As we saw in the last post, in temperate latitudes, the amount of solar energy reaching the earth varies greatly through the year. Ultimately, this is why we have seasons.
While we want to maximise solar heating in winter, during the summer months we may need to limit the amount of solar energy entering the building, in order to avoid overheating.
A classic way to do this is with roof overhangs. As you can see in this photo from Vermont, USA, taken in July, a good roof overhang will shade the south-facing windows in summer, yet allow low sun to penetrate in winter.
The right size for an overhang is based on latitude, which determines the height of the sun in summer and winter. Overhangs work best on the south side of the house.
Decks and balconies can also serve as overhangs for the lower stories of a building, as in this house in the USA.
Movable shading elements like thermal curtains, shutters, blinds, and awnings, are also useful for controlling the amount of sun that enters the building, allowing the occupants to modify their indoor environment without the need for fossil fuels.
Deciduous plants, which lose their leaves in winter, are a natural way of regulating the amount of sun that reaches the building, in a more flexible way than other shading devices.
So for example, a deciduous tree can block sun in late summer but allow it to pass in early spring, even though the sun angle is the same at both times of year.
Plants can also cool the environment around the building through evaporation in summer, block cold winds in winter, and provide shady areas to sit outside during summer, connecting the interior and exterior of the building.