@mcwatson1974 11m of bifolds, there’s your problem right there….
did you have a blower door test done on completion? It might have loads of insulation it but it might also leak like a sieve. What’s the construction method?
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
@hughf In that case, I don't like heat loss!! 😆 House was built only 5 years ago and insulated to death but I do have about 11 metres of bifolds going across the rear of the house and I don't think the fitting of them was great so think a lot of heat does escape out of them.
I was hoping someone was going to say, click this, or switch that, and your ashp will mellow when you get to your 21c! Ho hum. Never did like the winter!
I suspect that your 11 metres of bifold doors could turn out to be an expensive luxury.
@mcwatson1974 11m of bifolds, there’s your problem right there….
did you have a blower door test done on completion? It might have loads of insulation it but it might also leak like a sieve. What’s the construction method?
No, didn't have a blower door test and in hindsight, the company that installed the bi folds were toilet. I know I have heat loss through them as the doors don't fully seal and are poorly installed. But the company has gone bust now, not surprisingly. Build method is block and beam floors. UFH on both floors and throughout whole house.
@mcwatson1974 were those doors fitted when the heat loss survey was done or did you add them in afterwards? Your house must be incredibly efficient otherwise if you have that much window area and less than 7kW heat loss over more than 250 sq m. I wonder if bridging was considered when your installer did the heat loss calcs, since I know the better the insulation in general, the more effect the bridging has, and as @hughf says the ventilation becomes a big factor too, although I suspect this was tested if you had an EPC done anyway.
@oswiu I would say the info may either be misleading, or irrelevant. I say this because the heat loss info was defined by the company providing the heating system including the Ecodan, UFH and all the gubbings that go with that. And it was defined from the build plans. The bifolds and all glass stuff was provided by a different company, and not installed perfectly. So even if the heating company said the heat loss was x, the actual loss is probably y being the bi folds are installed far from perfectly.
@oswiu I would say the info may either be misleading, or irrelevant. I say this because the heat loss info was defined by the company providing the heating system including the Ecodan, UFH and all the gubbings that go with that. And it was defined from the build plans. The bifolds and all glass stuff was provided by a different company, and not installed perfectly. So even if the heating company said the heat loss was x, the actual loss is probably y being the bi folds are installed far from perfectly.
The heat loss calculations should have been obtained from a detailed measurements taken at your home, not from plans that may or may not have included the bifold doors. I would suggest that you download the MCS or other heat loss spreadsheet and carry out your own heat loss calculations.
Since you say that your installer may not have been too friendly to red indians, his heat loss calculations may have been driven by the fact that he had an 8kW heat pump that he wanted to offload.
This post was modified 2 years ago 2 times by Derek M
The heat loss calculations should have been obtained from a detailed measurements taken at your home, not from plans that may or may not have included the bifold doors. I would suggest that you download the MCS or other heat loss spreadsheet and carry out your own heat loss calculations.
Since you say that your installer may not have been too friendly to red indians, his heat loss calculations may have been driven by the fact that he had an 8kW heat pump that he wanted to offload.
The info I shared earlier was in fact from the proposed installation. I have just found the Compliance report which is a 50 page report listed an astounding amount of facts and figures, and measurements done post the build that I couldn't possibly understand. I had forgotten I even had it!
It has Thermal Bridging reports, Sap worksheets, Fabric efficiency info and god knows how much info. Ultimately, it led to these ratings!
My memory is rubbish but after the build had finished as far as I know so with the bifolds. The bit below is the heat loss section. Dunno what it means though.
My memory is rubbish but after the build had finished as far as I know so with the bifolds. The bit below is the heat loss section. Dunno what it means though.
Let me explain the heat loss sheet.
The Net Area (A) should relate to the area from measurements taken.
The U-value defines how well building materials insulate. It is a measure of how many Watts of energy will leak through 1 square metre of the material with a difference in temperature from one side to the other of 1C.
A x U indicates how many Watts of energy can be expected to leak through that portion of your home with a temperature difference of 1C.
If one totals all the A x U values for your home it comes to almost 156.2W. If this is now multiplied by the standard temperature difference normally used (21C indoors and -2C outdoors) = 23C, the total calculated heat loss would be approximately 3592W. A 8kW heat should therefore be more than adequate to supply this heat loss and also hot water requirements.
I therefore suggest that you check the installers measurements and also the U-values used, particularly those for the bifold doors.
I suspect that the vertical rectangular object, which appears to be inside black insulation, with several pipes connected, is in fact a buffer tank or low loss header. It is often the case that these are a prime source of efficiency problems in ASHP systems.
If one totals all the A x U values for your home it comes to almost 156.2W. If this is now multiplied by the standard temperature difference normally used (21C indoors and -2C outdoors) = 23C, the total calculated heat loss would be approximately 3592W. A 8kW heat should therefore be more than adequate to supply this heat loss and also hot water requirements.
This is what I came to, but then I couldn't understand how there could be 3.3kW of ventilation losses in a house that's only 5 years old, since OP said the design heat loss was 6.94kW in this post https://renewableheatinghub.co.uk/forums/postid/12712. I thought houses had to be fairly air tight nowadays.
If there wasn't a blower test done, then I reckon this is solved. 7kW quoted heat loss with an 8kW heat pump with temperatures colder than designed for and a huge number of doors leaking more than they should so pushing up the heat loss. Those factors combined could easily mean the heat loss at the moment is more than the heat pump can output.
@mcwatson1974 I suggest you try to get those doors draught proofed and maybe add blinds or curtains to keep the heat in a bit more at night if you don't have them already.
It won't add up to much additional loss probably, but how long is your piperun outdoors to the heat pump? How well is it insulated? Are there any exposed metal spots?
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