underfloor heating, sufficient?

[Coolhurst]

We're in the throws of building works which consist knocking through two rooms of the exisiting house and adding an extension to form a 60m2 open-plan area. We'll have bi-fold doors along the face of the extension and intend to fit engineered wood flooring. We are considering UFH (water) to heat for the entire space. At the moment we're working with our builder and his plumber to assess the best system but I'd like gather independent views based on experience. Also, we've had a few comments from friends who've chucked their sixpence worth regards UFH as a sole source of heating...I'd appreciate views on:
1. Friends (with UFH) reckon heating a room of this size with just UFH won't give a truly warm environment in the winter, we'd be as well to add a few rads as 'back up'.
2. Warm up time is long (I thought UFH is always left on?)
3. It's expensive to run
4. Thickness of the flooring is important and should be no more than 15mm engineered (oak)
5. New extension is a screed floor, existing house is a suspended floor - different style of pipe work will causes issues? (Two zones, two thermostats I guess)
6. For the instalation should we be lookng for a specialist plumber/fitter and is it normal to expect a warranty of some kind? Our builder's plumber has fitted before but isn't a specialist as such.

Personally, with proper calcs done for the system required plus a competent plumber, I can't see why UFH can't do a job on it's own but there again I've no experience in this. Any views/advice welcome.

 

[jj4091]

Think you would be better in plumbing/heating section, but I have heard all the same comments as you have if that helps.

 

[Lectrician]

I have worked with plenty of installs with wet UF heat. It does take a little tonger to warm - it depends on how it's installed though. If in a screew it is longer. With a wood floor you can have a concrete subfloor with battens sat on it. Insulation between and then foil. Pipes run on this. Floor on top (proper 22mm wood). The warm up with this method is far quicker than if the pipes are in a screed.

Modern UF heat installed in this way does not need to be left on.

I would look for a plumber who does work with this all the time.

The best thing to do is to get a spec from a company for the lengths of pipe (number of coils) and install methods for the floor structures.

Try NuHeat - we fit their kit all the time and always to their spec.

 

[Coolhurst]

thanks for replies chaps. Have reposted in plumbing, not sure how i clicked electrics.

 

[mointainwalker]

1) Really don't see relevance to size of room: there aren't going to be any strange dynamics like in a football stadium, It's all W per m2.

2) Another strange comment. If you like your house to be at 18 C or whatever from October to April, then whatever heating you have is going to be "on" (i.e. in a functioning mode, whether sctually working at that moment is a different matter)

It is usual to drop the screed temp from (say) 18 C to 15/16C during the night.

Starting from cold my UFH takes about 2 hours to warm a 7 cm screed.

3) Since the water is only heated to 40 C it is likely to be cheaper than radiators which are at 70 C (?). Also bear in mind that air heated by v hot radiators is liable to rise to top of room and be of little use. Air heated by the floor surface at 28C ( supposedly) only rises to about 1.8 m, therefore the height you are sitting/standing and is more useful. There are lots of graphs to show this.

4) Correct. No set max thickness as such, simply the thicker it is, the less efficient it becomes.

5) No difference in pipe. What will be different will be the way you choose to transfer heat to suspended floor e.g. speader plates, pug etc

6) You are not going to get away with just 2 zones for 60 m2. A pipe-circuit should not exceed 100 lm which is going to give you 1 kW if pipes are at 10 cm spacing.

Depending on house-construction, your location, whether you plan to minimums or prefer a good safety margin, i guess you are looking at 4 to 6 circuits.

My opinion is that you should try to find a specialist and I would also prefer someone who knows enough to source his own parts instead of just buying a pre-assembled kit. If he is knowlegeable he ought to save you some cash by eliminating the profit-margin of the kit-assemblers.

I don't know , but assume that a specialist would be able to design the circuits himself -it's not very difficult - based upon a heat-loss calc done for your house.

if he can't then i would doubt that he is a specialist.