Hi Dan, Thanks for your question. Ventilation ductwork to upstairs rooms can be routed within the thermal envelope typically by use of dropped ceilings. Often, this is only required in a small area (e.g. 1st floor landing), with ventilation ductwork penetrating the partition walls to the bedrooms and ending with wall-mounted terminals above the doorways. You can learn more about this and many other aspects of ventilation system design on our Certified Passivhaus Designer course: www.passivhaustraining.co.uk/designer/ Hope this helps!

Had Several MHRV units in my loft over the last 35 years. Ducts are enclosed in 200mm insulation. I use the loft ladder and boarded floor to access the unit for filter and unit servicing. Nice picture of the Itho control, we have two of them. Apart from this I agrre with your other points.

Very well laid out presentation with powerful conclusions