Solid Wood Over Underfloor Heating.

[RoyMacDonald]

There is a restaurant in Burgess Hill that has had solid oak square edged boards nailed to joists over underfloor heating for so long I can't remember, but over 12 years at least.

I'm considering doing the same as I like the floor very much.

Does anybody have any experience of this type of floor and anybody have any opinions?

Roy

 

[mointainwalker]

I imagine that your boards will be at least 20 mm thick: this alone will make the floor relatively inefficient. From memory 20 mm is the max thickness recommended as wood is a moderately good insulation material.

The other matter will be getting the heat into the floor and whether you have any mass to retain the heat.

If you don't want to raise the existing floor-height, using spreader plates under the boards is the usual method, but would, I think , be a hellish job fitting stiff, unco-operative 16 mm pipe in a 400 mm space between joists as well as continuing the circuit into several other joist-spacings ( circuit length up to 100 lm).

If you just use spreader plates this will heat the floor but there is no mass to store heat so it will heat up and cool down quite quickly, thus losing one of the major benefits of UFH.

You don't specify if this is going to be DIY or professionally fitted. Which ?

 

[RoyMacDonald]

I imagine that your boards will be at least 20 mm thick: this alone will make the floor relatively inefficient. From memory 20 mm is the max thickness recommended as wood is a moderately good insulation material.

The other matter will be getting the heat into the floor and whether you have any mass to retain the heat.

If you don't want to raise the existing floor-height, using spreader plates under the boards is the usual method, but would, I think , be a hellish job fitting stiff, unco-operative 16 mm pipe in a 400 mm space between joists as well as continuing the circuit into several other joist-spacings ( circuit length up to 100 lm).

If you just use spreader plates this will heat the floor but there is no mass to store heat so it will heat up and cool down quite quickly, thus losing one of the major benefits of UFH.

You don't specify if this is going to be DIY or professionally fitted. Which ?

Professional install for the UHF. The fitters are coming this morning.

Spec is spreader plates over 100mm Rockwool between joists on nettting. (I've already installed that in conjunction with improved subfloor ventilation. As a matter of interest the subfloor is 150 mm of tarmac. I have a 100 year old house of slightly strange construction.

They have CAD drawings for the install and I've sent them photos of the insulated foorboardless floor. They seem happy enough with the preperation.

I realise the floor will not have the same mass as a concrete floor but there is a lot of mass in the walls and floor, system water etc. combined and the amount of heat needed is not great from the amount heating I have in the other rooms. I have a weather compensated Vaillant boiler and the flow temperature with an outside temperature of 7 C is 35 C with the rest of the system.

I've uploaded some photos of the floor in the resturant and of my prepared floor.

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[mointainwalker]

For my personal interest . can you tell me if the CAD drawing calls for the pipe to ,remain between a pair of joists and then one notch at end to continue into next pair or what ?

How many W/m2 do they say the system will give at temps quoted ?

Can't really agree very much about mass in walls etc. There is a very major difference between water at 40 C passing its heat directly into a screed surrounding it on 360 o and a wall being warmed by air at 22 C only on one surface for part of its height..

 

[RoyMacDonald]

Basically yes, but the drw was incorrect so the install had to be different, but only in respect of the joists being the wrong way round. The fitter annotated the dwg and took it back so that I could have a corrected copy.

I think the output was 70 watts per m2 if I remember correctly.

As far as the themal mass goes I wasn't too worried as the main reason for fitting was to get rid of the radiators. The house is slow to lose heat anyway so it would only be improved by the additional heat stored in the water and floor, however small.

In the kitchen I removed the suspended floor and filled the void with insulation and cast a reinforced concrete slab on top with the underfloor installed under the screed on underfloor heating insulation. To do that in the rest of the house would have been a very difficult and expensive option because of all the gas pipes. primary heating pipes and electrical and network cables.

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