How do I insulate a crawl space ceiling and walls?
I'm desperately looking for some advice on how to properly insulate the crawl space. I live in eastern Massachusetts where it has recently been in the teens and 20s for low temps in winter.
I have a large crawl space under my kitchen and 3 season porch ranging in height from 1' to 4' with no venting to the outside. I recently air-sealed the entire rim joist with an expanding foam and added a heavy mil plastic sheeting over the dirt floor, making sure to overlap and seal all edges. We also insulated the copper pipes in the space with closed cell insulation tubing and taped all joints to prevent the pipes from freezing. The kitchen is still very cold.
I would like to ideally insulate the space in between the floor joists and possibly the exterior brick foundation walls but are getting conflicting info on what to do.
- Could use a poly spray foam kit, but the max R-values I have seen are only in the 7-10 range and its not anywhere close to warm enough outside to prevent it from failing. Everything I read says not to use apply when below 60 degrees or it will not cure properly. Its barely in the 30s right now! Also, the exterior walls are not all that clean and the foam might not stick.
- Floor joists are not evenly spaced and range from 17"OC to 22"OC so batt insulation is going to be a pain.
- Could use blown-in insulation but how do I get it to stay up there? Someone told me to use a plastic sheeting across all the joists with furring strips for extra support and then simply blow the insulation into each joist cavity, but I am worried that the plastic sheeting is too much of a vapor barrier and will cause mold inside the joist cavities. If the crawl space is already moisture sealed, am I OK? Do I need some sort of barrier up inside the cavities on the bottom of the floor?
Also, do I really need to insulate the brick foundation walls and will this show a big difference? Because the dirt is not evenly distributed and some areas are tight to get into, getting rigid foam board would be nearly impossible.
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