View Full Version : Underfloor Heating

24th Jan 2015, 21:39
I have a tiled kitchen with underfloor heating cables, and a poured patio with embedded heating cables, both of which work well, but were ungodly expensive.

I am re-doing a bunch of the basement (which is poorly heated) and ran across a product which supposedly can be used under carpet and engineered wood floors. Basically, it comprises a flexible plastic film with embedded printed carbon resistance heat elements.

The stuff seems to have been around for a while, and is an order of magnitude cheaper than cable, plus, it is approved for under-carpet installation over here, at least.

Does anyone have any experience with this stuff, or is it a bad idea?

west lakes
24th Jan 2015, 21:49
On another forum a lot of caravanners have retrofitted it and seem quite happy with it.

24th Jan 2015, 22:05
I don't have personal experience with it myself, but a good friend had this heating in the house he had when on secondment, where he had a couple of problems.

He had a small fire when the furniture he put on the carpet created too much of a heat build up and in the next room he managed to put a couple of nails or screws into the circuit (not knowing the exact location of the elements) when fixing a baseplate to the floor, which put his power off on a couple of occasions when the Ground Fault saved him & family from close contact with ac power... He learnt from these mistakes.

Overall & despite these issues, he liked it, but felt that it wasn't something he'd use back here in the UK due to the relative cost of electricity for heating. He felt it was halfway between convective heating from wallboards or radiators and poured slab/embedded cables or pipes, but wasn't as immediately responsive as the convective systems.

24th Jan 2015, 22:19
I would consider using some underfloor insulation (if you have the headroom) and going with convention heating. It's a lot more flexible and cheaper to fix problems with.
How often you use the basement is another consideration. Underfloor systems are best for steady constant heating.
This is what I've done in my own house, but I designed it myself so I included the headroom for it. 1 1/2 to 2 inches should be sufficient.

24th Jan 2015, 23:38
Older, very big house with three separate gas furnaces, entire basement is finished (before I bought it) and absolutely no basement floor level air outlets.

It's icy down there even with all three cranked up, and, unfortunately, there's not really any way to repurpose the ducting to a zoned system.

25th Jan 2015, 09:05
Temperature outside this morning 5c/38f, wind gusting over 100mph/45mps, humidity under 20%. Shutters lowered overnight, internal blinds down, central heating on, stove lit. House very cold, wife complains.

I would like to have underfloor heating as I believe it puts the heat where needed, but solid floors render it impossible.

(Two freighters moored up in the Bay below me. Forecast: wind continuing until Thursday.)

25th Jan 2015, 11:25
I have underfloor heating in the shower rooms and bathrooms. They are cable under tiles and it seems to work all right, it's nice to come out of the shower to a warm floor. I have a long hall and that has heater mat under a laminate floor. That runs most of the day and tends to keep the centre of the house comfortable so that one does not notice the main central heating is off even during a cold spell.

Not cheap to run though; expect a penalty of about 5/room/month. Despite that I would, as a matter of choice, like to have the whole house converted to underfloor. However, not only the cost is a problem but also beefing up the domestic electricity supply to cope.

Underfloor heating using heating pipes with electrical contol valves is expensive to put in but is cheaper in the cost of energy.

25th Jan 2015, 11:41
Underfloor downstairs, convector radiators upstairs, (water in the pipes) all running off a heat pump with a lot of underground pipes outside. Snuggly cosy and uses a lot less leccy than direct heating of any kind. Best run at a constant temperature, but it is zoned so we can heat different rooms as required. And a big wood burner for the pleasure and in case the leccy gets cut off. Lots of insulation, all done in a major renovation.

25th Jan 2015, 11:45
Solid floors - no problem.
If you are prepared to put up with the (relatively) minor inconvenience of raising your floor levels by one inch, then you're in.

Some years back, I was involved in trying to market the (well developed) concept of 'ceiling heat'.
It's based on the principle of 'radiated' heat.

Lots of advantages, including no dangerous 'hot spots' and much cheaper installation.
It involves attaching foil, then the heating element wiring to one's existing ceiling and then plastering over that.
Above-ceiling insulation is, of course, recommended if you don't already have it.

The principle is that the radiant heat warms the objects in the room.
Subsequent re-radiation and convection warms the room to a thermostatically-controlled temp.

The big problem trying to sell it, though, was that everybody 'KNOWS' that HEAT RISES, don't they?
RADIANT heat travels in any given direction. Only relatively warm fluids, including AIR, rise - you dumb sh1ts!

Anyway, I tried.

25th Jan 2015, 12:16
I've built one, and renovated two houses. I've put Wirsbo/Uponor (https://www.uponor.co.uk/information-sites/underfloor-heating.aspx) warm water underfloor heating in all three. Works a treat, not that much more cost to install than conventional radiators, and cheap to run. Needs 100mm polystyrene insulation under solid floors and 100mm rockwool insulation in wooden joisted floors.

25th Jan 2015, 13:17
Probably to do with the design/specs/installation/paints or whatever of your particular set-up.
As you would well know yourself, you gotta get things right - otherwise, they can bite you.

Four people of my acquaintance who had our design installed in the early 70s report no problems, nil maintenance and low power consumption.

I might have installed it myself except I don't need that kind of thing where I live.
On a cold (10deg C) night, I might pull out the two-bar radiator.

25th Jan 2015, 13:40
Just to cheer everybody up since my last post at 11.25 my central heating boiler has gone tits up. The pump runs but no lights or control and no heat or hot water. The fixers won't be told untill Monday and then God knows how long.

Should it be a new boiler the insurance company will carry me for 950 but it could well cost me another grand. It would be a good time to consider changing over to reliable elevtrics but it's the wrong time of the year.

I have just turned up the hall floor temperature so that it can step into the breach.

25th Jan 2015, 14:03
421 - It really depends on the cost of your electricity. Underfloor as described is great, provided you can afford to power it.

Our electricity is very expensive and the Canton is subsidizing home owners to move away from electric heating.

So we are moving to a geo-thermal / heat pump operation. Should reduce our electricity bills by CHF5,000 or more a year. Problem is it will take 15 years to cover the cost.

(Don't ask what CHF5000 is worth in your currency, since the devaluation of the euro/dollar/pounds/etc. etc. it is going to be a lot)

25th Jan 2015, 14:48
Not very helpful for retrofit, but to give you an idea. I've designed/built my own house. The first trick is insulation. I have conventional 2x6 walls (easy and cheap to construct) with fiberglass batts(carefully fitted by me, not some trainee on piecework) with 1" of foam outside that. 3" of foam under the basement slab, 10" batts in the attic. Next is insolation. House faces exactly south, 21% of south wall is windows, 3% of north wall is windows. Lastly, heating: because the sun is intermittent, constant underfloor heating is not as efficient as fast response electric convectors & sunshine. These are on a wireless programmable zonal system with a thermostat on each convector (very cheap these days). Optimum thermal efficiency would be with underfloor in the basement and electric above, but this isn't economic for my medium (2000 square foot) house. Energy bill last year: 8568kWh = C$1620. Last winter was the coldest/longest for 40 years, this winter started milder than usual, so average bill would be $1500.
And if a convector breaks, I buy another one for C$130 and change it myself in 5 minutes.
One does need a generator/panel in case of power outage with an all electric system, but this is cheap if done during initial build.
With the insulation and well positioned windows, I've found AC in summer is not needed.

As a child I lived in a house with ceiling heat. It was so ghastly we got radiators fitted. In fact this probably triggered my lifelong interest in domestic heating!

25th Jan 2015, 15:05

I would like to have underfloor heating as I believe it puts the heat where needed, but solid floors render it impossible.

Not if you can sacrifice 22mm of headroom...

google Nu-Heat, retrofit. It's a wet system, which will always be cheaper than leccy.


25th Jan 2015, 15:22
My wood house has a heat pump system with water piped underfloor heating.

It seems to cope with outside temperatures, on occasions, down to -37c but often below -20c from middle Dec to early March (not this year, so far).

The house is well insulated and has an air moving system which has a heat exchanger which extracts heat to reheat the incoming outside air.

The only disadvantage is when there is a sudden change in temperature and the house can be a bit warm or cold as it is fairly slow to react.

The downstairs floors are solid and act a bit like storage radiators.

A bit of forward planning (looking at the met forecast) is needed, which took me 2-3 years to work out.

I would recommend underfloor heating.

We also have a wood burner but I have an attached forest so wood is free - just lots of effort - don't need to go to the gym!!!!

25th Jan 2015, 15:23
CharlieGolf - doesn't Nu-heat use electricity as its heat source?

Electric radiant heat allows homeowners to lower their central heating system while still being comfortable.

That only works where Electricity is cheap. Not in Europe then, ...

25th Jan 2015, 15:24
google Nu-Heat, retrofit.

A bit advanced for Spain. They've only just come to terms with the woodstove (and we buy them from France, come to think of it).

25th Jan 2015, 15:37
I can't find the sketch I did originally, so I'll have to describe the heating system I invented.

1) In some south-facing area you build a small greenhouse/glasshouse.
2) This is connected to your house by two perspex tubes, each about a foot in diameter, one situated at each end. Fill the greenhouse with sofas and comfortable chairs.
3) At the point where one tube enters the greenhouse you fit a one-way cat flap; at the point where the other tube enters the house you fit another one-way cat flap.
4) All you need now is the medium for transporting the heat, which is *cats* and the fuel to run the system which is *cat food* (preferably a good brand such as KittyKat.)
5) Put half-a-dozen cats in the greenhouse, where they will luxuriate in the warmth. When they get too hot they will seek a place to cool down and find their way through one tube into the living room, where they will radiate heat. Meanwhile the other half-a-dozen cats you've placed in the living room will get chilly and find their way through the other tube into the greenhouse. And so on ad inf or until the sun goes down or until you forget to feed 'em.

The system can be fine-tuned by - in the winter - adding more cats, and in the summer, when less cats are needed, you can cull the herd and serve the surplus cats for Sunday lunch.

25th Jan 2015, 16:45
Finncapt - excellent system!
If I lived at your latitude I'd do that too. We get significant winter sunshine here so mine works better here.

OFSO - looking at the numbers, it may pay you to open a Chinese restaurant - open summer only. ;)

25th Jan 2015, 19:01
Except you pump it very slowly so summer heat arrives in winter and winter coolth arrives in summer.

The Romans did this with their thick tile roofs. Took ages to heat up and ages to cool down.

But cats are nicer to stroke !

was gingernut
25th Jan 2015, 19:42
Dearest thing round here is water, the pubs have to beer their water down.... :-)

25th Jan 2015, 20:59
I appreciate all of the input, the specific sort of thing I am considering is this:
Underfloor Heating Carbon Film for wood and Laminate floors (http://www.floorheatingsystems.co.uk/underfloor-heating/laminate-underfloor-heating.htm)

and that was what I was looking for experiences with. It installs over a thin insulated underlayment (3-5 mm) and has a vapor barrier plastic over the top. Doesn't change the floor height significantly (like I said, my kitchen floor tile is cable heated, so I know how that works)

Thanks again,


25th Jan 2015, 21:50
I did look at this for mine. My rough calculations showed I would be losing too much energy downwards with the thin insulation above a concrete floor. I note their website does not appear include overall running cost comparisons, and I'd be surprised they omitted this if it makes them look good. I would suggest you investigate this further.

It would work fine above higher level wooden floors (as it does in your kitchen) but with my house's design I need faster response.

26th Jan 2015, 04:55
If I were to build a new house from scratch (or do a major remodel), it would most definitely use hot water floor heat (either boiler or heat pump). I've stayed at several places that had floor heat and I loved it.
I did a pretty major remodel a couple years ago - at what was formerly my family's house (after my mom passed I bought out my sisters shares). My current employment at Boeing means it's not practical for me to live there but I plan to retire there. It cost a pretty penny, but I had the radiators removed from the bathrooms and converted them to floor heat (it was part of getting rid of the 40 year old linoleum floors and doing proper tile floors in the bathrooms). I think ceramic tile is the only proper flooring for a bathroom, but over an unheated crawlspace they can be rather unpleasant on a cold winters night :eek:
The house is currently rented (to one of the guys that helped out with the renovation :ok:), but he thinks the floor heat is great!
If/when the current furnace craps out, I plan to look into a heat pump. But the relatively high cost of electric and relatively low cost of natural gas in the area still suggest natural gas as being more cost effective.

26th Jan 2015, 05:27
Heated ceilings received grants in Canada for several years and then the recipients received compensation in large quantities because it was either dangerous or inefficient. Wouldn't be my choice.

While most people, even around here, think oil or gas is hugely cheaper than electricity we did a comparison calculation for son's house about four years ago and there was very little in it at all as his oil furnace operated at about 60% efficiency.

We have put electric cable under several kitchen and bathroom floors and it is very comfortable but we use it as a supplement to central heating or baseboard convection.

We have several houses around here with either stone or wood floors with electric cable under all. They do take time when you turn them on. Currently in this house we have regular electric baseboard, it's not fashionable but I do like it, however we have older design heaters which I prefer. Some of the latest ones have top vents and heat the wall above the heater rather than the room more directly.

Ancient Mariner
26th Jan 2015, 06:58
We've had houses with electrical ceiling and underfloor heating. Prefer the former, although the latter is friendlier on your bare feet.
Where we had ceiling heating we had floor heating in the bath rooms and other areas with tiled floors. To me the ultimate solution.
Do not understand waterborne floor heating, not efficient, too slow to respond to temperature change and possible leaks.
We had electrical underfloor heating at our cottage, when we left we pushed a button to reduce the temperature to a set level around 8 degrees C, the day before we arrived we called the cabin and and re-set the temperature to "comfort level", normally around 23 degrees C.
The only thing you have to consider with electrical underfloor heating and wooden floors, is to set the secondary thermostat to a level low enough that the wood will not shrink or crack.
Took me some time to adjust all the thermostat settings to the right levels.
Had to set:
"Slumber" temp
"Comfort" temp
Max. floor temp
And then needed to calibrate numbers on steam dials to real temperature.
More modern digital thermostats will be easier.

26th Jan 2015, 13:27

CharlieGolf - doesn't Nu-heat use electricity as its heat source?

Yes, but this one is wet system. They do both. As do several others.

26th Jan 2015, 15:14
I had a gas hydronic system in a hangar in Missouri which was phenomenal and cheap to run. (about $150/month in winter to keep hangar at 60 degrees F)

Basically it involved a commercial instant water heater, a re-purposed hot water tank, a big aquarium pump, and about $200 worth of PEX.

it was cheap to run, (as long as you were committed to keeping it on), and had a remarkably fast recovery time due to the fact that the slab stayed warm.

The only downside related to the fact that I had to sub-slab insulate and think about it before I built the building.

26th Jan 2015, 18:50
If you're concerned with the cold and the cost of heating a home to overcome the cold, maybe you should consider moving.

Here in the USofA, South Texas and Florida have very mild winters, along with no income taxes and an overall low cost of living.

26th Jan 2015, 19:02
Build the house with a hypocaust and get the slaves shovelling - or these days, a wood burning stove and an electric fan. Just updating a 2000+ year old idea......

cockney steve
26th Jan 2015, 20:08
About 30 years ago, my mother and step-father built a house in Norfolk.....There was a 2" polystyrene sub-floor in the slab, full cavity and roof insulation and a fuel-bunker filled from outside but accessed from the attached garage. It was warm, energy -efficient and years ahead of it's time.

26th Jan 2015, 21:03
If you're concerned with the cold and the cost of heating a home to overcome the cold, maybe you should consider moving.

Here in the USofA, South Texas and Florida have very mild winters, along with no income taxes and an overall low cost of living.

Was happy and entertained when I lived in Galveston, but the missus demanded temperate climes,

Just trying to make the best of it.

26th Jan 2015, 21:05
If you're concerned with the cold and the cost of heating a home to overcome the cold, maybe you should consider moving.

Here in the USofA, South Texas and Florida have very mild winters, along with no income taxes and an overall low cost of living. Was happy and entertained when I lived in Galveston, but the missus demanded temperate climes,

Just trying to make the best of it.

Loose rivets
27th Jan 2015, 01:27
KenV You're fairly new about these parts, did you see how the family's house just up the road from you at Canyon Lake was heated?

4000 sq feet of iron, glass and steel 1200' AMSL on its own mini-mountian. You'd think it'd be difficult to get up to temperature, wouldn't you? :hmm: