Insulation layer for shorter time constant?

[Alan Ambrose]

Is there an advantage to putting an intermediate thin-ish insulation layer under UFH screed in a PH-style house? We have 300mm XPS with a 150mm slab on top and we plan to have 100m screed with UFH. But I’m wondering whether, say, a 30mm insulation layer and then 70mm screed would provide a shorter tjme constant for more rapid heating & cooling. I know some peeps subscribe to always heating to 20/21 degrees and cooling to 25 degrees 24/365 using the slab as a big heat reservoir. But that assumes you never want to change the temperature any, and if ever you do, then it’s going to take days i.e. a v long time-constant.

[Mike]

Only if you think that more rapid heating and cooling is good. In which case why not use radiators?

[JohnMo]

 

2 hours ago, Alan Ambrose said:

70mm screed would provide a shorter tjme constant for more rapid heating & cooling.

If want a short time constant for some reason, you could use Jaga Strada fan radiators, so you can cool also. Cheaper than fan coils, and designed to provide above dew point cooling. Also way smaller than radiators.

 

Seems a strange design choice to do 150mm concrete then another 100mm screed on top.