Running UFH-ASHP pipe work inside Warmcell filled walls.

[MikeSharp01]

I have a plan to bring the ASHP-UFH 25mm (PEX-AL-PEX) flow and return pipes along inside the walls of our build. The Warmcell (other brands are available) insulation will be blown in around them to insulate them and they would be 150mm apart and 150mm from the inner surface of the insulation. The system will run in cooling mode and heating mode depending on season.

 

Any thoughts on why I should not do this?

 

My own thoughts are around the possibility of condensation forming on the pipe when in cooling mode and water and Cellulose fibre insulation are not good bedfellows!

[IanR]

I feel you need to continually insulate the pipes from outside to in. Makes an air-tight seal around the aperture more difficult.

 

Is it too late to duct under the slab/foundation?

Edited March 25, 2022 by IanR

[MikeSharp01]

2 hours ago, IanR said:

I feel you need to continually insulate the pipes from outside to in. Makes an air-tight seal around the aperture more difficult.

Sealing it is no problem and where the pipe comes out of the walls it is (will be) insulated at both ends. Getting under the slab is a non starter at this stage, the original intention was to run the pipes down the outside, buried in pea shingle, and bring them in through the wall and this is still possible but I felt I could save a lot of cost (insulated pipe runs in 25mm dia are expensive) by using the in wall insulation and any heat lost will come into the house.  

[IanR]

That sounds like you don't intend to continue the pipe insulation through the wall, but rely on the blown cellulose within the wall.

 

That feels to me a condensation risk, as you suggest. Could you use a pre-insulated twin-pipe duct for the external portion of the run and through the wall, then swap to your PEX-AL-PEX once inside the thermal envelope.

 

Edited to add:

I've just re-read you OP. You're not just crossing the wall, you intend to run within the wall for a distance. I feel you need to insulate the pipes separately within the wall to stop water vapour getting to the surface.

Edited March 25, 2022 by IanR