As we all know light exposure is a very important part of garden design. Evaluating the light exposure in the context of the sun’s movement through the sky both daily and season-to-season will help us understand the influences of the sun. With this greater understanding our designs can harness the warming light when we need it and block it out when we don’t.
In the two pictures included, we can see how the sun’s angle changes based on the season we are in. The winter brings low angles which can easily shine into a southern window, while the summer sun is nearly straight overhead.
If we think about skylights in this context we realize that they get direct solar exposure in the summer and just glancing light in the winter. In this way we are increasing heat in the house, and with the window at the ceiling (where the heat goes) we are likely losing heat in the winter, both are the opposite of what we would want from a sustainable design.
Furthermore we know that the sun rises in the east and sets in the west. People commonly state in a clever, know-it-all way that “you can save on your cooling bills by planting a shade tree on the south side of a house,” but with the sun taking its long flight overhead in the summer, it has little opportunity to shine on the south face of a building. In fact, the south side of a building should be as clear as possible to take advantage of the warming sun which will shine deeply into the house in the winter when we need it the most. If you are worried about the house heating up in the summer you are much better off planting those shade trees to the west and then the east or creating seasonal awnings with vining plants.
Knowing where to place different plants in our designs or how to orient our buildings are good ways of using this info, but it can also be useful in evaluating or designing microclimates in the garden. South facing brick walls or large rocks in the garden can capture the low-riding sun in the winter and help make the garden a more hospitable place for plants that prefer milder climates.
Investigate, experiment and share your comments below!
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