need building wood advice

Buffy said about termites:

This won't be adequate.

Ouch! More math! So any engineers our there that could tell me if this will work? Ok here it is. Posts around the perimiter every three and a half feet. Inside posts every seven feet on center. these posts are 6"x6". These support girders that are 6"x6" which support beams that are 4"X4" (every 3 and a half feet). The beams support 2"x4"s that are the roof. Then a layer of foam board insulation. This is covered with a very thick plastic. Then 1" of sand, and another layer of plastic and then 3" dirt. Oh, and the house is going to be 21 feet north to south and 84 feet east to west.
Its hard to explain in words but if you go to the website maybe pictures will help. If I use posts and beams much larger than this it will be prohibitivly expensive. The only alternative I can see is to chunk the earth roof and just have a metal roof on it just above ground level. Of course that kind of defeats the purpose since it will be vulnerable to tornadoes and it wont be "hidden" any more.
Gobug, any advice on termites?

Buffy
My advice is that if you must use wood for the structural support, then either get pressure treated or use Bora-Care to treat your own. Bora-Care is boric acid dissolved in ethylene glycol which gradually soaks through the wood fibers. In a year, a 2x4 will be completely penetrated and preserved. The cost to treat the wood in a normal house would be about $200.