75mm or 100mm Kingsland Thermafloor TF70 PIR insulation board

[Alex Carr]

So informative were the posts I've been reading on this forum I became a member. I'm about to embark on extensive renovation of 92²metres of space extending over the lower two floors of a 4-floor, 200 yr old Grade B listed building and would really value advice on making the right choices about various aspects of the work. For example: With regard to wet underfloor  heating. I'm about to have the basement tanked, on top of which will be laid a concrete slab (150mm estimated depth) and on top of this either 75mm or 100mm foil-backed insulation boards & above this a layer of visqueen + screed with all the pipework gubbins embedded in it. My preference is to use 75mm insulation boards because they cost less, but is there is a measurable advantage in using 100mm boards instead?

Edited July 22, 2023 by Alex Carr

[Conor]

Can you dig deeper? I'd be aiming for 150mm. We put in 200mm (new build tho). I'm not sure 75mm would pass BC.

[JohnMo]

Min 150mm ideally 200mm. 75mm will have way to much downward heat loss. Making UFH a costly mistake.

 

Pay once, not every month you have the heating on.

[Temp]

We have 80mm and wish we had fitted more. If building again I think I'd fit at least 150mm.

 

 

 

[jon-lee]

16 hours ago, Alex Carr said:

So informative were the posts I've been reading on this forum I became a member. I'm about to embark on extensive renovation of 92²metres of space extending over the lower two floors of a 4-floor, 200 yr old Grade B listed building and would really value advice on making the right choices about various aspects of the work. For example: With regard to wet underfloor  heating. I'm about to have the basement tanked, on top of which will be laid a concrete slab (150mm estimated depth) and on top of this either 75mm or 100mm foil-backed insulation boards & above this a layer of visqueen + screed with all the pipework gubbins embedded in it. My preference is to use 75mm insulation boards because they cost less, but is there is a measurable advantage in using 100mm boards instead?

what is the area, perimeter and U values you have specified??

 

[HughF]

240mm here in the extension... funny how the levels ended up