There’s not always a lot of freedom to control roof angles like that - it might eg be directly determined by the orientation of the street - and even if there is, it might come into conflict with other thermal considerations. For instance, perhaps orienting the building such that the roof midline is E/W and the surface is due south results in more windows pointed due south, which in turn drives much more solar gain on the interior and greater cooling loads as a result - maybe the increased solar output outweighs those gains, maybe it doesn’t. You have to run some thermal sims to check. On the other hand, you will have more solar gains in the winter, which will decrease your heating demand.
So it’s not universally applicable - but it is absolutely true that it will increase solar output!
> more windows pointed due south, which in turn drives much more solar gain on the interior and greater cooling loads as a result
C'mon ... people figured this out in 70s ... and centuries before that in various parts of the world.
You put a shade above the window the excludes direct summer sun, but allows direct winter sun to enter the window. The angle and extent of the shade depends on where you are in the world.
On my old adobe in New Mexico, a roof at about 30 degrees with about an 18" overhang prevents all direct summer sun from entering our south facing windows, but provides 6-10F of additional ambient temperature during the winter from direct sunlight.
Oh I’m totally with you! There is a long and storied history of passive design strategies, and exterior shading is one of the oldest ones out there!
But what I stated is plainly true, and many people simply don’t want exterior shades (or just don’t think about it).
The point I was trying to make was just that there are thermal implications to the orientation, and you should think those through (using thermal simulations can help detect these issues) and come up with appropriate strategies (thermal simulations can help validate them). Maybe you don’t want shades, but you would be okay with emissivity coatings for your windows. Or maybe you just want to position windows on both sides of the home with continuous air volumes connecting them to promote natural ventilation. Maybe you can take advantage of thermal mass. The list goes on…
Overhangs are considered exterior shading in the industry/practice/academia. Any obstruction that prevents solar gains by blocking radiation from entering the window falls within the general category of external shading, whether that’s a fancy high tech actuated shading system, a grille, a simple awning, a structural overhang, vertical fins, etc.
That's terrible advice unless it's tied to local energy storage.
When every roof and every solar panel is angled the same way, a sudden cloud (or a sudden lack of clouds) can cause huge fluctuations in power output. Diversity is protective.
Unless there is something I'm missing, the sun still shines from the same direction regardless of the cloud coverage so I'm not sure how having panels pointing in other directions could improve the matter. Perhaps there is a case for optimizing panel area for different times of day but since panels are so relatively cheap it seems the advice is just to get more panels than spend much time worrying about such things.
Are you signing up to point your panels north and take a 30% efficiency hit? Or east/west for a 15% penalty? People point them south because it's the most efficient fixed orientation north of the equator. A more efficient solution is to use a tracker which keeps them pointing directly at the sun as it traverses the sky.
Not every roof allows for perfect southward angling (obviously).
And I'm obviously not saying that you should point panels north either. I'm disputing the parent commenter's claim that it would be beneficial to have all panels aimed directly due south. Because that way you get one strong peak at noon, which is the time of day when solar energy is most abundant but also least used.
The potential for mechanical failures in trackers makes them quite unpopular now (unlike in the 70s when they first started to appear, and seemed like an obvious win).
You're better off just adding however many extra fixed panels you need to make up for the lack of tracking (and its normally not very many).
It might be that south gives you the most electricity (I’m southern hemisphere so north for me), but if you’re after power for yourself, early am and late PM energy generation is very helpful.
A battery helps negate this issue but not entirely.
Pointing west is a reasonable option in California. Pointing west reduces production, but also shifts it later in the day, and addresses some of the duck curve.
