Home>Discussions>YOUR HOME>Seasonal Upkeep>Can I close off vents to my crawl space during cold winter months
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Can I close off vents to my crawl space during cold winter months

I have a 1952 bungalow with hard wood floors that are freezing cold all winter is it okay to close off the vents in my crawl space to help reduce cold air from outside. I have read that by doing this I could have moisture problems considering I live the in the Pacific NW. Another option I had considered was insulating the floors from below by I have heard that this could cause issue with pipes freezing because it would prevent warm air flow from the warmer house to the crawl space and I could have frozen pipes. A third option is to put down a heavy vapor barrier over the earth floor in the crawl space to prevent moisture then close outside vents and then insulate the whole thing walls and between floor joists. I have no idea which one is the best idea for my old house or what potential problems each could cause any help would be appreciated I would like to get this done before winter.

Re: Can I close off vents to my crawl space during cold winter months

The crawl space needs air to breathe and rid itself of moisture.

My first vote would be to spray foam insulate under the floor.

Re: Can I close off vents to my crawl space during cold winter months

I live n the Portland, Oregon area. Regardless of what you do, the bare earth should have a moisture barrier on it, as does my house. The underside of my floors have fiberglas batts suspended there. I only temporarily close my crawl space vents when very cold temps are anticipated - about 25 degrees. This is done to prevent the pipes from freezing.Sufficient heat excapes from the house into the crawl space to keep the pipes from freezing. In the eight years I have lived here, it has gotten down to 15 degrees a couple nights and the pipes have not frozen.

There is a new movement in this area to close and seal the vents permanently, seal the bare earth, insulate the walls, and have the crawl space become a part of the house envelope, to the point of having furnace heat diverted down there. If the crawl space is heated, your floor above is now warm. If your feet are warm, you feel comfortable! If the furnace is circulating air down there, mildew is not a problem.

This is not unlike my native Chicago area where deep basements and crawlspaces were treated as part of the house envelope. Unlike the Portland area, where the furnace and hot water heater are in the garage, in Chicago, they are in the house envelope with you, usually in the basement.

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