Underfloor heating??

[huw169]

Not sure if this should be in thi section, or Electrics, or Plummbing & Heating, but here goes anyway..........

I am doing a single story extension and knocking a load of walls around downstairs. All the rads are in poor positions, so i was going to re-plumb downstairs as well as move the boiler.

I have been toying with underfloor heating. Total area is about 75msq. I have costed it at around £2300 with 4 thermostats and 6mm insulation board.

I have been doing some research and I can only find old posts where people say:-
"it can not be used as a primary heat source" - which is what I was planning.
"it will cost more than gas"
"for the same cost as gas you will only get 30% output"

Is there any truth in these statements?
Has anyone got electric underfloor heating installed as a primary source of heat? is it ok?
Have things moved on a lot recently?
Should i stick with my gas central heating as I will still have rads upstairs and therefor need a boiler...?

Any help would be great.
Many thanks
Huw

 

[Fluffster]

We install quite a few wet underfloor heating systems.

They can be more effecient as they run at a lower temp however need a longer heat up time.

We usually advise to have a set back temp so the slab never gets cold and so this reduces the reheat time.

The more zones you create can help reduce your gas costs along with the correct amount of screed at least 65mm on top.

I would advise at least 30mm of insulation such as Kingspan or Celotex.

I would not advise electric for that size area also electric cables/mats have a reduced shelf life compared to pex pipe.

Have a look at this website for more detailed info.

http://www.gasapplianceguide.co.uk/UFH questions.htm

Good luck
Pete

 

[huw169]

Thanks Pete
That is a good site.
Water sounds better, but I have an issue with raising my floor level.
I wonder if I could insulate between the joists and then lay heater pipe on top so it sits just under the floor boards. It may not be that effective though.
Maybe I could just run the return from the radiator under the floor, so it supliments the rads?
Thanks again.
Huw

 

[huw169]

Should maybe take this to the plumbing section now.
Many thanks
Huw

 

[Fluffster]

Between the joists is never as good as a whole slab heating up and emmitting the heat slowly.

Do not bother with the allloy spreader plates as they do not make much of a difference.

You could always have a mix of rads and ufh.

I have a good contact for the ufh components if you are interested as your pricing seems v high for 75sq m.

Pete

 

[huw169]

Hi Pete
Thanks for the offer, really appreciate it.
However, decided to stick with the conventional radiator system with some added insulation.
Thanks for your comments, and will certainly give you a shout if i reconsider UFH.
Thanks again.
Huw

 

[huw169]

Hi Pete
I'm back on this again.
The boss has decided she wants tiles in the kitchen, downstair loo/shower, hall and lobby area.
The other areas downstairs will have wood flooring and rads on the walls.
The kitchen, loo and hall have no place for rads. The lobby will have oned though.

As mentioned before, i have an issue with increasing the height of my floor significantly.
I have read that even for the 2-3mm under tile heating, I would need to put a 12mm board down first, then the cable, then the tiles (~8mm thick). This would mean an increase of ~25mm!

I am laying onto floorboards with 100mm rockwool insulation below, so should be reasonably well insulated from below.

My house layouts are here - //www.diynot.com/forums/viewtopic.php?t=188692
Basicly, the lower half of the house as viewed on the plan will be tile and the upper half wood.

Also, i'm not sure how to do the thresholds from wood to tile.

Any tips/advice would be greatly received.
Thanks
Huw

 

[Fluffster]

Hi Huw
Are you now saying that you want to lay electric cable ufh?

The probs with having just a tile and a few mm of adhesive is that the heat will dissapate very quicky and will not be as effecient as a slab holding the heat and emmitting it at a sustained rate.

Especially given the price of elec per kw to gas kw

I will have a look at your plans later as I have to dash now.

Pete

 

[huw169]

I know electric is probably a little more expensive to run, but i am only planning on under tile heating - not primary heating. The main reason for the choice was not to increase the floor height - however, i might have found a way around that.

I also don't really have anywhere for a manifold if it was a water system.

Is there anywhere that shows the cross sectional layup of each system & dimensions? What parts I would need to get as extra - wood board, etc, so I can cost them?

Many thanks
Huw

 

[huw169]

OK
Been making a few phone calls and doing some research and i am 'definatly' not going down this route now.
Been advised by a few people who could have sold me kits & know my property that it is not worth it.

Many thanks for your advice Pete.
Cheers
Huw