The major obective of installing a solar, geothermal or heat exchanger system is to reduce the fuel bill through preheating of the winter ventilation air. It is important that before a preheating system is installed that the recommended levels of insulation in the walls, ceiling, perimeter and foundation be used. The major consideration in selecting a preheating system is the initial cost per crate or nursery pens. Other benefits of a preheating air system include: a more constant air temperature entering the building, less draft problems with preheated air and possibly better air quality in the building for pigs and humans, since a higher air flow may be used if the fuel costs are low. This paper is designed to be helpful in the selection of a preheating system based on the problems of these systems, actual performance data on these systems and owner experience on installation and management of these systems.