Anyone got...

[Rose]

Underfloor Heating? 

We're interested to hear comments about cost of running and how good it is.  We're thinking of having it downstairs, along with a woodburning stove.  Also considering about upstairs too but it would be our only source of heating in the bedrooms.  We're also thinking of the 'dry' electric matting type.  I really like the idea in principle but have a few reservations... so just interested in what you've got and how you  find it...

thanks! [:D]

[Cat]

We've got it.  It's a wet system, powered by aerothermie (bit like geothermy, but uses a heat exchanger to extract the heat from the outside air).  It's very effective, and heats the house up a treat.  The running costs would depend on the heat source for your underfloor heating, and how well insulated your house is, but the heat distribution is very even (no hot or cold spots).  We've only been running ours for a few months, so no idea of running costs yet I'm afraid.  Another benefit is that, as there are no radiators, no wall space is lost.  Ours is zoned so that we can set different temperatures for different rooms/zones in the house.  We can run ours in reverse mode as well, so that it cools the floors in summer, but that's due to the heat exchanger for the aerothermie, and would depend on your heat source.

Even when the temperature dropped to -11 outside, as it the other morning, the house was lovely and toasty.  We do have a log fire as well, but so far have not needed to light it.   

There are a few cons though.  In a well insulated house, underfloor heating works a bit like a giant storage radiator, which is fine if it is consistently cold, but if you get a lot of sunshine during the day you easily end up overheating quite quickly. Also, it's a good idea to take photos of the layout of the network of underfloor pipes before the actual flooring goes on.  That way, if you ever need to drill into the floor (for plumbing or wiring for example) you'll have an idea where the pipes are, and won't puncture them.

 

[Rose]

Thanks Cat for the reply... on the whole it does all sound good.  I really like the idea of no visible radiators and also the temperature zoning.  I've been reading so much about  UFH on the web that I think I've overloaded myself so it's good to hear from others who have it.  We have very little height to play with and we think the dry system (the matting) is going to take less space, hence our choice.  I did suggest to OH that we dig up the existing concrete floor to give us more height and he looked at me as if I had gone mad... I still think it's an ok idea?  [:$]

How long does it take for your system to heat up - we've read it can take up to an hour - have you found this a problem?  Also, I've read that you shouldn't put the heating under kitchen cabinets and that makes sense but I've also read that it can cause other furniture that is placed on the UFH to sweat and can cause damage to said furniture... this seem bizarre - has anyone had any problems with their sofa or other furniture?  

As for costs - we've also read that the electric system is very expensive to run.  Our old house in the UK had a very inefficient oil central heating system that costs us around £2,500 each year in oil... anyone got any ideas how the UFH would compare?

What a good idea about the photo CAT! [:)]

 

[Cat]

I does take a while to warm up or cool down, it's definitely not instant.  It should be thought of as a relatively constant heat source in winter, rather than something you can flick on for instant heat (that's what you'd use the log burner for [:)] ).

Although we've had no problems with furniture, I have heard that the older systems were not as efficient, and so the water in the underfloor pipes ran at a much higher temperature.  This used to cause wooden joints in furniture to dry out and shrink, sometimes coming un-glued in the process.  The modern systems run at a fairly low heat, the floor is never more than luke-warm, as it only takes a raise in temperature of a few degrees, over such a large area, to raise the temperature to a comfortable level.

 

[Rose]

Thanks Cat - that reassures me.  I think we just need to go and price it all up.  We're renovating upstairs and down and have to instal a new heating system - I really think UFH is the floor me, I love the idea of invisible heating and I love the idea of warm tiles underfoot. [:D]  OH has taken a bit of convincing but he is now very keen... we just wanted to hear other opinions!  [:)]

[Catalpa]

We've got - and had working for about a year - wet underfloor heating. We have solar panels which heat our hot water tank when it's sunny and an oil-powered boiler for other times. We would not have considered electric u/f heating on the basis of cost.

U/f heating is superb. As Cat says, no hot spots - we run ours quite cool (water into the pipes is about 30 deg C and water out is about 22 deg C) with the rooms running at about 18 - 20 degrees. That isn't hot but it is a constant temperature throughout the rooms so there are no chilly areas making a room feel colder. Cost obviously depends on size of house and effectiveness of insulation.

We have shedloads of insulation and at the moment (we don't have -10C so far [8-|]) the only rooms in which the u/f heating is running is the bathrooms and part of the kitchen - with some gain in the areas where the pipes run to the bathrooms from the manifolds. We do have a wood-burning stove in the sitting room for evenings but that's as much because we like it as anything else. We could just run the underfloor heating.

There are enormous installation implications because of floors being dug up and the potential loss of room height. Allow a minimum of 10cm for:  insulation + pipes on top + a liquid screed (chappe liquide) to cover the pipes. These specialist screeds have an increased conductive qualities and an additive to enable minute expansion and contraction as the floor warms and cools - particularly necessary over large areas. If you tile afterwards (bearing in mind carpet isn't a sensible option as it prevents the heat rising out of the floor) then you may need a) a primer for the floor, depending on the screed type used, b) additive for the adhesive for the tiles - again, to allow the slight expansion / contraction of the joints and c) additive for or special grout.

We have probably done ours to a high spec, but we estimate with a,b,c above, we've added 10 euro per metre square to the overall cost, ie, on top of what it would have cost to use concrete + Bricodepot adhesive and grout. I've no idea whether we'd have got away with using standard Bricodepot products but we decided not to risk it.

[zeb]

Friends of ours have the aerothermic heat exchange pump to run their central heating system and heat the pool, but they've got rads not underfloor as the floors were already tiled and good. I seem to remember them saying that their electricity bills shot up last winter after having it all installed but will try to get a figure from them. It's a large house, and a large pool, but they also have solar panels + chauffe eau and an electric oven, so....mostly electric and no other bills (apart from the occasional gas cylinder for the hob and some wood).

I've stayed there a few times and whilst the house is comfortably warm, the heat exchanger thingy outside makes a tremendous noise when it's running. Is this normal Cat?

By the way, the whole system was expensive to install but they got some help (as they are fiscally resident in France) for the heating system to the house and the solar panels by way of tax credits and departmental grants.

[Rose]

Hello Catalpa and Cat... this is my third attempt at a reply as my laptop is on a go slow today!!!  I am so envious of you both and your lovely warm houses!!! me thinks we're in for a chilly winter with lots of dashing between rooms! [blink] [:)]

We are insulating as we speak and double glazing being done in January (that's the earliest we could get a date!) - not sure if this equates to your shedloads but we're not going to skimp.  The overall floor size isn't huge - over 2 floors it will be about 240m2.

Ceiling height is going to be our biggest problem downstairs.  The floor is concrete already and has been finished to a good standard and ready to go... OH says he will not dig it up so this really isn't an option for us (I know when I'm beaten!) [:$] He says we only have 10cm to play with for floor and ceiling to keep a sensible and reasonable ceiling height.  The ceiling needs a layer of insulation and plasterboard so the bulk of the 10cm can be used for the floor.  We think the electric matting system will take less height and will fit but I am sure others with greater experience can confirm or deny this. I really hope so as this is going to be the deal breaker for us...

Would it be fair to assume that the actual quality of heat/the heat acheived is the same regardless of the method?  or is one method better than another?

Like you we will also have a woodburner... there is just something about a fire that makes a room feel just right - I've always wanted one!

Finally - I was assuming that you run UFH like central heating - it's on timed for the morning (allowing enought time to raise the temperature) and then on again for the afternoon/evening.  Do you just leave yours on all the time?  

Sorry to be a bit dense, hope my questions aren't too obvious!  just trying to get it clear in my mind as I really want to convince OH that this is the right way to go... he's ok but wavering especially when I told him about the 10cm! [8-)]

very grateful for any information [:D]

[Catalpa]

I don't think it is your laptop, Specs... I always have horrendous problems posting on CompleteFrance whether I'm on a laptop on dialup or a desktop with 2mb haut debit. [:P]

Right. I can only talk about wet u/f as we didn't look at electric systems at all.

It needs to be on (where you want it to be working) all the time because

of the length of time it takes water at 30deg (say) to heat a mass of

floor to bring it to a temperature where it will maintain (say) 20deg

in a room. This - as Cat has said - isn't instant response heating.

If you want a room maintained at 20C, it will draw / drain heat out of

the floor to do that. Therefore the pipes need to be at a constant in

order to keep replenishing the heat used by the room. Otherwise there's

a time lag while the floor reaches temperature again. I'm not

explaining this technically but you can probably see what I mean. A

metal radiator works on the same principle but of course there's a few

millimetres of hot metal before you get the heat, not centimetres of

screed + tiles, etc.

BTW, the 30C I refer to is when the day is averagely cold in Normandy -

if it was Cat's -10C we'd probably be heating water to 40C for the

pipes to get a 20deg room temp. Our system does this automatically

basing the warmth of the water on some calculation with the temperature

sensor outside.

[Cat]

For our system, there is no timer.  It is designed to work to maintain an ideal temperature, so uses something very like a thermostat.  In well insulated houses, I believe it is more economical to keep the house at the desired temperature than to allow the house to cool and then heat like crazy to reach the desired temperature for a few hours per day.  Perhaps for electrically heated systems it might make more sense to heat during off-peak hours though.

 

[Eos]

We have wet u/f heating in the rooms that have concrete floors and tiling.

Although slow to heat up, which can be a bit of a disappointment if the weather changes quickly, and to cool down, which can be wasteful as windows may have to be opened particularly with frosty evenings and mornings but sunny days, it is great to have with small children or boys of any age who use the floor for Lego ect. Or even those of any age who love toasty toes!

We have a woodburner in one room that has u/f heating but the thermostat never lets it come on in there as the stove keeps everything cosy and also retains heat well even when empty.

[andyh4]

Quite a bit of experience with this system over 12 years in both Germany and France - both wet systems.  Would not change either, for all of the advantages already posted.  Costs - well as a low temperature system it is going to be one of the more economical systems around, but electricity and gas in France are expensive fuels.  Typical examples -15° outdoors the system input runs at just over 40°.  Up until the last week the temperature of the infeed has been running at just over 22° to give room temperatures of 20° - it's that efficient and is why some use solar/"geothermal" to provide the heat source.

Cat said it is like a giant storage heater - no it's not - it IS a giant storage heater - the concrete floor being the heat sink, and as has already been said there is a disadvantage when the outside temperature is very changable (autumn and spring particularly) where the system is slow to repsond and can take up to 2 days to fully settle down.  This is not really a system for a maison secondaire unless you want to install complex internet controllers.

BIL installed electric underfloor in his new conservatory.   One circuit broke down within a couple of weeks - just after the tiles had been laid..  He got his money back but replacing the circuit would cost a fortune.  It's the only example I know of with electrical so it may or may not be representative.

You can get furniture problems (and we did in Germany).  The dry air causes wood to shrink and its then that you find Norm Abraham was right about cross-grain glueing, and that the furniture manufacturer was wrong.   However I think this is more due to the very dry atmosphere in winter (low temperatures mean that the water in the air outdoors freezes out) coupled with a heating system that does not generate any moisture (the same would be true for rads or for electric heating of any type).  Simple solution - buy a humidifier, or dry your washing indoors - anything that will put humidity back into the air.  It's not really an UFH problem as far as I can see.

[LesFlamands]

Circulating water underfloor heating is very good if properly designed and installed.

Electric mats are not a good idea (IMO)

[Cat]

[quote user="zeb"]Friends of ours have the aerothermic heat exchange pump... I've stayed there a few times and whilst the house is comfortably warm, the heat exchanger thingy outside makes a tremendous noise when it's running. Is this normal Cat.[/quote]

It does make a noise, but I certainly wouldn't say it was temendous, although it does depend how you would define tremendous I suppose.  We stuck ours against the garage wall, so it has the garage and a storeroom between it and "the living quarters" (partly so we wouldn't hear it running, and partly because pretty it ain't).

 

[Jonzjob]

We bought our house 2 1/2 years ago. The under floor wet heating was installed when the house was built about 25 years ago. It runs off of LPG. A 1000 litre tank at the back of the house.

We toyed with the idea of Ground source heating, but horizontal was not possible because of the garden layout and the number of trees we have. Verticle, well 16,000€ was out of our bracket for the holes without the kit! Air/water was also ruled out because the colder the air gets the less efficient the heat pump gets, just when you need it most! So we are replacing the old gas boiler with a new condensing boiler. It will be much more effecient with the min of fuss to install. No noise either...

As in another post. We are also looking to back it up with an evacuated tube solar panel system, possibily some time next year. The water temp from the boiler on ours has normally sat at just over 30 C to give a room temp of about 20 C in the very cold. Our system doesn't have any room stats or fancy control at the moment. That will come with the new boiler. The temp control is the dial on the boiler and adjustable restrictors on the outley to the various rooms. We already have solar water heating and as the water tank is only a couple of foot from the boiler it will make it nice and easy!!

As a matter of interest we haven't put the heating on yet as we want to wait till the boiler's changed. Not really needed yet, our big open fire does the job for us.

 

[Rose]

Thank you all for your comments - it sounds as though those of you with UFH like it but still no-one out there with electric dry system.  If there is anyone, dont be shy, I'd love to hear your experiences.  We have been looking on other DIY forums and some have said the modern electric matting is better than it used to be... but it would be good to hear from someone who has it... if there is anyone out there?  The wet system I think is just not an option for us.  [:)]

[Owens88]

My limited understanding is that  wet UFH is the way to go on any new build or restoration - it delivers the heat where you want it and the low 'actual' water temperature allows for any of the newer energy sources to work well. So even if you started off feeding it electrically and then somebody invents a hamster wheel / kitchen waste converter / plasma screen re-director that will power radiators then you can just connect that in to the UFH.

 

BUT it is not designed for quick on/off heating. Wall radiants would be better for that.

Electric mat UFH ? I would happily use it in a bathroom or bedroom (which has quite clearly focused usage times) but not all over the house. the 'lock-in' to one energy source is too high.

 

Another comment. We recently put a system in our apartment in france (electric boiler feeding the existing wet rads). What was surprising was the sophistication of the programmer and the standard expectations. Both are different than in Britain.

*Standard expectations - run the system constantly just vary the target temperature according to time of day/ day of the week.

This includes running it overnight but drop the target down to 15 deg C or so. 

Subjectively I agree with that though I find it difficult to prove on pure physics ! 

*Sophistications - the thermostast includes many overrides (even a Monday strike day or 'throwing a sickie' - I kid you not !) and it even learns about heat up and cool down rates and chages its instructions to the bolier to meet your targets.

Overall I belive that to be more efficient as you then set targets for what you want for comfort and the system balances more smoothly than humans do.

Whereas in the UK  I bet 'most' thermostats don't even differentiate between days, and the most they do within the day is on/off.

 

 

[Rose]

Thanks for your comments John...  I like the sound of your programmer! [:)]

[Benjamin]

We have electric underfloor heating and I can endorse everyones' comments as to how well it works.

As far as costs are concerned EDF provide a service if you visit one of their offices whereby you tell them all of the electrical appliances you have, how many people will be living in the house and the sort of temperatures you want and they will give you a fairly accurate costing.

On a practical note we have a modern/well insulated bungalow of 110 sq mtrs with three bedrooms and all of the toys and our costs since moving in in 2005 have been 765€ for 2006 and 825€ for 2007. We don't have any costs for gas, oil or logs.

[Rose]

Benjamin - thanks you so much for that information... OH is an accountant so he really appreciates having the figures you quoted. We have read a great deal about how good the wet systems are but there is not so much about electric dry systems.  As only the dry is suitable for our situation it's great to hear that it seems to work as well!  We had read that the electric system was expensive to run so we have budgeted on costs being about the same as in the UK.  However, our last oil bill in the UK for central heating was over £2000 and we had electric and bottled gas on top of that!  So even if we double your costs our figures still look good. 

Really appreciate the feedback - and still interested to hear from anyone else too!  [:D]

Thank you!

[BIG MAC]

Hi Rose,

I note you are tight for headroom?

Have you considered battening the sides of the chamber joists and isulating placo between them for the trad look. Or insulation between and just a single layer of placoacross the faces to minimise intrusion?

Either way of installing UF heating you will need to consider heat loss going the other way down through the existing slab. Also damp being pulled through it by capiliary action (Heat atttracts dampness bit like water climbing paper if touched against it)  perhaps baseboard heating may be an option in your tight headroom areas.

[Framboise]

We had LPG gaz radiator heating /HW installed which we have found very good, once the boiler decided that it was going to behave itself as it did not appreciate being turned on and off  regularly as we came and went.

Because the house was a complete renovation job we were fitting concrete floors downstairs as the dirt floors were like the foothills of the Himalayas, thus all the CH pipes run underneath the tiles.   This actually makes almost underfloor heating throughout downstairs as the pipes track from the boiler, in fact the spot in front of the sink is Lovely when I am washing-up and my dogs are going to be firmly planted on the hotspot under the boiler itself.  Downside of CH is that we are plagued by damp still because the house was abandoned for 15 years, but its a small price to pay.