tweake:
dustysmurf:
You could also look at this as option rather than the Ardex product, directly from manufacturer here in NZ https://conquerornz.co.nz/pir-product-range/pir-insulated-roofing-solutions/ it has zinc aluminium coated steel bonded to the PIR insulation.
I was previously looking at adding the ceiling panel version these under my existing title roof , between the rafters, but ended up going with a ducted heat pump.
When I got a quote from them (Sep 2022), the 90mm R4.38 was $165+gst for the 1200x2400 (plus shipping)
this is not a bad idea. have them fitted a bit short at the top so moisture can vent up through the roof cap. even better if its spaced up a bit so there is airflow underneath. otherwise moisture will accumulate at the ridge as it can't go through the insulation.
however as a ceiling panel in a normal roof, its not a great idea. you have to be very very careful on using non-permeable products.
Actually these look better than building a safari roof, and then a raised roof cap as @tweake says.
It does look like it would need barge boards and fascia boards to protect the insulation component, and purlins to attach to, page 5 here Conqueror-Roof-Wall-Panel-Specs-1 (conquerornz.co.nz)
