Installing large heavy solar panel arrays on existing older buildings often creates major structural engineering challenges, because many older roof frames were not originally designed to support the extra dead load weight of dozens of photovoltaic panels. The EPS Cement Sandwich Panel is the perfect solution for this problem, as it can be used as a lightweight insulated overlay on top of the existing roof structure to add full thermal insulation while only adding a very small amount of extra weight to the roof frame. The rigid cement top facing of the EPS Cement Sandwich Panel creates a strong, stable, flat base that solar mounting brackets can be securely bolted directly into, eliminating the need for extra separate sheathing layers. This roof system adds almost no significant extra dead load to the building structure, which means most existing older roofs do not require expensive and time consuming structural reinforcement work before the solar panels can be safely installed. The excellent thermal insulation of the EPS Cement Sandwich Panel also reduces the amount of heat that the dark solar panels transfer down into the roof structure, which helps keep the building cooler and improves the overall energy efficiency of the entire solar power system. Many commercial warehouse and industrial buildings that are adding large scale solar installations have already adopted this panel system to solve their roof load and insulation challenges at a very reasonable total cost.