Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

September 27, 2013

I Knew It Was the Fall Equinox On September 22 Because My Sun- & Shade-Harvesting Sculpture/Calendar Told Me So!

by Brad Lancaster © 2013

I designed the sizing and placement of the roof overhang/gutter and windows on my garottage (one-car garage turned cottage) in Tucson, Arizona, to let the sun’s rays in when I need them for heating, and shade the sun’s rays out when I need cooling.

The sculpture shown in the photos below celebrates both the sun’s seasonally changing path and how the building was designed in relationship with that path. The sculpture also acts as a calendar, building on a long tradition of such calendars among Native American cultures in the southwestern U.S. See here for virtual tours of ancient sun calendars at some of the archaeoastronomy sites that have been surveyed in the Verde Valley of Arizona.

Note that while the angle of the sun is the same on the spring and fall equinoxes, there can be more than a 20ºF (11ºC) difference between the outdoor temperatures on the two equinoxes. This leads to a design challenge of how to let in more spring light and heat, while providing more fall shade and cooling. I solved this by designing for a seasonally extendable/retractable awning for the south-/equator-facing windows on the ground floor (see figure 4, above).

For more on how you can better design and live with the seasonally changing patterns of sun and shade, see:

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