Does anyone have any practical experience of underfloor heating? I'm thinking of adding it to the bathroom. Plumber says it's nice but expensive to run. Cheers.
We have underfloor throughout our new house (new build)
In a properly insulated house with reasonable airtightness, it isn't expensive in my experience so far
There will be a lag time, compared to rads that takes a while to figure out
I've estimated we need the heating on 3 hours earlier than 'normal' -- that's with a 50mm liquid screed & oil boiler
I have it (living room, kitchen and bedrooms) but barely use it.
That's about the sum of it.Originally Posted by beechcustom
My house is early 1930s build and is genuinely atrocious from an energy efficiency point of view. Think its an E epc rating or worse! I need to get extra insulation in loft but the loft access is so small I'm not sure the material would fit through the opening!
My parents have had it in their last 2 houses and loved it. It’s always on low in the background and start up from cold is a long delay from turning it on. They just boost it for a couple of hours a day & it holds its warmth. Theirs is water based.
When we did the kitchen, and the bathrooms we went electric. During colder months it sits at about 15C from memory and we boost it that to 19C when we will be using the rooms. Makes a big difference, especially in the kitchen which was always a cold room given the size vs the radiator in there.
Would not hesitate to do it in bathrooms again, cold tiles are never pleasant.
If your putting it in a bathroom,you will only want an electric mat which will warm the tiles,but not really a replacement for a radiator.
Doesn’t cost a fortune to supply and fit ,so just use it when you want.
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Our house is of a similar age and we have both electric (bathrooms) and water (kitchen) UFH.
We leave them on all the time and, as they are thermostatically controlled, don’t cost that much to run.
If you’re heating through tiled floors, it’s generally more cost effective to just leave it switched on I’m my opinion.
It’s a very nice feeling to walk on warm floors and you do notice if, for any reason, it’s switched off.
Built my own house and put it in all rooms on the ground floor. Have radiators upstairs but much prefer the heat in the ground floor rooms. It is a much nicer warmth as well as not restricting wall space/furniture planning.
Our 3 storey house - built in 2000 - has underfloor heating downstairs and it’s excellent, and not expensive to run imho. Each room has a thermostat and it runs continuously apart from switching it off totally in the summer months (every plumber I’ve had in the house has said thats the best way to run it). Apparently once you’ve heated up the concrete slab under the house it uses less energy to keep it at a stable temperature than let it cool down completely then repeat the process. Part of the system failed last year and I was surprised how long it took to get the house warm again. Ours is a wet gas powered system, my Dad has an electric system in his flat that is ruinously expensive.
Had electric underfloor heating in a bathroom of a renter we took whilst our house was being built. From memory it was 2.7 kw. The landlord had left it on , so it was running in background .
We only had it on for about a week , once we did a re check on the leccy meter we had to lie down for a while. As others have said “ ruinously expensive “
We had the electric underfloor heating installed in all 3 of our bathrooms and used it daily before the spike in electricity costs. Very expensive to run, over 100w per sqm if I recall correctly.
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We have electric underfloor heating in 3 bathrooms and a large 10x4.5m kitchen/dining room.
After 1 year of paying for it, the bathrooms are all off and the big room gets it sparingly. I installed an air conditioner with a heat pump as it's far far cheaper to run.
Last edited by guinea; 20th November 2023 at 17:48.
What's the deal when it goes wrong? I always think it's a great idea until I think about having to have the floor ripped up to fix a problem.
Not sure about eleccy, but ones cast in concrete pretty much can't leak.
If installed right there's nothing really to go wrong. Mine flooded under a foot of water, but was still working fine.
Under wood it's easy to lift flooring, not so simple under tiles though...
We've just installed water UFH downstairs, and elec UFH to bathrooms upstairs in our 1930's houses.
Some observations:
-UFH works best with a tiled floor, and some tilers don't like laying tiles on a old house with timber joists, so you might find your bathroom floor levels needs a ply wood covering, then a decoupling membrane, then tiles. Ours added 30mm above original floorboards, so you may be left with a small step in to the bathroom.
-UFH isn't going to dry towels, and in an elec setting won't retain much heat, so you will most likely also want a towel rail.
-Elec UFH in a bathroom isn't going to warm the room a great deal, we use it to give a nice warm floor tile whilst using the room.
-You can get standalone thermostat. Ours was about £70 and can be controlled via your phone - we set ours to come on an hour before we wake up for 45 minutes. But that won't heat a house.
For interest / reference - our upstairs uses traditional rads. Downstairs / kitchen is a wet UFH under a large concrete slab. The downstairs is also far better insulated.
Also aside from the kitchen when I’m in it cooking, I really don’t like the underfloor heating in my parent’s lounge, end up with warm feet the whole time, which I don’t like.
They have in their kitchen a single large tile they didn’t put the heating into (builder cutting corners?) but when the heat is on proper warmth standing there is the only place I’m comfy!
I’ve got 120m2 of wet system downstairs.
It’s absolutely fantastic walking in on a cold day it’s blows radiators away.
However……..
It takes at least 90 mins to get up to temperature and you’ve got a trial and error situation the first few months of it being installed to get your temperature correct. You essentially have to turn it off before it gets too hot, and turn it on before it gets too cold.
Once it’s on and up to temp it will stay warm for literally 10+ hours.
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Very interesting.
can you elaborate:
What controller/system are you using to provide the graphs?
Is it possible that your boiler is throttled back on a low firing on the radiators, but full tilt on underfloor?
So boiler firing times might not be an absolute comparison.
Blackal I think its more to do with starting point temp and set point. Look its lower than upstairs. Also a set point of 18 results in nearly a 22 deg C output temp. A delta T of 4 degrees is unusual for a feedback loop controller. Since at 20 deg C the underfloor heating shouldnt have come on at all at 03:30 ?
Last edited by higham5; 20th November 2023 at 19:27.
Had electric underfloor heating in a large orangery/conservatory. National grid would phone and ask us to turn it down because they couldn't keep up.
Started out with nothing. Still have most of it left.
Orangery
Water-based Underfloor is arguably much more efficient, fo a few reasons.
One, you do not need to heat the water to such a high temperature, so the heating is more efficient. The lower temperature is also MUCH more efficient if you are heating using a heat pump (the lower the temperature, the higher your performance coefficient).
Also, the whole floor being the same warm temperature means that in the space, people act as conductors, setting up warm convection currents that take the warm air at floor level and convecting it up higher in the room. So overall, you heat the room to a lower temperature, while people feel warmer (they reckon this makes over half a degree difference.
You can put water-based underfloor into a radiator heating system, using what they call a conservatory kit, which uses slightly larger bore pipework. We did that when we dug out our basement to put a new kitchen in. It's lovely and toasty in there. But one (possibly 2) rooms is the limit for a retro fit to an existing radiator system.
But electric underfloor is a mugs game, it's only advantage is that it is cheaper to install.
The only way to make that cheap to run is if you fuelled it exclusively from your own solar-generated battery storage. Not much use in the winter (wear slippers instead), but could certainly keep the chill off bathroom tiles in the summer
The people are conductors and cause convection??
Is I’ve said ours seems very efficient and keeps the house warm. However, the kitchen - which is directly beneath our bedroom - is either a little bit too warm or my wife complains it’s too cold. It’s tiled and seems to make a big difference compared to the carpeted areas of the house - which we manage to keep adjusted correctly without the Goldilocks too hot/too cold nonsense. I’ve changed the thermostat etc, but I think it’s just much more efficient at transferring heat into the room. It’s certainly very nice to look across a frosty garden with toasty bare feet on the tiled floor for my morning coffee!
I put an electric system in the bathroom which was an awful idea. It cost a fortune to run, the bathroom window is always left slightly open to prevent damp so heat just escaped. When you think about how much time you spend in each room, the bathroom must be one of the least, and most of the time spent in there is probably in the shower.
When we re-did the bathroom I didn't bother refitting the heated floor. However we do have a wet UFH system in most of the ground floor when we built the extension and it's well worth it.
Have it in the kitchen and the main bathroom, both tiled floors. Use it in the kitchen as we forgot to put a radiator in there but never used bathroom except to check it worked.
Yes. Sounds odd, but
The warm air heated by the floor has little means of setting up convection, because the heat is all over the floor, and it all wants to rise, so none can.
People are warm in and of themselves, and so by being on the floor (standing or seated) the person effectively become a wick that allows the warm air at floor level to rise up around them, heating them as it goes.
By contrast, a wall radiator relies on convection, as they only heat (and to a high temp) in one place, and need the convection currents to distribute the heat, leaving most of it towards the ceiling, where the people (usually) aren't.
Combined effects can make UF heating 20-25% more efficient than a radiator system.
Google is your friend ;-)Orangery
Started out with nothing. Still have most of it left.
I know what one is, just find it amusing you call it that.
"Oooh, get him and his orangery"
I know you did.I know what one is, just find it amusing you call it that.
"Oooh, get him and his orangery"
It’s what the company who built it for us called it. They can tend to be a bit bigger than the average conservatory, which is why I said it as the underfloor heating area was pretty big and therefore expensive to use.
To be honest I always called it the conservatory anyway, but then I’m not posh.
Started out with nothing. Still have most of it left.
On our new build, the architect had a room labelled as 'orangery' on the plans (which it technically is) but I made him change it to sunroom prior to submission to planning :-)I know what one is, just find it amusing you call it that.
"Oooh, get him and his orangery"
I think that even in an empty inside room - the heat in the air isn't trapped at floor level. Add an external wall (without even a window) and significant convection will be propagated. Add in a window (even a triple-glazed one) and you get more than enough convection.
Really? Why?
Started out with nothing. Still have most of it left.
It sounded a bit 'grand' in my opinion, which I'm certainly not
It does get hot enough in summer to grow oranges in it though!
We force the downstairs UFH heating on for one hour a day. The floor takes about 2 - 3 hours to get warm from the heating being turned on. If we ran the heating until the room got warm, the room would then it would continue to get hotter and hotter over the next 6 - 10 hours and be uncomfortable. As you can see, the room never gets near 18c, so 18c essentially means the heating is off, and 22c gives it a 1 hour boost.
As people have said, a wet UFH system set in concrete can take a long time to get warm and be hard to control - but once hot acts like a huge storage heater, even once the heating is off.
Regular combi boiler does the whole house, with a single output to a manifold that diverts hot water to rads and / or UFH. Controller to the manifold is a Heatmiser wiring centre.
Thermostats, associated controllers and web app are from Heatmiser.
The main differences are:
-downstairs floor radiates warmth all day even if the heating is on for only 1 hour a day
-downstairs has very good insulation
-rads upstairs aren't as efficient at holding heat over long periods of time
-upstairs insulation isn't so good
I agree it’s baloney. That a human is a conductor is a red-herring, a chair they might be sitting on will equally help to encourage convection by encouraging air to flow around it.
Don’t believe that it’s cheaper to have underfloor heating on permanently either. Is rather like the claim that it’s best to keep immersion on permanently.
Anyone here have a pinery?I know what one is, just find it amusing you call it that.
"Oooh, get him and his orangery"
I'm going to guess that it is related from an underfloor installation 'engineer'.
If I was to consider underfloor heating on ground floor (not so important on upper floor) - I would have several inches of insulation between the hoses and ground below. The notion that the big slab of concrete acts like a heat-bank is only valid if it is entirely insulated in every direction other than upwards into the floor.
And of course - there is no heating system that is more economical to leave on all the time, be that immersion heater or CH system.............
Estate Agent speak:I know what one is, just find it amusing you call it that.
"Oooh, get him and his orangery"
- Orangery - Conservatory
- Study - Office or just a space with a desk
- Cloakroom - Downstairs Lavvy.
That seems pretty good on the underfloor, which appears to be not losing much to exterior (foundations). I still think that the boiler might be full load on the short time that the boiler is firing, and perhaps not so with the radiators. All that means (if correct) is that there is not a direct correlation between the two system firing times.
Yep, meant to insulate first
Exactly. Fine if you live in a stately home, otherwise it’s a conservatory
Perhaps in my original post I would have been better showing a picture, to try to convey the area being heated by underfloor heating, rather than words. I agree with the estate agent drivel though, I've been caught out a few times by their waxing lyrical about houses.Estate Agent speak:
- Orangery - Conservatory
- Study - Office or just a space with a desk
- Cloakroom - Downstairs Lavvy.
Thankfully it is now someone else's responsibility to keep warm, although the better half has bought a swim spa (or 'big hot tub' as some might prefer) to continue our funding of the electricity industry.
Started out with nothing. Still have most of it left.
I have a electrical heating in bathroom. Thermostat is set to 1h in morning and 2h in evening. As it is semi-smart, heating starts bit before set time and switches off when desired temperature is reached. Overall it adds around 20-30kwh per month, but warm tiled floor is very convenient.
May I ask what that equates to per month? Quick Google suggests £8ish?
I've got something similar.
Only on in the morning and in the evening for approx the same times length as mentioned.
Would say it's worth it for those times Vs the small cost
I also thought the notion of keeping the underfloor on permanently was crazy, however 8 years into living with it our heating bills are lower than for our neighbours without UFH and with less bedrooms. It’s not actually on permanently - it clicks on and off when the room thermostats call for it. Moving from a 1930’s 3 bedroom mid terrace to a 2000 built 6 bedroom detached house has been an eye opener - our energy usage is only about 20% more than the old house!
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