It all happens so quickly each year that my Passive Solar Home “automatically” switches itself from summer/fall cooling mode to winter heating mode. See how the macro environment helps make this happen.
Summer with Deciduous Trees Shading the South Elevation
With the winter solstice approaching the sun is at its lowest angle in the south sky. The next picture shows how far the sun will penetrate into a south faced solar home on December 21.
All that is needed to have your solar home heat itself is to first: properly site it. Second, take advantage of deciduous trees. If they don’t exist on your site, plant them. You’ll be surprised how fast a sugar maple tree will grow in the northeast.
50% of the heat for the solar home pictured is supplied free from the sun. There are no rooftop collectors and the east, south and west windows and patio doors serve as the only solar collectors. At north latitude 40 degrees, a vertical south faced window on December 21 will collect almost three times more solar heat than it will on June 21 due to the difference between the low angle of the sun in winter verses the high angle in the summer. Thus, south faced glass will “automatically” collect more solar heat in winter than summer. Summer cooling is enhanced when deciduous trees are used strategically.
Another key element to the functioning of a passive solar home is the use of mass to store heat – we’ll talk about that in a future discussion.