I was reviewing articles discussing radiant heat installation, and I noticed that there appears to be a change in best method between historical articles and recent articles. Specifically, my question is whether it is best-practice to lay the rigid foam insulation first, cover with stone and then lay the wire mesh for the tubing and pour the concrete, or should the stone be set first, then the foam and tubing directly in contact with the concrete? What are the pros-cons of each? Additionally, with both methods, should vapor barrier still be used?
Thanks,
Replies
I've never heard of the method where one puts gravel fill over the foam but two thoughts come to mind. First: from a heat loss standpoint, I'd be a wash either way. Second: I would think it problamatic to compact the fill over the top of foam. Too much jiggling and vibrating of the foam... it'd keep the gravel loose. (Of course if you hire the bonehead excavator I had for a while, there'd be no "problem" because he didn't believe compaction as necessary. But that's another story.)
I've always laid my foam directly on well compacted, smooth, and flat fine gravel/sand. The concrete goes right over the top.
Another choice for you will be to staple the pex directly onto the foam or tie it to mesh that is brought to mid-slab during the concrete placement.
6 mil poly always, 8 mil would be better.
Do not
put gravel or sand over the foam. Put the gravel on grade, level and compact it as well as possible, lay down a vapor barrier sheet (I don't use poly but a lot of people do) and tape the overlaps and penetrations, lay down the foam, install a mat of rebar on 1-1/2" dobies, tie the tubing to the mat.