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| Wayne N. Aspinall Federal Building and Federal Courthouse Grand Junction, Colorado gimole.com |
Historic preservation is, in my not so biased opinion, is one of the greenest profession around. The major goal is the retention of the historic integrity of a building during its period of significance. Sometimes, that can be a difficult task to accommodate modern technology into an older building and still it's historic fabric. Roger Chang posted a recent article on the Preservation Leadership Forum titled "Innovation, Sustainability, and Historic Buildings," which looks at the renovations of the General Service Administration's Wayne N. Aspinall Federal Building and the United States Courthouse in Grand Junction, Colorado and how they integrated more energy efficient systems into a historic building in a low-impact manner.
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| Archival image designcurial.com |
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| The IRS Office in the Aspinall Building gsa.gov |
Air is the most typically used medium for cooling or heating a building. However, fresh air has a poor relative heat capacity when compared to water or chemical refrigerant. You can move an equal amount of energy with a one-inch water pipe than with a 14"x14" air duct. Said pipe size can be further reduced by using a refrigerant. In the Aspinall Building, a VRF system was installed, consisting of a modulated compressor unit that moves heated or cool refrigerant to individual fan coil units in the ceilings near the spaces they serve. The method minimizes the amount of duct work installed in the building. The fan coils come in multiple styles, including low-profile modules under ten-feet tall, allowing for integration into shallow soffits or within custom spaces, thereby reducing the impact on the historic integrity of the space.
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| Interior of Wayne Aspinall Federal Building prlog.org |
All-air variable volume (VAV) is the most commonly used ventilation system used in commercial buildings. The amount of air brought to the individual space is regulated by a VAV box. When a space needs more cooling, the amount of air is increased. Multiple boxes are served by a large air-handling unit, some reaching the size of a typical living room. A different strategy used at the Aspinall Building was not only to provide the amount of air needed to ventilate the space, and use a separate system for cooling and heating, such as a VRF system. The result was a reduced amount of air required by a factor of factor of 3 or 4 while minimizing the amount of ductwork that wove its way throughout the buildings. In this particular case, an old boiler shaft was used for ventilation ductwork. Only one air-handling was used for the project, significantly cutting down the demand for a mechanical room area.
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| Aspinall Building solar canopy thebusinesstimes.com |
Unlike the outdoors, the ground temperature remains a constant all year round. The ground temperature in Grand Junction holds steady at 62°, while the air temperature can vary from a frozen 0° to a sizzling 100°. Contemporary air condition systems either take in or reject ambient heat. At the Federal Building, a GeoExchange system was put in place, consisting of thirty-two closed loop wells installed vertically up to 475 feet deep. As water circulates through the loop, it exchanges energy with the ground. During the year, the amount of heat taken in balances with the heat kept out. The system increased the efficiency the air-based system up to two times and reduced the need for that annoyingly loud clunky outdoor mechanical equipment. These effective technologies allowed for tall floor-to-ceiling spaces, maximizing natural daylight and preserving historic volumes. The corridor and lobby were restored, while the mechanical systems worked in the background to maintain a level of comfort.
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| The mechanical room of the Aspinall Building recool.com |
The project architects and engineers used other energy-efficient methods to reduce the demand for energy. One strategy was the installation of new lighting fixtures. Typical office lighting is designed to meet current energy code with a power density of 1.0 watts per square foot. The lighting system in the Aspinall Building is operating at below 0.3 watts per square foot, due to the installation of more efficient fixtures controlled by daylight and motion sensors.
Other changes incorporated reducing the energy demand for computers and other office equipment, which represents about 25% of a building
s energy usage. An average office may be designed to a power density of 1.5 watts per square foot for this type of load. However, the Aspinall Building is operating at nearly 0.25 watts per square foot because of the installation of occupancy controlled power strips and high use of laptops, instead of desktops.
All of these changes have resulted in a decline of energy use in the building. From March 2013 to February 2014, the Federal Building operated at an energy use intensity level of 21 kBTU/yr-gsf, before renewable energy production is factored in. This number represents about 70% less than the a similar type of building. Energy modeling played a crucial role in the design process, permitting the testing of energy and load reduction measures. The design team found that insulating the existing walls of the building had the greatest result of any one energy usage reduction method. Using a high-performance solar control film in the interior storm windows significantly reduced peak cool requirement, allowing for a smaller fan coil and ductwork sizes.
Design innovation for historic building focuses on reduction of the volume of systems, allowing the original building spatial and architectural defining features to be preserved and come to the forefront. At the Wayne N. Aspinall Federal Building, the original thermal mass and daylighting scheme were complementary to the technology used to reduce space and energy requirement. The result is a mutual integration of historic preservation practices and miniaturized technology making innovation at the Aspinall Federal Building possible.
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