Insulation next to PEX ?

[Doctor G]

In my new garage I've installed PEX tube in the slab for heating, but also have attic space above. I decided to add another loop under the floor above to supplement heat to this area. I plan on using fiberglass batts to insulate between this and the area below. Should they be in direct contact to the PEX tube and plates? Would a vapor barrier be a good or bad idea? The ceiling in the attic area will be insulated with a vapor barrier and drywalled. Anyone with any experience with this setup?

Thanks, Doc

 

[HoosierBuddy]

In my new garage I've installed PEX tube in the slab for heating, but also have attic space above. I decided to add another loop under the floor above to supplement heat to this area. I plan on using fiberglass batts to insulate between this and the area below. Should they be in direct contact to the PEX tube and plates? Would a vapor barrier be a good or bad idea? The ceiling in the attic area will be insulated with a vapor barrier and drywalled. Anyone with any experience with this setup?

Thanks, Doc

When you say "plates" are you talking about the aluminum plates that the PEX clips into?

Phil

 

[Doctor G]

Yes, heat transfer plates. These are stamped steel, not aluminum,but they are made to serve the the same function.

Doc

 

[HoosierBuddy]

OK great. If you see the earlier post I made about the lessons I learned on installing radiant loops, I'm pretty down on using pex in the joist space using the plastic clips every couple of feet.

I think you'll find the plates will help your heating system a lot.

In response to your earlier question, I'd use a reflective product such as FBF about 2" away below the plates, perhaps stapling it to the joists, and then install 6" of fiberglass batting under that.

The FBF might not be required. I know with aluminum plates, the emisitivity is so low that the plates just can't really transmit radiant energy, and thus you can get by without a reflective layer below the plates. But steel may be different, and with any plates you are going to have gaps between each plate, so it would be a good idea to use something to reflect radiant heat back towards the subfloor.

I'm not sure about the vapor barrier. My insulation installer used paper backed batts below my bonus room, above the heated garage, but I'm not sure if that was required or not.


Phil