Underfloor electric heating - does it work?

Underfloor heating generally can be a wonderful thing. Electric heating can be a very expensive thing...

It's a bit of a compromise. Most underfloor heating is done with 'wet' systems - HW pipes buried in a carrier or screed below the finish, which usually requires 50mm or so depth to do. Electric heating mats offer an easy retrofit into existing buildings, but may or may not help.

The 100-200W figure you mention is the key here - is that total, or per square metre? The former is barely enough to raise the temperature of the surface, the latter is more than enough to heat a room.

Three comments:
1) Raising the floor surface temperature is a very comfortable thing to do if you expect to stand around on it a lot (eg tiles in a kitchen)
2) Underfloor heating tends to let you get away with less energy input because the radiating area is so large that you 'feel' warmer than the air temp alone would suggest. Typically, a floor surface temp of just 27-28degrees C is the setpoint.
3) If you already have a domestic heating boiler, extending the loop into the kitchen and finding space for a small rad/heated towel rail will be, in most cases, a much cheaper-to-run solution for full heating of the space. And it dries the teatowels!

HTH.

Why not fit a kick space radiator/heater under the cabinets so it blows warm air at floor level, thus warming the room.

http://www.kitchenheaters.co.uk/?gclid=CMTZjdyZyokCFTFrMAodk2TSLw

Beano

We installed underfloor electric heating, of the type you are considering, in our ensuite bathroom. However we only use it as secondary heating as the room also has a radiator. We leave it permanently on, but at a very low thermostat setting, just to take the chill off the clay floor tiles. For that purpose it is wonderful and I highly recommend it. Very low running cost at low setting too.

As primary heating for the whole kitchen, I very much doubt that 100 or 200 Watts will be up to the job, but it depends on room size and quality of insulation. There are online guides that will tell you the heating capacity requirements in Watts for a given size of room.

Of course, if 200W is not enough you are still left with the problem of how to heat your kitchen. Kickboard heaters are effective, but you still have the electricity bills to pay. Same if you use freestanding radiators. I agree with felix that if you can get your central heating into the kitchen this will be the best option in the long run. You can get some really stylish space-saving radiators these days. Try www.bisque.co.uk or www.arbonia.com

Good luck
Dunstan

A ski house I stayed at in Colorado had tile floors with in floor heating and it worked quite well for the reasons enumerated above. Standing on the tiles with bare feet was very pleasant. I can't comment on how (in)expensive it might have been.

Norman

When doing some 're-modelling' of our house we installed water based underfloor heating in entrance hall and utility/shower room. As Felix, Cosmoliu and Dunstan pointed out, it is very nice standing on warm floor tiles.

What you decide to go for depends on a number of factors. eg.
- What is the general layout of the house? Is the kitchen a large / self contained (eg dining also) room, or do you have other rooms adjacent with heating that could 'spill' heat into the kitchen (FWIW, our kitchen has no heating, but is open to a corridor and dining room and I have never experienced it as feeling cold.) How many outside (ie 'cold') walls does the kitchen have? Size of windows? Double glazed? Is the kitchen 'drafty' (Quality of outside doors/door glazing etc.), General traffic through the kitchen (eg doubles as generally used entrance to house)?
- What flooring will you have? Ceramic tiles tend to feel cold, wooden (Not laminate) floors warm.
- What existing heating do you have? If you have a water based system, it would, I believe, be worth considering a water based system. (You need a separate pump as you do not want/need your floor (large area) to be as warm as your radiators (small area).
- How much work are you doing? If you are ripping the kitchen out and starting again, then it should not really matter whether you do a wet or electric system. Electric are very low profile (basicly a tracked foil sheet), whereas water based need 1.5" or so of depth for the piping; say 3/4" pipe set 3/4" under the surface. If you have a concrete floor then it very easy to cut channels for the piping for a wet system. (That's what I did). If you have a suspended floor then I guesss a wet system will probably build 2-3" including insulating backing etc, which you could almost certainly sink between the floor joists. If you go electric, you would be well advised to insulate under in any case , so you have the job of lifting boards and putting down insulation anyway...

Get quotes for both systems as far as installation and, as far as is possible, running costs.

Maybe also worth considering alternative/complementary sources of heat, eg install a heat pump as part of the kitchen re-vamp to complement the existing heating system. A big problem (As I see it) with many UK houses is that it is difficult to find space for alternative heat sources such as heat pumps/exchangers. If you are re-jigging your kitchen it would not be unreasonable to build that into the plans rather than as an afterthought... Energy ain't going to get any cheaper, so it is, I beleive, worth investing in long term solutions.

A related (although short!) thread here. I sustect that the contributors would be happy to share their views/experiences.

Good luck!

/dl

Max,

We installed a wet system under our kitchen floor when it was being re-modeled, because the new arrangement did not have wall space for radiadtors.

It was much more expensive to install than an electric system but should be cheaper to run longer term. The floor was originally a suspended wood floor, which as David has pointed out, it is possible to install a wet system but it is more complicated. As the whole place was being gutted it was decided to put in a concrete floor.

A concrete floor with underfloor heating acts like a big storage heater and so stays warm long after a conventional radiator has gone cold. Very nice on your feet first thing in the morning. Ours is linked directly to the combi boiler and has its own thermostat and timer system, although it can only draw heat when the main house timer is set to run.

Underfloor heating is ideally suited to low temperature systems supplied for instance by ground source heat pumps, but that is another subject. The cost and disruption of retro-fitting these in an existing home often puts people off, but if I was starting from scratch it is what I would do.

If you look at the attached picture you can see the pipe loops are placed in the main area of the floor wher you walk, with a single loop running under the area of the units. This is to prevent the possibility of cold bridging and condensation.

The system we had installed is clipped directly into the slab insulation, before the last layer of concrete or screed is laid on top, and it is tiled. It works extremely well, and we are delighted with it. If you need more detail I can always look out the stuff I kept from the project.

Regards

Nic

quote:

Underfloor heating is ideally suited to low temperature systems supplied for instance by ground source heat pumps, but that is another subject. The cost and disruption of retro-fitting these in an existing home often puts people off, but if I was starting from scratch it is what I would do.

Which is why I suggested considering this if Max's kitchen was being completely gutted. Easier to plan for a cupboard to contain the inside bits of a ground or air source heat pump at the drawing board stage than later. Also, if the kithen is being gutted, it may be that the central heating boiler (?) is a.) hanging on the wall and b.) due for renewal/replacement and hence another reason to consider ground/air source heat pump.

FWIW, when we installed our wet system we had two loops. One loop in the new cast part (ca 5m2) with pipework tied down to the re-bar net which sat over a thick layer of polystyrene insulation and had a single pour of concrete. And a second loop in the existing cast concrete floor (ca 7m2), which is where I cut tracks for the pipe to be layed in, then fill out with a cement slurry. The two loops run in parallel. Having several parallel loops is, I believe, quite common if you are talking large floor areas. In areas/rooms we will be putting wooden flooring down we installed new (wet) radiators.

/dl

Another recommendation for the dry underfloor heating of bathroom tiles. Had it installed last year and still thrilled by the feel of warm floor on my tootsies at night, when the prostate calls.
It has made no detectable difference to our electricity bill, (but I do have two daughters who run the washing machine 24/7 for single pairs of knickers).

Thanks for all the responses.

Of course I should have clarified that I am referring to 200w a square metre.

The whole kitchen including the floor is coming out so I guess any option above is a possibility. I will get to work on going through each of the thoughts you have given.
Thanks again

Max