Best way to insulate for staple-up radiant heat?
I have 1/2″ PEX w/ O2 barrier w/ aluminum heat transfer plates stapled up to bottom of 3/4″ subfloor w/ 5/8″ engineered hardwoord and 3/4″ tile above. I also have 1/2″ pex installed in the concrete basement slab and have 3 zones. One is the basement (which is currently unfinished 10″ block walls w/ 2″ XPS on exterior side. I currently have no insulation under the staple up (main floor). My basement and house stay warm but the basement zone rarely runs and the main floor runs a lot. My heat source is a Thermolec electric boiler and my electric bill jumps $100-500/month depending on the temps. I live in Climate zone 5A (northwestern part of PA). My thoughts for not insulating were that the heat would rise and continue to heat whole home, however, I’m wondering if I insulated w/ R-13 or R-19 faced fiberglass my electric bill might come down and boiler run less by separating the zones?
The main floor is separated into 2 zones, one is main living space (family/dining/kitchen/foyer) the other beds and baths. Main floor is 2050 sq ft. I believe my water temp is around 115-120 degrees F. I, eventually will finish 65% of basement and install drop ceiling. Does anyone have any input or experience with this situation? Should I insulate under the staple up or leave alone? I will also say I ran my 2″ XPS up over my rim joist and I insulated the ends of the joist cavities w/ R-23 Roxul. If the recommendation is to insulate, should I snug it up tight to the bottom of the PEX or leave a 1″ or more air space?
Thanks for your help in advance.
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