[QUOTE=EastCoastCB;390260]my strategy is- seal the roof properly and paint it with whatever you paint the bus with. NOT house paint.[/QUOTE
I agree, sort of.... you might want to paint it first to get good adhesion of the paint then seal the leaks with a elastomeric or sealant (the paint may not stick to the elastomeric /sealant or vice versa)
Elastomerics are a roofing product, not a paint. Their big claim to fame is that they seal and stretch, allowing the seal to be maintained on roofs that move/expand/shrink a lot. They are white because it only makes sense to keep the roof temp down in the summer and its good for sales. Compared to the costs of re-roofing, they are cheap, although most applications are done incorrectly and therfore the warranty is void.
When they first came out they were sold mostly to repair metal roofs. Now they are used on most every type of roof. The early formulations were merely extra thick latex or acrylic latex paint, if I remember right. The roofing contractors salesmen that peddled them would paint pieces of glass with several coats, then peel off the paint and use it for samples to put in the customers hands so they could stretch and pull on it. Now there are many formulations including silicon. They are meant to be reapplied every so often and are not meant to last like paint. In roofing, reapplications are where the money is.
Remember...Elastomerics are a roofing product, not a paint. If you read the instructions you will see that caulks and reinforcing fabrics are supposed to be used on cracks and problem areas. Is your roof leaking? You can find out with a water hose. Did you make a lot of penetrations/holes in your roof installing stuff on your roof? If you did you should be more concerned with your roof leaking than how good it looks or how good an insulator/reflector it is.
I'm guessing that a good urethane or epoxy paint would be a good choice. Good prep is the key to good paint.
My question would be what kind of paint do/did the bus manufactures use? It seems to last and does a good job of sealing and they actually have a stake in whether it works good - or not.