Depending on where you live and what type of wind speeds your collectors will be exposed to, wind loading may or may not be an issue. Any side-to-side movement in the mount should be eliminated with additional triangulated support members, since any lateral play will allow strong winds to weaken the mount over time.
For collectors that aren’t angled more than 4 feet above the roof, 3/4-inch angle iron or 1-inch aluminum angle have been used repeatedly without failure, since the wind loading is significantly less at lower tilt angles. Square stock and pipe may be used in the same dimensions for each respective material.
If building officials feel uncomfortable with a mounting system, they may require an engineer’s stamp on the system drawing. Also, if you live in an area with high winds, having your mount engineered may save you some headaches down the road. Many collector manufacturers will be able to supply you with wind-loading calculations should they be required. For more information on wind and other loads, see “Dealing with the Forces of Nature”.