Underfloor heating running costs - help

Re Rahman and Ennisjim.
I am looking at the same type of system and was considering boosting the oil with solid fuel via a stove or back burner.Ennisjim you mentioned solid fuel any information you can give me on the dual design and how it works would be appreciated. Thanks and good luck in the new house.
 
Hi TomC,

500litre buffer tank is heated directly from oil boiler (Grant 15-26kW condensing indoor). Charnwood SLX45 multifuel stove drives a coil in buffer tank. Buffer tank output goes to circulation pump which feeds (i) UFH manifold (210 sq.m bungalow), (ii) 'attic' rad zone (insulating large attic and preventing from getting too cold - has a simple stat), (iii) 300litre DHW cylinder upper coil. All are on separate timers. Lower coil of DHW cylinder is heated from solar. Motorised valves on each 'circuit' allow individual control from timer controller. UFH stats/controllers are Heatmiser.

Haven't moved in yet so don't know how good this design is.

Hope this helps
 
Ennisjim,

Thanks for the information and specifications, it is very beneficial. Two last questions, how far is the stove from the 500L tank and what kind of spec is the tank, thanks a million.

Tom
 
you should use fan coil rads upstairs rather than conventional rads with an underfloor system downstairs.
 
did you hear about thieves stealing oil from the tanks it was in the galway paper the morning. unbelievable. so be on the look out.
 
Also, there's really no point in discussing heating costs without talking about your insulation. What kind of construction (concrete, timber frame etc) is your house, what kind of insulation, what kind of windows etc etc.
 
In my opinion under-floor heating is not suitable for a working couple who only occupy a house for a few hours of the day
 Especially so if they are also away at weekends. I do get requests from such people to have under-floor heating replaced by radiators.
 A conventional heating system with low water content radiators and proper controls can be far more responsive to the unpredictable Irish climate, solar gain and the lifestyle of a buildings occupants.
Renovating older property? A properly insulated solid concrete / floor slab will hold heat and be considerably warmer to the touch than the older type un-insulated solid floor.
When renovating. You do not have to install under-floor-heating to have a warmer floor.
Just ensure that the floor is insulated below the slab or timber as per recent building standards.
It is preferable to install a domestic heating system that you can afford to run.
 

Hi Plumber, You seem to be in the minority with this opinion. I've asked this question a few times and all responses seem to think underfloor (especially with new build) is the only way to go. I believe underfloor is a good method if the house is going to be occupied every day in really long cold winters but, like yourself believe it's not suited to Irish weather that changes so much.

Can you specify why exactly some people are unhappy with their UFH systems and replaceing it with radiators... UFH not working properly, too expensive to run, too slow response time, difficult to manage for different parts of the house, hard to predict when the house will be occupied, etc.?
 

Its funny that you didnt include in that list the possibly most significant reason for the switch from UFH.... the unsuitability of the dwelling construction.....
people are quick to blame the UFH for the slow responsiveness, but in reality the generated heat is pising out of their houses through bad construction detailing or bad fixtures in opes etc.
UFH works perfectly in well built, airtight dwellings with Heat recovery Systems.
I have often stated that i wouldnt dream about incorporating UFH into a conventionally built 310 cavity wall house with passive ventilation. There are way too many chances of having bad construction detailing to risk it.
 
Yes Syd, I suppose there are a lot of variables. However let's assume the house is well constructed, airtight, etc. For a couple who don't be in the house during the day, then is UFH still a good option or just use radiators when required?

It seems to me there is a certain inefficiency with UFH when you consider the house may be unoccupied during the day and/or weekends, nights out, spring and autumn days when the heating simply isn't required but you don't know beforehand etc?

Take a couple who decide to head off for a weekend. The UFH must be left on over the weekend (at a low rate but it's still on). Also in autumn and spring the system must be kept ticking over for the odd cold day.

Anyway good to hear different ideas on this as I may yet go for UFH!! - playing devils advocate!!
 
UFH only has slow responsiveness if the standard of construction determines it.
If there is high thermal mass to be heated before the ambient air, ie a thick concrete slab and plastered 100 dense concrete block inner leafs, then the responsiveness is going to be slow. However if there is only say 65mm or less (easi-screed etc) screed and the inner walls are SIP panels or ICF panels, then the heat is reflected immediately back into the ambient air.

Personally i believe only internal walls should be designed as the thermal mass 'emitters'.... they should gain passive solar heat in winter, and be protected from gaining solar heat in summer.... and because they are located within the insulation envelope they shouldnt loose heat at the same rate as your external walls.
 
27th November - put in 1000 litres of oil into our tank. Empty on the 8th of january. So it was all used up in 6 weeks...

Underfloor heating on both floors (precast floor), buffer tank, oil condenser, plenty of drafts (have to seal a few more up at the wkd.) But i think i will be switching to the timer now. It was on 24/7 as recommended by the plumber

Size of house is a 3000sq ft dormer. 40mm insulation with plasterboard on the inside of all external walls. 100 xatherm in the pitch between rafters. 300mm fibreglass top of the attic.
 
I would go with UFH again as I think its is a very comfortable heat. However I would put in insulated slabs as I believe that heating block walls is a waste.

If I turn on my Rad in the upstairs it becomes nice and warm but the minute I switch off the rads the room loses 2/3 degrees within a 1/2 hour. I put in Kingspan insulation and sealed around all windows.
 
Currently have underfloor installed in a 2000sq ft house on ground level. Have rads installed on the second floor which was converted.
New build and moved in almost a year ago.
Block build, 4 inches of hytherm in floor, 65 mm hytherm in walls, 8 inches of rockwool in 9 inch joices and 145mm of hytherm in rafters.
When I started underfloor I used up 1/2 tanks of oil very quickly as zones were on 24/7.
got 1000 litres of oil last april and it lasted until end of december when i was running heating on a timer.
timer heats water from 5-6, then underfloor is on from 6-7. Comes on again from 1-3. Then from 5-7. Finally from 7.30-9.
After 7.30 boiler is usually never on as rooms have required heat so stats have turned off the boiler.
i built my house on a height so can be cold but have to say underfloor works great.
 
Plumber here again I´m sorry but but no matter what way you dress it up radiators is the most efficient way to to maintain a minimum air temperature in defined space. (given Identical build)

What certainly tips the balance in favour of radiators is responsivnes esspecially to solar gain and nights out.

UFH users are wasting energy everytime they pop down to the pub for a couple of hours. I didn´t think of that.
 

Anyone think UFH is more efficient?
 
The plumber makes a very valid point about wasting heat while down the pub for example. But I still think the comfort of the ufh far outweights this relatively minor draw back (especially when you don't get to the pub much!! ) Plus solar gain will serve to reduce the amount of time the room stat is calling for water for the ufh, so sorry if I'm missing something there, but don't see how radiators are better in that sense.
For a house that is empty alot of the time, then yes radiators would probably be cheaper for heating the house for short periods.
If the house is occupied most of the time, I'd say ufh is cheaper.
 
bobby04 said:
The plumber makes a very valid point about wasting heat while down the pub for example.
Click to expand...

Is ther not a lot of heat also wasted in the spring and autumn months when some days require heat and some don't? Doesn't the concrete slab have to be kept heated (at a low temp) even during the days when the heat is not required?

Surely UFH is for winter months only and another heat source such as a stove should also be used for spring/autumn days?
 
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