UFH to cool FF slabs above kitchen

[Mr Blobby]

As it says,  I have the option to run a couple of UFH loops in the FF bathrooms, which are above the kitchen diner in our passive build.  I figure it would be handy for cooling as much as heating but as far as I can tell, the clip rails would need to be attached to insulation and then the screed on top.

Can I attach the clip rails directly to the hollow core slabs?  My builder and plumber were appalled at the suggestion, but I think because of the labour required, not because it is a bad idea.  Has anyone on this forum ever attached clip rails directly to the slab?  Is it impossible?  I only expect to install two loops for the bathrooms and a bit of landing so not a massive area, about 30 m2.

 

To install FF UFH our builder has suggested a 30mm insulated screed under the UFH pipes to clip the rails to as it is failrly maleable for a number of days and easy to fix to.  And he says it gives a sturdy and level base for the rails.  The screed then goes on top.  My concerns with this are the extra weight of the extra 30mm screed.  Has anyone ever installed UFH on insulated screed on the FF?  Or should I just stick to PIR.

 

Or is it just a cr4p idea to install the UFH on the FF to cool the hollowcore slabs above the kitchen?  Maybe the current heatwave is affecting my thinking 🤔

 

 

[Conor]

We did 50mm insualted screed. It weighs nothing, mostly polystyrene balls. Originally I  wanted to go directly to the slabs, but they were too uneven and we have too many steels to go over, was never an option. Eventhing works fine.

[Mr Blobby]

On 16/06/2023 at 17:07, Conor said:

We did 50mm insualted screed. It weighs nothing, mostly polystyrene balls. Originally I  wanted to go directly to the slabs, but they were too uneven and we have too many steels to go over, was never an option. Eventhing works fine.

 

Thanks @Conor

It sounds like you have the same insulated screed my builder is suggesting.  From alpha flow screeds in Omagh?

Did you then poor a standard screed on top of the UFH pipes? How thick?

I think we're looking at 30 insulated screed and then 50 ISH standard screed on top. 

Edited June 18, 2023 by Mr Blobby

[Conor]

Yeap, alpha. 50mm TLA then 50mm liquid on top. 30mm TLA may not be enough as you need plenty of depth for the staples. We used extra long staples. Have loads left if you need them! And a stapler, pipe decoiler etc.

[Nickfromwales]

@Mr Blobby Have a day off mate!! Why do you think you need to cool a small area over the kitchen!?

 

On 16/06/2023 at 16:45, Mr Blobby said:

Maybe the current heatwave is affecting my thinking

Yup.

[Mike]

16 hours ago, Mr Blobby said:

It sounds like you have the same insulated screed my builder is suggesting.

If there's a suitable local contractor, you could alternatively use a suitable sprayed PU foam insulation, rather than a screed.