How best to insulate crawlspace in Northeast
eoindeb
| Posted in Energy Efficiency and Durability on
I am trying to decide how best to insulate my crawlspace in my home in the Northeast. The crawlspace was added ~20 years ago for a family room addition, and is connected to the original home’s basement. The basement has a finished room on one side, and a mechanical room on the other. The crawlspace currently vents into the mechanical room, with no other vents anywhere on the exterior walls of the crawlspace. The crawlspace is noticeably cold in the winter, and I’m worried it’s contributing to the stack effect of my house, and perhaps poor air quality since it vents directly into the basement. The floor above the crawlspace is also noticeably colder than floors above the original basement. I insulated the rim joists a couple of years back, but given that the large vent is there, I’m wondering if that was even worth it or not.
Would closed cell spray foam on the walls and rim joist be the best option? I’d consider a DIY project in the Spring by doing foam board up the cinder block wall, and then spray foam the rim joists (as well as removing the existing insulation). I’m not sure if that would be sufficient though, or given the layout of the crawlspace, whether spray foam is the only option that will work effectively.
Appreciate any advice or feedback. Thanks.
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Replies
This article is good:
https://buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces
I like to use Polyiso for this application. I’d do an encapsulation project first though using polyethylene sheet, then tack up polyiso (reclaimed roofing Polyiso works great here). You can use spray foam on the rim joist, or cut’n’cobble rigid foam (I usually use EPS for this), and foam it in place with canned foam. Note that you usually need a fire barrier over the foam, but exactly what you need varies with the jurisdiction in these difficult to access spaces. Sometimes you’re ok with just a flame retardant paint. Ours local building department people can tell you what is required in your area.
I would rip out all the fiberglass batts in the joist bays once you decide to do this project. Those batts looks to be in pretty rough shape, and they aren’t really needed after you insulate the crawl space. You’ll want to pull them out prior to doing the encapsulation project so that you don’t make a mess in your newly sealed crawl space.
Bill