Gas/Wet Under Floor Heating (UFH) - expensive to run ?

drock

I'm going to rent a flat, about 50 sqm area which has underfloor heating. The agent wasn't sure if it was electric or gas, but since the flat has a boiler she believed it was gas wet heating and will confirm me later.

In the mean time, I wanted to check whats the running cost of Gas UFH and it seems thats about 15-40% cheaper than conventional radiator based Gas heating. Is that correct in reality ? The flat is nicely insulated, is on 2nd floor and I will probaly need to turn my heating on 24/7 anyway as my wife and kid will be at home all time. Let me know if anyone have experience with Gas/wet UFH

BTW - Is Electric UFH more common than Gas UFH ? There are so many resources about Electric UFH but not many on Gas UFH.

fred7777

I was always told it was cheaper to run for the following reasons:

1. The boiler runs at a much lower temperature making it more efficient.

2. The heat comes from all over the floor making it much more even and eliminating cold spots/uneven heat in a room which mean many heating systems produce more heat than they need to to get the room to feel warm all over.

3. Ordinary heating doesn't heat the floor well (heat rises from the radiators before circulating down) so ordinary heating is often set higher to stop people getting cold feet.

4. Ordinary radiators are often put under windows which is just about the worst place for them.

Pincher

If you have a hot water cylinder, you WANT the boiler giving maximum output whilst heating it, otherwise it will take forever to recover.

What you want is a very well insulated flat, so you can keep the UFH on 24 hours a day, due to the heat up time, and cooling down time.

When operating on a 24 hours basis, the heat loss of the flat determines the cost, not radiator or UFH. The lower flow temperature is only an issue if your control system doesn't know when to modulate. What with weather compensation, digital thermostat, and a non-E-Bus programmer, my boiler only modulates when it's configured correctly.

gas4you

The boiler will run at the normal temp with UFH. You should be looking at a boiler stat setting of about 65C if you have a hot water cylinder.

The UFH will have its own pump and blending valve that will mix the return water back into the flow water to drop the temp down for the UFH.

UFH never goes off, when it is an 'off' period, the temp is just set back to approx 15C.

drock

gas4you wrote: »

The boiler will run at the normal temp with UFH. You should be looking at a boiler stat setting of about 65C if you have a hot water cylinder.

The UFH will have its own pump and blending valve that will mix the return water back into the flow water to drop the temp down for the UFH.

By normal temp do you mean 65c. i.e., keeping it at it's Peak output?

But still, however high the boiler's output power is set at, the "consumption" of hot water is controlled by the thermostat kept on the wall and eventually by the UFH pump that controls how much hot water needs to go to the UFH system.. so in turn, even though the boiler is set at max because I would need hot water from the tap, it should turn off automatically, and remain off more time than it would have if I was using radiators. So, I still get the benefit of UFH, don't I ?

Sorry... I am a bit novice about this - I am new to UK and the heating systems here. Can someone with Gas UFH tell me how to use it properly and how much is the cost ? I did go through most of the posts but most of them are about installation cost and not running cost. The apartment I am going to is newly built one, and mine is on 2nd floor.

Cardew

Are you sure that the underfloor heating is not from a ASHP(Air Source Heat Pump)? These are getting quite popular in new build flats and UFH is the most suitable heating method as ASHPs are more effective with the low temperature water needed bu UFH.

Failing that I suspect it will be electrical UFH.

Pincher

Ask how they meter the hot water for heating.
They have to put in a meter and heat exchanger per flat,
integrated into the manifold housing to save space: which can cost more than having a boiler per flat. It's quite specialised, and they can't find anybody who will come for £20 an hour.

It goes something like, there is a company out there that will sign a contract for £50k a year to maintain the system, so of course the building management actually signs with another company that can't do the job for £30k.

It took the building management ten years to work out how to meter and charge for each apartment individually for one of my properties.
Before then, they just apportioned the gas bill according to flat size. Keyboard monkeys.:mad:

drock

Cardew wrote: »

Are you sure that the underfloor heating is not from a ASHP(Air Source Heat Pump)? These are getting quite popular in new build flats and UFH is the most suitable heating method as ASHPs are more effective with the low temperature water needed bu UFH.

Failing that I suspect it will be electrical UFH.

Thanks Cardew and Pincher !

I thought presence of a boiler pretty much means it's Gas/Wet UFH and not eletrical UFH or ASHP (even that is electrical too). I can't know for sure until next week.. The lady from the agent firm said it's Gas UFH and there was a closet in the hallway where it gets "distrubuted" from (it was very warm inside the closet!).. The boiler however was in the kitchen.

This is a big complex of around 10 buildings, built in 2006.. some of the flats of this complex has conventional gas radiator heating too, so from a common mind, one wouldn't choose electric UFH when there are options for Gas radiator or Gas UFH (well, i assume).

I plan to call British Gas tomorrow to check if they supply to that flat and somehow try to get the bills of last few months

drock

Turns out it's "Southern Electric" who is supplying the GAS and ELECTRIC to the apartment... the estimated direct debit is £25 for each...

So guess it's gas UFH there, not electric UFH or ASHP cause then the electric's direct debit amount would have been much higher I suppose.

Pincher

You HAVE a GAS boiler in the flat?

To do WHAT? Assuming your heating comes from a central boiler in the basement.

drock

Pincher wrote: »

You HAVE a GAS boiler in the flat?

To do WHAT? Assuming your heating comes from a central boiler in the basement.

To heat the tap water and to flow warm water through the UFH system I believe !

Sorry did I say something stupid ? .... To recap > There IS a boiler in the flat in the kitchen and there IS an Airing cupboard too.. and there is NO radiator ... and there is UFH system (claimed by the agent as running on Gas and wet system)