Bill, I understand exactly what you are saying. The problem is when you are standing in front of that bonfire, feeling all that radient energy, if you put a sheet of plywood between you and the bonfire, you will certainly feel cooler. Now, paint the plywood surface FACING YOU with a reflective radient barrier. You will feel NO difference. The energy that comes through the plywood is CONDUCTED and no painted on radient barrier ON THE INSIDE is going to help. The surface finish of the plywood is too rough to get a low emissivity. In order to get any benifit to prevent the "secondary radient transmission" the radient barrier would have to be installed off of the underside surface of the plywood.