Radiant Floor Heat & Thermal Resistance
I would like to install a hydronic, radiant floor heating system beneath my subfloor. The subfloor is 2″ douglas fir, and it is covered by 3/4″ knotty pine. To determine if this system is going to be adequately efficient, I’m trying to figure out the thermal resistance of this floor. I have found a couple of sites that state that 3/4″ pine or fir has a R of 1. Does this mean that my floor has at R of about 3? Or are R values not simply additive?
Your advice is appreciated!
Replies
You add R-values together, so yes, you have about a 3.
However if you are using any of most mfg's output charts, keep in mind that most joist system charts have a 3/4" subfloor assumption already built in, so if you use one of those, you would use a 2 or a 2.5 R figure.
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