I have decide to heat my kitchen and dining room tile using PEX tubing under the sub floor, which would in turn heat the two rooms right? Adjacent to these rooms is my living room with baseboard but I think I will take this out and heat under that subfloor. Which would heat that room right? The contractor that came over yesterday said it would and also said it wouldnt be a bad idea if I replaced my boiler. The system is water fueled by Natural Gas. The boiler is only 9yrs old but "he siad" is about 80% efficent. If I upgrade now to a 98% efficent boiler it would pay for itself in 4 yrs. Especially since the government is giving a $2000 refund. This true? What do you guys think of me doing this.

I've just installed Joist Trak extruded Aluminum heat transfer plates under the subfloor in some addition spaces. Time to insulate. I've read all of the documentation I can get my hands on regarding the topic as it pertains to this type of radiant panel. I've seen the study of the difference between 5/8" gap under the plates and 2" gap under the plates. I've read John Siegenthaler's recommendation in "Modern Hydronics"- push the insulation directly up to the plate with no gap. All of the information is good except for discussing in detail the "goods" and "others" of insulation types. They mostly just mention that most people use fiberglass for this detail. That said, my preference is to dense pack (blow) cellulose right up to the Joist Trak and to fill the entire joist cavity....unless someone can provide a compelling reason not to. Personal experience or recommendations greatly appreciated. -Scott