Insulation retrofit for radiant floor heat
I’ve searched this site and found a lot of useful information but no clear consensus on what is the “best” method for retrofitting insulation in radiant floors. The situation is exposed hydronic tubing stapled up to the subfloor with no heat transfer plate. The joist bays are relatively accessible from the insulated basement and crawl spaces. Climate Zone 6.
The information I’ve gathered points me to spending money on insulation products rather than radiant barriers. It seems like the best approach would be to install foil faced polyiso fastened and sealed up to 4″ down from the tubing. The air space created will boost the R-value a bit beyond the polyiso. This will be labor intensive in several areas due to odd framing spacing and other things in the joist bays.
A lower cost option would be to install faced fiberglass stapled to the bottom of the floor joists. It doesn’t seem like it would matter much if there was an air space between the fiberglass and tubing since it will not be a sealed installation.
It seems that any type of insulation would be much better than having it uninsulated as it is now. That would at least reduce the heat loss to the basement and crawl spaces below and improve distribution, although it’s tough to say how much. We plan to compare the cost of the distribution improvement with the cost of adding cold-climate heat pumps.
Thanks for the help.
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