UFH layup

[GTM_88]

I had an idea and wondered why it's not common practice, or where the logic fails

 

I keep reading that radiant foils reflect some crazy percent of radiant heat and when used with an air gap have a very good R value.

 

In regards to a conventional joist floor, upstairs, purely to make it easier to picture. 

 

Why is the insulation always installed level with the top of the joist and not dropped slightly with a foil on top, creating an air gap.

 

Or, install the insulation flush with the tops of the joists then lay a foil over the entire floor covering the insulation and tops of the joists flat, and add 16/25mm battens on top of the joists, sandwiching  the foil, then lay 18mm plywood floor with the underfloor heating on top. 

 

 

Edited February 27 by GTM_88