We want the house designed to take advantage of passive solar heat gain but also prevent unwanted gain in the summer. This can be done by studying the angle of the sun throughout the year and adjusting window size and location along with window shading.
Things to Note
This animation shows the sun shadows on 12/21, the winter solstice.
This animation shows the sun shadows on 8/1, late summer. This is the day that worries me the most because the hot afternoon sun is creeping in.
Turns out Google SketchUp works very well for depicting shadows and sunlight. The images below show shadows on our current design at several different key days. These help answer questions like: How much overhang? How tall a window? How low a window? Where to have windows? How do you block hot afternoon/evening sun on a west facing house (lakeside)?
The overhangs on this design are ~3ft. It has 9ft walls. Roof trusses allow for 2ft of insulation. Top of all windows and doors are at 7ft. Bottom of low windows are at 18 inches. Porch on front is outside of conditioned space but still moderately insulated. Porch faces west.
Porch shading the main house from evening summer sun. Overhangs block most of the southern summer sun but allow winter sun through windows. The garage windows never get direct summer sunlight. Garage doors get little summer sun but lots in winter.
Rooms used during day - kitchen, dining, living, porch - are bright and sunny.
This animation shows the sun shadows on 6/21, the summer solstice.
If you want to learn more:
www.pveducation.org - gives all the gory details on calculating solar energy.
sun position calculator - shows where sun is in the sky based on location, day of year and time of day.