Water UFH is wet underfloor heating expensive to run? - Tile Advice

[alex kirby]

I am in the middle of house remodelling and I am wanting to install wet underfloor heating across a 128 square meter area but I have been told by my neighbour that it is really expensive to run and to look in to it.
He told me that it cost him £500 in heating oil in one month to run his underfloor heating in his 5m x 5m kitchen.
Since then he was told by his builder that underfloor heating is expensive to run which made his mind up to de-commission his wet system.
I am very confused because everywhere online states that underfloor heating should be cheaper to run than the traditional radiator systems.
Others say you should run both underfloor heating and radiators at the same time?

 

[Chalker]

Heating has a cost to run. A room will need an amount of kw to get it to a required temperature. Weather you heat it with rads, electric, ufh or a blowlamp , it will still need the same kw.
Running cost can be reduced by better insulation, or turning down by a degree or two.
Here's where you problem lies. Underfloor heating works at low temp, around 45-50 degrees. This is achieved by a mixing station connected to your manifold. Your primary pipework from the boiler should be set around 65-70 degrees. A gas boiler can fully modulate to control this accurately, but an oil boiler can't, so it's constantly on/ off this is called cycling. And is inefficient.

So gas is cheaper on ufh, but your mate is massively exaggerating with £500

 

[widler]

If im honest , ive never heard one person who i know who has wet UFH say
" i can't believe how cheap it is to run"
Not one, nada, zilch

 

[White Room]

I know a women who had wet ufh and hates it....

 

[WetSaw]

Mrs Whitebeam?

 

[White Room]

No mate, this women has got money

 

[Ajax123]

wet underfloor heating works on the principal of radiant heat rather than convected heat. for this reason it is more efficient than traditioanl radiators. it is however important to take consideration of a number of factors.

1. heat loss to the outside. the more insulation you have underfoot the better. typically a U value of less than 0.21 will offer a good level. the lower the u value the better. also the fewer drafts there are the better.

2. the heat transfer medium. the more responsive the better and the lower the required flow temperature the better. i other words low temperature and fast response is good. you need to use as little energy as possible to create thermal inertia. once you have the inertia it needs to stop reasonably easily if you get too hot. the best materials in the market are the anhydrites. i would say that eh... but there a plenty of independent studies to confirm. these are followed by the self compacting concretes which have a lower conductivity and larger mass so its more difficult to create inertia and response. the diffuser plates and low mass systems are the least efficient.

3. controls. think about zoning and mixing valves as well as the heat source. an air or ground source heat pump will be more efficient than a gas boiler but the gas boiler will be more efficient than oil for example.

4. pipe sizing and spacing. the less wate you have to heat the better so this is direcrly related to the above.

5. floor coverings. every time you add a layer to e floor you reduce its efficiency. the more intimate the covering the more efficient so the most efficient would be a polished anhydrite screed. a tiled floor is probably next and carpes and wood floors are the least efficient

there is no reason why, if designed correctly and installed properly, a wet underfloor heating system should give you a saving. i can give figures specific to anhydrite. the flow temperatures can be reduced by up to 20 degrees C and for every 1 degree you should save around £10 a year on your gas bill (defra figures)

if you have a choice go wet heating in high response anhydrite screed. e.g.

http://gypsol.co.uk/media/1256/18-gypsol-htc-sheet.pdf

 

[Ajax123]

blimey... not done a proper long post for ages

 

[White Room]

The one I mentioned she a standard screed at 70mm thick.

 

[Ajax123]

trouble with sand cement especially at deep sections is the amount of entrapped air which effectively lags the pipes making it less efficient. typical thermal conductivity of sand dement at 75mm is 1.1w/mk where as Gypsol for example is 2.3 that couples with the lower mass leads to a lower e nergy input for a higher energy output.

 

[Ajax123]

my typing hasnt improved any...

 

[Chalker]

The one I mentioned she a standard screed at 70mm thick.

Is that a recent install? 55mm is the norm, with lightweight anhidrate screed.
As Ajax says. A well installed sysem in a well insulated property. Heated by an efficient heat source, will be as cheap as rads.

 

[White Room]

Is that a recent install? 55mm is the norm, with lightweight anhidrate screed.
As Ajax says. A well installed sysem in a well insulated property. Heated by an efficient heat source, will be as cheap as rads.

Probably earlier part of the year

 

[Kyle Knowles]

I know a women who had wet ufh and hates it....

I did a job around 100 sqm on wet system u underfloor heating and obviously the lady didn't to her research she has bin on to the builder moaning it takes to long to heat up the silly sausage was expecting to just be able to flick it on and it heat up instantly

 

[Dan]

500 quid for a 25m2 room?!?! Did they forget to install a thermostat lol