Greetings, I am about to construct a top-of-floor radiant system. I am seeking a load-bearing insulating material of about 3/4" thick to construct 'stringers' out of that would go above my existing floor, and below the flooring material I will use. I'll be using aluminum spreader plates. All advice appreciated. -AC

What kind of flooring are you planning on top?

While there are some high density foams, why not just use wood? I'll add that for an attic, I once used 1/4" OSB over the cheapest EPS foam available and I was impressed at how it didn't compress when walked on. In other words, XPS foam covered by Hardibacker and then tile might be rigid enough.

Have you considered Warmboard?  And what about placing the insulation below the sub-flooring?  We have free hydrondic radiant floor heating design software on our website if you want to run the numbers and gain a better understanding.

> We have free hydrondic radiant floor heating design software on our website if you want to run the numbers and gain a better understanding. I would like to see that software. Please include link. Thank you, -AC

We have a radiant panel that is 7/8" thick and is made out of 3 pound high density EPS foam. It is insulated providing you an R-value, has grooves so that you can walk the tubing in without the use of staples, and is very easy to install. You can go to our website at radiantgreenflooring.com or email me at XXX-XXX-XXXX (Phone #'s and email addresses are not allowed in forum posts). Thank you!