In John Michael Greer's entertaining post on the Energy Bulletin of April 6, 2011, Alternatives to Absurdity, he noted that passive solar opportunities in existing construction are more limited than in new. He went on to inform his readers that passive solar requires that "a good part of the south or south-east face of your house receives direct sunlight during at least a significant fraction of each winter, spring, or autumn day."
Around winter solstice is the crucial period to check thoroughly, for if the south wall is in sunlight for the critical hours between 9 a.m. and 3 p.m. one can be assured of sufficient sun in spring and fall as well. Old Sol will not soon alter his course through the heavens, and deciduous trees will spring into leaf and later let their leaves fall just when it will benefit the passive solar householder the most.
Where John Michael Greer's missive may have been overly enthusiastic, it seems from this humble writer's viewpoint, was in a bit of advice given to homeowners in the latter half of the essay. That is, I wish to add a note of caution, lest an army of intrepid Do-It-Yourselfers begins casting new Trombe walls in living rooms across America for passive solar heat storage.
