applications can be done through the use of solar air heating panels. This configuration operates by drawing air from the building envelope or from the outdoor environment and passing it through the collector where the air warms via conduction from the absorber and is then supplied to the living or working space by either passive means or with the assistance of a fan. A pioneering figure of this type of system was George Löf, who built a solar-heated air system in 1945 for a house in Boulder, Colorado. He later included a gravel bed for heat storage. Ventilation, fresh air or makeup air is required in most commercial, industrial and institutional buildings to meet code requirements. By drawing air through a properly designed unglazed transpired air collector or an air heater, the solar heated fresh air can reduce the heating load during daytime operation. Many applications are now being installed where the transpired collector preheats the fresh air entering a heat recovery ventilator to reduce the defrost time of HRV's. The higher your ventilation and temperature the better your payback time will be. Process heating Solar air heat is also used in process applications such as drying laundry, crops (i.e. tea, corn, coffee) and other drying applications. Air heated through a solar collector and then passed over a medium to be dried can provide an efficient means by which to reduce the moisture content of the material. High temperature process heat can be produced by a solar furnace. Solar air heating collector types Collectors are commonly classified by their air-ducting methods as one of three types: through-pass collectors front-pass back pass combination front and back pass collectors Collectors can also be classified by their outer surface: glazed unglazed Through-pass air collector Offering the highest efficiency of any solar technology the through-pass configuration, air ducted onto one side of the absorber passes through a perforated material and is heated from the conductive properties of the material and the convective properties of the moving air. Through-pass absorbers have the most surface area which enables relatively high conductive heat transfer rates, but significant pressure drop can require greater fan power, and deterioration of certain absorber material after many years of solar radiation exposure can additionally create problems with air quality and performance. Back, front, and combination passage air collector In back-pass, front-pass, and combination type configurations the air is directed on either the