Solar Panel Question
Solar Panel Question
(OP)
I was recently asked to look at an existing metal building by a client. The client does not own the building, and at the time, I thought the client was going to lease the building from the owner. The addition of a new sprinkler system was part of the scope of work. Part of my due diligence required me to measure the existing roof frames and purlins. The building was constructed in 1989.
Code analysis revealed some issues with the roof (due to AISI code changes) but my analysis of the sprinkler system revealed that we were increasing the gravity load by 1% (which is under the 5% limit allowed in the IEBC). I wrote a letter of my findings which I gave to my client.
A few weeks later I found out that my client was looking to actually purchase the building and part of the purchase included a lease to a solar panel company (which had yet to be implemented). The lease was written in such a way to allow a 15% increase in the gravity loads on the building. From my analysis, I know this increase would require reinforcing of the existing roof, but no reinforcing was proposed. I informed my client that adding the solar panels to the roof is not a good idea and that they should negotiate their way out of the lease (they think this is possible).
Do companies that install these systems actually check to make sure the existing structures can support the added loads? Or do they just hope the structures can support the added loads? Or do they only care about adding to their bottom line?
FYI, I know specifically what my deficiencies are as I have a colleague who works in the metal building industry and can analyze these roof systems quickly.
Code analysis revealed some issues with the roof (due to AISI code changes) but my analysis of the sprinkler system revealed that we were increasing the gravity load by 1% (which is under the 5% limit allowed in the IEBC). I wrote a letter of my findings which I gave to my client.
A few weeks later I found out that my client was looking to actually purchase the building and part of the purchase included a lease to a solar panel company (which had yet to be implemented). The lease was written in such a way to allow a 15% increase in the gravity loads on the building. From my analysis, I know this increase would require reinforcing of the existing roof, but no reinforcing was proposed. I informed my client that adding the solar panels to the roof is not a good idea and that they should negotiate their way out of the lease (they think this is possible).
Do companies that install these systems actually check to make sure the existing structures can support the added loads? Or do they just hope the structures can support the added loads? Or do they only care about adding to their bottom line?
FYI, I know specifically what my deficiencies are as I have a colleague who works in the metal building industry and can analyze these roof systems quickly.






RE: Solar Panel Question
RE: Solar Panel Question
I`m not sure how thorough they are, but we made it clear that there are numerous hung loads within the space that needed to be accounted for in their analysis.
RE: Solar Panel Question
RE: Solar Panel Question
Since this solar power craze started (and don't even get me started on it).....I've had a number of panel installers call me for roof evaluations.
Whoever wrote that lease doesn't have a clue. You need to be sure you aren't connected with it in any way.....and be sure you document you've told them it would take a evaluation (on your part) to be sure of that 15%.
RE: Solar Panel Question
Not saying that building departments are against them, but just that solar panels are very much on their radar for a number of reasons.
RE: Solar Panel Question
RE: Solar Panel Question
The typical systems available currently do not add much weight to the roof and I don't think the added gravity weight is a problem for most building, however the PEMB systems are notorious for having no excess capacity so adding anything beyond the code minimum at the time of construction could be a problem. I also believe the bigger potential problems are the panels installed on elevated frames/racks where the loads are concentrated and there's a significant wind component. The uplift from a rack leg can be quite large and it introduces reverse bending in a roof member that is most likely unbraced on the bottom.
The above is just my local E coast experiance so it may not be accurate in other markets.
RE: Solar Panel Question
I have a unique experience here since I was ask about the ramifications of adding sprinklers to the building. I measured the existing purlin sizes and sent them off to my colleague for review and continued on to see what the IEBC said about my sprinkler situation. I'm in an odd position with this building but can justify adding the sprinklers through code references. However I know for a fact that a 15% increase will not fly without major reinforcement. I informed the potential buyer that they have two options:
1 Negotiate the existing building owner to terminate the solar lease prior to the sale
2 Reinforce the existing roof
I just find it odd that a solar panel company would enter into a lease with a building owner for a load increase of 15% without some investigation (FYI, no solar panels are on the roof...... yet). I have always wondered about these when I drive down the road and see all these building that now have solar panels. Seems like the dark side of the business that no one talks about.
RE: Solar Panel Question
I personally never liked the idea of justifying a reduced live load based on the assumption that the solar panels basically block live load. It's logical, but I have always sort of viewed roof live load as a cya construction load, and you never know what some people will do during construction. Also, I don't know if code authorities would accept this logic.
If the shell game with the loads doesn't work out, then the scope for a true structural analysis of the roof load path expands substantially, and it seemed to me that there was never a realistic understanding of this or willingness to support this, in principal or financially, on the part of the owners and/or solar suppliers.
Curiously I never get calls about solar installations anymore. I suspect all of the suppliers in my area must have developed relationships with other engineer's that they preferred to work with, maybe because they had more lenient opinions about the roof evaluations. I also wonder if maybe things have changed in the way the codes address solar panels on roofs. For example, it could be codified that it is acceptable to reduce live load at solar panel locations.
RE: Solar Panel Question
Would be incredibly interested in exploring a SSE/EOR arrangement for this type of project and would love a referral if you guys are willing???
Thanks,
-Huck
RE: Solar Panel Question
Be really careful on PEMB’s with the plinths. If a PEMB is built more than 25 years ago, you will undoubtedly find the plinth too small and under reinforced.