Reflective slip membrane ?

[bmj1]

Proposed GF buildup:

 

1) beam and block (already done)

2) radon barrier

3) 75mm phenolic insulation

4) slip membrane

5) UFH pipes

6) 40mm liquid screed

 

We are very height constrained..

 

I'm just wondering if there is any kind of radon barrier or slip membrane that would help me reflect the heat upwards ?

[JohnMo]

Reflective membranes need an air gap to function.

 

Poor insulation for UFH, maybe not want you hear, install radiators.

[bmj1]

44 minutes ago, JohnMo said:

Reflective membranes need an air gap to function.

 

Poor insulation for UFH, maybe not want you hear, install radiators.

 

Thinking was that 75mm phenolic is like 90mm PIR...

 

Should be okay? Especially with a liquid screed so heat won't have much resistance going upwards

[JohnMo]

2 hours ago, bmj1 said:

Should be okay?

I personally wouldn't, but your call