Underfloor heating - types and manufacturers. Do we have a favourite?

bigmondy · Jul 25, 2011

Getting asked more and more to install and have never quoted.

Considering trying it out installing an undertile element in a new 1.7m x 1.5m wet-room I am working on where we have insulated under the floor surface - 18mm ply - with 100mm insulation blanket between the joists and polystyrene sheeting tacked to the underside of the joists ( just to be sure we layed aluminium foil underneath the 18mm ply). It will be well insulated and will be the only source of heat in the room.

I was wondering if there was a preference amongst the experts on the following:

1. Mat or cable (easier instal, more economical, less call-outs/faults etc)?

2. Manufacturer (I noted that members of the forum get a discount at a supplier - however are there other favourites)?

3. I will be tiling as well (I know) and wondered if a self levelling screed is advisable prior to laying adhesive and minimising air gaps?

4. Do you always complete the warranty card and do certain types have issues when taking the IR and continuity readings?

5. Am I right in saying it is there is a recomended (not sure if it's 100w) heating cable that is used over timber floors - is this because of heat loss?

6. Fixed fuse spur on 6mm supply will be from a low level cupboard next to the wetroom would there be an issue (apart from crouching inconvenience) in placing the stat beside it?

7. Ebay seem to have good deals available (tin hat on)?

8. Newbie - so be gentle with me?

Thanks Gents.

bigmondy · Jul 25, 2011

Sorry - question 5 is badly worded (probably they all are

).

But I was trying to determine if I stepped up to 200w/m2 would there be any benifit since it will be the sole heating source for the wet-room?

Appologies.

bigmondy · Jul 25, 2011

Oh dear. Duplicate of above. What a numpty!

Short Circuit · Jul 25, 2011

bigmondy said:
Getting asked more and more to install and have never quoted.
I was wondering if there was a preference amongst the experts on the following:

Morning Mondy,

1. Mat or cable (easier instal, more economical, less call-outs/faults etc)? The matting is much quicker and easier to install, just lay it out! Make sure you plan the layout first. If you are putting it on the timber floor as you seem to be, use a staple gun to hold down the corners of the matting - dont staple the cable! Cant see why mat or cable would make a difference for faults.

2. Manufacturer (I noted that members of the forum get a discount at a supplier - however are there other favourites)? When i suuply it, I have always used Devimat, never had any problems with it. I get mine from a tiling centre which is quite competetive, but the net is great for most things so search around. If the customer supplies it, i will fit anything as long as they know there is no warranty on the mat - just the wiring

3. I will be tiling as well (I know) and wondered if a self levelling screed is advisable prior to laying adhesive and minimising air gaps? Not too sure about the screed - i'm sure it can be put down on wooden floors. If you tiler properly (ie not just the corners of the tiles) you shouldn't get air pockets

4. Do you always complete the warranty card and do certain types have issues when taking the IR and continuity readings? Yes, could be your saving grace at a later date of anything does go wrong. If it goes wrong within the warranty period, at least you can show you have followed the makers instructions and there is more chance they will compensate you and help with the repair!

5. Am I right in saying it is there is a recomended (not sure if it's 100w) heating cable that is used over timber floors - is this because of heat loss? I know Devimat say the 100w is for the wooden floors, and the 150 of concrete but i am not too sure of the reasons why, i kinda suspected it was something to do with fire !

6. Fixed fuse spur on 6mm supply will be from a low level cupboard next to the wetroom would there be an issue (apart from crouching inconvenience) in placing the stat beside it? Why 6mm supply? If the supply is small enough to go in a fused spur, you dont need 6mm! No harm in spur/switch at low level but wouldnt recommend the controller down there too - just put it at switch height for convenience, as long as the mat cable and stat reach!

7. Ebay seem to have good deals available (tin hat on)? Hmmmmm...... Like i said earlier, no harm in internet shopping, just make sure you buy it from a dealer, not joe bloggs who has one spare as they will be selling it for a reason like its crap, or you will have no come back later!

8. Newbie - so be gentle with me? Welcome to the forum mate

Thanks Gents.

Hope this helps

alanl · Jul 25, 2011

I fitted some last week. Warmup cable. Comes in a cable reel, 50 or so metres long, maybe less. It really needs to go down onto insulation/concrete board. If it is being tiled over wooded floorboards, then that is going to be done anyway.The boards are only £7 each from Topps, just under a metre sq.
Dead easy to fit, lay it down, and tape it in position. Took me an hour or so to go round a bathroom with it. 1.5mm sq. cable feed for it - only 3A max. I fitted an 6A RCBO to feed both the underfloor and bathroom lighting (no RCD in the house) I used the proper Warmup controller too, which is quite expensive but is really good, giving lots of options, as well as letting you know how much energy it has used. Cost £200 total for a 2m sq bathroom. It can be had cheaper, I bought locally.
Testing it and I was surprised at how good it is, after 20 minutes the floor was getting warm, and after an hour was nearly up to full temp - 22 deg.
The customer was really happy with it.
Alan.

bigmondy · Jul 25, 2011

Great replies Gents. Really appreciate it.

The 6mm was installed as the plan was to install a radiant panel or oil filled heater - realise that it will be overkill now.

Ah - fire rating - I suppose that is a good reason for timber floors to have the 100w/m2 and the concrete can go up to 200w/m2.

Given the amount of insulation we have installed on the job I wasnt planning on using the insulation boards - do we really need the additional layer of insulation - or is that essential because of combustibility issues as well?

Cheers.

bigmondy · Jul 25, 2011

Stupid question alert:

Surely the closer together the higher the sq m rating will be?

Since it is primary source - I was thinking of spacing around 50mm - to increase the output. If using the 100w/m2 cable - how close can you put the cables together if the issue is combustibilty?

Short Circuit · Jul 25, 2011

Like i said earlier, i have always stuck to the matting so not too sure about how close you can or cant put them together - but bear in mind you need to run your thermostat between the runs so that doesnt want to be too close otherwise it'll keep turning it off. i wouldn't be too worried about trying to increase the output, it will work fine!

bigmondy · Jul 25, 2011

Noted short Circuit.

praxiscnc · Jul 25, 2011

ere's a different angle to take into account:
You've said that it will be the only source of heat in the room, so you really ought to do a heat loss calc. first.
if you don't know how that's done then maybe ask a friendly heating engineer.
The heat loss calculation will tell you how many watts you need in the room, then divide that value into the available floor area (ie, the floor area that's not covered by the bath, wc etc.
Only then will you know how many watts per square meter you need; anything less is pure guesswork!
The best underfloor heating is warm water with set-back control, but sometimes electric is the only option.
Cheers.