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 plus other windows and intend to fit engineered wood flooring. We are considering UFH (water) to heat the entire space. At the moment we're working with our builder and his plumber to assess the best system but I'd like to 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 looking 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.

 

[John67]

Sounds like your friends have an envy problem, are they speaking from experiance? None of the comments are correct in my oppinion and as for efficiency a study was carried out recently that proved ufh was more efficient than rads. It is possible that with the two different floor structures you might get a slight temp difference but i would say go for it.

 

[Onetap]

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.

1) You should employ someone competent to calculate the required heat input and the heat output of the UFH. There should not be a problem with a building constructed to current Building Regulations; the UFH output at an appropriate surface temperature is often inadquate for refurbishments, with less insulation.
2) Yes. It usually is left on.
3) Should be cheaper; it will be more expensive if the underslab insulation is inadequate. The return temperatures are mush lower so condensing boiler efficiency is higher. The heat loss by radiation from people is lower so the air temperature can be lower to achieve a feeling of comfort.
4) See 1.
5) See 1.
6) Yes.