: 6 ft. high, concrete floor
No windows
The only existing opening is a 6 inch pipe going out side.

---------- Reply

BC is a problem area for crawl space humidity since often ventilating creates more humidity than not ventilating. You're the one who wanted to move to the coast! Normally the concrete floor will help to reduce humidity from coming in from the soil below, but 6 feet deep means that there is a lot of cold concrete to create condensation. I would first recommend a concrete sealer to cut down on migration of humidity up from the soil below. Then insulate the walls with at least R-5 foam boards. If you have no heating system in the crawl space you won't need to cover the foam. If the furnace is in the crawl space, you will need drywall over the foam -- probably water resistant drywall.

That should reduce the moisture coming in, and warm up the walls -- hence reduce the humidity. You could try cross ventilation but often on the west coast it is not useful.


Keywords: Humidity, Crawl Space, Moisture, Relative Humidity, Ventilation

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