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What is the best practice to insulate a crawl space floor?
austin Fanning
March 16, 2020Updated: Sept. 10, 2020
Rear porch was was enclosed. Framed walls, insulated and drywalled
Crawl space has dirt floor, 3 cement block walls, open lattice wall to access crawl space, exposed floor joists 24'' o.c., height from ground to bottom of joists is 36"
If you have a three-sided foundation wall with lattice work on one side and a dirt floor, the whole underside of the house is exposed to the exterior temperatures. I think you first need a plan to close in the fourth wall, then insulate all four. What was your plan for that last wall, are you planning to continue the block wall? The first page I would point you to is the following about how to insulate crawl spaces -
Crawl Space Insulation Tips for Insulating Crawlspaces Properly
Once your walls are closed in you will need to decide if you are heating the space or keeping it cool, that determines whether or not you’re better to insulate between the joists or directly on the dirt. And what climate zone or region are you in? To find the best method for insulating crawl spaces or basements starts with knowing the temperatures that it will be exposed to. Important to remember is that concrete block foundations are not as strong as poured concrete, so in very cold climates they are more susceptible to cracking if left to freeze and thaw.
Hey Mike,
Plan for 4th wall( Lattice wall) was to cover interior with 1/2" P.T. plywood. The living area above crawl space would be heated with split unit or continuing existing hot water baseboard heat from adjacent room.
Also , project is located in 6b region, nort New Jersey
Hey Austin, so are you leaving the crawl space cold then? Correct me if I'm wrong but it sounds like
your plan then is to insulate between the joists for your upper floor (crawl space ceiling). If so, be sure to lay a poly membrane on the dirt to keep moisture in the ground.
Are you by chance laying down any new flooring on it? Wondering if you had a plan for an air and vapor barrier between your conditioned space and unheated crawl space below. If you only had a subfloor then it would be easy to lay down a membrane first and put new flooring on top, that would be good for an air barrier, it would also keep the vapor barrier on the warm side.