Any advice please on insulating a floor with electric underfloor heating

[HoneySuckleDreams]

Hello

We are just about to embark on renovating a bathroom. The floor is already tiled (concrete substrate) and we intend tiling over with new tiles. However, I want to install an electric underfloor heating mat of about 4m2. Is there anything I can buy in France similar to the 10mm Warmup boards you can get in the UK?

 

Thanks

[woolybanana]

There was something like it on offer on Bricodepot a couple of weeks ago.

[Chancer]

The problem that you would have is that it would make a thin unstable substrate apon which your new tiles would probably crack.

I have used the green compressed wood fibre 7 or 8mm brico insulation under my heated floors but I have used laminate flooring above so no cracking issue.

One thing I have found, learning by my mistakes as ever is that whilst the mats can be laid directly on the insulation and the laminate directly on top the heat transfer and response time is far inferior than if the mat is skimmed first with ragréage.

[Théière]

Something like Marmox boards? is sold in bricodepot and Wedi board in Lapeyre etc. it provides a very strong surface for tiling on to.

[Yonner]

I too installed electric u/f heating in our bathroom and

shower room here in France.

The key thing I would consider if I was in your position

HSD, is the level of insulation below the electric heating pad/webbing.

We lose a significant amount of heat from the system

downwards, because we were limited to about 10 mm of hard foam insulation

beneath it – beneath that is a thick concrete plinth over a cellar. I removed

the old tiles and adhesive to give me that 10mm “gap” but if I was to install

again, I would want much more insulation and a reflective surface below the

webbing.

With regard to cracking, we have suffered from that, but now

I’m more experienced, I know that there are much better flexible adhesives

available, and having used these on other projects, know that they would solve

the problem – Porcelanosa do an excellent one for example.

If the u/f heating was our only source of heat in the rooms,

we’d be disappointed  in winter months. I’m

not sure if its simply because of the lack of insulation underneath, but the

tiles are warm, not hot, and it takes  a while

to achieve that. So I’d encourage lifting the tiles, insulation as much as

possible, and getting the benefit.

[Angie]

We did exactly the same as you.  Had old tiles on top of concrete floor; used Marmox boards (which cost almost as much as the actual u/f heating mats!) and then laid the mats followed by the new tiles. These have been down for 5 years now with no cracking or movement whatsoever.  The initial heat up took around 2 hours but they stayed continuously very warm. The main electricity cost is in the heating up from scratch but the Marmox boards reduce this time considerably, however, we don't turn ours off at all now, its on 12 months of the year, 24/7. Thermostat set at a constant 25oC in an adjacent room and it costs virtually nothing to use because I assume as its on all the time we don't have the cost of this "heat up" each day - even in the summer its nice to get out of the bath onto a warm floor. 

[basquesteve]

I'm interested in the virtually next to nothing cost 365 days at 25 degrees How much is it

[Benjamin]

[quote user="basquesteve"]I'm interested in the virtually next to nothing cost 365 days at 25 degrees How much is it[/quote]

Having seen it the first time around I'd assumed it was a typo but on reflection maybe it wasn't.

Having owned a well insulated modern built French house (less than 10 years old) I wouldn't have dreamed of leaving heating on all year long.

I know the costs of keeping warm and comfortable with electric u/f heating so it will be interesting to see how much next to nothing is. Or is cost all relative to your circumstances?

[basquesteve]

Most areas in France I am sure have an average temperature well below 25 degrees, even in Summer for the most part to keep a wet/damp area at this temperature must have a cost let alone the remaining 4 months when it never exceeds 9 degrees, lets forget the sub zero extended periods

[Chancer]

Lets not forget that the thermostat is in a seperate room [:-))][8-)]

That 800 watts of UFH certainly has its work cut out.

25° [:-))]

Glad I am not paying.

[Rabbie]

I, for one, would find 25C unpleasantly warm. The heating bills would not improve my comfort either[:)]