Quality wood floor underlay for underfloor heating

Troy McClure

There are tonnes of underlays out there and alot say they are suitable for under floor heating.
Can anyone send me a reccommendations for a proven quality underlay for engineered wood flooring that has excellent thermal conductivity and doesn't cost the earth.

thanks:)

Do-more

This is something I have looked at as well and it's not just a case of comparing the thermal conductivity of the different underlays.

What you really need to avoid is getting any pockets of air either between the sub-floor and the underlay and/or the underlay and the wood flooring as the enclosed air is a good insulator and will severely inhibit heat transfer.

Even small high and low spots in the sub-floor can result in large air pockets so a good quality self levelling compound is advisable.

You will I am sure have come across underlay which has self adhesive on both sides and one of the main reasons for this is to eliminate air pockets.

Independent test reports of this kind of product show a 10 degree C drop in temperature across the underlay and (a representative sample of) wood flooring. So for example your sub-floor will need to be at 35C for the surface of your wood floor to be at 25C.

I'm told that for every 1 degree C in temperature difference your floor will emit approx. 10W/m2 so if your floor is at a uniform 25C you will be adding 50W/m2 to a room at 20C. So depending of the heat loss from your room you can figure out what your floor temperature should be and consequently what your water flow temperature should be. This of course will vary with ambient temperature.

The most efficient method of installing wood flooring over UFH is to glue it down directly to your sub-floor so that you have no air pockets and no underlay to inhibit the heat transfer, but unfortunately I can't find any independent tests to show what the temperature drop is compared to the self adhesive underlay. (Different types and thickness's of wood flooring will of course give different results)

If you are going to use an underlay rather than glue down, IMO you are best using the self adhesive type to get good uniform heat transfer and no possible colder spots on the floor.

As for the price, that's another matter...

muffler

Moved to C & P

Troy McClure

Thanks Do-More
I dont want to go the glue down route as you never know, down the road, if you may want a change, and removing glued down timber flooring is best avoided.
Can you PM me something you would recommend for the job?

Do-more

PM sent.

Peanut81

Hi "Do-More" could you PM that info as well please.
Thanks.

K3v

Do-More could you PM that info to me aswell please.

cuculainn

Hi Do-More,

Can you pM that info on to me also

Thanks

Do-more

PMs sent.

dos30

Do-More,

Can you pm that info on to me as well

Thanks

Do-more

PM sent

bellucio

Wouldn't mind a PM also if you don't mind please Do-More.

Do-more

PM sent, sorry for the delay my interweb was banjaxed.

GilltownJoe

Could someone pm me the name please.

tash115

Hi Do-More,

Can you PM me that info also please

Thanks

GilltownJoe

I ended up gluing our floor down, delighted with it but messy enough job, would recommend though so maybe worth a thought for some

Tuttlinghorn

I realise I am resurrecting an old thread but I'm curious whether anyone who had installed UFH with Engineered flooring can now either recommend (PM) a particular underlay, or to just glue the floor down ? We are trying to keep engineered floor as thin as possible, 16mm I think. Cork underlay is being recommended by the flooring supplier.

We are completely dithering and have a concrete floor with water UFH which was laid about a month ago. At the time we decided not to go polished concrete floor in favour of engineered - which I'm not really sure was the right choice ... And now we have about 25mm of flooring to put in
Need to have some kind of floor in place by Oct 12 though !! ( kitchen installer)

Troy McClure

We ended using a product Quicktherm Underfloor Heating Underlay which has a really low tog value. We used 14mm engineered wood flooring as we have geothermal. Everyone told us not to glue it down as apparently you nearly have to take a jackhammer to get it up again should the day arise. We got the underlay from a supplier in Roscommon called Irish flooring products. The low tog is important.
We have our floor down 3 years and have a million dents from the thousand thomas the tank engines we have as they have magnet tips on them. Don't know if this would have happened regardless of the wood floor thickness but I think there will be a day when we'll have to change at this rate. Wouldn't like to be looking at a glued floor at this point.
The floor doesn't move very much which is why we stayed away from solid, but you always get some movement.

Mahogany Gaspipe

Just out of personal interest how do you find your underfloor heating performs when covered with what I'd imagine is more effective as a insulator rather than a conductor?

Tuttlinghorn

Troy McClure wrote: »

We ended using a product Quicktherm Underfloor Heating Underlay which has a really low tog value. We used 14mm engineered wood flooring as we have geothermal. Everyone told us not to glue it down as apparently you nearly have to take a jackhammer to get it up again should the day arise. We got the underlay from a supplier in Roscommon called Irish flooring products. The low tog is important.
The floor doesn't move very much which is why we stayed away from solid, but you always get some movement.

Thanks Troy for the recommendation. Glueing the floor down seems to cost over double what a floating floor costs to lay - more reasons to avoid!
do you have floor thermostats or any way to compare temp of the wood vs temp of water / concrete underneath ? (if this is even possible ..?)

Troy McClure

We didn't go that deep into it. Suffice to say the UFH is working fine. You need to keep the resistance to a minimum. UFH works very slowly and is not on demand such as rads. Good insulation is important to retain the heat. We have MHRV so we dont have holes in the wall with the heat flying out.
As for other question. Anything you put on top of your floor will insulate it. If your happy with concrete or tiles this would work best. You can get low tog underlays and even low tog carpets that are suitable for UFH. The are insulators and you may have to turn up your UFH to compensate. It's important to do your research on underlays or carpets. It's personal choice. We would not like to be walking on tiles so we made that choice. Some underlays have such a low tog rating I dont think they'll make much difference.

corcadorcha

Do-More,

Can you PM me info also please

Thanks

Do-more

corcadorcha wrote: »

Do-More,

Can you PM me info also please

Thanks

The info is out of date and the product is no longer available I'm afraid.

I did do a new floor 2 years ago and in the end used a 1.6mm underlay from a large DIY store, it was not specifically for UFH but had the lowest heat resistance of any of the lower priced underlays I could find at the time, it doesn't have any adhesive on it, just for normal loose laying.

It was solid black colour and almost like rubber in texture.

Have had absolutely no problems with heat transfer and we run the UFH at around 30ºC flow temperature as we have a very low heat demand.

I would suggest that if you are using a thin underlay your floor needs to be extremely level, ours was very good and I only needed to level two small hollow areas. We have no "spring" in the floor and it feels very much like the fully glued installation we had in our previous house.

I live in Sweden now so little point in giving you the product name as I am pretty sure it is not available in Ireland and can only suggest that you look around for something similar.

I no longer have the packaging but as far as I remember the thermal resistance was 0.046 (m²K)/W

murphy31ie

I am looking at using an underlay with the below values.
Tog value 0.7
Thermal resistance of 0.07
It is 3mm thick

You think that should be fine?