SIP wall thickness: diminishing returns?

[joshwk]

Interesting, thanks both. I actually made a separate post on the MVHR sub-forum about this topic as I was trying to determine the pros/cons to both. In the end, we opted to proceed with a rigid branch system using a who have experience working with our appointed SIPs supplier. We were led to believe the benefits of a rigid system was that it's more "hygienic" and PasivHaus themselves opt for rigid ducting in their testing (which may have just been sales-BS).
 

Currently, we've opted for supply only. The MVHR supplier is quoting ~£4K to carry out the install and although I appreciate it's a premium expense, I'm tempted to have them undertake this so there's a single point of contact for any issues in the future (and also avoid the headache of installing this myself). Alternatively, I could ask with my builder if they'd be prepared to take it on (and get a quote), but wonder if people have had positive/negative experience with this?