DIRECT GAIN UNIT: The simplest of all the solar heating systems used in the project. Large south windows in this house allow sunlight to flood the floor and walls of the main room during the day and the resulting warmth is stored in the adobe and flagstone. Heavy curtains are pulled across the windows at night to prevent heat loss. Eaves over the big windows have been designed to block the high, hot summer sun but admit the rays of the low winter sun.
Illustration by Mark Chalom