"SFUF" with wet UFH

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I'm sizing up some of the local screeding firms to see if they have any solutions for fitting insulation and wet UFH in 45mm. I've dug up the the existing tiles and screed and left with only that much depth to play with. Initially I expected that some of the concrete floor could be skimmed, scored, cut out though the feedback so far is that they use "SFUF". To me, insulation needs to trap air and stop it moving heat about, so thicker is better. However this SFUF stuff, at only 6mm deep he claims to be eqivalent to 25mm of celotex. I don't know if they can simply stack it up, 3 layers to give the equivalent of 75mm? I always think if something seems too good to be true, there's a good reason for the unease.

https://www.superfoil.co.uk/sfuf/#tech

Who has experience with this stuff installed in their home or for their clients? UFH isn't going to be the only heat source in the room - it just seem daft to not fit the coils now I have the screed dug up (I already have a manifold in service with spare ports)

Nozzle
 
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I have read all the maker's specs and it certainly looks as if it is impressive.

Yet I still see roofs with 100 mm thick insulation! I might wonder why if the 6 mm stuff could be used in far thinner layers!

Most of those thin layers only say they are equivalent to a thickness of polystyrene and not the rather better urethene boards.
 
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Its serves a purpose but the applications whee all the data seems to come from is when its uncompressed and when compressed I would bet it has different performance values.

We have a job currently where the floor has 100mm celotex through out except a small area above a cellar. That was already concreted level with the top of the celotex. We used multi foil under the pipes and whilst the heat does come up if you go in the cellar you can feel the heat coming downwards aswell
 
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Some great feedback there, thanks folks - it does rather confirm my initial suspition that it is too good to be true. I do note from link that endecotop that the traditional insulation manifacturers spat their dummy out the pram that new kid on the block achieved these startling results with a particular test, and so they wanted the test changed.. I also note the claims in the document

"Tests carried out by the National Physical Laboratory (who have UKAS accreditation) using test methods in accordance with BS EN ISO 8990 have indicated an “R” value for multi-foil products in a range of 1.69 to 1.71 m2.K/W. Those manufacturers who use comparative testing are however, claiming “R” values for their products which range from 5 to 6 m2.K/W. In other words, multi-foil manufacturers who have used the comparative testing route are claiming the insulating properties of their product to be approximately three times better than can be verified using existing National, European or International test standards."

This firm do at least claim sensible R values (0.8) rather than anything out of this world, then they give an example to how to achieve a U of 0.25... 1x layer of superfoil plus 35mm HD foam board... I suspect most of the resistance comes from the celotex in these examples, and just suplemented by the Superfoil.

The particular screed firm whom suggested this to me also recommended "lo flo" UFH.. which I can't find a specific product for, but sound rather "small bore UFH" to me, which with a combo of my steel radiators is asking for sludge-trouble.

Nozzle
 

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