Underfloor Heating and Carpet Underlay

[Marakith]

Hello!

I'm planning an extension and scheduled to start work in March. Whilst doing this we're going to swap out our boiler for an Air Source Heat Pump (plus external insulation) and fit wet underfloor heating to the floor of the extension and the rooms we're extending out from. We've worked on our house top-down. From the loft, to a refurb of the first floor and now the ground floor.

Our house is quite old. The first floor is built with joists and the floor is timber (not chipboard). We had carpet laid on the first floor, with the underlay being a rubbery sort.

As part of the knocking through process the builders are going to have to redo the ceilings on the ground floor, and I noticed that there's a product to allow you to install underfloor heating from below (see picture). Utterly genius idea!

My question is - will this work? Will the heating make it through the ceiling timber and the underlay and carpet? Is it safe to do this (I worry about the underlay giving off fumes).

 

[RoyMi6]

Google is your friend: https://www.carpet-underlay-shop.co...loor-heating-carpet-underlay-from-5-25-per-m2

Definitely an option, if you’ve got concerns get stuff that says it’s designed for it.

 

[PermaChanged]

This was the one we opted for, basically the same thing but slightly more thermal resistance than the above linked; https://trade.qaflooringsolutions.c...ave-8mm-pu-underfloor-heating-carpet-underlay

 

[Marakith]

Google is your friend: https://www.carpet-underlay-shop.co...loor-heating-carpet-underlay-from-5-25-per-m2

Definitely an option, if you’ve got concerns get stuff that says it’s designed for it.

Thanks - I had seen this stuff already but we'd rather not pull up the carpets and replace the underlay (which is not perforated). So my question remains whether this would be a sensible idea or not.

 

[Minato]

Just be aware that carpets will block a certain amount of the heat coming up from between the joists. The thicker, the more blockage. Tiles and certain type of wooden flooring e.g. LVT work the best. Not to say you won't benefit at all, but don't expect the same results as you might have seen in a bathroom for instance.

 

[Kamakazie!]

I'd say it's unlikely to work well but ask the manufacturer of the product you want to install.
Carpet, underlay & floorboards is a hell of a thermal barrier. Especially as it looks like you wouldn't fit much insulation below.

 

[Marakith]

I'd say it's unlikely to work well but ask the manufacturer of the product you want to install.
Carpet, underlay & floorboards is a hell of a thermal barrier. Especially as it looks like you wouldn't fit much insulation below.

Yeah - I think you're right. We might just do it so it serves the landing upstairs only - just to take the chill off

Thanks

 

[Nathan]

No.
I fitted a wet UFH in the last house on both floors. The ground floor majority of engineered oak was brilliant. Low tog rated underlay and carpet on first floor. It was terrible, so cold upstairs. Never again.

 

[SoliD]

IF i've read this correctly you'll be only adding UFH to the new bits which would obviously comply with the 150mm PIR under the floor, i'd advise adding to this another 100mm or 150mm as the losses through the ground are half of your heating bill. Bigger your insulation and energy store (screed) the better, will take longer to warm up, but once it's there will be lovely.

From everything i've read carpet on UFH is pretty rubbish and you're best of sticking to radiators.