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 environmental factors. By ensuring that the insulation is water-resistant, UV-protected, easy to install in all weather conditions, and properly sealed, professionals can significantly enhance the performance and lifespan of ASHP installations. Regular maintenance further ensures that the insulation continues to function optimally, providing consistent energy savings and durability.
This article was written and provided by Primary Pro. Their bespoke insulation solutions not only maximise heat pump efficiency but also enhance the aesthetic appeal of your customers’ homes, guaranteeing a high-quality finish designed to meet the unique needs of professional installers. Primary Pro offer a comprehensive range of insulation products and tools, from various insulation sizes to innovative sealing solutions, all designed to make installations smoother and more efficient. For more information, visit their website or contact them at info@primarypro.co.uk.
Thank you @David Smith and @Mars. This is just how an “infomercial" should be; heavy on the info and clear about the vested interest for the contributor.
Good article.
Just need to maths to backup the facts stated. Optimization of the insulation thickness for different climates and flow temperature would be good. Otherwise worthless advertising.
@johnmo Primary Pro have a tonne of literature. I’ll ask @David Smith if they have a document that provides some of this info.
’Fraid I can’t agree, @johnmo.
What the article says may seem really obvious but we only need to look at the many many examples of badly finished installs to see that basics like this just aren’t front dead centre of many customers’ minds. In many ways if there’s some lagging on the pipes then “the installer must have done a thorough job, mustn’t they?”
To my mind the article is simply laying out some reasonable standards that can save a significant amount of money year on year. We often get caught up in technical rabbit holes for improving performance but the basics deserve an airing too from time to time.
@Majordennisbloodnok bang on. That was the motivation behind the article, because external insulation is often neglected and forgotten about, especially on short outside runs to the house. This is just a reminder to homeowners to raise this with their installers. Dave was kind enough to write this piece, which is not a paid or sponsored link – I just thought it would be something helpful and interesting for homeowners.
Some shoddy external insulation examples for us to gasp at.
What parts of the air source heat pump should I be insulating?
Shocking indeed, except possibly the second one. Are you certain this isn’t a pair of anti – freeze valves?
@JamesPa I bought a pair of these for my anti freeze valves.
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.
@Rod 28mm Primary Pro is just under £10 per metre (ex vat) at BES, Rod
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?
@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 😲
None
You insulate the piping, valves (not anti freeze valves) between the house and the ASHP. So from the outlet connections on the ASHP to and through the house wall.
Don’t forget the pipework inside also needs to be insulated.
There is a school of thought, that says not to bother if the pipes are inside the heated environment, especially if you are running low and slow on a single zone. See Heat Geek for more information.
@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.
Weekend upgrade, Primary Pro done properly, unlike my installer’s attempt. Less heating the street hopefully 😉
@AllyFish hopefully not to rodent taste too 😬
What make is the insulation?
Hi – fyi – there’s a dead image link in the ‘Optimal Insulation Efficiency’ section. (hopefully tagging @Mars)
Game time!
Here’s the trunking that hides our wiring, heat pump flow & return pipes. What do you reckon is waiting under the cover?
Place your bets before I lift the lid… 👀
@Mars I’ll go with shocker 😁
@Mars 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.
@Mars I’ll try and keep a little faith…
A few rough edges but nothing major
I’ll go with the standard grey open cell foam insulation you see indoors (as it’s protected from UV), with the normal 45deg cut corners. Surely they cannot get that too wrong, can they?
Interesting. I’ll let you all decide.
@Mars yep… pipe size is more of concern maybe?
Insulation can certainly be improved!
Not sure what we are looking at, other than evidence of an installer who says ‘here is a hole, let’s shove everything inio it’
Yuck, yuck and more!
Others have pointed out lots already and yet your installer claimed that he did a great job!
In order of horror level
@Majordennisbloodnok ‘ s spot of totally inadequate pipe size! Especially given the size of ashp!
then rodent ingress opportunity
then not vibration isolation nor insulation to the wall
then lack of insulation to air around the bend
A great example of putting lipstick on a pig/ whatever phrase springs to mind. Just so untidy, slapdash and shows zero understanding of what matters, but just cover it up.
@Mars now you’ve done the HG module on flows what size pipe should have been used on your ashp, and what is the maximum heat which would flow through the minuscule ones fitted?
What size are those plastic pipes Mars?
@bontwoody, not big enough (an excellent spot) 😉
Indeed. If the primaries are not big enough to carry the heat into the property, heat loss due to poor insulation is the last of your worries as there may be insufficient heat flowing in the first place.
Are you going to replace with 28mm or 35mm copper, and properly insulate?
Mars currently has a GES Caernarfon 18kW ASHP.
The data sheet (Caernarfon) shows approximately 14kW of heat energy at multiple points, including -4°C. At DT5, this would result in a mass flow rate of 2400 litres per hour. A 28mm John Guest plastic pipe can’t handle that flow rate without exceeding 300 Pa/m. Neither can the DN32 plastic underground pipework that the plastic pipe is fitted to.
So, we have a bit of a conundrum regarding the best plan of attack here. I think we will be designing a hybrid system and some clever DT work internally to get this all operating as it should. Not ideal, however, we don’t have many options here.
Also loads of water ingress… the foamy insulation is damp, which leads to more unnecessary (and completely avoidable) heat loss.
And mice or other pests given the gaps.
My first concern is that the hole through the brickwork doesn’t appear to be sleeved.
There should be an outer casing which takes the weight of the wall above.
That allows the inner pipes to move freely as they expand/contract with temperature.
To achieve that, all those existing pipes and electrical connections would need to be drawn out.
The hole should then be bored out with a TCT/Carbide core bit of an appropriate diameter for the sleeve.
You don’t need diamond bits to go through brick. It’s ‘soft’.
The hole needs to slop downwards to the outside at around 5°.
Any rain or condensation will then not enter the house.
The sort of sleeve you’d be looking for would be a 110mm orange (underground) soil pipe.
That will leave enough space for pipe insulation to continue straight through the wall.
The best person to get this right is the home-owner.
A DIY approach is preferable because you’ll care about getting it right !
We have a lot of work ahead to get this done properly. All valid points above.
I’ve been trying to find a demonstration of the pressure loss which occurs when water passes through a tight bend.
There are loads of YouTube videos which explain the phenomenon at degree level, supported by copious calculations.
However, I think the following 3-minute clip, narrated by a hands-on tradesman, is at the right level for most householders to appreciate:
In order of pressure-loss the following hierarchy gives us a good rule-of-thumb for changing the direction in which water flows through a right-angle
The order of that list can be amended, depending on the actual situation.
But I hope it provides a starting-point from which householders can assess the efficiency of the pipework in a heat-pump installation.
I’d love to take credit but I think it was @bontwoody. No disagreement with the ordering, though, @Judith.
At the risk of over-simplifying the issue…
… please explain why running TWO pipes in parallel isn’t a possible solution.
I think we are at a point where Mars doesn’t want 25 meters of driveway dug back up. Its going to be bad enough digging up each end to fix the terminations (where the pipework in the ground hasn’t been fitted/insulated properly). So we are kinda stuck with DN32 (26.5mm internal bore) plastic pipework. My inital calculations are suggesting we can get 10kW down it happily enough. Anything more than this and we are going outside of good hydronic design practices, which I am not willing to do.
As for doubling up pipework, it might give you more flow and reduce presure drops, but you are just adding to copper cost, wall space and visually it would look really poor.
I presume he needs that much!
We are yet to do a heat loss calculation, but I’m currently ‘assuming’ the house will need this and possibly a bit more.
We’ve never had a proper heat loss calculation, James. Our only one was seven years ago with a rep from GES, back when we were new to heat pumps.
The rep proposed an 18kW unit (which was the largest they had) but the story gets worse. The only document he provided calculated our actual heat loss at, wait for it, 50.6 kW.
To be clear, our heat loss is absolutely not over 50kW. This huge discrepancy perfectly encapsulates the state of the industry at the time, and I’m not convinced it’s improved much since given what we regularly seem on the forums.
Our next step is to get a correct heat loss calc, and we’re arranging for someone to visit us, and to get the process started properly.
And our heat pump is not even close to be being 18kW at sub-zero, so it’s going to be hugely insightful to see what unit we end up with.
Thats rather easy to understand, although it begs the question whether relocation is an option but Im sure @mars has already considered that!
Wow, What planet was he on (obviously one with a much colder climate!)
Im sure you don’t need me to remind you about my experience with heat loss surveys, GIGO definitely applied as I have said on many occasions.
Have you got any data which might allow you to sense check. Given the problems with pipe size etc this is going to be a more important parameter even than ‘normal’, you need to be as certain as is humanly possible.
This whole process is going to be fascinating, albeit Im sure distressing and stressful for you.
@JamesPa, 😀, and the thing that has pissed me off the most is that this is a direct result of a horribly bodged retrofix. The irony!
But the positives will be huge, as we will be able to showcase all the bad things that get slapped into systems and what to look out for and avoid, with the content being ready for next year’s mass installation season that will hopefully save loads of homeowners the heartache.
I doubt it.
The Flights to Rwanda programme was scrapped by the Government last year.
But it’s certainly worthwhile noting that Rwanda has far fewer complaints regarding heat-pump installations than Britain.
Perhaps MCS would consider a fact-finding mission to discover why.
@Transparent I think the committee might get into some very heated discussion! Toodles.