Experiences of wood floor with Underfloor Heating

[cf-leeds]

Hi all,

I've recently put UFH in the newly united kitchen/dining rooms, as part of a totally new extensive project. This is water based with three pipe runs that provide good coverage of the space.

On top of the UFH is a QuickTherm Vapour Underlay, as recommended by the flooring supplier. The flooring is 15mm engineered oak finish, with the following spec:

Approx. veneer thickness of 3.2mm Locking Joint - Floating install

The advice for underfloor heating from the flooring install guide is as follows:

"Maximum allowed temperature on top of the floor underneath the floorboards is 27 °C. Please note that normal loose carpets/rugs insulate i.e. increase the floor surface temperature by about 2 °C!"

I have the UFH running at 27 degrees C - After several hours, the floor is just not getting noticeably warm, neither is the room.

Does anyone have any experience of running a higher temperature under a wood floor. Most manufacturers seem to state 27 degrees max, but are they just covering their arses ? I mean, If I ran at 35 degrees for example, would it really be running a risk with the flooring.

I went to my neighbour's house, as they said that their UFH (installed a year ago) was working a treat with their wood floor. I looked at their UFH manifold and was amazed to see they're running it at 50+ degrees. I think they're oblivious to the guidelines.

Thanks for any advice (even if that includes adding rads and shutting off the UFH)

c.

[Tim Watts]

My UFH under ceramic tiles runs at 50C +/- 5C and the surface temperature is 26-30C.

You need to jack the water up a bit - I would have said 40C water would be safe for wood as the surface will never get anywhere near the water temperature.

[newshound]

I agree, it is great under ceramic tiles, also OK on carpet over concrete. But personally I don't think I'd want to use it this way.

[harry]

How effective your UFH is depends on several factors. If not working adequately, there's too much insulating material covering it, the UFH pipes are too small/short, there is insufficient insulation beneath the floor slab or the water is not hot enough. ie all design errors. Increasing water temperature will increase the heat transferred but reduce boiler efficiency.

It takes a few days for UFH to warm through, they have to be permanently"on". They respond only slowly to weather changes, which is why many people have a "mixed "system (ie UFH + some radiators.)

[Andy Burns]

How much insulation is under the UFH?

[cf-leeds]

Thanks -

I'm asking myself what degree of insulation the underlay is providing. Maybe the piping is at 27 degrees, but the underlay must be insulating the pipes to some extent. The the underlay is a lightweight closed cell polyethylene material.

Looking a the spec sheet, it has a tog value of .303.

c

[cf-leeds]

It's pro-warm 25mm EPS floating insulation boards on T&G wood floor.

[The Natural Philosopher]

First of all 27°C in the pipes will be nowhere near 27°C at the floor surface. The ratio of pipe surface area to floor surface arae is small

There is quite a lot of drop through the screed.

I run mine with around 6mm engineered flooring flat out. 50°C+ It gets up to around 35°C under rugs, under furniture.

No. The issue with wood is that you may get shrinkage. That is not too bad with engineered stuff.

The 27°C is just arse covering.

Increase temps till you can actually feel the floor getting warm after a few hours or so.

Depending on hhow deep the screed is I'd say 50C in the pipes will be about 30C at the room surface.

[The Natural Philosopher]

its fine with engineered wood too.

there is just more unwanted insulation than with tiles

[The Natural Philosopher]

some but you have totally missed the point. The surface area of te floor is much gfreater than the surface area of the pipes inside it: so the heat drops massively anyway on its way to te floor surface

I've run my floor bare to test it with no thermostat flat out overnmight. Even than it barely got above 30°C with a 50W/sq meter estimated input at 50°C

add a bit of underlay and some engineered wood, and it wont exceed 27°C at the wood surface.

[The Natural Philosopher]

Didnt think EPS was legal under kust a wood floor. Not screeded then? is there no air gap?

[cf-leeds]

The EPS has an outer aluminium layer, which is apparently for heat distribution, then there's the underlay, then the Engineered floor.

[The Natural Philosopher]

where are the pipes?

[cf-leeds]

The pipes are run in a channel that is already sunk into the boards. The thin aluminum layer is therefore also in the channel.

[The Natural Philosopher]

OK. Id prefer to see a picture of this.

BUT if the Al is doing the spreading rather than the screed as in my case its pretty much the same process. The Al will be at lower temperature than the pipe water as it spreads the heat over a larger area.

So the answer is the same. Bang the water temp up till te wood is near enough 27°C on the top.

[Andrew]

What is under the original T&G floor ?.

if this is a suspended and well ventilated ground floor, then in your location, with only 25mm of EPS, you are going to lose quite a lot of heat (and thus money) heating your underfloor space.

[Andy Burns]

Given the 15mm(?) pipe is embedded in the EPS, there's only about 10mm of insulation below the heating pipe.

[Tim Lamb]

This stuff does come in other thicknesses. I used 40mm but as you say this still leaves less than 25mm of EPS below. Mine is on uninsulated concrete:-( I don't think the OP has said.

Somebody with better maths than mine can explain *edge effect*. Basically only the heat conducted into the floor near the walls is totally lost.

>

[The Natural Philosopher]

yep. This is ok on an upper floor, but its not how I would heat a ground floor for sure

Modern practice is concrete beams with 6" EPS blocks between, and another 6" EPS on top with the pipe pegged to that, and then screed or concrete.

If I had a suspoende firun floor Id lift the floor, put celotex between the beams, 100% seal it witl foil tape and expanding foam as appropiate then a system such as described on top...

[The Natural Philosopher]

Normally the walls are lined with inuslation before screed is dumped in