I have entered this late but wish to learn what the problem is.
It seems to me that photovoltaic panels (which I believe weigh about 3 lbs/sq. ft.) will prohibit anyone walking on the roof (for which we design for 16psf on a 4/12 slope) and thus the load is less not more than typical design load. Is this what is of concern?
Stan Scholl, P.E.
(someone with a very low PE number)