Has anyone seen this. https://www.greenbuildingstore.co.uk/mvhr-dos-donts-ducting/, frankly I don’t agree with it but would love to hear input from others. I have used plastic flexible pipework (mine is yet to be commissioned) . They talk about high pressure but as far as I know air pressures is very low. I bent my pipe without crushing it or radii too small. It is smooth bore although ridges externally. My airflow regulation will take place at the manifold to stop noise at the terminal. If put together properly why should it leak!. Yours not convinced!

Looks like a company trying to persuade people to buy more expensive, harder to install, metal ducting to me.  It's dead easy to clean out any ducting with a bit of light string and woolly pig, so the dust build up argument isn't really there.  Correctly designed there's absolutely no reason why a semi-rigid plastic duct system shouldn't work just as well, and last just as long, as a semi-rigid one. 

 

I'd love to know where they get their "15 year life" for PVC duct from, as it's plainly bogus.  Our old house has the original PVC guttering and downpipes from when it was built in the early 1980s, over 30 years ago, and even constantly exposed to the weather they are all in good condition.

I think they blur the lines between semi rigid and flexible too - the cheap wire wound plastic film coated stuff can be crushed easily and does attract muck and dust.  Proper semi flex you can stand on and not damage and I would go as far as to say it’s more resilient than steel duct.