As the use of solar energy installations continues to grow rapidly around the country, IBHS examined the effects of wind on roof-mounted photovoltaic (PV) solar panel arrays and whether panels are being attached properly to structures so they are able to withstand high winds. Detached solar panels and arrays can cause extensive damage to roofs, weakening a building’s protection against severe weather; they can also become flying debris, which becomes a hazard to anything in the vicinity.
Currently, there is no nationwide guidance on the attachment requirements of solar panel arrays in order to resist wind loads. In 2012, the Structural Engineers Association of California (SEAOC) published guidelines on appropriate wind design loads on low-profile solar photovoltaic arrays on flat roofs. Work has begun to produce nationwide guidelines by adapting the SEAOC guidelines into the 2016 edition of the American Society of Civil Engineers (ASCE) 7 Standards for Minimum Design Loads for Buildings and Other Structures. IBHS’ 2014 research will help validate or improve the submissions to ASCE and provide preliminary information to inspectors and underwriters of these systems as it relates to best practices for array attachments.
Large-scale Commercial PV Arrays
Large-scale commercial PV arrays are becoming increasingly common, with significant growth in both roof-mount and ground-mount systems. Roof-mounted systems on large flat roofs are particularly attractive as they occupy largely unused space on the roof of a building. This document below addresses wind-related concerns for ballasted roof-mounted commercial PV arrays with rigid panels installed on built-up (BUR) or membrane roofs. Ballasted PV system designs must consider both wind uplift and movement due to wind loads. Most systems are engineered based on wind loads derived from small-scale model tests that are frequently peer-reviewed. However, there is no consensus on performance criteria regarding how much uplift or sliding is acceptable. Consequently, the amount of PV movement allowed may vary greatly.
When a PV array is first installed, a baseline inspection should be conducted and the location of key elements should be clearly identified. Following a strong wind event—with wind speeds exceeding the greater of 70 mph or 70% of the design wind speed of the building provided by ASCE 7-10 or later—steps should be taken to identify and address any change or damage that may have occurred due to the wind event.