It seems a distant memory as we move into the heat of summer, but just a few months ago roof collapses were making headlines as never before. Massive accumulations of snow crushed everything from the Minneapolis Metrodome to schools, homes and churches. Media coverage stoked worries about structural integrity and whether building codes were sufficient for the extreme storms of a changing climate. Last winter saw major facility owners taking preventative actions to avoid dangerous roof collapses. After conducting an evaluation with the help of structural engineers, the operators of the MassMutual Center, Springfield, Mass., for example, canceled some events