The nation’s largest energy user, the Department of Defense (DoD), is learning how to transform some of its 577,500 buildings and structures into state-of-art energy-saving powerhouses, by retrofitting old buildings with new high-tech roofing systems. In partnership with the Metal Construction Association (MCA) and the Department of Energy’s Oak Ridge National Laboratory, the DoD is host to a demonstration project for reducing a building’s carbon footprint and lowering demand for energy and water. The demonstration project was part of the DoD’s Strategic Environmental Research and Development Program (ESTCP) at Goodfellow Air Force Base (GAFB) in San Angelo, Texas. The model will be replicated at potentially thousands of DoD buildings throughout the country.
“We are thrilled to see this technology come together. Both the MCA and DoD see a great benefit to the broader U.S. economy when new and retrofit buildings throughout the country adopt this high-performance roofing design, and work toward net-zero energy buildings,” says Scott Kriner, technical director, Metal Construction Association.
The dynamic roofing system was installed at the Security Forces Building at GAFB and performs many functions, using a combination of technologies that heat and cool air and water, produce electricity and collect rainwater. The metal roof retrofit system can be installed over an existing roof, saving installation costs and keeping old roofing material out of landfills. What makes this roofing system unique is that it brings together multiple functions in one holistically designed, integrated building envelope system that can be used on flat or sloped roof designs.
The technology used is a hybrid of metal roofing, insulation, hydronic solar thermal systems, engineered air pathways, and photovoltaic (PV) cells, all designed to work symbiotically. This high performance system includes a retrofitted metal roof installed over the existing roof, which creates a cavity between the existing and new roofs. Within that cavity insulation, solar thermal heating systems and cooling of air and water for the building can be installed. More specifically, the technologies incorporated into the metal roof system are:
1) Cool metal roofing: high solar reflectance coatings on metal save up to 25 percent in summer cooling energy costs and helps mitigate the heat island effect in urban areas.
2) Solar thermal water heating: sun is used to preheat water for use inside the building, reducing the use of fossil fuels or electricity for hot water heaters. The heated water can also be used for space heating using a heat exchanger.
3) Rainwater harvesting: this subsystem harvests, manages and reuses rainwater for non-potable applications such as watering landscaping or flushing toilets.
4) Solar electric (PV) panels: thin film solar panels laminated on the roof provide energy for the building and even allow electricity to be sold to the grid.
With the roofing system installation at GAFB, the DoD and the MCA are demonstrating how integrating energy efficiency and solar technologies with a retrofit metal roofing system can reduce energy and water consumption, mitigate the building’s environmental impact and lower construction and operating costs.