I have been in the vinyl siding business for ten years and have come accross melting due to reflection 3 times. None of them had foil of any kind behind them. I am currently working on a house that has Georgia Pacific siding (blue) .040 thickness. We have repleced the siding with the same color but upgraded to .042 thickness. I doubt that this upgrade alone is going to solve our problems, as I have another house that has an .044 thickness panel on it. We are also going to experiment with tinting the glass however I will not have results until winter of 2008 as the sun is not in the right position until then. Getting back to the 044 thickness house. This house i sided in november 2006. we used a siding called Craneboard made by Crane. It is a double 7" panel with foam that is glued to the back side and is the best siding panel that i have used. The siding is cypress green which i believe has nothing to do with the melting. This melting also occured in the winter months. I replaced the panels once and the same thing happened again in the winter of 2007. I was also there at the right time one day to witness the reflection hitting the siding and it was to hot for me to hold my hand on. I don't believe there is any vinyl siding that can withstand this kind of heat. I am very interested in finding a solution for my customers. Any info would be greatly appreciated. I have spoke with the siding manufacturer and they blame it on the window company, and the window company blames it on the siding. I personally belive that this is a window problem, but i am left with no where to turn.