Underfloor heating: Electric or warm water?

normal7073

We are having a single story extension built on the side of the house. Although we will initially be stepping down into a porch area, there will then be a door into a 4.5m x 4m room i.e. approx 18 sq.m. ( though we will be purchasing the 15sq.m 150w kit as we won't need the system right against the walls)
The floor surface will be tiled and we are considering having underfloor heating, probably Warmup from Topp's Tiles, though you can get slightly better deals on the internet.
As there will be insulation provided in the sub floor build, to conform with Building Regs, do we still need to use the Warmup Insulation Boards that they claim will greatly increase the efficiency of the system?
If anyone has had this system laid I would appreciate your comments.
In addition, does anyone feel strongly enough that we should, instead, be going for a warm water system from the central heating system as our boiler is powerful enough to deal with it.
The electric Warmup system quotes the cost at being approx 80p per day for 8 hrs use. Does anyone have an idea what a warm water system would cost for a similar usage?

sillygoose

I installed a system in my conservatory with a 12m sq mat. First of all the Warm-up stuff is an utter rippoff!!!. Its twice the price it should be. Like a lot of things there has been a 'black magic' aura put up around underfloor electric heating to keep fat margins on it. The quote I got from a tiling company to install some was laughable so I did it myself.

I used this company because they supply professionals and their heating mats are top quality fully earth screened as good as or better than warm-up. 150watt 15metre is £358.

A lot depends on the heat loss from the room overall. As mine was a conservatory I went for 200watt as it make virtually no difference to the price but gives faster response of the system and more power in reserve, if the room gets up to temperature quicker then the heater will be switched off more so shouldn't make any difference to power use. Mine is directly in the tile adhesive bed and initially takes only 9 minutes to get the tiles noticeably warm. You also need to consider what you will put in there, furniture, rugs etc will slow the system down proportionally.

Insulation - I would not consider skimping on it, with a 150watt mat on a screed with normal celotex type building layer in it - it could take a very long time to have any effect on the room (hours!) Again warm-up stuff is a ripoff.

Marmox is one of the leading brands (sold by the above supplier too) and I used a 35mm layer directly between the concrete screed and the tiles. It comes between 6mm and 50mm and I would use the maximum you can depending on your floor level. A couple hundred spent on this now will save a fortune in the long run in energy bills. It was easy to lay and tile over and the floor is now superbly responsive, quite quickly the room has come up to temperature and the controller switches to quite a slow cycle of power on/off to maintain it as the tiles become heat stores. Power consumption has been not too bad.

ListysDad

Normal.

First a question. Do you intend to stay in the house? If yes, then without question fit water and here is why.

- It IS more to fit, but ultimately will cost you much much less to run. Gas energy is approx 20% that of electrical energy so over time runing costs will pay back all plus plus plus.
- You wil have a usable space all year round.
- It is more reliable and fixable under certain circumstances
- It responds much more quickly so you don't have to 'plan' to be in the space
- No draughts from the convection currents caused by radiators

Most of Europe use underfloor as its so effective. Its only us Brits who know sooo much better that use rads...

Knowing what I now know, I'd NEVER design a house without wet underfloor heating.

HTH

Sorry, forgot to answer re insulation. Take advice. Building regs dictates the MINIMUM needed and today one can safely add more and thereby save long term. In that case one does not need any other and the pipework goes directly into a screed on which you can put what ever floor you like. Its also a cheaper way of achieveing the same.

One other thing. Floor covering. If you're thinking of Amtico or Karndean or similar then electric will, probably ruin it, unless you bury it deep. These types of flooring can only withstand a surface temperature that quite low if discolouration is not required. Water underfloor heating is NO problem for any floor covering.

sillygoose

ListysDad wrote: »

Normal.

First a question. Do you intend to stay in the house? If yes, then without question fit water and here is why.

- It IS more to fit, but ultimately will cost you much much less to run. Gas energy is approx 20% that of electrical energy so over time runing costs will pay back all plus plus plus.
- You wil have a usable space all year round.
- It is more reliable and fixable under certain circumstances
- It responds much more quickly so you don't have to 'plan' to be in the space
- No draughts from the convection currents caused by radiators

Most of Europe use underfloor as its so effective. Its only us Brits who know sooo much better that use rads...

Knowing what I now know, I'd NEVER design a house without wet underfloor heating.

HTH

I would totally agree with all above, spot on. Best thing with wet underfloor is the control on a per room basis that is possible as well as the energy cost saving. I should have said something similar , was just keen to make sure should the op go electric they get the best out of it.

bwoodward

Hi there,

Myself I have electric floor heating. I am not your typical user and I did a lot... of research before choosing which system to go for. First of all the decision to choose underfloor was easy becuase of the design limitations of other systems and the cost savings. Second I ended up choosing electric over water because the start-up cost is much lower, the running costs are failry similar and in some instances it is better to have water heating for examle if you are leaving you heating on for long periods of time. I simply chose electric as it seemed less hassle and I chose warmup for no reason other than my builder recommended it. He said there are a lot of cheap floor heating systems out there with no support and the guaranatees made spending a little more worth it. So the real question, how does it work? My home is well insulated and the rooms I have installed the heating are fairly small so it works perfectly fine. I definitely wouldn't recommend it for all households as the ideal system really depends on you insulation, room size, floor type etc etc. Only a qualified builder or technical rep for these companies should really be relied on to give sound advice. Also from what I read, no matter what type of floor heating you put down. DEFINITELY use floor insulation. It speeds up your heat up time and helps the room hold heat (not lost through the floor) essential... all the best

normal7073

O.K.
After further research to my original thread it's becoming increasingly obvious that running an electrical system will be far too expensive with my 18sq m extension at 8hrs per day coming to not far off £30 per month, which is half of my monthly total electricity bill in my 5 bedroom house.
Therefore, it's definitely going to be warm water underfloor system for me, BUT, which one?
Has anyone had a top quality, reliable system fitted recently that they could recommend?

ListysDad

Any from the likes of John Guest, Polyplumb or Hepworths (HEP20) are top notch.

THE single most important issue is that your plumber has installed silmilar OR understands it is important to enlist the support of these manufacturers - they do this for free for plumbers.

DO NOT choose based on price alone. Listen to your heart and you won't be let down.

Good luck.

PS DO NOT forget to put LOTS of insulation down in the floor screed FIRST

MX5huggy

I see a lot of http://www.nu-heat.co.uk/s.nl/it.I/id.396/.f?sc=7&category=40

on jobs that come across my desk