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Insulation Failure

 
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Air Source Heat Pumps (ASHPs)
Last Post by David Smith 36 minutes ago
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 L8Again
(@l8again)
Trusted Member Member
Joined: 5 months ago
Posts: 29
Topic starter 01/06/2026 9:30 am  

@david-s Thank you. That is very helpful. Do you have a link to the joint covers?



   
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 David Smith
(@david-s)
Eminent Member Contributor
Joined: 2 years ago
Posts: 20
01/06/2026 9:34 am  

 

From these photos, it is obvious that the joints have not been sealed to MIs ( see attached Link to PDF ) 

All materials expand and contract; it is important to not only bond. Seal and Cap as advised, but to allso use the  right amount advised ( one tube of Bond & Seal to 3 lengths of 28mm , if a bigger size than more needed)

 

Last year, we manufactured over 1.8 million insulation lengths in the six years since its launch. Our guidance has always been to form correct joints and ensure enough Bond & Seal is left to seal the sleeve through the wall, typically three tubes for every three lengths of 28mm insulation.

Based on this guidance, approximately 533,000 tubes of Bond & Seal should have been used alongside the insulation supplied. However, we identified a shortfall of around 290,000 tubes. This highlighted that joining can be time-consuming and messy for some installers, which led us to develop additional solutions.

As a result, we introduced joint covers for straight runs and 90° bends. These not only speed up installation but can also be used as a repair solution for issues such as those shown in the images in this post.

 

 


Creator of Primary Pro and Condensate Pro


   
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 David Smith
(@david-s)
Eminent Member Contributor
Joined: 2 years ago
Posts: 20
01/06/2026 9:36 am  

@l8again 


This post was modified 41 minutes ago by Mars

Creator of Primary Pro and Condensate Pro


   
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 David Smith
(@david-s)
Eminent Member Contributor
Joined: 2 years ago
Posts: 20
01/06/2026 9:50 am  

@transparent 

All insulation expands and contracts 

If not sealed correctly, it can leave a gap

The insulation you mention will have the same issues, and if sealed with tape, this can stretch, and the gaps is no visibel 

Also, check the thickness and conductivity, as all insulation is not the same 

Also, check that the insulation has a high water diffusion resistance 

shrinking

 


Creator of Primary Pro and Condensate Pro


   
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 David Smith
(@david-s)
Eminent Member Contributor
Joined: 2 years ago
Posts: 20
01/06/2026 10:01 am  

@l8again 

That's not right, if the MIs are followed and the correct amount of bond and seal this will seal the gaps 

Also, the manufacturers don't advise one tube to one length; they advise one tube to three lengths of 28mm 

Your installer is right about it's easy to rectify, just use the joint covers and add when every length of insulation needed ( making sire is fully bonded and sealed as advised 

Primary Pro How to Apply Bond & Seal August 2025.pdf

 


Creator of Primary Pro and Condensate Pro


   
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