In their simplest form, rotary air-to-air heat exchangers "heat wheels") typically exchange sensible heat only between two air streams, although several manufacturers offer a desiccant impregnated type, which also transfers moisture from one air stream to the other. Exchangers are typically used when a building or system requires large quantities of exhaust, and thus large quantities of make-up air. An important first step in incorporating rotary air-to-air heat exchangers into a system is to verify the need for large quantities of fresh air and exhaust.

This paper explores alternatives to consider, economics of use, and operating characteristics.