I live near Denver, Colorado (so northern hemisphere, some good snow storms in the winter, lots of baking UV in the summer) in a 1970s-built home and I'm putting a pergola over a patio in my back yard. Thinking about the pergola rafters, I'm seeing several design inputs:
- Want the rafters far enough apart to let in as much winter sun as possible
- Want the rafters close enough together to block as much summer afternoon sun as possible
- Want the distance between rafters to be aesthetically pleasing
- Want the rafters aligned either perpendicular or parallel to the back of the house for aesthetics
- Want the rafters aligned to let in the most winter sun and block the most summer afternoon sun
- Want the rafters straight up & down for aesthetics
- Want the rafters angled/tilted to let in as much winter sun as possible and block as much summer afternoon sun as possible
Realizing that several of these design inputs are in conflict, the "optimum" alignment and tilt of the rafters might be more art than science, but is there an app, web site, book, or guru that could help at least calculate some of the individual optima?
And perhaps just as important, I would want to know how much of a difference each adjustment makes. For example, if giving each rafter a 30° tilt and running it at 25° off direct north/south gave me 50% better sun coverage in the summer (over straight up/down north/south rafters), it might be worth the resulting "wonky" look, but if it only gave 5% better coverage the aesthetic concerns would win out.
Am I overthinking this? Probably, but they won't start construction for several weeks so I've got time to ponder the deeper questions.
According to Google Maps, my house and lot are about 12° E of due north: