How do I insulate my crawl space?

Old 01-08-18, 06:39 PM
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How do I insulate my crawl space?

I have 25' X 40' 1970s cottage. It has a cinder block crawl space 40" high with a concrete floor. Previous owners insulated between the floor joists with fiberglass insulation that is largely wet now from the humidity (it is lakefront). I want to winterize the cottage (all the walls/attic above the crawl space are insulated) and I need to know:
What is the best insulation for the crawl space?
What R-Value do I need to do it to with no heat source in the crawl space?
I prefer NOT to use spray foam as this will be a DIY job.
Thoughts? Thanks in advance!

Last edited by Scruffycat; 01-08-18 at 06:54 PM.
Old 01-09-18, 07:54 AM
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Hi Scruffy and welcome to the form.
Your location will help determine the recommended insulation and the use, seasonal or year round?
I'll dig out my favorite crawlspace link and add at the bottom. Photograph 5 would be perfect J.

Once a crawlspace is encapsulated it needs to be included with the conditioned space above and not sealed off with zero air exchange.

Here is the 09 insulation map but every location can choose what guidance they want to follow.

Old 01-15-18, 06:46 PM
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Hello! Many thanks for your response and links. My apologies for not responding sooner.
The cottage is on Lake Huron in Ontario. I believe it is a zone 6 insulation area. I LOVE the photo 5!
THis is what I am thinking of doing:
1) insulate the walls with 32" high extruded styrofoam up to the joists. Between the joists, on the wall, cut pieces of styrofoam to insulate the band joist (i think that is what it is called). I would use cans of spray foam to seal the cracks between the floor, styrofoam and around the joists/styrofoam.
2) no insulation on the floor concrete slab.
3) seal up the external vents in the crawl space (4)
My questions:
a) Is it okay to leave the fibreglass between the joists?
b) how thick (r-value) should the extruded foam be?
Old 01-16-18, 07:49 AM
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Take out the insulation in the ceiling if you're going the route of insulating the walls and opening the space up to the house air.

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