Hi Catalina- I think that Duncan's proposal is good. If it is more advanced than that, say if you have some sort of trellis, or advanced shading mechanism, it can be simplified through good old geometry. I wrote something on this about two years ago: http://energy-models.com/blog/11-11-10/simplifying-shading-equest-and-trace-700 Basically, it comes down to simplifying virtually any shading device into 1 overhang (or fin) However, Duncan's approach will probably work. (The main downside to the weighted average approach is that you don't necessarily get the full shading value at peak loads or in the summer months) Best Regards, Bob On Tue, Dec 18, 2012 at 3:07 PM, wrote: