Passive Solar Space Heating
I hope to heat both the cabin and the house exclusively with solar energy. Three features may make this possible. First, the structures with be very highly insulated with wall and ceiling insulation factors of R60. For comparison, our home in Texas has R13 wall insulation and ceiling insulation that may be as high as R25. Second, windows will have sliding panel covers that will, when closed, greatly reduce heat loss and greatly enhance security. Third, the entire south wall of each structure will be dedicated to solar heat collection.
The south walls will have direct exposure to the winter sun. The cabin will have about a solar collection area about 140 square feet. The house will have a solar collection area about 300 square feet.
A Trombe solar wall will be used for passive solar space heating. The wall involves south-facing windows with a massive wall constructed on the interior side of the glass. There is an air space of a few inches between the glass and the wall. The exterior of the thermal mass wall, constructed of concrete, block, or stone, is painted black to increase absorption of solar heat. The wall is heated by the sun during the day and emits that heat into the home during the night.
A Trombe wall may also have vents located near the floor and near the ceiling. While the wall is warmer than the interior space, a chimney effect occurs. Cool air is drawn into the space between the glass and the thermal mass wall as hot air rises and vented into the living space.
My plans include panels to cover the south-facing windows. These panels will be hinged at the bottom. When closed, these panels will be vertical. When opened, the panels will pivot at the bottom with the top subtending an arc from 90 degrees to 180 degrees or more. The inside lining of the panels will have a reflective surface. The sun's rays reflected off the panels will strike the Trombe wall. In the lowered or open position, the panels will increase the effectiveness of the Trombe wall.
When closed, the panels will reduce heat loss from the Trombe wall. The panels will have two or more inches of foam insulation sandwiched between the inner reflective lining and the outer water-proof covering. This insulation will increase the effectiveness of the Trombe wall.
When closed, the panels will also enhance security. The panels will protect the glass from vandalism and violent weather.
It is possible that the passive solar heating system will overheat the house on mild winter days. Some or all of the panels can be closed to reduce the heat stored by the thermal mass.
A wood burning stove will be used for backup in the event that the solar heating system is inadequate.
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