Underfloor Heating.

[melhook]

Hi, has anyone installed their own? Its going under tiles, in a kitchen diner. It it easy? can you lay it on concrete floor, or is it best to insulate the floor ? Any advice welcomed. Thanks

[northandy]

melhook said:

Hi, has anyone installed their own? Its going under tiles, in a kitchen diner. It it easy? can you lay it on concrete floor, or is it best to insulate the floor ? Any advice welcomed. Thanks

I put it in the kitchen when we re modeled it... couldnt use the piped water version so went with leccy (cable rather than matting)...

To be honest we only put it in as the old floor was stone cold, and we were putting slate down instead of the vinyl that was there, however we also raised the height (as there used to be a step down) and used 60mm kingspan boards, laid the cable on those then put the screed over the top, then the tiles...

I was worried it would cost a fortune to run, but tbh we dont use it a lot as the insulation has meant the floor doesnt get as cold anyway, it does take a while to warm, but once it has it stores the heat brilliantly...

When I looked piped water is definately the cheaper option for running costs...

[cjs]

A friend fitted the matting, had the floor tiled, connected up the electrics, thermostat and timer. Switched on for the first time...it worked for half an hour and then failed.

The problems were with the matting under a few thousand pounds worth of tiled flooring! Just a word of warning! He lost the cost of the underfloor heating, he now has a standard radiator fitted.

[skwdenyer]

cjs said:

A friend fitted the matting, had the floor tiled, connected up the electrics, thermostat and timer. Switched on for the first time...it worked for half an hour and then failed.

The problems were with the matting under a few thousand pounds worth of tiled flooring! Just a word of warning! He lost the cost of the underfloor heating, he now has a standard radiator fitted.

If using the cables (lay yourself in screed, for instance) then try to run in as many "circuits" as possible, interlocking (in a sort of "greek key" pattern, if you like). This will give you a lot of redundancy. If one circuit fails, the floor will still be warm. Matting tends to be installed as a single circuit - 1 failure = no underfloor heating.

But, in general, unless you're experienced with this stuff, I'd recommend using a professional to install - mainly so that their insurance will cover it if it breaks down

[Marcusfenix]

got mine from here the cable kit http://www.ambient-ufh.co.uk/under-tile-cable-kits... your suppose to test it before laying your tiles.
works great. easy to lay with superb results.....

[anonymous-user]

I've got one called speedheat which works well.

It's just a series of 'wires' which after placed out on the floor you screed in a liquid latex which when dry is only a few millimeters thick. You could tile on this no problem.

[BigBen]

I have devimat (I think) electric underfloor heating and it was pretty easy to install, it is based on wires in a series of S bends places on a sellotape type backing which you cut to suit your room layout. Put a latex layer over this then tile, job done. Also insulated under it with stuff called Ecoboard. Cost about a grand for a 20m2 area including insulation and heating stuff.

Ben

[h4rvy]

I fitted Devimat and Screwfixes own and it pays to go for the most expensive
( Devimat ).

[northandy]

skwdenyer said:

cjs said:

A friend fitted the matting, had the floor tiled, connected up the electrics, thermostat and timer. Switched on for the first time...it worked for half an hour and then failed.

The problems were with the matting under a few thousand pounds worth of tiled flooring! Just a word of warning! He lost the cost of the underfloor heating, he now has a standard radiator fitted.

If using the cables (lay yourself in screed, for instance) then try to run in as many "circuits" as possible, interlocking (in a sort of "greek key" pattern, if you like). This will give you a lot of redundancy. If one circuit fails, the floor will still be warm. Matting tends to be installed as a single circuit - 1 failure = no underfloor heating.

But, in general, unless you're experienced with this stuff, I'd recommend using a professional to install - mainly so that their insurance will cover it if it breaks down

good point, one thing to watch is that the manufacturers guarantee doesnt cover replacing the floor covering you put over it....

I used Devi-cable...

[skwdenyer]

northandy said:

skwdenyer said:

cjs said:

A friend fitted the matting, had the floor tiled, connected up the electrics, thermostat and timer. Switched on for the first time...it worked for half an hour and then failed.

The problems were with the matting under a few thousand pounds worth of tiled flooring! Just a word of warning! He lost the cost of the underfloor heating, he now has a standard radiator fitted.

If using the cables (lay yourself in screed, for instance) then try to run in as many "circuits" as possible, interlocking (in a sort of "greek key" pattern, if you like). This will give you a lot of redundancy. If one circuit fails, the floor will still be warm. Matting tends to be installed as a single circuit - 1 failure = no underfloor heating.

But, in general, unless you're experienced with this stuff, I'd recommend using a professional to install - mainly so that their insurance will cover it if it breaks down

good point, one thing to watch is that the manufacturers guarantee doesnt cover replacing the floor covering you put over it....

I used Devi-cable...

I accept that the manufacturers' guarantee may not cover the flooring component. I was more suggesting a contractor to perform all flooring and heating installation as a single job, the job being let on a spec calling for a minimum, say, 5-year life. Then there's some comeback if needed.

[Viper_Larry]

We had it laid in the conservatory of our new house. It was laid incorrectly and had to be replaced before tiling with a special thin mat from Spain. Tiled over this and it didn't work. They then had to break out all the tiles and screed to start again from scratch - 3rd time lucky it worked. It does cost a bit to run though - testing it today, around £1.20 a day if set @ 20°C

[skwdenyer]

Viper_Larry said:

We had it laid in the conservatory of our new house. It was laid incorrectly and had to be replaced before tiling with a special thin mat from Spain. Tiled over this and it didn't work. They then had to break out all the tiles and screed to start again from scratch - 3rd time lucky it worked. It does cost a bit to run though - testing it today, around £1.20 a day if set @ 20°C

The absolutely key thing is to ensure that there is plenty of insulation underneath the heating; the standard polystyrene slabs are simply not at all sufficient in my opinion. You need at least 50mm of Celotex / Kingspan (polyeurethane foam) underneath to ensure that the majority of the heat rises through the floor, and you need to ensure that there is no edge-bridging between tiles and cold walls.

Likewise, be wary of mats which might have any sort of material in them which would act as an insulant; everything around and above the heating elements needs to be as cohesive and conductive as possible to ensure the best possible thermal conductivity.

My preference would be for heating wires, laid in separate circuits, in a 50mm screed bed sitting on top of 50mm of Celotex, with edges fully insulated. Once the screed has set off, tile directly on top of this. The screed should be mixed with a polymeric admixture designed to enhance flexibility and resist cracking, as the whole thing will expand and contract as it heats up and cools down. However, that does require quite a bit of excavation in many cases

A nice side-effect of all of that screed, especially with tiling above, is that it has quite a bit of thermal mass. It can therefore be beneficial, if you have it, to use Economy 7 overnight electricity to run, say, half of the heating circuits, using all of that thermal mass as a night storage heat store.

A set-up as described above can be as efficient as possible to run. But if you go to that extent, the only reason for not using water pipes instead of heating wires would be if you have no way of heating that water with mains gas.

[Viper_Larry]

skwdenyer said:

Viper_Larry said:

We had it laid in the conservatory of our new house. It was laid incorrectly and had to be replaced before tiling with a special thin mat from Spain. Tiled over this and it didn't work. They then had to break out all the tiles and screed to start again from scratch - 3rd time lucky it worked. It does cost a bit to run though - testing it today, around £1.20 a day if set @ 20°C

The absolutely key thing is to ensure that there is plenty of insulation underneath the heating; the standard polystyrene slabs are simply not at all sufficient in my opinion. You need at least 50mm of Celotex / Kingspan (polyeurethane foam) underneath to ensure that the majority of the heat rises through the floor, and you need to ensure that there is no edge-bridging between tiles and cold walls.

Likewise, be wary of mats which might have any sort of material in them which would act as an insulant; everything around and above the heating elements needs to be as cohesive and conductive as possible to ensure the best possible thermal conductivity.

My preference would be for heating wires, laid in separate circuits, in a 50mm screed bed sitting on top of 50mm of Celotex, with edges fully insulated. Once the screed has set off, tile directly on top of this. The screed should be mixed with a polymeric admixture designed to enhance flexibility and resist cracking, as the whole thing will expand and contract as it heats up and cools down. However, that does require quite a bit of excavation in many cases

A nice side-effect of all of that screed, especially with tiling above, is that it has quite a bit of thermal mass. It can therefore be beneficial, if you have it, to use Economy 7 overnight electricity to run, say, half of the heating circuits, using all of that thermal mass as a night storage heat store.

A set-up as described above can be as efficient as possible to run. But if you go to that extent, the only reason for not using water pipes instead of heating wires would be if you have no way of heating that water with mains gas.

Good advice - we have 75mm polystyrene insulation + 50mm screed all on a suspended floor (same as the house)

[skwdenyer]

Viper_Larry said:

skwdenyer said:

Viper_Larry said:

We had it laid in the conservatory of our new house. It was laid incorrectly and had to be replaced before tiling with a special thin mat from Spain. Tiled over this and it didn't work. They then had to break out all the tiles and screed to start again from scratch - 3rd time lucky it worked. It does cost a bit to run though - testing it today, around £1.20 a day if set @ 20°C

The absolutely key thing is to ensure that there is plenty of insulation underneath the heating; the standard polystyrene slabs are simply not at all sufficient in my opinion. You need at least 50mm of Celotex / Kingspan (polyeurethane foam) underneath to ensure that the majority of the heat rises through the floor, and you need to ensure that there is no edge-bridging between tiles and cold walls.

Likewise, be wary of mats which might have any sort of material in them which would act as an insulant; everything around and above the heating elements needs to be as cohesive and conductive as possible to ensure the best possible thermal conductivity.

My preference would be for heating wires, laid in separate circuits, in a 50mm screed bed sitting on top of 50mm of Celotex, with edges fully insulated. Once the screed has set off, tile directly on top of this. The screed should be mixed with a polymeric admixture designed to enhance flexibility and resist cracking, as the whole thing will expand and contract as it heats up and cools down. However, that does require quite a bit of excavation in many cases

A nice side-effect of all of that screed, especially with tiling above, is that it has quite a bit of thermal mass. It can therefore be beneficial, if you have it, to use Economy 7 overnight electricity to run, say, half of the heating circuits, using all of that thermal mass as a night storage heat store.

A set-up as described above can be as efficient as possible to run. But if you go to that extent, the only reason for not using water pipes instead of heating wires would be if you have no way of heating that water with mains gas.

Good advice - we have 75mm polystyrene insulation + 50mm screed all on a suspended floor (same as the house)

That sounds good. How large is your conservatory? We did a floor like this for a friend's 1730 cottage some years ago. In his case we had joists, so we laid modified screed between the joists (100mm thick) to act as the thermal mass, with 100mm Celotex beneath the screed and beneath the joists. For a floor area of around 500 square feet, when combined with dry-lined (insulated) walls and insulated ground floor ceiling, we could maintain the inside at 20C when -10C outside with a total heat input of around 1.4kW. That would equate to around £2.50/day if run full-time.

For a conservatory, you're not going to get anything like the U-value we achieved in that cottage. Assuming your conservatory is smaller, nonetheless it sounds like yours is running quite efficiently. I can't think of any other electrically-powered heating systems which would give you any better efficiency or lower running-costs.

That said, have you tried running it overnight to build up some heat in the slab?

[Viper_Larry]

Conservatory is around 5m x 5m with 2 corners cut, if you know what I mean. Don't have Economy 7 yet, so can't heat cheaply at night.

[skwdenyer]

Viper_Larry said:

Conservatory is around 5m x 5m with 2 corners cut, if you know what I mean. Don't have Economy 7 yet, so can't heat cheaply at night.

OK, so around 250 square feet or so? In that case your quoted running cost doesn't sound too bad at all for a conservatory; I'm not sure you'd do any better with any other heating system!

[71notout]

I laid the electric wire kit when I had my kitchen done.

Night before the tiler was doing the floor I laid it all out....it ran out very quickly - should have been roughly 64m but only got 1/2 that - turns out someone had nicked half the wire!!

Totally useless as both ends are thicker for 2m or so which you can run up the wall to the RCD and thermostat.

Got it replaced from the shop and tried again on the next night - tiler came and fitted the slate tiles, job's a good 'un.

2 days later I took the thermostat out it's box and found the temperature probe wire in the box - I had forgotten to fit it under the tiles

Luckily I was able to just remove some grout from between 3 tiles, sand down the head of the probe (a lot of insulation on it) and it fitted between the tiles. Bit of new grout and job done.

Have no idea how much it costs to run as I have still to get it wired up