UFH under or over screed?

[Chris Miles]

Hi,We are partway through a new build house and I’m really struggling to find definitive guidance on wether to install my UFH pipes embedded in the screed (we need approx 70mm) or on top in an insulated board such as Wunda rapid response system. 
It makes sense that the over screed option has quicker response times but I’m being told it’s less efficient, which I can also partly understand. 
Likely there isn’t a straightforward answer (it nearly always (“depends on…”) but the guidance I’m getting seems to be very different and from an entrenched perspective. 

[Conor]

What's your full floor build up?

[JohnMo]

Why pay for system when you already have one for free. Clip pipes to insulation and screed over done. Way more effective, run low and slow, use the depth of screed as a big buffer for the heat.

 

Had a system similar to Wunda, was cr*p, high flow temp required to get any output. Disconnected it in the end.

 

Hook up to a heat pump - no pumps or mixers, single zone, set weather compensation, cheap and effective to run. You get cooling for free.

[Chris Miles]

2 hours ago, Conor said:

What's your full floor build up?

Beam and block floor so far. Design is to add 150mm PIR then 75mm screed. 

[Chris Miles]

2 hours ago, JohnMo said:

Why pay for system when you already have one for free. Clip pipes to insulation and screed over done. Way more effective, run low and slow, use the depth of screed as a big buffer for the heat.

 

Had a system similar to Wunda, was cr*p, high flow temp required to get any output. Disconnected it in the end.

 

Hook up to a heat pump - no pumps or mixers, single zone, set weather compensation, cheap and effective to run. You get cooling for free.

Thanks. Seems to be the view of everyone except Wunda…

[Conor]

Put another 25mm insulation on, then UFH pipes, then 50mm screed.

[Dave Jones]

id stick to 75mm screed, not much cover above the pipes with 50mm