Typical methods are
an eight- to twelve-inch-thick masonry Trombe wall or a water wall of tubes or barrels placed behind
the glass. During the daytime, solar energy passes through the windows and is collected in the thermal
mass. The thermal mass slowly warms and then releases its heat into the living space overnight. The
delay as the mass warms and then releases heat keeps the temperature of the area fairly consistent. An
added benefit is that the heating of the living space occurs later in the day, when it is typically needed
the most. As in all passive heating systems, a thermal mass such as a Trombe wall must be shaded
during the warmer months and insulated at night during the cooler ones.
Materials with high thermal mass—which have the ability to absorb, store, and reradiate heat—work
well for passive cooling. During the day, thick walls of concrete, adobe, or brick act as a heat sink,
absorbing energy. At night when temperatures drop, the mass slowly releases the heat. For maximum
effect, thermal mass must be exposed to the living spaces. High-mass buildings have up to three
square feet of exposed mass for each square foot of floor area.
Isolated Gain or Sunspace—An attached sunspace or greenhouse is usually built so the collection
and storage units can be shut off from the rest of the home during times of severe heat and cold.
Normally, the sunspace consists of a separate room on the southern wall of the home, with an
expansive glass or Plexiglas area and some type of thermal storage mass. The sunspace may extend
out from the house or the house can partially surround the sunspace, allowing less heat loss and more
thermal mass to be situated inside. If the sunspace provides the primary source of heat, it will need
the ability to be thermally isolated from the rest of the home, with doors or windows to control excess
heat from entering living spaces.
This three-walled sunspace allows daylighting as well as absorption of solar heat.
Originally a typical tract-style residence, the Fisher-Castilliano Residence in Palo Alto,
California, was redesigned to take advantage of natural passive solar opportunities.
Builder Drew Maran and Lindy Small Architecture studied the site to achieve the best solar
orientation, maximizing natural lighting, providing ample shading, and minimizing heat loss
and solar heat gain.