Humans have been designing homes and communities for centuries to maximize the air heating potential of the sun on cold days. Today's solar heating technology spans a wide variety of applications, both active and passive. Examples of passive solar air heating include sun facing thermal mass, such as thick stone walls that absorb the sun's heat and release it slowly to the living space, and placing windows to face the sun. Much of today's buildings unfortunately do not take advantage of the significant potential of many cost effective technologies and design considerations that could use the sun's energy for heating (and cooling) while reducing operating costs and fossil fuel use. Some newer solar air heating technologies became commercially available in the 1970s and commercialisation has recently accelerated.

Two major types of solar collectors can be employed for air heating. The first one is the traditional sealed panel with glazing on the front, black metal interior sides and an interior air space with piping for air to pass through. By placing the panels facing the sun, the air inside the collector is heated. An electric fan/blower brings air into the collector from inside the house through a duct and returns hot air to the house through a different duct. This type of panel collector is often used in fairly air and energy tight houses to reduce the use of gas or electric heat. The second type and most commonly used collector for large spaces is the perforated-plate or transpired solar one. Perforated-plate solar collectors are a mature technology widely commercially available in Canada.

Perforated-plate solar collectors double as exterior wall cladding and mount to a south or southwest facing wall of a building leaving an air space between the metal cladding and the exterior of the building. The collector is a dark coloured metal cladding with small holes throughout. As the sun hits the cladding, warm air enters the space between the dark cladding and the exterior wall of the building. The air is heated and rises to a ventilation system, which distributes the warm air. Perforated-plate solar collectors are used in a variety of applications where heated air is required such as agricultural drying, industrial heat processes, warehouse and office building heating. The majority of installations are on larger buildings, however new applications of the technology have been developed for smaller buildings and household applications. The collectors contribute to destratification of air, assist with dehumidification and fresh air circulation. The collectors can be connected to an existing or new ventilation system. Canada is a world leader in solar air heating technology. Conserval is a Canadian company and inventor of Solarwall, a leading high quality perforated-plate solar air heating collector.

The economics of solar air heating depend on the application and technology employed. Projects typically have a payback of 1-5 years and because they double as wall cladding can be installed on new construction for little to no additional cost. Where fresh air circulation, air destratification or heat assistance with dehumidification are desired the perforated-plate solar collectors provide multiple benefits.

For more information on this topic, please read the full technology report and visit: www.cansia.ca