solar panels on existing roofs

huangyhg

solar panels on existing roofs
i am getting more requests for installations on existing commercial roofs with the new administration. i am comfortable with reinforce concrete buildings as the dead load is very high of the existing structure. however, does anyone have any thoughts on the effect on large span steel trusses as in a gymnasium.
a structure has a finite amount of load it can withstand.  it doesn't care whether it is dead load or live load.  if you increase the dead load beyond its design range, you cut into the available live load capacity.  in short, each case would have to be analyzed for its effect.  you need to be careful with long span trusses as they have likely already been factored for large tributary areas, so adding load to them can certainly have a greater detrimental effect than for shorter span members.
don't forget that solar panels affect the waterproofing integrity of the roof as well.  often this is only considered in passing.  it can have a huge detrimental effect on the performance of the roof system and the structure.