UFH Running Cost

PaulKK

Hi folks,

In the process of buying a house and I was wondering if someone could provide an estimation/their experience of running underfloor heating.

Details:

2 storey house.
1950 square feet.
ICF Construction.
Gas fired underfloor heating throughout.
Concrete first floors.
8.5 foot ceiling height.
24.7kw gas bolier.

All floors are tiled/semi solid timber.

System is zoned and thermostat controlled in each room, approx 4 year old house.

Can someone tell me what the average cost of heating this house would be and the most efficient way of using such a heating system?

I have read various techniques, e.g leaving it on constantly, but reducing the temp at night and during the day so that the boiler never has to heat from cold etc.

Any advice appreciated.

Paul

Outkast_IRE

Sorry Paul but impossible question to answer , what will determine your heating cost are, your heat loss through Windows , walls, roof , floor , ventilation.

You need a pro to get a good calculation done. I have been in homes similar in size to that where annual heating bills were anywhere from 3500 to 1200.

Sorry would love to help but you need to get a pro if you want good figures.

As for techniques advice i can give you loads of that .

No1. make sure everyone living in the house realises that underfloor is not like Radiators , you cant just flick it on and expect a blast of heat 20 mins later. Doesnt work like that make sure everyone understands that.

No2. Your Goal with underfloor is to always maintain the house at a comfortable ambiant temperature, Thus Timing it right to come on/off is key combined with good thermostats .

No3. As your goal is to Maintain that temp its so important that people understand things like leaving a window open in a room will destroy this maintaining , and the air temp will take a good while to heat up again in said room.

No4. A draught lobby is a huge plus with underfloor this ensures evertime you open the front door the heat isnt dumped and your back to square 1.

I can think of loads of others but a lot is dependant on the house as i said insulation etc. As for constantly leaving it on , that is house dependant too, if the house is well insulated once the slab is heated once in the day , the heating could shut off and llow the slab to release this heat throughout the day.

PaulKK

Thanks for that, would you suggest then for example, to have it on for say 1 hour in the morning and maybe 2/3 hours in the evening and allow the temperature built up in the slab to maintain room temperature for the rest of the evening?

I realise that the system is not as responsive as traditional rads, and that droughts/leaving external doors/windows open are a disaster for UFH.

The house is very well insulated, ICF with high quality hardwood double glazing. The air tightness would be quite good, there are no wall vents installed so there should be no heat loss in that respect.

BryanF

PaulKK wrote: »

Thanks for that, would you suggest then for example, to have it on for say 1 hour in the morning and maybe 2/3 hours in the evening and allow the temperature built up in the slab to maintain room temperature for the rest of the evening?

I realise that the system is not as responsive as traditional rads, and that droughts/leaving external doors/windows open are a disaster for UFH.

The house is very well insulated, ICF with high quality hardwood double glazing. The air tightness would be quite good, there are no wall vents installed so there should be no heat loss in that respect.

paul im dealing with several existing UFH homes at the moment where the clients are well pissed off paying 2,3,4g a year..
there systems are set-up just like yours with the exception of you having icf, which is probably better from an insulation perspective, but answer me this:

1. has your architect removed all the thermal bridges (and please don't say your builder had a chat with the window installer) this includes particularly the floor and threshold details, windows perforations, socket boxes, first floor slab etc
2. has your air-tightness specialist and architect agreed/set a very low target for good mvhr efficiency? this includes window door details, wraping the first floor slab, roof/ dormer details, perforations etc.
3. has your architect or heating engineer told you that UFH should ideally be left on all the time with a set constant temp.. meaning the boiler may be clicking on and off regularly, reducing its lifespan. (this happens in a poorly insulated homes anyway) and that if you installed a buffer tank you could go with perhaps a timber log gasification boiler that could just be fired up once a day..
4. did anyone give you a kwh/msq figure so that we can assess your heating requirements?
5. and hows your provisional BER looking?
6. or better yet did anyone suggest you do a phpp design calculation.
7. as a matter of interest how was your boiler sized?

Kristopherus

As I understand the opening post, the house is already built, as he is buying it.

BryanF

Kristopherus wrote: »

As I understand the opening post, the house is already built, as he is buying it.

my bad:o

paul would it be too cheeky to ask for the bills for the last heating season or two? most of what i've said in the other post can be adjusted for you as a purchaser

PaulKK

BryanF wrote: »

my bad:o

paul would it be too cheeky to ask for the bills for the last heating season or two? most of what i've said in the other post can be adjusted for you as a purchaser

I'm afraid this is my first house that I will be living in that wasn't a student house so I have no comparison to provide.

Generally the house will be vacant during the day as we both work full time, and then obviously at the weekend more heating would be required. The sitting room also has a gas fire in case a top up is needed.
The BER cert was obtained last week, however I have not recieved it yet, but I was told the other houses in the estate got good B ratings.

I appreciate my details are vague but any advice is appreciated and thanks for the replies so far.

BryanF

sorry Paul, I meant ask the seller for their gas bills.. its worth a try..

PaulKK

BryanF wrote: »

sorry Paul, I meant ask the seller for their gas bills.. its worth a try..

Ah got you now Bryan, cheers. House has been vacant a good while and a certain organisation are selling it, so I might ask the neighbours if I can bring it up discreetly

Outkast_IRE

PaulKK wrote: »

Ah got you now Bryan, cheers. House has been vacant a good while and a certain organisation are selling it, so I might ask the neighbours if I can bring it up discreetly

ya thats the best option , as for running it for an hour in the morning , i dont think you will get away with that little run time ,

it all depends on the house, i would be looking initally at a run time of a few hours in the morning obviously for example if you were getting up at 7am i would like to try the heating on from 4-7am or 5-8am and use that as a base point along with another time of maybe 6-8 or 6-9 in the evening and see if that is enough of too little and work it from there.

BryanF

Paul
what the external wall surface area like? and is it a dormer?

the reason i ask is - where UFH is concerned, if these homes were built mid-boom you may want to consider EWI & changing windows etc in the next few years. and from my experience, this is a hard place to be if the house has lots of external surface area:(. also is there an area that could be put aside for a buffer tank preferably next to the boiler/connections for the UFH (same size as a modern hot water cylinder) - so that in the future you will have considered what internal alterations are required if you need an alternative boiler to oil or gas

PaulKK

BryanF wrote: »

Paul
what the external wall surface area like? and is it a dormer?

Nope its a standard 2 storey, there is also scope to go into the attic, some of the houses in the estate had this converted with dormer windows and were sold as 5 bed 3 storeys.

The external wall surface area, I am not too sure.. it has a half brick and half render finish.

BryanF wrote: »

the reason i ask is - where UFH is concerned, if these homes were built mid-boom you may want to consider EWI & changing windows etc in the next few years. and from my experience, this is a hard place to be if the house has lots of external surface area:(.

The build date would be approx late 2007.. apologies for my ignorance but what is EWI etc? One thing I will say is that these houses were not slapped up, the fit and finish is very good and top quality fittings were used, so I don't think it is a typical low quality boom estate.

BryanF wrote: »

also is there an area that could be put aside for a buffer tank preferably next to the boiler/connections for the UFH (same size as a modern hot water cylinder) - so that in the future you will have considered what internal alterations are required if you need an alternative boiler to oil or gas

Yep, there is scope for this beside the boiler, there is a tank in there already and to be honest I'm not sure if its a buffer tank or not as there is no hot press in the house. I took a load of pictures of the boiler and I'm raging I didn't take one of the zoning and tank!

Outkast_IRE wrote: »

it all depends on the house, i would be looking initally at a run time of a few hours in the morning obviously for example if you were getting up at 7am i would like to try the heating on from 4-7am or 5-8am and use that as a base point along with another time of maybe 6-8 or 6-9 in the evening and see if that is enough of too little and work it from there.

Ok cool, but the best option is still say a few hours on and then off until a couple of hours before its needed again? I must say I was dubious about the 24 hour running myself.


Thanks again for the advice it is extremely helpful.

bruschi

PaulKK wrote: »

Ok cool, but the best option is still say a few hours on and then off until a couple of hours before its needed again? I must say I was dubious about the 24 hour running myself.


Thanks again for the advice it is extremely helpful.

I have UFH, but with geothermal and a heat pump, so its electricity bills I get for it. it didnt work out that expensive to be honest over an annual bill (only slightly higher than the ESB average). but I personally wouldnt advise having it switched off. I have it set that the heat it produces when we are generally not there reduces by 3-4 degrees, but that it will always have a constant running

PaulKK

bruschi wrote: »

I have UFH, but with geothermal and a heat pump, so its electricity bills I get for it. it didnt work out that expensive to be honest over an annual bill (only slightly higher than the ESB average). but I personally wouldnt advise having it switched off. I have it set that the heat it produces when we are generally not there reduces by 3-4 degrees, but that it will always have a constant running

That's something I would be interested in trying.. how do you manage this may I ask?

Each room seems to be individually controlled by a thermostat in my house, is there any way to set this to be controlled by a timer and have it at say 15 or 16 the rest of the time?

I presume the idea then is that the heating only kicks in for maybe 5 or 10 mins an hour to maintain this lower temperature during the day.

bruschi

PaulKK wrote: »

That's something I would be interested in trying.. how do you manage this may I ask?

Each room seems to be individually controlled by a thermostat in my house, is there any way to set this to be controlled by a timer and have it at say 15 or 16 the rest of the time?

I presume the idea then is that the heating only kicks in for maybe 5 or 10 mins an hour to maintain this lower temperature during the day.

no, it is always on at a constant, that there is no extra boosting. in its very simplest terms, if the cold leaves the concrete screed, it takes longer to get back up to the desired temperature, and then will have to work harder to pump the heat through. so if you have it on the whole time, even at a reduced heat, it doesnt have to work as hard to raise the temperature then.

Each system will be different, so the best thing you could do is find out what heat pump (your central unit that has the overall controls) is used.

On my own one, the way it is set up is that each bedroom and living room has its own thermostat to increase/decrease temperature which is throughout the house. This overall temperature goes to the open areas and toilets, and this is controlled at my central unit.

So if I have my central unit at say 21 degrees, the bedrooms thermostat can make this go slightly up, or slightly down. In the bedrooms that arent being used, I'd have it down, and the main ones at a central point.

It is this overall heating constant that is adjusted by the couple of degrees, which I can do in the control panel of the central unit.

Hope this explains it a bit for you. It will also depend on the thermostat unit in each room if you can use a timer on it. some digital ones will have it, some wont, and then some are just simple dials that change the temperature.

If you want to PM me if you need more details or if you dont understand what I mean above feel free to do so.

PaulKK

Thank you bruschi for the detailed explanation I think I understand alright.

I only have analog thermostats as opposed to digital ones, maybe I will look into upgrading these at some point.

cokecans

You could use this SEAI calculator to give a rough estimate:

Domestic_Heating_Cost_and_Carbon_Comparison_Tool_October_2011_xls.xls

Outkast_IRE

bruschi wrote: »

no, it is always on at a constant, that there is no extra boosting. in its very simplest terms, if the cold leaves the concrete screed, it takes longer to get back up to the desired temperature, and then will have to work harder to pump the heat through. so if you have it on the whole time, even at a reduced heat, it doesnt have to work as hard to raise the temperature then.

Each system will be different, so the best thing you could do is find out what heat pump (your central unit that has the overall controls) is used.

On my own one, the way it is set up is that each bedroom and living room has its own thermostat to increase/decrease temperature which is throughout the house. This overall temperature goes to the open areas and toilets, and this is controlled at my central unit.

So if I have my central unit at say 21 degrees, the bedrooms thermostat can make this go slightly up, or slightly down. In the bedrooms that arent being used, I'd have it down, and the main ones at a central point.

It is this overall heating constant that is adjusted by the couple of degrees, which I can do in the control panel of the central unit.

Hope this explains it a bit for you. It will also depend on the thermostat unit in each room if you can use a timer on it. some digital ones will have it, some wont, and then some are just simple dials that change the temperature.

If you want to PM me if you need more details or if you dont understand what I mean above feel free to do so.

Sounds like a nice setup you have going on there, its very similar to what i would reccomend when installing these systems but most people dont want to shell out for all the extra controls and dont really hear you when you talk about saving money in the long run.

bruschi

Outkast_IRE wrote: »

Sounds like a nice setup you have going on there, its very similar to what i would reccomend when installing these systems but most people dont want to shell out for all the extra controls and dont really hear you when you talk about saving money in the long run.

yeah its true. I know of people building, and they prefer to have money spent on things you see rather than future proofing the house. our ESB last year was cheaper than a lot of people I know, and that has our heating included, whereas you could easily shell out 1-2k a year on oil and coal etc on top of electricity. all about knowing what is the best situation for each individual house and family.