solid floating floor + underfloor heating

[trevw]

Hi,

I have a new extension and am doing as much as I can myself. I am looking at options for the floor, I have underfloor heating to fit and need to put down 70mm of celotex or equivalent.. the standard option as I understand it would be re-inforcing mesh and screed, but I was looking at the following kinspan solid floating floor option:

http://www.insulateonline.com/index1.htm?floors3.htm~main

my underfloor heating came with clips for joist so if I could lay the floor as above, then lay timber down (i.e. roof battens or similar) then fix the pipes to the battens and put a floating floor on top then this would allow me to do it myself and fix issues with the underfloor heating long term without digging up screed..

this kind of thing:

is this a good/bad/indifferent idea? and what would a building inspector think of it?

thanks

Trev

 

[noseall]

looks ok to me, but plywood would be better.

only use chipboard if i have to.

 

[trevw]

looks ok to me, but plywood would be better.

only use chipboard if i have to.

thanks noseall... is that even with the moisture/mould resistant stuff?

so would you say ply (would wbp do or do I need marine) for the bottom layer but if I was going for a floating floor on top then a chipboard floating floor or would you say ply again - which I would then presumeably have to fix? (was leaning towards floating as screws near all those pipes makes me nervous )

the battens would be at 400 centres for the underfloor heating to work ok

 

[Fluffster]

I always use marine ply if there is any chance of moisture penetration. Not a fan on chipboard at all as it has no way near the strenght and fixing qualities as ply. Do not forget a vapourshield lining too.
Pete

 

[mointainwalker]

If I have understood your drawing correctly, I think you are going to have a terrible result from your system with very little heating.

1) Are the pipes really going to be suspended in air ? That is how I see it.
If so, absolutely crazy. Total waste of time and money.

2) You are then proposing to fix the pipes to joists, directly below a chipboard floor. Wood is generally regarded as an insulator so your heat transfer is going to be poor. Making it a floating floor just makes the problem worse as it diminishes heat-transfer (not that there is much to start with )

3) Your more or less random pipe -spacing is being taken from the joist intervals rather than your heating needs.

Have you done a heat-loss calc ? If you haven't then how do you know how close the spacing of the pipes needs to be ?

From memory, pipes on 10 cm centres ( yes 10 cm !) in screed with tiled surface give a max of 100 W/m2 at 30 C tile surface temp ( max legal ). I would guess your set uo will give you around 10 W/ m2 and maybe you intend to put carpet on top of the chipboard just to totally eliimate any heat transfer !!


Absolutely mad, mad mad.

 

[trevw]

Hi mointainwalker,

the system has been down for a couple of years now and seems to work okay, only just seen your reply which was a little late to affect the approach I took , there are a few details not visible on my drawing that might make the difference? Firstly the pipes are supported in aluminium support brackets that are about a 18inches long, you fix these to the joists with only about a 4 inch gap between them and they keep the pipe pressed up against the floor. You then cover the whole lot with thin sheets of aluminium before fixing the floor down, I assume this is in an effort to absorb the heat and conduct it more efficiently through the chipboard? and maybe to add to the ineria of the system.

No argument on the pipe spacing - it is dictated by the joists in this system, but surely even though the chipboard/carpet are insulators they are not as effective as the dedicated insulation below, therefore on balance most of the heat will eventually have nowhere else to go but up and the chipboard will just slow response?

One thing I would do differently is ditch the floating floor and fix the chipboard down properly.

I would have rather gone with a screed system downstairs ideally, but the mixed nature of the floor types made that impossible. However in the recent (very) cold spell, even with only about half of the underfloor heating online upstairs the house was still very comfortable.. haven't had the gas bill yet though so I can't comment on its efficiency..

cheers

Trev