Metateps

Passive solar design is a method of heating and lighting a space with the least input from the grid. Here are the major parts of the solar design puzzle:

South-facing windows. These should allow low-angled winter sun to enter. The sunlight is converted into heat and stored in a thermal mass.

Thermal mass. This is heat-absorbing material in walls (known as Trombe walls), floors, and ceilings, and includes brick, stone, concrete, drywall, tile, and earth materials. The function of thermal mass is to convert sunlight to heat, radiate that warmth, and store excess heat for later use (to keep you warm all night long).

Overhangs. Overhangs regulate solar gain. As we all know, the angle of the sun relative to the earth changes. It's greatest in summer and lowest in winter. The overhangs (the eaves) control how much sun gets into the house by shading windows and walls from the high-angled summer sun. As the angle of the sun gets lower in winter, more sunlight gets inside, making more heat.

Insulation and window coverings. These should form an uninterrupted layer through walls, ceiling, foundation, and over windows and skylights. This insulation layer will keep warmth inside during the winter, and heat outside during the summer.

Ventilation. Necessary to spread the warm or cold air evenly.

There are many ways of designing a home to take advantage of solar energy. The simplest designs are sun-tempered, a term that means the design takes advantage of the most obvious methods of collecting the sun's energy. For instance, solar heat collection will be maximized when the long axis of the house runs east-west; when there are many windows or a few very large windows along the south side; and when the house is well insulated, or may have thermal mass added.

A true solar design includes even more south-side window space, more insulation, and more thermal mass. This structure gets lots of direct heat gain from sunlight through the windows, which is retained by the thermal mass. Attached sunspaces can collect heat through their south-side windows and transfer that heat by convectionand with the help of small fans through doors, windows, or vents into the house. This is referred to as isolated-gain passive solar. The true solar structure will have an effective thermal mass, often called a Trombe wall, made of earth, brick, or cement and often painted black.