ELECTRIC UNDERFLOOR HEATING - RIBBON OR CABLE?

northseagirl · 20 Nov 2008

I have been looking into the various types of electric underfloor heating and wondered whether ribbon or cable electric underfloor heating is considered the best system?

Also - can it be used successfully as a full heating system or is it best to
have a few radiators in the living areas?

My plumber says that if you use say 150w or 200w systems the floor can get very hot? Anyone had any experiences of electric underfloor heating?

I cannot do wet system as it is an old flint cottage and cannot raise the floor levels.

electronicsuk · 20 Nov 2008

If you go for electric heating all round of any sort other than night storage then it's going to cost you a fortune to run. The tiles should never become unduly hot as a thermostat (with temperature probe buried below the tiles) is used to regulate the temperature.

The most powerful kits I've seen are 200w/square metre, and I believe 150w/metre square is generally the recommended minimum if you want to use as your primary source of heating, rather than just for comfort.

Now, I'm in the process of having my kitchen and hallway tiled, the floor area here is approximately 24 square metres. To heat this area with electric UFH alone at 200w/m2 I'd be looking at a total load of 4.8kW. Granted that there wouldn't be a constant power draw as high as that once the system is up to temperature and cycling on the thermostat, but running costs will still be high. Also consider that it may take significantly longer for the mass of the tiles to warm up than would be the case with central heating, so they will need to be switched on well before the heat is needed.

stem · 20 Nov 2008

Unless you have a modern well insulated building underfloor heating is generally not really upto the job as the main heating source.

You can find an on line calculator that will calculate the Kw's you need to heat your house, calculate the floor area multiply it by the watts per square metre and you will find out how much heat you will be geting from the underfloor heating to see if it's suficient. There are other factors involved, but this will give you a guide.

Having said that, if you use any form of underfloor heating, the insulation under the heating elements or pipes is important, otherwise the heat will be conducted away into the ground. My (limited) experience of this, is that the insulation is much deeper that pipes used in water systems, so if you don't have room for water pipes, you won't have room for electric either

Taylortwocities · 20 Nov 2008

Most electric underfloor heating is considered as background, not the main heat source.

If you think about it, 300W is the equivalent of a handfull of light bulbs and you wont keep cozy warm in January but turning on a few lights.

Back to the original Q. I would steer clear of ribbon (carbon film) syatems if you have an old cottage with stone floor areas.
I recently had to sort out a problem with a ribbon system laid under a wooden floor. If a person was standing on the heated wooden floor and touched someone standing on an adjacent area that was stone flags (a good earth) then there was a significant potential difference between them - 90volts plus.

This is because a voltage was induced into somone standing on the wooden area. For these applications the cable type is better as the element is encased in an earthed shield.

BTW the carbon film systems must NOT be used in bathrooms etc unless an earthed screen is laid on top of the heating element.

Steve · 21 Nov 2008

The most efficient underfloor heating system utilises a heat pump, which extracts heat from the ground, and is 400% efficient. This in turn transfers its heat to a coil of pipework under the floor.

northseagirl · 21 Nov 2008

Thank you all for your advice and comments.
Unfortunately I am stuck with electric as there is no gas in the village and there is no room for the oil tank - I had a survey and they said not poss.
Would love to do ground source but again no space. I have very limited wall space for radiators so I think I will do a mix of both underfloor and radiators.
I will also use the recommended insulation.
The ribbon type electric underfloor manufacturers say they warm up quicker than cable type - but then I guess they would! Thanks for warning about the voltage shocks!
Electric type definitely takes up less space than wet system.

galliano2001 · 22 Nov 2008

What makes you say you don't have room for a ground source heat pump?

northseagirl · 23 Nov 2008

I don't have much ground with my cottage. Just a small patio and small grass area.

galliano2001 · 23 Nov 2008

You know you can get vertically sunk systems now that don't require more than a couple square meters at the surface?

northseagirl · 23 Nov 2008

Thanks for info but I can't even get the drilling rig into my garden.
I did look into it all and I would love to use this system in a future project but I can barely get my car into the yard.

Steve · 23 Nov 2008

galliano2001 said:
You know you can get vertically sunk systems now that don't require more than a couple square meters at the surface?

Doesn't even require that once its covered up

Someone after my own heart, another GSHP fan?

hairyben · 23 Nov 2008

stem said:
Unless you have a modern well insulated building underfloor heating is generally not really upto the job as the main heating source.

You can find an on line calculator that will calculate the Kw's you need to heat your house, calculate the floor area multiply it by the watts per square metre and you will find out how much heat you will be geting from the underfloor heating to see if it's suficient. There are other factors involved, but this will give you a guide.

Having said that, if you use any form of underfloor heating, the insulation under the heating elements or pipes is important, otherwise the heat will be conducted away into the ground. My (limited) experience of this, is that the insulation is much deeper that pipes used in water systems, so if you don't have room for water pipes, you won't have room for electric either

This is true. You might "get away" with 10mm insulation boards, but it really needs 50mm minimum. Any less and you will lose heat to the ground, and it'll take ages to heat up. I did a kitchen a while ago where the builder made no allowance for insulation, so it went down straight to the concrete, I don't evan think they bother using the heated floor now.

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ELECTRIC UNDERFLOOR HEATING - RIBBON OR CABLE?

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