Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Grid Angle for Optimum Solar Interaction
Name: Byron B.
Status: Other
Age: 60s
Location: N/A
Country: N/A
Date: March 2004


Question:
I live in Dallas, Texas. I am constructing a pergula (patio with a wooden grid on the top). I would like to angle 1 x 6's on the top so that sunlight will come through during Jan 1 through Mar 15 but thereafter will be blocked or shaded during the summer months when the sun angle moves more directly overhead.

I assume that I can orient the boards on a true east-west line on their respective edges, but at what angle should I "tip" them to accomplish what I am trying to do? And what spacing should I use to that they effectively overlap during the "hot" months?



Replies:
Your latitude is 32 degrees, and you want to accept as much winter sun as you can. At winter solstice, the sun is over a latitude of 23 degrees south, and you want to pass as much sunlight as you can, so you should orient your boards at 32+23=55 degrees from vertical (leaning south, of course). At spring equinox in Dallas, the sun will be over the equator, its rays making a 23-degree angle with your boards, and you want each board to just barely shade the board below it, so the free space between boards, s, should satisfy



s/w = tan(23 degrees) = .4245 where w is the width of the boards. For w = 5.5 in., s = 2.335 in., or roughly 2 3/8 in.

Tim Mooney
Advanced Photon Source



Click here to return to the Engineering Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory