Analemma Over the Porch of Maidens

I do not want to imply that I will be starting a daily word post.  I just wanted a catchy title.

I tried to come up with my own definition but the concept is a little heavy.  So I will let NASA do it:

If you took a picture of the Sun at the same time each day, would it remain in the same position? The answer is no, and the shape traced out by the Sun over the course of a year is called an analemma. The Sun’s apparent shift is caused by the Earth’s motion around the Sun when combined with the tilt of the Earth’s rotation axis. The Sun will appear at its highest point of the analemma during summer and at its lowest during winter. Today, the Winter Solstice day in Earth’s northern hemisphere, the Sun is at the bottom of the analemma.

This quote is from http://apod.nasa.gov/apod/ap081221.html. See also http://www.uwm.edu/~kahl/Images/Weather/Other/analemma.html for a neat photo.

Sun Path Diagram courtesy of AECbytes

What does this have to do with architecture or design?  Well, in my readings of Sun, Wind and Light, I came across the concept of sun dials (used to evaluate effects of existing site conditions, impacts of building massing, etc.), sun path diagrams (which show the path of the sun in the sky dome as projected on a horizontal surface (Libbey-Owens-Ford, 1974) and solar radiation (amount of energy put off by the sun; used in determining occupant comfort and potential for solar heating in buildings).  The picture to the left is generated by Ecotect (from an AECbytes tutorial on Ecotect) and shows the sun’s position throughout the entire year.

This analemma is inside that picture.  Can you see the figure “8″ in there?  However, there are a number of analemmas in the Ecotect picture because the picture shows not just one specific time (i.e. 8:30am) but displays all sunlit hours of the day.

The sun’s position throughout the year plays a role in designing sustainable and comfortable facilities.  Architects design windows and fenestration taking into account these kinds of things to maximize occupant comfort by insuring not to much heat gets in the building and minimize energy bills by using the sun when possible.  It is just amazing!

For further reading:

• http://www.analemma.com/
• http://en.wikipedia.org/wiki/Analemma
• http://www.geoastro.de/analemma/index.htm (roll your own sundial!)