Copper roofing and insulation

Factual Questions
1

One of my neighbors is replacing the copper roofing material over a bay window. The guy doing the metal work says he needs to insulate it well to prevent condensation, and he was asking me about this. I wasn’t sure what to say, so I told him I’d ask some experts I know and get back to him.

So, it’s not really a roof in the conventional sense, but it’s the protection over the bay window and sweeps back to the stucco siding. The bay window is about 8’ across, just out about 2’, and the copper sweeps up and back about 4-5’. So, it is like unconditioned attic space, but the concern is condensation inside that space and subsequent water damage over time.

There is not venting in the space and no good way to vent that wouldn’t impair the watertight-ness of the roof. There is no overhang or anything. We were thinking of just spraying on some foam (like Hilti Foam) to cover the inside surface.

Any thoughts from people in the know about this?

2

There are ways to vent spaces like that. One is called the Smart Vent. Others use various proprietary names because of patents. It might not work there and the look may not be appropriate. A venting solution does exist though. They can be found on the Internet.

A small area like that should be covered with snow and ice shield. The name changes in warmer climates to storm shield. Most codes require this now on the bottom and sides of roofs under shingles or other top material.

I wonder why the copper is being replaced. If there is no condensation damage from the previous design, then I would not worry much about how the replacement would last. With an opening to the space, he could dump in cellulose insulation from the home building store. It’s cheap, non-toxic and user friendly.