Q:   I just purchased some Johns Manville polyisocyanurate foam and want to know why are the edges yellow? Will this have an adverse effect on the product performance?

A:  The simple answer is No. If polyisocyanurate foam has been exposed to the sun, it can discolor the foam exposed at the edges and the edges may become powdery. This only affects the surface and doesn't impair the performance of the product. Note that we don't recommend storing the product outdoors.