The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
Designers are urged to provide for multiple penetrations such as air-conditioning ducts, by using a separate plant room that is not only the most weathertight method but also the most economical one.
For large penetrations, the supporting framework should be in position before the roof cladding is fixed. Alternatively, if the position of the penetration can be adjusted to suit the profile, the supporting framework should be in position before the hole is cut in the cladding.
Small vent pipes and ducts less than 150 mm do not require additional structural members unless more than one rib is removed.