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What is the best approach for primaries in heat pump installations?

Thermostats, Volumisers, Buffer Tanks, TRVs, Pumps, Piping, Valves, Radiators & Controls

Last Post by Judith 2 years ago

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AdamK

(@adamk)

Reputable Member Member

Joined: 2 years ago

Posts: 226

Topic starter 17/03/2025 11:02 am [#2202]

Was speaking to my builder this morning and he was saying about putting the primaries in the cavity when he rebuilds a rear wall, think hes trying to eliminate the need for trunking/insulation on the rear of the house. Im not sure about this as although there will be fibre glass insulation in the wall and themalite type block work internally im not sure it would be as good as using the zero loss insulation and trunking?

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JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 4 years ago

Posts: 5561

17/03/2025 5:54 pm

Personally I would want them inside the heated envelope if possible. Then the heat loss is useful during the heating season. Obviously its a bit situation dependent. Inside the cavity (preferably near the inner leaf) is, I guess, better than outside!

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Judith

(@judith)

Prominent Member Member

Joined: 3 years ago

Posts: 554

18/03/2025 9:49 pm

Posted by: @adamk

↑

…….. block work internally im not sure it would be as good as using the zero loss insulation and trunking?

Don't forget there is no such thing as zero loss insulation and trunking! So inside the envelope is best everything else looses some heat to the external world rather than heat the house.

Don’t let your builder run the primary pipes in the space between the insulation and the external wall, it’s nearly as bad as running them uninsulated outside! Under the insulation in specially carved channels is not too bad

2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with SCOP >4) open system operating on WC

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