We are getting a two story extension built onto our house next year (planning permission permitting!).

Architect we are using for the initial ideas / sketches / drawings is very keen on underfloor heating, reckons there’s only a 10-20% premium over radiators price-wise.

I’m quite keen as it seems a tidier and more aesthetically pleasing solution, but I’ve heard conflicting views on it.

Q for those who have / had it: does it warm a room as well as a radiator? Do you just get a warm floor but cold room? Is there an issue with choosing floor coverings?

(NB: room sizes will be approx. 4 x 4.5m)

Cheers

not sure about his figures.

Yes it will work as well probably better than radiators.

Yes can be an issue with floor coverings, but go to a company that will do the design. Loads of companies around few actually do any design which can be critical.

I work with David Robbens a lot, used others never again, they are not the cheapest but when you are putting a system in you need to get it right first time.

Where are you in the country, if you are local to me you are welcome to look at some of their systems.

Insulate
Insulate
Insulate

Whatever heating you choose will only be as effective as the way you insulate the build.

Airtightness (with controllable ventilation) and insulation are key. If a building is insulated properly, it needs hardly any additional heating. And it’s easy to achieve this at build stage.

Heat recovery ventilation is fairly simple to install at the build stage too, so might be worth looking at that ?

Be careful re. the control system if you have a mixed underfloor/radiator system. You will find that underfloor takes a long time to heat up so needs to come on earlier than the radiators, but conversely stays warm longer and so can be turned off earlier. If you have them on two separate circuits with separate control systems it would be a good idea.

It’s great and works well. However it takes a long time to heat up so if you only like to put your heating on for an hour at a time it isn’t for you. You can switch it on for a couple of hours and then off again, it just isn’t as fast as regular radiators.

Your boiler will also need to be able to drive two circuits as the water temp in the underfloor is lower that regular radiators. This may just be a case of a separate pump and mixer valve but if your controller can’t already handle that you may end up with a new boiler. Worth checking in advance so you don’t get any surprises.

cats love it of course 🙂

Edit:beaten to it by the Fopster. That’s what I get for being long winded

Are you talking wet system or electric folks?

Edit: doh. Wrong question.

I suppose i really want to know if an electric system works ok…….

No.

I proposed it for my extension, looked into it in more detail and decided NO. Way too much trouble.

Integrating it with an existing LPHW system was problematic. It would also require a fundamental change to the way I would have to use my boiler. i.e my boiler would have to be on longer as the heat up times are longer.

I’ve used it in commercial developments but generally as part of a combined solution for a large room area / volume

It can be used with wooden floor finish subject to an underside temperature requirements and installation requirements.

I put electric UFH in the kitchen area under the tiles. Works very well and the dogs love it but I reckon it expensive so I rarely use it or need to use it.

Is there an issue with choosing floor coverings?

I think the answer to that is yes. It’s fantastic with tiles, works with wood but I imagine that any other sort of floor covering would act as an insulator which sort of defeats the purpose. I may be talking bollocks of course but I did my own including the calcs and you you are battling between getting the heat up into the room rather than down into the ground so I wouldn’t want to put anything in the way that stops it going up.

http://www.underfloorheating1.co.uk/blog/underfloor-heating-floor-types

we love it. the place is evenly warm all the time. Only thing we miss sometimes is having a hot radiator to lean against when coming in from the cold. But otherwise – ace. We are in a well insulated new build flat, mind.

im an electrician and wire the control side of heating systems weekly. if i was to build a house or ever redo mine id put underfloor heating in without a doubt.
you can create a constant temp’ throught the downstairs no hot spots no cold drafty spots. yes, it does take longer to heat up but if you have an efficient boiler then you just leave it tick over constantly. once the mass off the floor has heated up it takes little work to keep it at that temp’
like said before insulation is the key too, as its going to be an extension building regs will ensure your insulation is up to standards but going a little further with it wont hurt.
once its all in and working you can sit back and enjoy a warm house and look at all your spare wall space and smile 🙂

a good underfloor system will have water temp control on it so the boiler being able to drive is irrelevant.
I deal with a fair bit, not just Robbens but for the NHBC reapiring or sorting faults out on poorly designed and installed systems. Choose wisely.

I have had it in a house, and would recommend it if you can afford it and the building is suitable.

Thanks all – some food for thought.

Bear – I’m in Bristol.

Do a bit of research on building to “passive house” standards. If you do then one very small radiator is all you’ll needs.

It’s very popular in SA – underneath both tiles and carpets. I don’t have it but I’ve visited places with it and the rooms have been very cosy. They tend to use element wire over here though – not hot water piping.

Apparently the initial start cost when winter arrives is heavy, but then it ticks over fairly cheaply for as long as you leave it on.

Don’t know about the costs (was already installed) but it works awesomely and cheaply in our well-insulated flat.

David Robbens

I thought that name rang a bell… he used to sail with my Dad, and we went on lots of holidays with him and his family. Nice bloke 🙂

Dave

I’ve fitted an Alternative

An ancient aunt has underfloor heating the house is like a furnace. Nowhere really to escape the heat it is hot everywhere.

Most points covered above, UFH needs a separate circuit from the boiler and separate controls. It takes longer to heat up, but only needs the boiler output at a lower temp’ so can your current boiler cope (not too many boiler are modulated well). Having said that my extension (well insulated) has UFH off an older Ideal boiler (12 years old) and is OK, rest of house (stone built not well insulated or sealed, so next project) runs off rediators. So the UFH is on midnight to 7am, them raditors take over!

From other forum here are some points;

“…the more significant issue is the risk of overshoot. The heat stored in the thermal mass of a UFH system is very high and if it gets too hot (might only be ~25C) then it will continue pumping heat into the room long after it has been turned off. This runs the risk of it getting too hot, and someone wanting to open a window to cool down, leading to significant inefficiencies.(depending on level of insulation and controls)

If the slab could be accurately temperature controlled to around 20C or 21C with no risk of overshoot then it could work very well in my opinion. Response time would be slow, but that probably isn’t such an issue in a thermally massive PassivHaus 9i.e. insulated well). If this can be achieved then, apart from cost, UFH seems like an elegant solution and could allow the use of low temperature solar input.

…controlling the floor slab temperature is actually quite easy. Simply put the thermostat in the slab to control the valve (run it through a piece of UFH pipe so that it can be replaced if necessary. The thermal mass of the screed is enough to prevent the slab getting too hot and a normal UFH valve will cycle to keep the slab at the right temperature.”

We have a engineered oak floor, which does have a little movement through the seasons, make sure the floor finish is suitable and in contact with the floor to transmit the heat.
If you insulate the new extension well, the rest of the house will feel different!

NG has a good point, depending on the use of the rooms, if very well insulated and air tightness done well, heat recovery can work well, especially if you have space to build in the ductwork.

Read around passivhaus, but as always the more you learn the trickier it gets! Unlike my biking;)

Good luck

love mine. Nice gentle background heat. Have ours set at 16deg during the day and 18deg peak hours.
fitted it throughout 1,500sq ft ground floor.

6 zones, single room stat to control pump, drawing from middle of thermal store.

/hijack/

Are your solar panels contributing anything at present, Stoner? After several cloudy days water from our solar tank is down to 17°C with mains water at 12°C. 95kWh consumed so far this month and only 48kWh produced. Only 0.5 m3 of wood consumed so far this exceptionally mild heating season.

nah. Ive effectively turned them off as I really didnt want to run the risk of pumping hot water outside – remember I have 17m outdoor runs.

Instead Im burning logs in the furnace and its working nicely and costing me nothing ATM as it’s from pollarded willow from earlier in the year.

Floor overshoot should not be a problem in a well designed system and not something that I’ve encountered. It can be a problem if the pipe layout and heat loss is not done and just a random amount of pipe installed in the room in one of the patterns that the company recommend. Get it designed properly.

David Robbens was one of the early guys behind Wirsbo, set his own company up and recently sold to a German group so that he can sail his yacht more! His brother still works for them though.