Although it has all the disadvantages of a basement, a crawlspace is too low to be useful beyond a few boxes of ornaments and a folded Christmas tree. A great alternative to a basement is to build a slab-on-grade.
It is best to insulate crawlspaces from the ground and treat it as if they were a normal part of your conditioned space. Although we don't like spray foam because of its emissions, this is an area where it might make sense. You can also look for the best crawl space insulation service through various online sources.
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Spray foam can be applied quickly and efficiently. It also provides an air and moisture seal, filling all of the small holes. Spray foam is not something you can do yourself so it won't be an inexpensive option.
However, it will work well and someone else will be crawling in your crawlspace. It will act as a vapor barrier so there's no need to put down poly before it starts. You can just stick it against the dirt.
There are two ways to insulate walls. The Building Code requires that crawlspaces greater than 5 feet tall have fire protection. In this case, you can frame a 2×4 and 2×6 wall at 1 inch from concrete walls.
By placing small pieces of foam on top of the foam, it will prevent it from coming in contact with groundwater and absorb moisture.
As fire protection, the foam should be covered with drywall. This can be attached to a stud wall. Spray foam is sufficient to protect against vapors.