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Need ASHP advice for old (1882) stable development in SW Scotland - where do I begin?

Alan · 2024-01-19T22:47:10Z

If I get this posted in the right place I'm calling it a win, I'm in SW Scotland. I'm nearing the end of an old stable development built in 1882, 300sqm in all, split into two main spaces and a room, this adds to existing house, biggest space is 174sqm, and I'm looking at an ASHP to heat it...I think. 100mm PIR walls, ceiling and floor, new double glazing etc, will have a 10kw multifuel burner as back up, eventually this space will knock through to existing house which will then be insulted in the same way. I got one quote, £17k not including radiators which had me wondering if Elton John was playing during the installation. I'm very much at the beginning of the ASHP curve, my focus has been getting things finished, I'm after any advice at all really.

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Air Source Heat Pumps (ASHPs)

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 4 years ago

Posts: 1009

22/01/2024 11:05 pm

@heacol I find that faintly patronising Brendon when you have no idea what my scop is.

House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60

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Alan

(@alan22)

Eminent Member Member

Joined: 2 years ago

Posts: 29

Topic starter 22/01/2024 11:09 pm

Posted by: @bontwoody

↑

@alan22 Good experimental skills Alan 😆 What is the floor area of the barn?

100sqm, two room spaces connected by a wide corridor with a room in the middle.

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Alan

(@alan22)

Eminent Member Member

Joined: 2 years ago

Posts: 29

Topic starter 22/01/2024 11:28 pm

Brendon, I'm trying to work out how I access your experience, you are three and a half hours from me by car, do you go that far?

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 4 years ago

Posts: 1009

23/01/2024 10:45 am

@alan22 So given you have a 100mm kingspan envelope to the building, just using the very simplest estimator from heat geek.

I would imagine you wont be far from 20-30 W/m2. Multiply that by 100m2 and you get a heat loss of about 2-3 kW. Its very basic and I would advise that you might use some of the other methods to double check but if its -3C outside and your electric fan heater can heat your stable then you have verified that it isnt more than 3kW. My old stone cottage is about the same floorspace and runs nicely on a 5kW Samsung so I doubt that its far out. All heat loss estimates are less than perfect (thats why they are estimates!) but having experimental proof of the heat loss is gold dust. Keep up with the experimentation 🙂

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HughF

(@hughf)

Honorable Member Member

Joined: 4 years ago

Posts: 489

23/01/2024 11:02 am

@heacol SCOP only needs to be 2.8 to beat gas - and that's what it's all about... not costing more than a gas boiler.

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.

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bontwoody

(@bontwoody)

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Joined: 4 years ago

Posts: 1009

23/01/2024 11:24 am

@hughf Its also not that difficult to get SCOPs of greater than 5 in a well insulated new build with free radiator choice and low flow temperatures. (Ive done it) The challenge is trying to get a good SCOP in an old retrofit whilst not busting the bank and causing mayhem.

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HughF

(@hughf)

Honorable Member Member

Joined: 4 years ago

Posts: 489

23/01/2024 11:37 am

@bontwoody indeed, although I would question the viability of having radiators that don't feel warm to the touch, from a homeowner acceptance perspective. That would leave you running at around 37 degrees...

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.

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 4 years ago

Posts: 1009

23/01/2024 12:04 pm

@hughf I guess you just have to think of them as under floor heating on the wall! 😉

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HughF

(@hughf)

Honorable Member Member

Joined: 4 years ago

Posts: 489

23/01/2024 12:07 pm

Posted by: @bontwoody

↑

@hughf I guess you just have to think of them as under floor heating on the wall! 😉

good luck convincing anyone that their radiators will never be warm to the touch... That's why I stick with 38.5 as the hot end of my WC curve - it's just easier that way. Also, my fan coils switch off below 37 ish degrees, flow temperature switch inside.

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.

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Alan

(@alan22)

Eminent Member Member

Joined: 2 years ago

Posts: 29

Topic starter 23/01/2024 8:14 pm

Posted by: @bontwoody

↑

@alan22 So given you have a 100mm kingspan envelope to the building, just using the very simplest estimator from heat geek.

-- Attachment is not available --

I would imagine you wont be far from 20-30 W/m2. Multiply that by 100m2 and you get a heat loss of about 2-3 kW. Its very basic and I would advise that you might use some of the other methods to double check but if its -3C outside and your electric fan heater can heat your stable then you have verified that it isnt more than 3kW. My old stone cottage is about the same floorspace and runs nicely on a 5kW Samsung so I doubt that its far out. All heat loss estimates are less than perfect (thats why they are estimates!) but having experimental proof of the heat loss is gold dust. Keep up with the experimentation 🙂

The electric heater experiment failed miserably, the thermometer didn't move in 2 hours, it's a small heater and the ceiling is 4m in a 15x5m room, in two hours the heat didn't reach the other end! it was just a silly non scientific experiment but it gives me a feel for KW's maybe, essentially the space being big needs a few hours to heat up, my hope is that an ASHP keeping a low temperature then maintains it, looking on the bright side I think an ASHP is the perfect way to heat it, I think I'm going to need very, very big radiators.

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Alan

(@alan22)

Eminent Member Member

Joined: 2 years ago

Posts: 29

Topic starter 23/01/2024 8:21 pm

Posted by: @hughf

↑

Posted by: @bontwoody

↑

@hughf I guess you just have to think of them as under floor heating on the wall! 😉

good luck convincing anyone that their radiators will never be warm to the touch... That's why I stick with 38.5 as the hot end of my WC curve - it's just easier that way. Also, my fan coils switch off below 37 ish degrees, flow temperature switch inside.

It's a fair point, I'm used to coming in from work and lighting a multi fuel burner and feeling skin burn, the idea of tepid radiators is not exactly appealing but.....I have a friend with underfloor heating, when you go into his house it;s the same temperature all the time, never gets hot exactly but it never feels particularly cold, it's a different sort of environment, one I'm only starting to understand, how you turn that up a bit when it's cold though...

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Brendon Uys

(@heacol)

Prominent Member Contributor

Joined: 5 years ago

Posts: 415

23/01/2024 8:25 pm

@bontwoody it is easy to get SPF's above 5 in ANY house, including old draughty solid stone buildings, I have hundreds to prove it. Get the design and operation right, and it will work. Get it wrong, like most, and it will not. Simple.

If you follow the manufacturer's recommendations, you are 99% guaranteed to get it wrong.

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