OK to insulate an addition built on piers?

I am building an 8 X 20 porch on concrete piers. I would like to have the option of insulating the porch and heating it in winter ( I am located in the Northeast USA). I have not put in the piers yet, but am wondering if it is workable to do this, by using rigid foam between the floor joists, or if I would be better off pouring a foundation for the porch or using concrete block. I would really like to use piers because of the ease of installing them ( I can do it in a day with a post hole digger, instead of having to excavate below the frost line). Thanks,
-- Jeff
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Don't see why not. You'd need proper vapour barrier on the 'warm' side of the floor, as well. Much the same as an insulated country cabin built on posts/piers. A manual post hole digger is adequate for 8 to 10 holes. Several non insulated wood frame storage sheds and one lakeside cabin I have built have all been on posts/piers. You have to size the floor joists adequately. Depending on frost depth in your area and amount of snow cover you may have to go as deep as 36 inches; also depending on the compactness of the soil. Here previously undisturbed ground is very much full of stones and is 10,000 year old glacial till with only a few inches of natural topsoil . However in the vicinity of a building the ground may be 'back fill' and somewhat loose, wet and/or mixed debris! Our concrete front step, for example, settled twice before final level. Mention all this because your proposed porch may be over a backfilled area around your house?
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<< I would really like to use piers because of the ease of installing them ( I can do it in a day with a post hole digger, instead of having to excavate below the frost line) >>
You know that a pier without a footing, and above the frost line is going to move up and down with every seasonal change, don''t you? Before you decide on the best way to build, why not consult your local building codes? You will have to get permits and submit plans anyway, and codes really have a lot of common sense content. Consider using something like Big Foot piers with cast in footings to save time and money. Web site at www.bigfootsystems.com. HTH
Joe
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Maybe not, if it's 3' inside an airtight skirt.
Nick
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I did plan on putting footings under the piers. By digging a 12 inch hole down about 4+ feet, and pouring a foot of concrete in the bottom of the hole with a piece or 2 or rebar sticking out, to fasten the piers. The area around the house is all backfill with sand so it will be easy to dig the holes.
-- Jeff
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