If you want to construct a building to use solar energy it is a good idea to build it in the sun. But how much sun will shine on a particular site? You cannot easily tell by one or two visits, because the sun changes its apparent location from hour to hour and season to season, and these changes are different for every latitude.
    However, with some camera equipment (see left) and a computer, it is easy to decide if a site is suited to a solar building.
    I made these images with the “Sunpath” program developed by Pacific Gas and Electric.
                                             Email:   joeode@mcn.org  
                                             Phone / Fax (707) 937 - 5774  
                                             POB 984, Mendocino, Ca. 95460 USA
 This direction is the sunny South.
This is the East, and Sunrise.
This is the West, and
This is the chilly North.
This is the high path of
 the sun on June 21
This is the low path of
  the sun on December 21
This is the middle, Equinox
path of the sun
Noon Line
360 Degree Horizon
— How a sunpath diagram works —
at 39 degrees North latitude.  The middle of the circle is straight up. Looking at the top of the circle is like looking south, with East on your left and West on your right. By studying the curving lines of the Sunpath you can tell the following things:
        This Sunpath shows the entire sky above a small lot east of the town of Mendocino,
• The winter sun will shine on this for lot only about two and one half hours,
   where the low path of December 21 crosses the sky, and the two months on
   either side of the winter solstice will not be much sunnier.
• On the equinoxes, the lot will get about eight hours of sun per day.
• By deep summer, the high sun of June 21 will shine here for 10 hours.
• The bank of trees on the West (the right side in the photo) shades the lot
   after 3 pm sun time pretty much all year. If the trees were on the lot, you
   could trim them for more sun; but in this case they are not.
• On this sky dome photo you can see where the sun is by the glare, so you
  can tell that the photo was taken a bit after solar noon, about 2 weeks
  into June.
• This lot is not a shady place, but neither is it a good location for a solar
   building;  there is very little sun in winter & not much late afternoon
   sun at any season, and the sources of the shade are not on the lot.
Diagram shows local solar time.
Summer sunset
7:20 PM
4:40 PM
—  Sunpath diagrams for an actual project  —
Morning shade
      This is the sunpath at the location of the proposed new classroom at the Jughandle Nature Center in Mendocino County. It has good potential for solar energy;  the low winter sun path is mostly clear, and the morning shade comes from trees that can be trimmed back. (The early morning sun is important for warming a building after its temperature has dropped during the night.) The equinoctal and summer sun paths are good too, and in the coastal location of this project, solar heat is desirable all year.
Trees have taken over
     This is the sunpath at the existing campground kitchen area at the Jughandle Nature Center. It is proposed to build a sort of pavillion here to give the area some shelter. The diagram shows that having any solar demonstration equipment here - solar ovens, for instance - would not be a very good idea, unless the nearby trees were severly cut back.
—  sunpath diagrams applied to building interiors  —
This sunpath tells you what time of day the front porch will be sunny, for every day of the year.
This sunpath will show you where to put a new skylight in an existing roof, for direct sunlight at specific times.
This sunpath shows what time of day, and in what season, there will be direct sunlight at the kitchen sink.
—  sunpaths in other latitudes  —
At the Equator, every day of the year has exactly 12 hours of sun and 12 hours of dark, and the path of the sun is right overhead and changes very little. Anyway, you don’t need solar heating at the Equator. (The photo is actually in Mendocino.)
At the latitude of Trondheim, Norway, there are only 4 hours of sun in midwinter, and the sun is far down toward the horizon as well. Not much hope of solar winter heating in high latitudes. But in midsummer the sun shines in Trondheim 20 hours every day. (The photo is actually in Mendocino)
63.3 Degrees North
Nikon camera with  183º  fisheye lens, taking a photo up into the sky.
This service is available as an on-site consultation for $300 to $500 in anywhere Mendocino County, California. click here to see see the page “Solar Site Consultations.”
Joe Ødegård, Architect
—  Solar analysis with skydome photography  —