[cappuccino]

Can anybody advise me on this. I have seen a few houses that have this in the tiled areas (hallways, bathrooms) and wonder if a) is it expensive to run b) is it possible to control it i.e. turn it off in summer?

[M-Squared]

Hiya M! We must get together soon, I've missed our lunchtime meetups at cafes. :(

OK another friend of mine who lives out in the Wairarapa has a big old vineyard house with underfloor heating. It's extremely comfortable, however they do complain it's expensive to run. I don't know how easy it is to turn off (must be possible). I should point out that they have pretty high ceilings, about a couple of feet taller than ours.

[willsken]

I have a friend that has this in her kitchen. She tells me that it's really expensive to run. She also has a holiday home that has it. One month the holiday home wasn't even fully occupied and the electric bill came in at $600. She does think this is due to other heaters being used in the house and people not turning things off in the same way you would in your own home.... but still! She also said that the one they have in the bathroom floor has gone wrong and to fix it, it will need to have the floor ripped up.

I'm sure there are people out there with positives to say about it but she has put me off installing it when we build our house. :uhoh

[incredible hulse]

Have it in our hallway and bathrooms. Had it on for the first 2 weeks and then the electric bill arrived. Couldn't justify the 400 dollars when I could get a pair of slippers for 20 bucks

[buzztalks]

was in the bathrooms of our first rental. Not particularly effective (IMHO) as never in their long enough to feel the benefit. Extremely expensive to run when coupled with the unbelievable cost of electricity in NZ.

[benandclare]

Have to say it wont be installed in our new house :exit

[BigRod]

Well we have underfloor in our tiled kitchen and diner. These are electrical elements which are switchable and controllable.

To be honest we don't have them on much except the deepest darkest depths of winter, when we have them on low to take the chill off. If you turn them up then they become real money eaters!

Rod

[Caroline and Dave]

We decided against underfloor heating. For starters the cost of installation was a minimum of $15,000, then the heating bills would have been high. We are having a couple of heat pumps installed at less than half the price. We have a heat pump in the apartment we are in now and it is more than adequate and we only need it on a short time as due to good insulation the apartment stays warm for a long time. In the bathrooms we are having infra red lights/heaters. We found these to be very adequate when we first came over as they were in the house we rented.I know people say heat pumps are expensive but we do not find this to be the case. It depends how good your insulation is. Compared to underfloor heating, heat pumps are cheaper to run IMHO plus we have air conditioning in the summer.Another point to remember is it is very expensive to repair if it goes wrong

[mylesdw]

Can you not have the best of both worlds? An underfloor heating system of the wet type heated by heatpumps? If you are building it is hard to believe that putting the pipework in is a huge cost; you'd want good floor insulation anyway.

[Gar1]

We had a rental that had this. It extended from the tiled kitchen area into the carpeted lounge. Very warm, Very expensive.

Was controlled by a standard room stat, and was only on for the winter.

[canajanz]

Can you not have the best of both worlds? An underfloor heating system of the wet type heated by heatpumps? If you are building it is hard to believe that putting the pipework in is a huge cost; you'd want good floor insulation anyway.

You saved me the explanation
We have had electric underfloor heating in tiled areas of the house more than once now and truly could not justify the cost of running it.
However ... if you are running a woodburner with a wetback, or have some other means (including solar) of heating the fluid, then a wet system seems to work out fairly reasonable.

I gave up trying to find a plumber who wanted to take on the work (and its attendant guarantees) and I went for passive solar which worked so well that we had almost no use for our large and very efficient woodburner.

[aberdian]

Electric underfloor heating is a money drain and next to useless - at least ours is.

Our neighbours have a solar run water/glycol filled underfloor system and it's fab, the solar provides all the heat for the underfloor and the hot water (or about 75%) and they have a small wetback for the really cold days when the underfloor just needs a kickstart to get the place toasty in the mornings. He swears by it, whereas we just swear at ours.....

And it's cold down here in winter.....

[PeKaJoSa]

The biggest problem of direct underfloor electric heating is that it is "inefficient" at producing usable heat. There is a technical term "Coefficient of Performance" (COP) which gives you a value for a heating system to show how much energy you are using compared to how much energy you get out. (Yes, that is technically a simplification, but please bear with me...!). You can then use COP values to work out the relative efficiency of different heating systems.

Electric heating (such as underfloor, or an electric fire, etc.) typically has a maximum COP value of 1.0 - in other words you get a maximum of 1 KW of heat out for every 1 KW of electricity you put in. In practical terms (as BigRod said) it's really only useful for taking the chill from a cold tiled floor.

However a heat-pump 'moves' heat from the outside environment, and typically has COP value of 3.0 or thereabouts - in other words you put in 1KW of electricity and get around 3KW of heat out. If you can install an underfloor pipework system to run off a heat-pump then it is obviously vastly more cost effective than running direct electric underfloor heating systems.

This is a complex area, and I've made some sweeping generalisations here - but the bottom line remains the same: Compared to alternatives (including heat-pumps) choosing to heat a house using underfloor electric heating will be eye-wateringly expensive!!

Cheers,
Pete.

[KerryS]

I have just moved into a new house (well, new to me, the house isn't new), with underfloor heating upstairs, and a heat pump downstairs. The old occupants said it was cheap to run, as the underfloor heating ran off the heat pump. How does this work? I am a complete knownowt when it comes to things like this.

[PeKaJoSa]

KerryS -

Is there a large box outside, which looks like an air conditioning external unit? If so, you probably have an "air-to-water" heat pump system. It works by extracting heat from the air and "moving" it indoors, into the fluid in the pipes under your floors, making the whole upstairs floor into one giant "radiator". Think of that external unit as a sort of "central heating boiler".

The efficiency of the system generally depends on the temperature of the outside air, and if the one in your house is relatively modern then it can probably still work right the way down to an outside air temperature of minus 5 degrees Centigrade. However if you are in Auckland, I doubt you will be seeing too many days below minus 5 degrees.... ;)

It is worth mentioning that the efficiency of the system does reduce as the outside temperature drops. For example if the outside temperature is around 10 degrees Centigrade, your underfloor heating will be putting out around say 3KW per every 1KW of electricity used by the heatpump. If the outdoor air has dropped to zero degrees Centigrade then the pump has to "work harder" to pull the remaining heat into the house. In fact you might only be getting around 2KW for every 1KW of electricity used. To make matters worse, if the outside air is at zero degrees then the bigger difference between indoor and outdoor temperature will mean that heat will 'leak out' faster, just at the time when it's costing you more to get hold of it in the first place...

The moral of the story is to ensure your house is as well insulated as possible!

Cheers,
Pete.

[KerryS]

I've never noticed a box outside, but then I'm not particularly observant. I doubt it would get down to zero here, it hasn't in the last 6 years... I have no idea about the insulation levels, but one wall is glass, which I'm sure is going to make it quite chilly when winter comes round again next year.

[PeKaJoSa]

If there is no box outside, then there is a chance that it might be in the attic - have you looked up there?

However there is another alternative - you might have a 'Ground Source' heat pump (GSHP). That works by circulating a fluid - either salt water, or water plus antifreeze - through pipes which have been buried at least 1m down in the ground outside your house.

If you've got one of these, then you are VERY lucky - it's a MUCH more efficient bit of kit, and would have probably cost the previous owners over $20k for the heat pump alone - plus extra for installing the pipes in the ground.

But I'm very surprised that the previous owners didn't tell you where the heat pump is installed. Have you tried to contact them for more info?

Cheers!
Pete.

[nellyt]

We had electric underfloor in the tiled areas of our first rental. It never got switched on again after the first months electricity bill.

Heatpumps to drive hydronic underfloor : yes they exist. That is what we intend putting in our new house.

GSHP's seem to only just be turning up in NZ. They cost at least $10k more than a heatpump or diesel system. Everyone will say they can do it at present but ask carefully and you find that everyone knows how to do it, knows someone who knows someone thats done it, or is about to goto Europe for a training course. I don't believe there are any in the ChCh area doing more than heating the tap water.

[gil]

Agree with everyone else - we have it in our house and used it for a couple of months at first until we got the electricity bill :eek: Not used it since and had heat pump installed which is brilliant! (And MUCH cheaper :yes)
Gil