Crawlspace in the Pacific Northwest
My question is about whether or not I should air seal and insulate my crawlspace walls or just put down a vapor barrier and leave the vents.
I live in Issaquah, WA 18 miles east of Seattle. The house is a 1300 sq. ft. 1961 ranch house at the base of Tiger Mountain, one of many built in the area for the families of the loggers who worked the hillside. When we bought the house it was heated with baseboard heaters which we have since removed. It is now heated with a ductless heat pump with a ceiling cassette in the main living area supplemented with a small electric resistance heaters in each of the 2 bedrooms. The crawl space is 2 feet high with no vapor barrier and no mechanicals except plumbing. The crawlspace seems mostly dry except for one corner with some grading issues on the exterior of the house that I am currently working on. I haven’t checked a humidity level, but I do know that we run a dehumidifier in the living area of the house and have to empty a gallon per day or so.
I’ve listened to many of your podcasts and read many articles about it and it seems like sealing the crawlspace is desirable, but I read Martin Holladay’s article Building an Unvented Crawlspace in which he cites a couple studies that in the said in the Northwest vented crawlspaces work acceptably most of the time.
So back to my original question, should I build an unvented crawlspace, or should I keep the vents? I know I’m going to put down vapor barrier at the very least. If the answer is I should build the unvented crawlspace how should I condition the crawlspace? I don’ t have any heating ducts I can tap into. If I put some registers in the floor to connect the crawlspace to the living area I’m worried that my current heating set up won’t condition the crawl space we’ll enough. It also think it would be very hard to convince my wife to do that.
Thanks for your consideration.
Tony in Issaquah
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