Heat Mat On Concrete In Wetroom- Is Insulation Required?

[EViS]

I'm going to be installing a heat mat (either Warmup, Devi or Uheat) in a wet room installation which has a concrete ground floor. Do most people lay insulation onto a concrete floor before installing a heat matt and SLC? Or is it quite normal to lay the heat mat directly onto a concrete floor?

I'm concerned that insulation will raise the floor too high, but at the same time I don't want to miss it out if it is a great benefit.

 

[DHTiling]

yes it is and marmox etc will also tank when installed correctly.

 

[EViS]

Thanks for the reply, but which question are you replying to with "yes it is"?

 

[DHTiling]

your thread title of course.

 

[Ajax123]

just have a think about how the heat mat works and how concrete absorbs heat. the concrete floor will act as a heat sink. You want the heat to radiate upwards not down into the concrete. If you dont put insulation down your heat mat will take several weeks to warm up and will cost you a huge amount of money. The more insulation you can put between the concrete and the heat mat the better. If you have no height available to do this you may be better to consider a different heat source.

in a nushell as Dave says...... Yes it is

 

[EViS]

Ah, the thread title . Thanks chaps! What thickness insulation is usually recommended?

 

[DHTiling]

10mm minimum..

 

[EViS]

And I imagine a couple of mm of adhesive underneath the insulation to fix it to the concrete, yes?

 

[DHTiling]

Yepp.. but they save you a fortune in heating costs..

 

[EViS]

Based on a 10mm insulated floor, how long before you use the bathroom should you be turning the heating mat on for the floor to warm up sufficiently for your feet to be warm?

And as a side question, are suspended timber floors usually insulated as well before a heating mat is installed?

 

[Ajax123]

With a suspended timber floor and you have no height available you could always insulate under the floorboards between the joists but the answer is still yes.


As for turning the heating on for your feet to feel warm the floor should at best feel tepid to the touch. If you think about it your body temperature is 37.5 degrees and your extremities are usually a couple of degrees or so lower so even on a cold day your feet will be maybe 33 degrees. The maximum surface temperature of the floor should be 27 degrees C so colder than your feet. A surface temperature maintained at 27 degrees will not only be expensive with an electric system but also uncomfortable.

In direct answer to your question it all depends on the heat output of your system in relation to the mass of the floor to be heated and the heat loss from the room.

 

[Uheat - Keith]

I agree with all of Dave & Ajax answers as above.
Also remember controller with a floor sensor in your floor is a must with any Electric underfloor heating. With your temp and time settings, this will enable your system to switch on & off and so not waste electricity.
Onto a base the 10mm insulation board will need an overall extra thickness of 12mm: 10mm board with 2mm powder flexible tile adhesive under the boards to fix.
Warm regards,