I am designing a system that uses cement siding furred out from existing walls to provide a cavity in which plywood, metal grates, or other suitable wind resistent materials can be hidden until needed to barricade glass windows and doors. Having used thick rigid foam insulation for exterior walls and underlayment for roofs, I wonder if that material vs. plywood would be lighter weight and more easily used for such purposes.... I presume any material would have to be lifted up (if in a cavity below the window) or slid out, affixed with bolts or cleats, etc. so it has to be user (homeowner) friendly. I would welcome any info on the impact resistence of rigid foam vs. 5/8th plywood and other considerations to take into account. Also, am looking for links for inexpensive metal grating / screens to use for this purpose.