I am looking to do a staple up radiant floor system on my house. The original plan was to use staples and just have the tubing run under the sub floor with 8 inches of Polyiso under it. Then at a home show I laid eyes on Heatsheetz which is the same thing as Crete Heat. Could I lay my radiant tubing in the Crete heat then push it up to the floor in the joist bays which are 24 oc. The foam will have to be trimmed to make it a nice tight fit in the bays but it should hold the tubing in place and provide a nice start to the insulation. I already have a ton of poly iso so I would most likely do another 4 inches of that under the Crete heat. Here is the website with the info on the crete heat. http://www.barrett-inc.com/creteheat.php

I have looked at Barrett Enterprises products, and like many of them.
I called them and asked if the Crete Heat could be used without concrete. I was interested in SIPS on the ground instead of concrete. They said yes. So it could work between floor joists. I just wonder if it could also use a layer of aluminum between the Heat Crete and flooring to help spread the heat across a larger surface area of the wood.

I was going to run 4 loops in a 24in bay. Tubing is cheap and I have all the hot water I could ever need from a wood boiler. I see nothing wrong with higher BTU output in the house. That should eliminate the need for aluminum transfer plates.