Hey, good catch, Doug. I dislike those so much I must have blocked the idea from my mind...

I don't know. I can see rock wool having bleeding problems.

I don't like the gapped siding plans at all. Actually, I think they are stupid, a fad that is going to be sneered at like vertical T&G siding is (or should be) today. Or, even better, the diagonal T&G... Many of those "rainscreens" with the "open" design have been installed with products that aren't going to last, and are going to be great places for wasp & bee nests. Not to mention the rat who looks in there and thinks it looks like a good place for the family.

Rational rainscreens (without the open plan), I don't think that there's any significant increase in fire problems. Perhaps in a fire zone, but for the fire to get back there it's already burned through the siding, meaning it was probably going to start a strong fire anyway. The open design- yeah, that's a very good ember trap.

Rational ones- I look at them as giving the benefit of an un-insulated wall cavity that allows a lot of vapor movement without affecting the siding and WRB. The "open" ones- you lose the benefit of protecting the WRB from the weather and sun. When they are 3/4" material, then you have a lot of edges that aren't going to get maintained. It would probably be a good idea to install them over perf stainless steel to reduce the insect problem, but who's going to go to that expense?