According to data from the Solar Energy Industries Association (SEIA), five million square feet of building-integrated solar air heating collectors are now installed in North America. These systems represent 250 MW of thermal energy.

Solar air heating systems work by heating incoming ventilation air before it is brought into a building’s heating, ventilation and air conditioning (HVAC) system, using wall-mounted collectors that are typically made of metal and have 30-plus year lifespans.

According to BEAM Engineering, a Boston-based energy consulting firm, solar air heating is the most efficient renewable technology for generating thermal heat, and costs are as low as 6 cents per kWh.