11. http://www. greenhouse. gov

12. Passive Solar Design N S E. Burch Solar View Estate Swarthmore, PA
Summer rays at solar noon N S
Winter rays at solar noon A
15 cm
West windows
3 cm
3x3
3x3
11 cm
74.5 degrees B
South window
12 x 8 (C)
27.5 degrees
14 cm
Ground level
All measurements in centimeters…drawn to full scale

13. Calculating Solar Angles
Spring/Fall
Equinox P N P
27.5 degrees
above the ground
Parallel Rays
To the Earth
Winter in NA
Sun
Difference in tilt =
or 47 degrees N
Summer in NA P
74.5 degrees
above the ground

14. What is the Tropic of Cancer?
Summer in North America
Tilt of Earth on its axis is 23.5 degrees N S
Tropic of
Cancer
23.5 N Lat.
Equator
Sun’s rays
Equ.
At solar noon, sun angle is 90 degrees above the ground
if you live on the Tropic of
Cancer
If you live in Philly sun would be
90 – 15.5 = 74.5 degrees above
the ground
15.5o
39o
23.5o
EQU.
Philadelphia’s Latitude