How would one go about assigning a equivalent R value to a material. Or find the U value and go from there. I have a rude lab set up where I am measuring the heat rise of a pound of water by ten degree F under a material I am testing, and doing the same with know insulating materials, and then basically stacking insulation on top of the insulation I started with until the time it takes to raise the temp ten degree matches the time it took with the material I am testing. It is a "thermal barrier" material. The person I am doing this for will argue that it is not a radiant barrier, but to me it is just a play on words. However and anyway, I am doing this because I find it very interesting to do, and a good project. Any input would be appreciated.