"For Aggressive Efficiency, Choose Passive Solar"
As we discussed in the November/December issue, low-hanging solar-responsive design strategies reduce a building's energy consumption and typically cost less than the high-hanging solar-collecting technologies--or nothing at all. (See "Choose the Low-Hanging Fruit" by Lechner.) In this issue we focus on passive solar heating technologies.
Most passive solar space-heating systems are of three major types: south windows, also called direct gain; Trombe walls, where south-facing glass covers a mass wall; and sunspaces. A Trombe wall system delivers no light, only heat into the space. Although sunspaces are the least efficient and most expensive, they are popular. Besides their basic construction cost, they are expensive to insulate and shade. The most sustainable sunspaces are those that have no east, west or overhead glazing. In effect, they are south-facing building spaces that are not mechanically heated or cooled. Their south facade would be all glass and may be more than one story high.
There is no truth in the idea that solar energy is too expensive to collect. It all depends on the system.