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Seal the Deal: Don't Let Your Heat Pump Leak Energy

David Smith · 2024-08-13T11:05:37Z

In recent years, one critical aspect of air source heat pump installations has often been neglected: external pipe insulation. As the demand for energy efficiency increases, the importance of using the best possible external insulation for ASHPs cannot be overstated. So let's delve into why high-quality external insulation is essential and what characteristics make insulation effective and reliable. Water Resistance Moisture can drastically reduce the thermal efficiency of insulation. When insulation becomes wet, its thermal conductivity increases, leading to energy loss and the deterioration of the material. Therefore, insulation with high water diffusion resistance is crucial. Additionally, sealing all joints and gaps is essential to prevent water ingress through capillary action. If the insulation is not protected and every joint and gap is not sealed correctly, efficiency is seriously compromised. Optimal Insulation Efficiency The primary function of insulation is to minimise thermal loss. This requires materials that fit well without being compressed, as squeezing insulation into tight spaces can reduce its effectiveness and cause thermal bridging. Ensuring that the insulation is properly clipped on the outside and sealed around pipes and fixtures is vital to maintaining efficiency and preventing moisture penetration. The issue is exacerbated when using standard plastic trunking designed for smaller air conditioning pipework. For instance, the typical 140mm trunking hides multiple issues because the two insulated pipes have to be squeezed in to fit, reducing insulation efficiency and potentially causing thermal crossover that can affect the heat pump’s operation. What's more, installers using thinner wall thicknesses than the 19mm standard compromise insulation further. Since it is impossible to clip on the outside of the insulation correctly, many installers resort to clipping the pipework first and then insulating it, using tie wraps to hold the insulation together around the clips. This method leaves gaps and makes it difficult to ensure a consistent seal, reducing the system’s overall efficiency. UV Protection and Air Contamination Resistance External materials are subject to degradation from UV rays. Insulation must have built-in UV protection to withstand outdoor conditions over time. Furthermore, in areas with air pollution, such as near factories or busy roads, insulation needs additional protection to prevent contamination that can impair its function. This level of protection should be present out of the box, as adding UV protection during installation in varying weather conditions is impractical and often ineffective. Through-Wall Sleeving When pipes pass through walls, sleeving protects the insulation from damage and prevents pests from compromising the system. Proper sleeving and sealing ensure that the integrity of the insulation is maintained, thereby preserving the overall energy efficiency of the building. Standard shrouds on plastic trunking are often not large enough to cover two separate insulated pipes, leading many installers to use a 4-inch core and soil pipe. This approach is problematic as it is not waterproof, allowing moisture to enter through joints and gaps, creating a microenvironment that can never dry out, further degrading the insulation. All-Weather Installation Capability Professional installers often work in varied weather conditions. Therefore, insulation products must be easy to install regardless of the weather. This requirement ensures that installations are not delayed and that the insulation performs as expected in both extreme heat and cold. Products must be designed for general weather conditions to help the professional installer complete the job efficiently and effectively. Sealing of Joints and Gaps To maintain efficiency, all joints and gaps must be meticulously sealed. Proper sealing prevents thermal leaks and moisture ingress, which can undermine the insulation’s performance and longevity. The insulation products need to support easy sealing, ensuring that every joint and gap is closed, including those through the wall. If plastic trunking large enough to house the insulation correctly were available, it would need to feature high water resistance, be sealed on all joints, and clipped externally. Ease of Maintenance Regular maintenance is essential for sustaining the efficiency of ASHPs. This includes inspecting and maintaining external insulation and ensuring that all joints remain sealed. High-quality insulation products should facilitate easy maintenance, helping to ensure long-term performance and reliability. Annual services on heat pumps and systems must include checking the external insulation and all joints to maintain and protect the system’s efficiency and all external products. Closing Thoughts Investing in high-quality external insulation for air source heat pumps is crucial for maximising energy efficiency and protecting the system from env...

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Insulation

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Mars

(@editor)

Illustrious Member Admin

Joined: 6 years ago

Posts: 4959

13/08/2024 9:50 pm

@johnmo not entirely sure I agree. Heat loss is still heat loss, regardless of whether the pipes are inside a heated environment or not. Insulating the pipes ensures that the heat is used more effectively where it’s needed, especially in a low and slow single zone system. Why would I want to heat my plant room? The goal should be to maximise efficiency, and pipe insulation is one way to help with that.

Of course, different situations might warrant different approaches, so I appreciate the perspective and will check out what Heat Geek has to say on the matter too.

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Anonymous 5011

(@Anonymous 5011)

Joined: 4 years ago

Posts: 562

14/08/2024 8:02 am

Posted by: @editor

↑

@johnmo not entirely sure I agree. Heat loss is still heat loss, regardless of whether the pipes are inside a heated environment or not. Insulating the pipes ensures that the heat is used more effectively where it’s needed, especially in a low and slow single zone system. Why would I want to heat my plant room? The goal should be to maximise efficiency, and pipe insulation is one way to help with that.
Of course, different situations might warrant different approaches, so I appreciate the perspective and will check out what Heat Geek has to say on the matter too.

Heat loss is still heat loss, - not entirely correct, if within the thermal envelope it either contributes to the heat emitter surface area via the pipe surface area, and or balances the hot and cooler areas (voids etc) so heat doesn't migrate away from area where the radiator is.
Insulate DHW duty pipes, as these would heat the house in summer - not good
It's a heat geek video on YouTube.

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 5 years ago

Posts: 1062

18/08/2024 12:19 pm

@jamespa I bought a pair of these for my anti freeze valves.
-- Attachment is not available --
https://www.bes.co.uk/primary-pro-insulation-for-28mm-anti-freeze-valve-26215/?srsltid=AfmBOoorh-4WIzAjeoCU76_wv1E1cCJNuh4sRi8EoTD1OWIHmSIGqPbN

House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
10kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60

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Rod

(@rod)

Eminent Member Member

Joined: 4 years ago

Posts: 24

10/10/2024 10:49 am

Any recommendations on reasonably priced exterior insulation or alternate methods to insulate - e.g. boxing in the exterior pipes and using something else to insulate other than foam? I have about 20m of pipe and am seeing prices of £17 per meter so a £350 cost. My installers used standard grey foam interior pipe insulation on the outside pipes, I didn't know enough to challenge them and it's quickly degraded.

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 5 years ago

Posts: 1062

10/10/2024 12:07 pm

@rod 28mm Primary Pro is just under £10 per metre (ex vat) at BES, Rod

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Rod

(@rod)

Eminent Member Member

Joined: 4 years ago

Posts: 24

10/10/2024 2:07 pm

Many thanks - that is a saving, but still seems pretty high! Has anyone found inexpensive solutions to exterior insulation where there is the ability to cheaply box-in the pipework over whatever is insulating them?

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 5 years ago

Posts: 1062

10/10/2024 2:14 pm

@rod Well as long as you are boxing the pipes in, I suppose a closed cell expanding foam might work well. Dont use an open cell one though, I tried that in my early heat pump years and when I came to remove it, the whole thing was full of water 😲

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AllyFish

(@allyfish)

Prominent Member Contributor

Joined: 4 years ago

Posts: 520

03/02/2025 12:07 pm

Weekend upgrade, Primary Pro done properly, unlike my installer’s attempt. Less heating the street hopefully 😉

👍

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seatonian

(@seatonian)

Joined: 1 year ago

Posts: 1

12/07/2025 2:45 pm

Hi - fyi - there's a dead image link in the 'Optimal Insulation Efficiency' section. (hopefully tagging @editor)

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Mars

(@editor)

Illustrious Member Admin

Joined: 6 years ago

Posts: 4959

25/09/2025 1:30 pm

Game time!

Here’s the trunking that hides our wiring, heat pump flow & return pipes. What do you reckon is waiting under the cover?

Professionally lagged to perfection?
A few rough edges but nothing major?
Full-blown shocker?

Place your bets before I lift the lid… 👀

🤠

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 5 years ago

Posts: 1062

25/09/2025 1:51 pm

@editor I'll go with shocker 😁

😂

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Toodles

(@toodles)

Famed Member Contributor

Joined: 4 years ago

Posts: 3043

25/09/2025 2:23 pm

@editor In light of the previous postings on the matter, I think Shocking is the nearest but may lack true strength to describe the magnitude of the real situation! Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

👍

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