Structural Engineering Considerations
Having a setback from the roof edges is also very important for structural engineering reasons too. In many projects, we’ll have our structural engineer advise on truss loads, reinforcing requirements, and similar matters.
Your rootop solar array installation may be in place up to 30 years and longer. The solar array (and roof) will take a beating from mother nature) and must stand up to high wind, hail, rain, snow, sleet, etc. The perimeter zones around your rooftop are exposed to the greatest forces during high wind and thus areas to try and avoid locating panels.
A 3-foot setback as a general “rule-of-thumb” will generally keep your solar array away from these areas of high wind turbulence and extreme forces. The figure on the left illustrates the “caution” zones that are determined by a structural engineering analysis. Placing panels in this area is possible but may require additional reinforcement.