I am currently working on a project with several rooftop canopies with photovoltaic arrays across the campus. Many of these canopies are several feet above the main roof levels. We've reviewed ASCE 7-16 Sections 29.4.3 and 29.4.4 regarding wind loading on rooftop solar panels. Based on the language in the referenced sections, we still have some question about the applicability of these sections in certain situations. I've been looking for a well-documented answer to the questions below, but have been unable to locate anything.
Concerning Section 29.4.3, my interpretation as well as those of my colleagues, is that this section is intended only for solar panels attached directly to the roof of the building structure (ie. roof slab or roof deck), or possibly attached to the top of a rooftop dunnage structure as long as the h1 (less than or equal to 2-ft) and h2 (less than or equal to 4-ft) limits are still met. Is there any differing opinions on this interpretation?
For example, consider a scenario where solar panels are attached to the top of an open rooftop dunnage structure (open-grid framing, no deck or sheathing element is present, no vertical cladding), with the top of dunnage steel 1-1/2 ft above the top of the main roof surface (resulting in h1 less than 2-ft) and the top of the solar panels are less than 4-ft from the roof surface. It seems that this scenario would satisfy the intent of Section 29.4.3 and that this section can be followed.
Following up on the above scenario, if there was a roof deck at the top of the dunnage and therefore, below the solar panels, in this case, would Section 29.4.3 still be applicable? The language of Section 29.4.3, does not seem to prohibit such a set-up.
Conversely, if the rooftop dunnage was say, 8-ft tall, with a roof deck below the solar panels (still an open structure, no vertical cladding), it seems that this would violate the requirements of Section 29.4.3. However, if the dunnage was cladded, resulting in an "enclosed" structure, could this case then follow the procedure of Section 29.4.3? Conceptually, it seems that this latter scenario would not be very different from a partial roof level.
Concerning Section 29.4.4, SEAOC 2017 Section 5.3.4 modifies this section to allow the procedure to be applied to any roof structure--it is not limited to enclosed or partially enclosed buildings. I realize this is outside the jurisdiction of ASCE 7, but conceptually, with the SEAOC commentary, it seems that the procedure of Section 29.4.4 could be applied to an "open" rooftop structure of any height above the base structure roof surface as long as the rooftop structure has some sort of roofing/sheathing (assuming that all of the other requirements of Section 29.4.4 are met). Thoughts?
Thank you in advance!
#ASCE7-16
#ASCE7-22
#WindandWindLoads
#SolarandSolarPanels
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Matthew Waxman P.E., M.ASCE
Associate
Thornton Tomasetti
New York NY
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