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Crawlspace insulation, walls or floor

1553 Views 5 Replies 3 Participants Last post by  Gary in WA
I have a 50s ranch house near Milwaukee. The house has hydronic baseboard heat. Half of the house has a full basement. Half is a crawl space, about 4ft tall, with 3 ft below grade. The space is 26'x32'. Hot water pipes for the baseboards are all on one zone. The pipes in the full basement are not insulated, but the ones in the crawl space are for wrapped with fiber glass insulation. I suspect this was done to keep the pipes from freezing when the former owner turned the heat way down and left for the winter.

I have recently encapsulated the crawl space with a vapor barrier and am trying to figure out the best way to apply some insulation to make that side of the house more comfortable. I was going to put 2" rigid foam on the walls, but since it is not really a conditioned space, thought it might be best to do either fiberglass batts or spray foam to the underside of the floor. If I add the ridged foam to the walls, should I remove the insulation from the pipes so that the heat would somewhat condition the crawlspace? Anyone have thoughts on what would be more effective?

Thanks and Happy New Year,


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Rigid foam is best on the stem walls and make sure you seal up all the vents and the band joists with proper rigid/spray foams.

Often times, the heat sink from the upper floor will warm that space up and keep the crawl and framing warm enough.

Are any of the pipes that are wrapped the feed lines for the hydronic heat? If so, remove the insulation on them and they will condition the space pretty effectively.
Yes, it is the feed lines that are wrapped in the crawlspace. They are not wrapped in the full basement, which I suppose is what is conditioning that space.
In your cold location without any HVAC units/ductwork in the crawl, I would insulate the floor with f.g. and Tyvek and rims with rigid foamboard as WoW said. Canned foam around their edges to completely air-seal;

Beside just covering the dirt with a vapor barrier and closing the vents, more is required to meet minimum code- air exchanges and maybe cover the f.b.;

Check with your local AHJ on the wall's foamboard and if the crawl's air can be tied to the basements for enough air exchange or not. I have 12" of room under my beams (where I dug them deeper for access) , and 12" under the joists. Your picture invokes envy... Is that gravel, I see...

More expensive = but best way is SPF or f.g. and foamboard, to get a thermal break at the joists and from ground radiation;

"Anyone have thoughts on what would be more effective?"--------- The floors would be warmer with insulation in them- more cost effective than insulating the walls since no HVAC ducting (to condition it- you may require a fan or two), though the f.b. on joist bottoms (if used) would run the cost up quickly; Crawl Spaces.pdf

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