i have a greenhouse that im getting ready to build. its got a south wall that will be made up of 1/2'' laminated glass panels 8' long at roughly a 50 deg angle. i was thinking of using PT lumber inside, 2x6's on 24-30'' centers to support it. ive since thought about galvanized or aluminum tubing that i think might make a good choice vs the PT chemical wood.

Anyone have any idea what the equivalant in strength of a wooden 2x6 is in either aluminum or galvanized tubing?

thanks!