Quick Answer
Structural loads for a solar panel array can be calculated based on various factors including the weight of the panels, racking, and snow loads, along with wind and seismic loads. These loads are usually determined by a structural engineer or using load calculation software. The results are then used to select the appropriate mounting system and ensure the roof can safely support the solar array.
Understanding Structural Loads
Structural loads for solar arrays can be divided into two main categories: dead loads and external loads. Dead loads include the weight of the solar panels, racking, and other equipment. Typical dead loads for a solar panel array range from 1.5 to 3 pounds per square foot per panel, depending on the type and size of the panels. External loads, on the other hand, include snow, wind, and seismic forces.
Calculating External Loads
External loads can be calculated using various formulas and tables found in the International Building Code (IBC) and the American Society of Civil Engineers (ASCE) 7-16. For instance, the snow load can be calculated using the IBC’s snow load formula, which takes into account the roof’s slope, location, and other factors. A typical snow load for a residential roof in the United States ranges from 20 to 40 pounds per square foot.
Selecting Appropriate Mounting Systems
Once the structural loads have been calculated, the results can be used to select an appropriate mounting system. For example, if the dead load of the solar array is high, a mounting system with a high load capacity may be required. Similarly, if the external loads are high, a mounting system with wind and snow loads certified by a third-party organization such as UL or IAPMO may be necessary. It’s essential to select a mounting system that meets the calculated loads and complies with local building codes and regulations.
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