Underfloor Heating problems

paddy00

Hi all. Ive a 2500 sq ft new build. Highly insulated floors, walls, roofs. Nordan double glazing. Underfloor downstairs and rads upstairs. Oil burner and multi fuel running the lot. Cold bridges all insulated too. Two problems. One: motoring thro the oil - 1100 litres in 2 months (for the third time). Two - afew of the rooms never go past 18 degrees despite rooms temp controls all being set for 20. Heating man blaming the windows and window man saying theirs are the gold standard. is there someone like a mechanical engineer etc I can bring in to give the definitive answer so I can move on. Many thanks

bingobars

Its possible the UFH is undersized? Would you have the heat loss calculations for the spaces? Then output rating for the system. A building services engineer would look for details like this and run some numbers to find out where a possible deficiency is.

paddy00

Hey Bingobars thanks for that. I do have the sinking feeling it is undersized. Would a thermal survey of the building give me the info your talking about? I have emailed afew thermal imaging home survey companies today. Do you think they could help find the roots of the problem? Theres one company Thermal Vision who are consultant engineers. Im hoping they will be able to assist. For the rest of the cold snap it'll have to be hot whiskies:)

whizbang

Oil burner and multi fuel

Is this one unit or do you have a stove also?

I would suspect a plumbing issue. 1100 litres in 2 months is not the worst consumption in this weather, but for September/October in a well insulated house, its bad, no matter how the heat is distributed.

bingobars

paddy00 wrote: »

Hey Bingobars thanks for that. I do have the sinking feeling it is undersized. Would a thermal survey of the building give me the info your talking about? I have emailed afew thermal imaging home survey companies today. Do you think they could help find the roots of the problem? Theres one company Thermal Vision who are consultant engineers. Im hoping they will be able to assist. For the rest of the cold snap it'll have to be hot whiskies:)

Do you have an option to go back to the UFH company? The pipe gauge, flow rate and length of the system should have been designed to meet the expected losses through your buildings floor, walls, ceilings and windows. Usually they would find the losses incurred in the space at the lowest winter temperature and do all the sizing from there. They should have had the full bill of materials at their disposal for the calculation for the space. Losses for each room combined then the boiler is sized from. Boilers are spec’d at well over 100% full capacity. Maybe something like 130-150%. Boilers run with more efficientcy and longevity somewhere below full capacity. There is huge leeway in design on the side of oversizing. Even the UFH runs and the radiators should have been oversized. Undersizing of the system would be negligence. You’re not getting the efficiency nor the heat in your case by the sound of it. I’d work with the UFH fitters first to assemble the facts and determine that it is running as it was designed to. Thermal imaging companies may be more suited to builds where insulation is a problem to be addressed and you mentioned that this a highly insulated build. Finally a small consulting engineers may be a good place to get this one surveyed.

antoinolachtnai

There is something wrong with your construction or something fundamental wrong with the heating system design (i.e., heat from the system is escaping without reaching the envelope of the house). This is the same amount of energy as having four or five electric heaters running continuously for two months.

If the system were undersized it wouldn't be able to burn that amount of oil. An awful lot of heat has gone into your house in two months and it still isn't warm.

It could be oversized in certain rooms, certainly. But you can't really blame the heating guy for undersizing it if there is some construction problem that means that the house has a greater heat requirement than originally planned for.

I would get the building properly surveyed as you are proposing. This will mainly find faults in the building. It might find really big faults in heating system too.

It is really for the person responsible for the building overall to account for this. The heating system can't be considered in isolation.

paddy00

Wow lads I think Ive hit the brains trust here. What Im thinking of doing is this. I think Ill get the house surveyed by a consultant engineer. Ill get them to look at everything - heat, plumbing, insulation, walls, etc. At least this will be an independent overview. if I get the builder and plumber we'll be here til the next big snow arguing about it.

One other question is this. My plumber who did the UFH is blaming my double glazed windows saying they are transmitting either cold in or heat out. Not sure which he said. My windows although large are Nordan and are high spec. What do you think?? Is he just saying this??

antoinolachtnai

The windows themselves (and indeed all the other materials in your house) are probably fine. The question is how they are fitted and interconnected to be insulated, really.

Was there a main contractor who built this house?

You certainly need advice.

paddy00

I think you're right Antoin. Its a pity I have to go thro all this crap after spending a sizable sum on our dream house. There was a main contractor who is very reliable. The plumber was someone else I knew.

Do you think Im doing the right thing getting the independent survey first then talking to the rest?

antoinolachtnai

I would bring your problems up with the main contractor in a friendly and forthright fashion before you spend money on the engineer or surveys.

If that fails, I think your idea to get the thermal imaging survey done as part of getting general advice is a good one.

My concern is that this is going to get quite messy, because there may be significant remedial work needing to be done to bring everything to the standard that is expected for a new house. Perhaps I am being pessimistic. But I think you could be in quite a serious situation here.

You do need to think about how you know what you know. How do you know your main contractor is reliable? Just because he is a nice person and shows up on time does not mean he is necessarily a capable contractor or that all the subcontractors who worked on your project all did quality work. Equally, you say that you know that the cold bridges are all insulated. Again, how do you know this for sure?

I am not saying your problems are necessarily serious, but you do need to consider everything. Hopefully some straightforward resolutions will present themselves.

whizbang

I think there is still a major flaw in the heating system, but it may be a simple one.
If heat requirement calculated for the house, and the Airtightness testing seem ok, then look for easy solutions.

Get some sort of temperature measure, and check; Boiler water setpoint,
Boiler flow/outlet temp.
Boiler return temp.
check these temps again at manifolds, hot water cylinder, and any other accessible points on the line.

Is the circulation pump on a thermostat/timer that may have it running continuously.
Sealed / vented system, what pressures ? Are you heating your cold water storage tank by any chance..?


Any conspicuous snow free areas near the house??

Mad Benny

Hi Paddy, what was the problem?