Hello, Sunshine

Many people assume that solar heating makes no sense in the North.  "Not enough sun," they say.  In fact, solar heating is a daily reality in northern Michigan.  Think about what you find when you listen to the weather forecast: "Tomorrow we can expect a low of 22 degrees and a high of 48," says the TV weather person.  The low usually occurs during the dark wee hours of the morning.  The high occurs when the sun shines on our part of the earth.  A house will experience solar gain if the sun is allowed to shine through the windows.  Passive solar heating becomes possible when something inside the house soaks up and retains the sun's heat during the day and then slowly release that heat during the night.  That something is called a thermal mass.

My first experience of solar heating was at my family's home southeast of Cleveland.  We had a small back porch built on a concrete slab and enclosed with jalousie windows.  Facing due west, the porch received full sun in the afternoon.  During the winter we found that the porch often became so warm that we could open the doors to the dining room and sit out there, even in January!  The concrete slab on which the porch was built made a very effective thermal mass.  It soaked up the sun's heat like a sponge.  Unfortunately, the windows, better suited for Florida, let most of the heat escape as soon as the sun went down.

My house will be oriented to the southwest.  That means that during the winter I should have good exposure throughout the day as the sun tracks from southeast to south to southwest — or from right to left on the elevation shown here.  Large windows on the SE and SW sides of the house will admit as much sun as possible, while a masonry wall in the bedroom and living room will serve as a thermal mass.  This wall will will also pick up radiant heat from the wood stove in the living room.  At night the wall will slowly release its accumulated heat.  Convection should distribute the heat throughout the house, and because heat rises some of the heat will flow upstairs via the staircase.  (More of this free heat will be retained if my "window treatments" are thermal shades.)

You might think that Alpena is too cold and too cloudy for passive solar to work.  Actually, Alpena is one of the sunniest places in Michigan, and more so if Lake Huron freezes.  I was surprised to find that Alpena's solar heating characteristics are very similar to those of Norfolk, VA.  Go figure. •••