One of the first jobs I had when I started my career in the construction industry, back when I was working as an electrician, was installing electric resistance heating cables for a basement heating system. It took two people, one person pulled (me) while a second person pushed (my brother) and guided a small manual plow which installed electric heat cabling just under the surface of a sand layer. Concrete would then be poured over the sand; the result would be a heated floor. As it turned out, there was a high percentage of cable failures with this system, which resulted in many people having to install a new heating system.
I’ve written about sub-slab insulation and heated floors several times over the past couple years, this post is about something I’ve been thinking about for a while now, using a fibrous insulation, like Rockwool’s ComfortBoard 80 or 110 under a concrete slab with hot water heat. The questions I had about this strategy are one, will there be an issue with compression of the insulation when concrete is poured over the product? And two, will a staple be able to hold the hot water tubing in place?
Rockwool ComfortBoard being installed below a concrete slab. Photo by Travis Brungardt