The United States Department of Energy (DOE) calls transpired solar collectors “the most reliable, best-performing, and lowest-cost solar heating systems for commercial and industrial buildings available on the market today.”Transpired solar collectors (solar heating and ventilation systems that perform like heaters but resemble conventional metal cladding) are improving indoor air quality, saving money, and reducing energy costs for building owners across North America, Europe, and Asia. Years of research have facilitated a completely new approach to solar heating: an approach that is simple, inexpensive, highly efficient, and can be seamlessly integrated with many architectural styles. Transpired solar collector systems are similar to other metal walls and possess all the benefits of metal cladding, such as strength, durability, and aesthetic versatility – yet, they also have the additional advantages of improving indoor air quality while decreasing energy bills and CO2 emissions. As ASHRAE states, the best way to avoid illness due to poor indoor air quality is to increase the volume of fresh air entering a building. But, the negative impact of uncontrolled outdoor air is increased heating costs. Transpired solar collectors solve this problem by using solar energy to preheat ventilation air.The concept is straightforward and efficient. Perforated metal cladding is used to draw in heated fresh air off the surface of south-facing walls, where it can then be distributed throughout the building as pre-heated ventilation air. The genius of the all-metal transpired system is in the panel’s fundamental simplicity: With no moving parts, solar energy is used to heat fresh air, which is then brought into the ventilation system. It is easily integrated into new construction or during a retrofit, and fan units can be supplied if the existing system is inadequate or unavailable.Solar heating and ventilation systems are suitable for a wide variety of applications, such as manufacturing, industrial, and municipal buildings. And they’ve already been installed at facilities such as Ford Motor Co.; General Motors; Federal Express; Bombardier; NASA; Goodyear Tire; the United States Army; and the Cities of Toronto, Rapid City, Calgary, Minneapolis, and many others in over 20 countries. It is technology that is tried, tested, and proven to generate successful results. The concept of using solar cladding to produce free heat and ventilation air has generated tremendous recognition from the building community, garnering numerous honors and awards from the U.S. DOE, Natural Resources Canada, ASHRAE, the Toronto Construction Association, Popular Science magazine, R&D magazine, and more.Typical energy savings are in the range of two to four therms per square foot of solar cladding per year. This translates into a dollar savings of $2 to $6 per square foot each and every year, depending on fuel costs. Additionally, there are numerous tax incentives and grants available for companies and municipalities installing solar heating and ventilation systems. Some states, such as Illinois, offer grants of up to 50 percent of the total cost for businesses installing renewable energy systems. Also, the federal government offers an additional 10-percent corporate tax credit, thereby making the purchase of a system even more cost-effective.Now, building owners have a choice: a conventional wall with no payback; or a high-performance metal wall with a payback, a green image, and the ability to improve indoor air quality. The solution should be obvious – put those metal walls to work and get green back!Victoria Hollick is a technical writer at Toronto, ON-based Conserval Engineering Inc. ().