This is another salvaging success story.
My goal was to add another layer of insulation onto the roof that would help to keep our roof deck dry. And lo and behold, I found insulated roof pavers (or panels) on the reuse market.
These two by four foot, tongue and groove panels are two inches thick: 1 5/8 inches of XPS insulation, covered with a 3/8 inch latex modified concrete. They give me an additional R-value (insulation value) of eight, and only add 4.5 lb per square foot to the weight, which kept me well within the load capacity range of our roof.
I love that the panels combine the function of insulation and roof ballast in one product. Plus they provide a comfortable walking surface, and protect the roofing system from the elements, such as extreme temperature fluctuations, hail, UV radiation, etc. But they must be installed over a drainage layer. If not, they may sit in water for extended periods and may turn into a very heavy sponge. That would not only negate their insulation value, but also add a lot of weight.
After we hoisted the insulated roof pavers onto the roof, I set up a couple of mason lines and squared them. Those were my guides for laying down the panels, and in the process, minimize any cutting.
The areas that receive the forthcoming solar PV modules did not receive the insulated pavers. Fitting them around the solar posts seemed too complicated. Instead these areas will receive regular XPS insulation covered with regular roof ballast.