Project Barn Q6, Insulating the slab (and Lowes)

Project Barn Q6:

Went to Lowes and Home Depot to look into the foam board that I would put down over the vapor barrier and under the concrete. I was confused because the blue, white, grey and metalized foam insulated boards all said "wall", and none said foundation. I asked the staff (7 construction and hardware experts on break), and got a blank look. They never heard of insulating a pad.

Question 6:
could some one provide the precise brand of the under-foundation insulation board so I can get started?

You should read the following URL carefully. I was seriously onto the newer materials, but got my "bubble punctured". These people did the hard work and did a REAL WORLD test, in a very cold northern state, using all the common types of insulation.

http://www.naturalspacesdomes.com/be...st_results.htm

http://www.naturalspacesdomes.com/be...chive.htm#3-21

go down to the rows marked EPS/bubble/foam. The lower (below insulation) temperature, the better the insulator is functioning. Mark these pages, they are likely to make people as unhappy as they did me. Certainly popped my bubble-wrap bias!

Based on this, I am likely to use two layers, taped and staggered, with at least the bottom layer foil faced for the radiant, aka "infra-red."