under floor heating

[Redmurty]

I am building an extension at the moment I was looking at under floor heating. Does anyone have any experience with it good or bad cheers Spud

[special one]

I'm a builder mate so have a bit of experience with these, mainly two types, electric matting and piped system, the latter being the better but more expensive.

The electric ones are ok for back ground heat or heating a cold floor but they are not a replacement for conventional radiators, I've had two of these electric ones fail so won't fit them now, if a customer wants them I'll let them do it at their risk.

The piped ones are better but require more labour and more cost, again the ones I've experienced haven't been good enough for a replacement of a radiator, they still need additional heat.
There may be better systems around but so far they haven't impressed me enough to convert to them.

Phil

[Redmurty]

excellent thank you this is the sort of info I was looking for owe you a beer cheers Spud

[Willbrown1200]

Yes - i am a buidling services design engineer (design all the bits - wires pipes etc, that go into buildings to make them work) and have been involved in quite a few design projects with underfloor htg. In a domestic building it can be an excellent solution, as long as it is designed and installed correctly.

The htg elements form the floor slab creating a huge very low temperature htg element, the mass does mean it has a slow response and should be run more or less continually rather than on/off/on. The low temperatures involved work very well with modern condensing boilers as they are more effcient with low water temps - the condensing bit means you gain the heat normally lost in the flue gasses. Also, as the radiant component of the htg is higher than a radiator (which are actually more convector than radiant heaters in reality) system the air temperature can be lower for the same feeling of comfort. This also tends to give a 'fresher' feel as the air is a degree or 2 lower whilst comfort level is the same, or better.

Control is important - the water temp has to be contolled (easily done) and each room space should have its own temp control. The other important thing is the room should be kept at the preffered temp and only allowed to decay a few degrees when 'off' (known as 'setback') by using programmble thermostats. Its like a vehicle uses little fuel cruising but lots accelerating.

The building must be well insulated to avoid 'hot floor' as the system tries to put in more heat than is practicle for an underfloor system - this is why early attempts in the uk did not work well, it is a popular way of htg in europe and well tried and tested, they have very well insulated buildings and have made all the mistakes years ago and learnt from them.

Electric systems are ok for smaller areas (bathrooms typically) as the install cost is lower, but there is a balance between cheap install higher running costs.

Wet systems can work well with heat pumps as the low water temps allow good efficiencies. If you have PV panels your generated elec can help run a heat pump and be a good solution with lots of 'green' credentials.

The bottom line is a well designed and installed system will be an excellent way of htg in a home. Do a bit of research and you use someone who is competant and familiar - there are always optimists who think they can do anything without really understanding the nuances after all 'its only a few pipes in the floor'.

Take a look at: http://www.beama.org.uk/en/energy/underfloor-heating/

Hope i have not been too much of an anorak, but having been involved in services design for a long long time i have seen all sorts of systems that are great when down correctly and worthless when not.

[zimtim]

Had electric in old house was very nice but quite expensive to run as opposed to reads in the new house.
Do have underfloor heating in the conservatory the electric mat type fitted it my self as a t time there was no way to get a radiator in there. Had laid extra thickness of the insulator so more goes up as opposed to down. yet cost more to heat conservatory than it did for the rest of the house. I would if I could of done was to go with the pipe and had it linked in to the rest of the radiators plus still had a rad as extra. If you are just having a tiled floor then underfloor heating is nice but I wouldnt rely on it as heating.

[Willbrown1200]

Special one - if the underfloor does not heat enough to replace a radiator - its probably the level of insulation in the building or the infiltration of air. Underfloor systems have their limitations and are best in a well insulated air tight building.

Air leakage in/out of a building wastes a lot of heat energy. The latest building regs are focussing on pressure testing in larger buildings and gradually tightening up the quality of building stock in the UK.

[Willbrown1200]

Zimtim - whilst i am still on my soapbox. A conservatory by the very nature of lots of glass, and typically lightweight construction, almost certainly has a high heat loss compared the area of floor you can use as the heat emitter, in this case a mixture of underfloor background and a radiator as peak top up is probably the best way to go.

Right enough of me chundering on - as with all things you need the right solution for each problem, there is never one fits all answer (otherwise i would have been out of job years ago)

[Heff]

I have a 2200 sq ft house with underfloor heating on the downstairs only with radiators upstairs. Mine is the piped system with individual thermostats in each room. Also the main areas, hall, kitchen, sunroom, utility and dining room have tiled floors to aid heat transfer.

Good points
Excellent all round heat
No cold spots
No radiators so furniture placed wherever suits
Great on feet on cold mornings

Bad points
Cannot regulate the heat like radiators. It takes a while to get the heat built upthrough the floor when starting from cold
Takes time to change heat settings as the floor retains the heat longer
Can be expensive to run if not set up correctly
Needs to be professionally installed to get best spread of heat
Needs to have the correct amount of screed over pipes to ensure the floor doesn't crack with the heat produced
With the increases in oil prices it costs over 3 times as much to run now than when it was installed


Overall 7/10

Heff

[Hoggyf]

I'm a plumbing and heating engineer and have done exactly what you are talking about previously in my own home. I did it because everything was free left over from jobs and labour was my own.
Result I had a warm floor in the conservatory but still need additional heat to actually heat the space (which I new I would) Ideally the UFH needs to be connected direct to the boiler on its own pipe circuit so it an be run independanty from the radiators as UFH needs longer run times. Its not really viable as and addition to a system from a cost point of view. A electrician mate had electric UFH in his kitchen, in his works it was bloody brilliant, can't afford to run it but its brilliant :laugh:
What about a wet fan convector, blows hot air using the heating pipework, high output from a small heater?? Or be traditional and fit a radiator.

[BIG BILL]

I have had the Leccy matting in my bathroom for a few years now, it works, nice and cosy but expensive to run, I find we have to leave it on all the time in the winter months, it takes to long to heat up properly just for a shower etc.

BB