To insulate prior to UFH or not?

[Gromit1]

Hello. Going to have my kitchen tiled. Floor is concrete in my 1985 built house. The question is whether to put down Marmox boards or the like. I don't want to increase the height much so it'd be 6mm. I have a toilet also on a concrete subase with no insulation boards and have 200watt UFH mat and it heats up surprisingly quickly, perhaps because it's the higher power 200watt spec.

So I know that UFH will be effective on my floor, but what I don't know is whether I'll get any serious energy saving by putting in insulation boards. The tiler reckons it'd take him a day to put down the boards (13 square meters) and I've also got to look at the costs of the boards.

Thanks for reading.

 

[Gazzer]

I would definately go with the boards but i would also be inclined to use 10mm if possible. you could also drop the wattage down to 160 w if on insulation.
the toilet floor you already have will get warm as I imagine its a fairly small area ?

 

[Stewart]

As Sir Ramic as said above, go with insulation. The start up time is much quicker and is much more efficient with insulation.

 

[Daz]

I'd recommend using insulation boards. The thicker the board the more efficient the heating will be. As Sir Ramic says, it will also enable you to drop to a 160W mat.

As for a day to fix the boards? Presumably that includes fitting the UFH and self levelling compound too?

 

[DHTiling]

If you do not use Insulation boards then the running costs will be astronomical.... you will have to heat the full slab before any heat transference back to the tiles and continue to heat the slab to keep the floor warm , this will seriously increase your running costs.. 10mm is the min i would recommend for insulation boards..

The choice is yours depends how rich you are to run with out them.

 

[doug boardley]

yep, insulate all the way

 

[Ian]

Agree with all above. The amount of money you will save will pay for the system 10 times over with insulation boards. Without the boards you are throwing money away.

 

[Gromit1]

Thanks everyone - insualtion it will be. Yes Sir R the toilet is small - 2m x .75m He said a day for just insulation boards which I thought sounded a long time. I think they're put down with tile adhesive and preferably taped? But anyway seemed a long time to me which I was factoring in. Trying to work out the cost including installation versus money saved. Any idea if there are figures available?

 

[Gazzer]

I laid 20m2 of insulation boards recently and taped the joints and was finished by lunch time. I wasnt racing either. I think he is over estimating there.

 

[Gazzer]

Thanks everyone - insualtion it will be. Yes Sir R the toilet is small - 2m x .75m He said a day for just insulation boards which I thought sounded a long time. I think they're put down with tile adhesive and preferably taped? But anyway seemed a long time to me which I was factoring in. Trying to work out the cost including installation versus money saved. Any idea if there are figures available?

Not figures in the terms of money but warm up times etc , I was sent this by a manufacturer just before xmas
Quote
"Unfortunately thermal values are a minefield because there are differing standards, as here, and different ways of measuring them. However, in real life comparisons with cable underfloor heating the following approximate results were observed:

1. Onto bare concrete slab – took about 3 hours to reach max temp of 24°C.
2. Onto No More Ply 6mm – took about 40 minutes to reach 24°C and 3 hours to reach max temp of 27°C.
3. Onto Beavaboard 6mm – took about 30 minutes to reach 24°C; temperature 29°C at 3 hours and still increasing.

If you are going to use No More Ply under wire underfloor heating, you must remember to prime the surface with Mega® SBR as this helps to reflect the heat back up.

In summary No More Ply reduces warm-up time, increases efficiency and allows a greater maximum temperature. Beavaboard is cement-coated foam board of the same type as recommended by underfloor heating companies, and has the same effect but to a greater extent."

 

[Aston]

hi gromit

putting ufh on a concrete floor without insulation boards is a massive waste of time, energy and money...i can totally understand your need to keep the depth of the finished floor as low as possible but go with the correct insulation. as above, 10mm would be my minimum on concrete but obviously, the thicker the more the insulating properties.

 

[Mike]

i laid 10 m2 of hardi boards today, put down with addy and screws and only took 4 hours. i had to finish early to watch the football

 

[Gromit1]

Yes it did puzzle me that tiler wanted a day for the insulation. He was talking Marmox. Is there much to choose between the different boards? Sir R mention ed No More Ply.