[Closed] Underfloor heating question

Are you insulating under the floor?

He'll have to insulate the floor to meet building regs, this and roof insulation take up a lot of headroom.
electric heating isnt ideal, have you considered storage heaters ?
Of course, if its a diy "conversion" and doesnt alter the appearance of the house, why tell the council ? IF an uninsulated floor dont have underfloor heaters, just a thick wool rug and room heaters. Lots of people use their garage however they want.

Yes, we'll be insulating the floor - we (our builders) have removed the old concrete slab, put a damp proof membrane and new slab in with plenty of room for insulation.

Haven't thought about storage heaters - I'm not overly keen on switching tariffs just for one room.

Edit - we've told the council. Got lots of other work going on in the house at the same time so seemed daft not to.

As TheBrick says are you insulating the floor? we have somewhere between 60 and 90mm? of kingspan under our floor in the now bedroom but was a garage. We have the front wall which has a window and one side wall is the partition between the now half sized garage. With loads of insulation as per the councils guidelines its a cosy room with electric underfloor heating which to be honest isn't on much and because of that I haven't really noticed a rise in our electric bill.

Are you going to use the rest of the house whilst using the office?
If its literally an office then why not just insulate it and have a single oil filled rad that will heat it up in when use? Even the modern underfloor stores a lot of heat ... and leaks it away when you aren't using it.

Yes, we'll be insulating the floor. Think we've got 100mm to play with.

Probably won't be using the rest of the house during the day - kids at school and wife at work . It will be a dedicated office/man cave/occasional spare room.

Electric rads will cost you less as you'll lose more into the floor UFH plus they're cheaper to install.

We put electric underfloor into our kitchen last year but that was mostly because walking on cold tiles in bare feet gets old very quickly - so the UFH is there to take the chill off.
My initial heat setting was 21c which was lovely but probably not required so I've dropped it down to 19c and will see how that goes.

There's quite a lot that goes into an UFH system (insulation - decoupling mats - heat mat --- self levelling compound, etc) all of which take up both height and budget!

That said a warm floor is very nice and arguably better than having a warm room but a cold floor.

With 100mm to play with the floor shouldn't be too cold anyway.
We have UFH in the kitchen but rarely use it and its set to 15C
I just insulated Jnr's (new) room and had 50mm with (between joists) of expanded the vapoour barrier ,chipboard and then 5mm seltec and engineered laminate. The laminate is the same as my room and the difference is pretty big.

Electric underfloor heating will be so expensive you won’t use it. Know a few people who’ve had it fitted and none of them use it.

Thinking about it if your garage is part of the house then the floor level will be lower than the rest of the home abs you can get low profile wet systems that won’t raise your floor level much. With your garage floor level being lower than the rest of the house then you can afford to raise there floor. Still won’t be as efficient as proper wet UFH as it is surface mount but will be a lot better than electric.

We have UFH in the tiled floor bathroom, had it on for a couple of months and it was an expensive way of getting warm feet in a cold room. Never use it now.

i have low profile surface mount wet system under the bathroom. on top of gypsum mats - due to being a floating concrete floor (4 ft off the solem )

Its running off a radiator valve and acts like a radiator when the heating is on. Works really well as because surface mounted with the thermostatic valve on setting 1 - it takes the chill off the floor really quickly.

In my home office - i just have a bottled gas ceramic heater on 1 bar in winter. even an oil filled rad tanks the leccy bill.

@wobbliscott - that's the bit I'm most concerned about. With regards to keeping the room warm, how much more expensive would the electric underfloor heating be when compared to electric radiators. From the sounds of it, prohibitively so, but exact figures are hard to come by

@justinbieber you asking for the impossible,
1: very few will have actually noted down what there electric use is, if they have a oil filled radiator, and then moved to under floor
2: Once underfloor heating has been installed, the insulation characteristic of the room will have changed, so any figure record previously will be useless.

We had underfloor put in our kitchen (10 years ago), after the dinning room and kitchen were combined, so no records could have been kept. We use it, though at a very low setting, and wouldn't be without it, on our tiled (& insulated) floor. So stevexc's comment "With 100mm to play with the floor shouldn’t be too cold anyway." has not been our experience, as come late autumn it's fricken freezing when it's not on. As for temp fluctuations.. you won't be using the under floor heating to deal with that, it take too long to respond to changing conditions (unless your willing to wait 2 hrs).

Yeah, I get that no-one on here is likely to have direct comparison figures, but I'm surprised that those numbers don't exist somewhere on the web. Seems like the sort of thing that either a radiator or UFH company would have to help sell their products - it costs X to heat room A with an electric rad vs it costs Y to heat room A via UFH kinda thing?

If it's an office, so you're going to be sat in more or less the same place most of the time, then an Infrared panel might be worth considering instead of a standard electric convection heater. We have an electric underfloor setup in the bathroom but it's only used to give a bit more comfort to cold tiles - there's not that much floor exposed and the W/m2 calculation showed it was never going to be an option to heat the room properly

@wobbliscott – that’s the bit I’m most concerned about. With regards to keeping the room warm, how much more expensive would the electric underfloor heating be when compared to electric radiators. From the sounds of it, prohibitively so, but exact figures are hard to come by

I think it is unless some new tech has come to the market in the last few years. My dad has it in his bathroom and he uses it but its only a small area, literally a few tiles so he's not stepping out of the shower onto a cold floor rather than heating the room - there is a towel rail rad in there too. So in that application probably not too expensive.

I know of a few other people who had it in their kitchens when they got their kitchens done, so a larger area and intended to be the primary source of heating too and after a few months of use they stopped using it other than for short periods just to take the chill off the floor.

But like I said, in your case with it being a garage you can probably raise the floor and incorporate more insulation and maybe get some thickness of proper screed and a low profile wet system. I have an integrated garage and the garage floor level is a good couple of brick courses below the rest of the house level.

So stevexc’s comment “With 100mm to play with the floor shouldn’t be too cold anyway.” has not been our experience, as come late autumn it’s fricken freezing when it’s not on.

You can't be lose much through 100mm of Kingspan?

I've got a wet UFH system downstairs - it's brilliant, i wish i installed it upstairs as well, but i ran out of steam (metaphorically speaking) to continue to do modern stuff in my new build.

Anyway,

Tiles, irrespective of how much insulation you have get damn cold. My system had 120mm PIR, which i can assure you is a lot, but stone is cold - it takes not alot of cool ambient air to make solid surfaces cold.

Conversely, i built a cabin, which had 100mm on the roof, my thumb in the air measuremnet tells me it does the equivelant job of heat retention (and keeping heat out in the summer) as my 120mm in the house (floor)..

Just to challenge your point around not being able to get a wet UFH into your garage/office - is it that far away?? It's really not that hard to tea of your boiler and run some well lagged pipes into you new bit, you could even keep the manifold where the boiler is if the run isn't too long. If it was me, i might be put off if it was 10M plus from house, anything less i'd say is easy (ish) done**. A boiler will always be way cheaper, even with a bit of heat loss from pipes + you wont be worried about wasting a shed load of money.

If you've got
1. relatively easy access to your central heating pipes
2. if you've got 150mm of height of your main slab - good to go (insulation, membrane, pipes, screed ~35mm i think)

i'd say your good to go.

**i was even contemplating burying a looped hot water supply + heating ~50meters to my cabin - the only reason i didn't is becasue i couldn't be bothered to dig up the garden..

I’m surprised that those numbers don’t exist somewhere on the web.

Just too many variables - room height, aspect, number of windows and doors, glazing type, wall construction, floor construction, amount of floor insulation, amount of wall insulation, etc.

You could consider a underfloor heating like a storage heater and run it off of an off peak tariff really pump the energy into it during the cheap time and have it on tick over during the day.

Surely the obvious STW answer is a small wood burner, with a boiler feeding a thermal store to supply the UFH?

Something like a hobbit stove, then you can even keep your single origin coffee percolator on the boil on top...

Or just fit a warm carpet on a decent underlay and some electric rads/convection heaters...

@keithb - I'm both surprised and disappointed it took that long for someone to suggest this 😀

I'm not concerned about having a cold floor, more looking into the underfloor heating as a means to heat the room evenly.

We put in electric underfloor heating in the conservatory of our old house and in the kitchen. We found it wasn’t powerful enough to actually heat the room but it took the chill off walking barefoot on the tiles. It was expensive to run as well. We now have wet underfloor heating with a geothermal pump in our new house and it works very well.

I have electric UFH in my bathroom (floor and a section of wall instead of a towel radiator). The floor heating is nice to take the chill off but when I was experimenting seeing how long it actually took to warm the room up to 22c (door closed to try and keep out the central heating when testing) it was hours, you basically had to leave it fully on constantly (but then there's only 15mm insulation under it as I couldn't raise the floor height much). I think it was costing £80-90 a month to keep it on approx. 8-10 hours (so it was warm in the morning).

It's generally switched off now apart from in the depths winter where I have it only for a couple of hours early morning to take to cold out of the floor tiles. The wall panel works great though, with a towel against the wall tile it heats to about 45c and pretty quickly so only needs to be on a couple of hours a day to coincide with post-shower time.

Hmm, this all has me pretty concerned as we've just had it installed in our bathroom, after discussions with the builder about how 'it'll only cost us a few more pence a month' and how it's an ideal substitute for rads in the room!!

It is a very small bathroom though and in fairness it seems to be working. I found it most effective if left at what the manual describes as 'eco' temperature throughout the day and boosted for mornings and evenings. I was told by the installer that that uses less power than letting the floor cool right down and then trying to reheat it morning and night. Whether that's true or not, we'll find out!