Following on from my last post.

We rather like the idea of underfloor heating for four rooms (approx 600ft2) - the floorboards of which are suspended on rafters over a void (quasi cellar). Our architect is not terribly in favour nor was the first builder who came around today to price up.

Has anyone here got any experience of underfloor heating?

Any issues which should be taken into consideration? Two rooms may have wood flooring (possibly oak) and two rooms may have stone/tile flooring.

Thanks

Mike

Very common in Scandinavia, and very effective, but I have never seen it used under a wood floor. I think that the wood would shrink terribly and be ruined in a fairly short time. If you were to install a suspended concrete floor with under floor heating, and tiles it would be VERY expensive.

Fredrik

No experience, yet. We have just extended and had pipes cast into the new concrete raft for underfloor heating in the entrance hall area. We also intend to cut channels in the existing concrete raft in the utility room and to lay water pipes into this. Both areas will be tiled.

I would expect that with a water based system, you need some kind of 'mass' ie. the concrete, to distribute the heat evenly. If you have a suspended wooden floor, then you will probably be after an electrical system. Basicly a conductive foil which is laid over an insulating layer on top of the existing floorboards and under your wooden/laminate flooring. (Or tiles if the floor is stiff enough). I'll see if I can find manufacturer names for the electrical systems for you.

/dl

I put wet underfloor heating into the replacement concrete floors of our latest hovel. It provides a comfortable warmth in places like bathrooms where one goes barefoot. But is very slow to react (in massive concrete) and needs very heavy insulation beneath it. The Danes are insisting on 8" (200mm) of insulation now, I hear. I used 4" of under-floor polystyrene.

My wife didn't much like using the underfloor heating in the kitchen as it didn't react to changing air temperature. Particularly when she was sweating over the cooker in full winter sun. It would be better as gentle background heating under such circumstances.

I'd trust your architect and Fredrik! I would also fear the shrinkage of a conventional wooden floor construction.

The stone/tile(?) floors sound more promising if removed and a properly insulated concrete cast concrerte floors were substituted. But the details are very important and the work extremely heavy, noisy and very unpleasant.

A cold bridge at the edge of a badly made floor or unsupported walls aren't much fun. I think underfloor heating is better suited to a new building to take maximum advantage of it. Perhaps using a wet heat pump?

There is a form of electric overfloor cable heating. But it adds some height to the floor which means reduced headroom and cutting off the bottoms of doors!

I was keen to get underfloor heating under the slate floor in the bathroom in our extension. The advice we received generally though was that they were more hastle than they were worth.

You're correct in thinking that wood and heat dont go well together, however I've just worked on a place that did exactly that using engineered boards which are very stable and of high quality, and it is claimed, can withstand underfloor heating. The company is called element 7. Oh, and they cost an absolute fortune! worth a search though as there may be others out there for less.

good luck

roman

Underfloor heating by its nature tends to suit rooms with long hours of occupancy i.e. fairly constant temperature requirements.

I'd be reticent using it under an existing timber floor for this reason. U/F heating can work well under a timber floor specified for use with it (Gymnasiums come to mind - in fact I've just specced this in a secondary school) - but the key thing is tight control of moisture content in the floor. It's the varying of moisture content that does damage, so the key to success is management of the initial warm up (and at seasonal changeover) and subsequent use. If you try to use a wet system under a timber floor like most people use conventional central heating (come in and wind up the 'stat in the hope of instant heat) you'll have problems, and a squeaky floor in no time flat.

No such problems with solid floors though, and generally modern systems based on polyethylene pipe can be very reliable and long-lived - look for Agrement certificates from the propective suppliers.

used Junkers Beech solid timber flooring over my Wirsbo u/flr heating with excellent results

By way of update - two builders who have visited today have said that we could succesfully use underfloor heating but a)given the nature of the floor (eg suspended) we should use the electrical type systems b) in terms of installing in existing areas it will prove costly (insulating the gaps between the rafters underneath the heating element and suitable wooden flooring) etc etc. but would be more effective in the new build areas with a modest amount of coverage in an existing part of our house.

All the builders have mentioned that modern radiators are considerable more efficient that the 30 year old radiators we curretly have. That sounds promising.