Buffer Spaces Place rooms where they are compatible with the suns path. Buffer spaces should be placed to the north. Lightweight materials should be lighter in color. When light energy is absorbed, it is transferred into heat energy. If the material does not have sufficient storage mass, the material may heat up too quickly and release the excess heat to the room air, causing overheating.
Masonry walls can be any color in direct gain systems.
Actually, it is best to use colors in the middle range of the absorptivity scale to diffuse the solar energy over all the storage mass in the room. This can lead to overheating of the air, while other surfaces in the room may receive very little of the day's solar energy. Trombe walls should always be very dark to increase solar absorption. Do not cover the storage mass with furniture. Rugs and wall tapestries can also reduce the effect of storage mass to some degree.