Designing a landmark school in the unforgiving Alaskan terrain, McCool Carlson Green Architects set out to create a prototype for schools in the region employing sustainable design. While successfully securing LEED® Silver certification from the USGBC, the Fred and Sara Machetanz Elementary School fosters learning while utilizing the surroundings to enhance the creative spirit of the students.
Situated in a subarctic environment, snow covers the ground much of the school year. Winter days are extremely short (5.5 hours at solstice) and sun angles are low (7.5 degrees above the horizon at high noon of the winter solstice). Periodic 100+ mph winds sweep down the Matanuska Valley and across the site from the east. Among the challenges was designing a heating system that cut back on energy usage yet still allowed for the large open space that encouraged learning.
Completed in time for the 2009-2010 school year, the 54,000-sq-ft facility incorporates high ceilings and numerous windows to help capture the minimum amount of day lighting available. To maximize the severely limited light hours in the winter, classrooms all run along the southern façade with glazing to maximize the daylight while the interiors face the atrium itself. This 1,768-sq-ft, 36-ft high main atrium, which is the nerve center of the school, is lit by south-facing clerestories. This part of the building had to incorporate natural light and airflow, due to LEED certification, said Thomas Lytle, school principal.
CIRCULATING SAVINGSThe centerpiece of this space is a 12-ft large diameter, low-speed fan powder coated yellow, aiding in the thermal comfort of the occupants. “The fan helped improve the indoor environment of the building with a passive strategy of reversing the convection and getting our hot air off the ceiling back down to a floor,” said Jason Gamache, sustainability coordinator with McCool Carlson and Green. This is the exact effect, the destratification of air, for which engineers designed the fan.
Along with the lighting and heating system, the fan is incorporated into the BAS to accommodate the change in daytime and nighttime thermostat setpoints required to maintain the given temperature.
In the winter months, most notably between October and February, the daytime thermostat setpoint of 68°F is reduced to 55° overnight. According to Ricky Jensen, resource conservation manager for facilities for the Matanuska-Susitna Borough School District, the inclusion of the Big Ass Fan in the BAS at Machetanz has resulted in a significantly reduced heat time for the facility.
“There is really no comparison with that site and any other school in the district,” Jensen said. “The system kicks on at 5:30 in the morning to make sure the building is comfortable by the time staff and faculty start arriving at 6:30. The temperature recovery is almost immediate, taking only 15 to 20 minutes. Other sites take three or four hours to heat up. The movement of the heat throughout the building is almost perfect.”
By thoroughly mixing the air within the space, a reduced buildup of heat will occur at the ceiling, resulting in less thermal conduction through the walls and roof and more uniform temperatures throughout. “Even though the thermostat setpoint remains the same in the winter, the heating system does not have to work as hard to maintain the given setpoint,” said Christian Taber, applications engineer and LEED AP for Big Ass Fans. “By reducing the amount of heat escaping through the roof, it’s similar to turning the thermostat down five to seven degrees.”
PASSING THE TESTPutting the system to the test, Machetanz had to maintain 68° during the first year after the installation of their carpeting and laminate per the manufacturer’s instructions. If the temperature dropped too low, the adhesives would no longer adhere. In order to keep the warranty on the flooring, Jensen used the fan 24/7 to maintain the required 68° which, he said, significantly reduced the excesses use of the boiler system.
The colorful, open floor plan and natural lighting provides an appealing backdrop for learning but, given the size, can bring about mechanical concerns as HVAC systems have to work. The addition of air circulation goes a long way in creating a learning space that is both functional and intellectually stimulating while serving as a sustainable design element.