I am designing a house with a shed roof. There is a 2′ 6″ overhang to provide solar shading for the windows. I do not like the appearance of a thick SIP roof overhanging so need to provide support for the overhang and fascia/soffit details.

I am trying to keep costs down so trying to keep it simple. I also want to provide ventilation for a rain screen under the metal roof.

Attached is a drawing with the design I have come up with. At the front I have extended a plywood deck. This is supported above by 2x4s which are attached to the SIP. Below these is insulation with counter battens mounted on top. Do these need to be notched, air can flow through the ridges in the metal roof?

There will be felt and wrap on top of the SIP and under the insulation.

I would appreciate any help, corrections or improvements.

The siding on the walls is vented and has a gap at the top as will the space above the roof supports. I just haven’t shown these details.

An alternative, which may be cheaper, is to not use counter battens but put Cedar Breather or similar drainage mat on top of the insulation. Would this work? Can I put the metal roof on top of the insulation?

The house is in Washington state so assume Seattle weather.

Thanks in advance.