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Discuss Low profile overlay wet UFH - screed, grooved gypsum or insulation? in the Underfloor Heating Forum area at PlumbersForums.net

Buhar

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Hi folks, my first posting and hopefully it's a sensible question. I'm doing a renovation and intend to heat with wet UFH supplied from an ASHP. I have to go for minimal build up because of head-room, so I'm looking at the various low profile systems. Insulation of the property will be OK, but not superb (wood fibreboard over the existing stone walls). I an looking to work with a build-up of 25-35mm (excluding floor-coverings) and it's going over a concrete slab.

The low profile options mostly seem to use 12mm pipe at 150mm centres but within them there are:-
1. castellated plastic plates that are screeded (Nu-heat, Profix, Robbens)
2. gypsum or similar grooved boards (Warm-up et al)
3. similar grooved boards that are made from XPS insulation, some with foil as a heat diffuser some with plates (Continental et al).

Has anyone got views on the performance of these various types of system. The flooring will be 50% tiles 50% engineered wood and I would expect to set the heating cycles to optimise performance.
 

Brambles

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How much insulation are you proposing between the floor slab and the underfloor heating system? The norm is in excess of 50mm, it will work with 30mm, but performance will be (very) disappointing with less than that.

Don’t forget that you will also need a membrane between the slab and the insulation.
 
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Buhar

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Profix can supply their plates with a maximum of 10mm. It's XPS I think. Robben told me there isn't an insulation that is rigid enough and nu-heat say theirs will perform without.

In terms of height I included 10mm in my maximum build-up figure. I think even a thin layer is better than nothing if the system can accommodate it.
Alan
 

Brambles

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I would do a bit more research. If your floor slab is a solid concrete slab, either on the ground or cast over beams., without effective insulation, performance will be very poor. If you know the slab thickness, and your flow temperature you can calculate the heat loss into the slab.
 

Dave Marques

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Uponor's Minitec is 15mm total height, 3mm of renovation screed above 9.9mm dia pipes.
 

ShaunCorbs

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Buhar

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Thanks Brambles, it's concrete on the ground and I will have to live with the heat loss there. The question is given that, which of the competing systems will perform best. My question here is part of the research.

Thanks Dave for the Upunor pointer, I'll add that to the options.
Alan
 

Brambles

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Always good to research the market.

Be aware that underfloor heating systems come under Part L of The Building Regulations - which specifies the U value that needs to be achieved.
 
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Buhar

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I'm in Scotland, so completely different regs. It's gone through Building Standards already and as a renovation of a 150 year old building the approach seems to be "do the best you can".
 

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