Mvhr unit to ext vent pipe choice

[Alexphd1]

I need to run the pipes from the unit out to the soffits. I have 160mm female EPS connections.  Options are to reduce to 150mm and use plastic or galv metal or use the expensive pre insulated 160mm EPS pipe (verplas) . Any pros or cons in each pipe material . I am spraying open cell insulation afterwards so non insulated pipe is not a major disadvantage.

 

This is a diy system with the mvhr units bought cheap from fleebay. 

Edited March 6, 2019 by Alexphd1

[jack]

Open cell insulation won't be ideal as water vapour can get through it and condense on the ducts.

 

I have some  180 or 160 closed cell ducting left over from my own MVHR installation if you want it. Let me know and I'll go measure it.