A New Method of Insulating and Clipping Outside, Primary Pipework
The installation of a mono block air source heat pump requires the external primary pipework to be carefully insulated with pipe lagging.
There are various materials on the market used for pipe lagging but they are prone to degradation from the weather, water ingress and ultra violet light.
A common method has been to use Class O, Nitrile foam rubber pipe lagging but it has been seen to cause problems:
Acting like a sponge
Often, Nitrile pipe lagging it is not glued or sealed along the seam allowing the penetration of water.
Once water penetrates this type of lagging it acts like a sponge and transfers heat away from the pipe rather than containing heat.
Even plastic coated Class O, designed for outside, has problems being sealed properly and can end up being no better than a wet rag around heating pipes. 
Image above showing Nitrile rubber foam acting like a sponge
UV Degradation
Class O needs to painted with UV protection after installation and at regular intervals. This is rarely done and once degradation occurs it allows water penetration.
Image above showing UV and weather degradation
Tie Wraps
A common method to attach Nitrile Class O pipe lagging to pipes is to use tie wraps.
Nitrile is a closed cell material and relies on the small pockets of air within the cells to provide the installation properties. Squashing these cells with tie wraps reduces its ability to prevent heat loss.
Image showing the use of tie wraps
Tie wraps are often a clue to suggest Class O has not been sealed along the length of its seam, either with glue or a self sealing strip. Even the slightest gap of millimetres will allow water ingress via capillary action.
Pre Coated Polyethylene
Many plumbers and heating engineers are familiar with another type of foam insulation: polyethylene. It has been used inside the home for many years.
It is not as flexible as Nitrile rubber foam but has the advantage of being able to be mitred and cut neatly.
A new coating method has recently been developed by Primary-Pro enabling the pipe to be used outside. It is UV and water resistant. Along with special bonding called “bond and seal” the pipe lagging can be completely sealed eliminating any water ingress. 
Image above shows mitre joints sealed with bond and seal as well as where the pipe lagging enters the fabric of the building
Image shows that Primary-Pro is still flexible enough to be used on machine formed pipe bends
Image above shows how larger pipe lagging is used for valves
Image below showing the application of bond and seal to the mono block unit to prevent water ingress
Image above shows pipe work being supported with clips to the outside of the pipe lagging
How to Clip Pipework
It has long been good practice in the commercial heating sector to clip to the pipe lagging and not the pipe. This enables pipe lagging to be completely sealed along the length of the pipework. Polyethylene is much more rigid than Nitrile Foam Rubber and is perfect for this clipping method.
Using Polyethylene Outside
Not all polyethylene can be used outside as it is not UV and weather resistant. Even when a UV protective coating is applied with a paint brush it is likely to crack.
Primary-Pro, who also manufacture Condensate-Pro, have developed a unique technique where the required coating penetrates into the lagging.
This special coating is applied at the factory and enables heating engineers to quickly install the lagging to the pipe.
The bond and seal, unlike other types of adhesives and coatings, is able to be applied in all weather conditions and in all temperatures.
Engineers and Good Practices
With so many products in the heating industry it is completely understandable that engineers are often not aware of new developments.
Primary Pro quickly became a hit with some highly regarded heat pump engineers who all now use it. For more information visit Primary Pro