VRF Provides Historic Building with 25 Percent Energy Savings
Savery Hall was designed in 1917 by the architectural firm of Bebb and Gould in the Collegiate Gothic style. Founder and first chair of the architecture program at the University of Washington, Carl Freylinghausen Gould was a leading architect in the Pacific Northwest. With his partner Charles H. Bebb, Gould was responsible for many notable Pacific Northwest buildings including the Seattle Art Museum and the campus plan of the University of Washington (UW).Top 16: A Legacy of Green Building and Sustainability
With a legacy of green building excellence, UW is currently managing 26 LEED® projects, including Savery Hall. For the third year in a row, UW has received an “A” grade in the “Green Building” and an “A-” overall on the College Sustainability Report Card issued by the Sustainability Endowments Institute. Of the 300 colleges surveyed, the report card identified UW as one of the 16 best sustainability leaders.
In 2004, UW established a plan titled “Restoring the Core” to renew and renovate 26 significant buildings on the Seattle campus. The plan identified the deteriorating conditions of these buildings which total more than 900,000 square feet and house more than 40 academic programs. Aligned with UW sustainability goals, Savery Hall is one of the 26 “Restoring the Core” buildings. A top priority for these projects is lowering the cost of operation through the reduction of energy usage. To this end, Savery Hall is a LEED-NC v2.1 candidate for major renovation; the primary goal, to design an HVAC system that would augment a naturally ventilated building.
Overhauling the 90-Year-Old Building
According to Brian Berard, AIA, LEED AP, senior project manager for Savery Hall, UW Capital Projects Office, the mechanical, electrical and plumbing systems in the building were operating well but they had exceeded their service life; they did not satisfy current code demands and were totally inefficient. The 90-year-old building was in need of complete renovation.
Understanding UW’s dedication to sustainable design practices, reducing energy use and its carbon footprint, Berard’s team replaced all mechanical, electrical, telecommunication and interior finish systems to meet today’s classroom and academic program needs.
To comply with UW’s design criteria and reduce energy consumption, during the pre-design and schematic design phases, the team looked at a traditional variable air volume (VAV) system without mechanical cooling. After all, Seattle’s climate is mild – the ASHRAE outdoor summer design temperature is 85 degrees Fahrenheit.
Mitsubishi Electric VRF Zoning Solutions: Perfect for Historic Buildings
After further modeling and a natural ventilation analysis, it was evident that Savery Hall could not be adequately cooled utilizing natural ventilation alone. An alternative cooling system had to be selected. The team turned to VRF (Variable Refrigerant Flow) zoning systems. “We first looked into a 4-pipe system,” Berard said, “but we soon found that going this route would cost a fortune in installation costs, equipment and ducting.”
Berard and his team looked at multiple VRF technology systems and finally selected a system from Mitsubishi Electric Cooling and Heating Solutions, Suwanee, Ga. Berard said that the ingenious, multi-zone system was selected for Savery Hall because of its energy-efficient, high performance INVERTER technology; variable speed compressors; simultaneous cooling and heating capability; the extremely quiet indoor units; the light-weight, small footprint of the outdoor unit; and its capacity to orchestrate a mixed-mode solution employing both VRF and natural ventilation. Last but not least, Mitsubishi VRF systems require only a three-inch hole in the exterior of a building for piping and wiring, preserving Savery Hall’s historic architectural integrity.
Mixed-mode Solution: Making Use of Natural Ventilation
Berard’s team had its eye on UW’s mandated goals of sustainability and energy savings. This was a LEED project and the team had set its sights on nothing less than LEED Gold certification. To maximize energy savings, it was decided that a mixed-mode approach – a combination of the sophisticated Mitsubishi controls network and natural ventilation was the best way to achieve these goals.
Natural ventilation is the use of a building’s shape and orientation, coupled with wind and warm air buoyancy, to induce airflow through a building. This natural airflow ventilates and cools the building. Air is typically introduced at the windows and exits the building at a high point. Natural ventilation would play an important role in achieving LEED credits. In Seattle’s mild climate, one can typically open the windows from March through July and from late August through October.
The team developed a “Red Light/Green Light” operation for the exterior zones with operational windows. When the outside temperature is optimal for pulling in outside air, a green light turns on above the window informing the tenant that they could open their windows. When this happens, the Mitsubishi Electric fan coil turns off – goes into a “sleep” mode – saving energy and increasing natural ventilation. When the red light is on, windows are closed and the fan coil automatically turns on providing the tenant with individually zoned and controlled comfort. All the ducted interior zones are fed with outside air from a large air handler on the roof.
The VRF Role in the Mixed-mode Solution
Berard explains that the Mitsubishi Electric VRF system is designed to transfer cooling or heating from one of the building’s eight zones to another. This means that in the winter, heat is pulled from the side of the building facing the sun and transfers it efficiently to the cold side of the building demanding heat. The reverse is true in the summer, providing the building owner with considerable energy savings.
At Savery Hall, there are 12 Mitsubishi Electric R2-Series outdoor units located on the roof. Refrigerant piping connects the outdoor units to 19 circuit controllers and 161 indoor units, providing a means of energy transfer between the zones. Forty floor-mounted indoor units were specified to service the mezzanine office spaces which had no ceiling space to house heating and cooling ductwork. All other office spaces, as well as conference rooms and classrooms, use ceiling-concealed units. Each of the 121 ceiling-concealed indoor units was provided with direct-ducted outside air.
Rock Solid Technology: 25 Percent Energy Savings
Berard said the mechanical engineering consultants on his team are all LEED-certified professionals. They are estimating that the Mitsubishi VRF system will reduce the energy consumption by 25 percent annually with even greater savings obtained by incorporating natural ventilation. The sustainability manager at UW feels certain that the innovative VRF zoning solution will ultimately help secure LEED Gold certification for Savery Hall.
“The University has been very happy with the performance of this system and the quality of the equipment,” Berard said. “I am delighted that we chose to go with Mitsubishi VRF zoning systems - the technology is rock solid. For a 90-year-old structure, I believe our mixed-mode strategy delivered a dynamic lesson in performance.”
