Electric underfloor heating in a new build

[Franco50]

I am at the planning stage of a self build project of a timberframe bungalow (approx 90 sq m area). The building plot is in a rural location, so either electric, oil or LPG are the choices and I am wondering how efficient and economical electric underfloor heating is. My current house has an oil fired combi boiler supplying conventional radiators and for water heating but I was considering the all electric option for the new house but have no experience of it with regard to heating. I know a couple of people who have installed U/F heating in their conservatories but don't kow anyone who has done a whole house with this system. The timberframe kit, which will be pretty well insulated and have underfloor insulation, comes with T&G chipboard flooring sitting on floor joists - would this be suitable? How cost effective is it? Any comments welcome.

 

[frankkeddie]

I have a friend who has installed an electric underfloor heating system in his house. He installed the system in his kitchen, bathroom and conservatory. He used a company called REHAU who I believe have an office in Bellshill. He found them to be very helpful and willing to discuss the project with him. As far as I am aware the running costs he was quoted were very favorable as was the price of the system itself. I am also pretty sure that the system installed in the kitchen and bathroom was on timber joists. My friend would certainly recommend this system on his own personal experience.

 

[RF Lighting]

If you are still in the planning stages then I would advise you look at fitting wet underfloor heating as this is more efficient, and less likely to go wrong than electric UF heating

 

[Adam_151]

Direct heating with electricity is a pretty lousy way of heating anything and you are not helping the environment one bit (unless I suppose you were only using up spare grid capacity at times of low load - E7 type of thing* because the electricity would probaby just be dumped into ballast resisters anyway if supply outstrips demand, but thats beside the point...)

If you want to use electrity for heating, then you get much more mileage by using it to run heat pumps than using it directly (and even then, its not massivly different in terms of whole system efficency than just burning fossil fuels in a boiler yourself)

*Google for a idea called "dynamic demand" and their grid frequncy sensing idea, very similar to the idea behind E7 (smooth grid demands out) but based on continous measuring rather than rough guesswork, things like this might become pretty important if we get those new nuclear stations we need...

 

[baldelectrician]

Personally I would go for wet underfloor heating powered by oil, LPG, or electric (you get electric wet boilers), and some of them use a tariff called Economy 10.

If you have a wet system it gives you the option of changing the boiler to a different type at a later date.

PS as you are in Scotland check out this link regarding electrical work in building warrant work (new builds included)
http://www.sbsa.gov.uk/pdfs/Electrical Guidance for Verifiers 29Mar06.pdf

hope this helps

 

[Franco50]

Thanks for all the comments. I wasn't aware of electric powered heat pumps and boilers so at least I can now consider these and find out more about them with regards to a wet system. If I decided against UF heating can these heat pumps/boilers also be used with a more conventional radiator system? At the end of the day it may all come down to installation costs because the plot is in a rural location and I'm getting some scary quotes from utilities providers about supply to the site (eg £4500 for electricity as a new cable has to be run from the local transformer to the site). My budget may take such a hammering that I may have to stick with a more conventional boiler (oil probably) and radiators. My main reason for thinking about electricity was no tank to have to worry about topping up.

 

[Leila]

Heat Pumps on their own can only heat to quite a low temp, 40-50 degrees, this is why they are so compatible with UFH as it runs at a low temp anyway. Due to this it would be touch and go whether heat pumps would be enough to run radiators as they tend to require higher temps. If you went for UFH and a conventional boiler the water would have to be blended down from 80 - 40/50 anyway so you can see why heat pumps are becoming so popular.

In a new build I would say UFH everytime, it is by far the most economical,environmentally friendly and comfortable. For info on Heat pumps call a company called Ice Energy in Stirling, speak to Bob, 0845 600 1020 they are very experienced and based in Scotland.

 

[Steve]

For info on Heat pumps call a company called Ice Energy in Stirling, speak to Bob, 0845 600 1020 they are very experienced and based in Scotland.

i've said it before, and i'll say it again, ground source heat pumps are the future. Ice also have a website. search google. Although heat pumps dont heat as hot, the energy they put into the house is "free" from the ground and they can be up to 500% efficient. Say it has a 2kw compressor, it will put out 8-10kw of heat into the house at full throttle. Ice have a fully integrated system, which allows the use of wall-mounted room air conditioners on the same system in summer.

The air conditioners create a "thermal store" in the soil outside the house, which the system uses in the winter to heat the house.

As you're getting a new electricity supply, ask about 3-phase. This will enable you to use 3-phase heat pumps, which run better and more efficiently than single phase pumps. I dont think it should cost much more than single phase. Worth an enquiry IMO.

 

[Pensdown]

Ground source heat pumps are not just the future, there are the only ones that still work with an outside temp below about 2deg.

 

[Franco50]

Thanks everybody for the info about ground source heat pumps. I have emailed Ice Energy to ask more about their systems. Of course the problem with highly efficient heating systems is the initial cost and installation of all the kit - any ideas what sort of cost this would run to for a medium sized bungalow (90-95 sq metres)?

 

[Steve]

Dont budget any less than £5000. You will re-gain this within a few years though. The major cost is the main plant unit, and installing the ground source loop. Outdoor evaporators are available - this negates the need for ground loops, but they are less efficient, and as pensdown states, at lower temperatures they suffer.

Pensdown, a conventional heat pump will work at any temperature - down to 0'K - minus 276 degrees centigrade. At any temperature down to this, there is energy to extract from the air, and a heat pump will work. The issue, however, is condensation on the outdoor coil causing ice build up and frequent defrosting cycles. And of course, the lower the temperature outside, the less efficient the system becomes. Our cheapo heat pump did an adequate job of heating the conservatory when snow was falling last year. It was plenty hot enough.

 

[plugwash]

Dont budget any less than £5000. You will re-gain this within a few years though. The major cost is the main plant unit, and installing the ground source loop. Outdoor evaporators are available - this negates the need for ground loops, but they are less efficient, and as pensdown states, at lower temperatures they suffer.

yes, afaict britan is generally warm enough for it not to be a huge issue most of the year though. Lots of commercial buildings seem to use them as i belive they don't work out that expensive once you wan't air conditioning in the summer as well (many heat pumps can work both ways!).

Pensdown, a conventional heat pump will work at any temperature - down to 0'K - minus 276 degrees centigrade. At any temperature down to this, there is energy to extract from the air, and a heat pump will work

maybe true but as the outside temp goes down even in an ideal heat pump so does the efficiancy (there has to be an upper limit on the efficiancy of heat pumps otherwise we could use them to create a perpetual motion machine)

The issue, however, is condensation on the outdoor coil causing ice build up and frequent defrosting cycles. And of course, the lower the temperature outside

which further reduces the efficiancy (possiblly making it worse than a resistive heater) and if it goes cold enough the refridgeration fluid itself will freeze.

Our cheapo heat pump did an adequate job of heating the conservatory when snow was falling last year. It was plenty hot enough.

but was it actually saving you anything significant over resistive heating? hard to tell.

 

[Steve]

Our cheapo heat pump did an adequate job of heating the conservatory when snow was falling last year. It was plenty hot enough.

but was it actually saving you anything significant over resistive heating? hard to tell.

The way i look at it is that it would take a 2kw resistive heater to heat that conservatory adequately - running constantly (proved before we had the heat pump fitted). The heat pump consumes just over 1kw, and cycles on and off (not just to defrost - it did normal thermostatic cycles too). So it is saving us money.

It is an excellent dehumidifier - we had it on cold in the muggy thundery days during august, and the whole downstairs of the house was dry and comfortable! Obviously it cant cool the whole house, but it sure did a good job of dehumidifying!

 

[diybot]

crafty -how much did it cost to altogether to do your conservatory?

 

[Steve]

crafty -how much did it cost to altogether to do your conservatory?

how do you mean?

The air con/heat pump cost £340 in july 05 (it was in the sale on the B&Q website).

But a professional single room system will be around £1000-2000 - get it done in winter, it will be cheaper The pro system will come with a maintenance contract too, and it will be of better quality - probably a good brand like mitsubishi or toshiba.