King County Housing Authority

Chartered in 1939, The King County Housing Authority (KCHA) provides affordable housing services to the Seattle area.

Challenge: To transform an aging strip mall with light insulation into a 21st Century high-performance building with notable indoor air quality and impressive energy savings, within the confines of a tight budget.

In the summer of 2011, KCHA issued an RFQ seeking to consolidate multiple offices and departments under one roof. They had recently purchased a 36,000-square-foot, 1980’s retail/warehouse space, which required a complete interior renovation to meet the operational needs of the agency. The budget was tight but they persevered with an aggressive goal to create an affordable “Net Zero Energy Ready” building.

The RFQ was won by a team of local LEED®-accredited architects and engineers: Rice Fergus Miller Architects, Bremerton, Wash., and engineering firm, Ecotope, Inc., Seattle.

According to Ecotope’s Principal Mechanical Engineer, Jonathan Heller, Variable Refrigerant Flow (VRF) zoning engineering from Mitsubishi Electric US Cooling & Heating Division (Mitsubishi Electric) was a natural choice for meeting the high-energy bar set by KCHA. “VRF technology is absolutely the industry’s best,” Heller said. “In fact, we selected this system for our own headquarters in order to showcase a model of energy conservation.”

According to Heller, VRF zoning systems were ideal for KCHA because they offered: maximized zoning capability; extreme quietness; no extra space for a large, traditional central air system; large savings on reduced ductwork and compressor capacity; and large energy savings associated with reduced fan energy and high heating efficiency. Heller said that the industry rule of thumb is one ton per 400-square-feet of space. “With careful design and high efficiency energy recovery ventilation, we only needed about half that size, one ton of the Mitsubishi heat pumps for every 720-square feet.”

“As an engineer, Mitsubishi Electric’s VRF zoning system is easy to design,” Heller continued. “The zoning flexibility means that comfort will never be an issue regardless of the building’s siting. Mitsubishi Electric’s control system allows for the indoor fan coils and outdoor compressors to run only when the controls call for cool or heat. This leads to huge fan energy savings compared to a traditional ducted system.”

The only HVAC equipment that demands continuous operation is a low volume Energy Recovery Ventilation Unit (ERV) that operates during all occupied hours. The ERV is a machine that draws fresh air into the office and exhausts stale air. It transfers heat from the exhaust air to temper incoming ventilation air, providing a high level of indoor air quality.

Solution: The VRF zoning system from Mitsubishi Electric helped create an ASHRAE Award-winning, energy-efficient design that uses one-third the energy of its previous office building and has an Energy Use Index (EUI) of 26 KBtu/SF/yr.

“This project is achieving an amazing annual Energy Use Index (EUI) of 26 KBtu/sf/yr based on the first year of full occupancy,” Heller said. “This is one-third the energy use of the typical office building across the street and 70 percent less than the national annual EUI average for office buildings, which is about 93 KBtu/sf/yr. The strong results of this finding lead ASHRAE to award this project its Second Place 2014 Technology Award for Systems Innovation. The building achieved an ENERGY STAR® rating of 97, indicating that it is more efficient than 97 percent of office buildings in the country.

“Working with an extremely tight budget, it was a colossal challenge to forge a high performance building out of an old, worn out retail space,” said Greg Belding, principal at Rice Fergus Miller Architects. “We could not have achieved an energy-saving design without the ingenious VRF engineering from Mitsubishi Electric. A conventional VAV forced air system would never have worked.”