The City of Sitka, Alaska, has successfully reduced its reliance on expensive oil through three major energy-efficient retrofits. Renovations to the public library, the US Forest Service Office, and public convention center eliminated the use of fuel oil, according to a new in-depth case study from ASHRAE’s High Performing Buildings magazine.
In recent years, the city of around 9,000 relied on oil for heating that had been mined in the state, shipped to Washington for refining, and barged back to Sitka, ASHRAE’s Jonathan Heller explained. In response to energy challenges, the city invested $145 million to expand their hydropower resources, alleviating pressure on the local municipal electric system.
The three renovations profiled show how changes to existing buildings can help municipalities reach their carbon-neutral, energy-efficient goals. Here’s an overview of key lessons learned:
Sitka Public Library
The local library switched from an oil boiler to a heat pump system. Added envelope insulation and heat recovery ventilation lowered the heating energy requirement, Heller reported. A high-efficiency VRF heat pump system provides hydronic-radiant and airside space heat and cooling, plus efficient fans and LED lighting also lower electricity use.
Original plans for detailed submetering to track lighting, fans, heating, cooling, hot water, and various plug loads in real time had to be adjusted. A simpler system enables tracking total energy use and submetering of the heat pump system, Heller noted.
“The lesson learned is more communication with all parties early in the project is always better and local conditions and politics are often difficult to negotiate from outside Alaska,” he wrote. “Furthermore, it is important to know when to step back, as the client ultimately must make the decisions regarding final design and contracting issues.”
US Forest Service Office
Previously the US Forest Service office located on the edge of town relied on an oil boiler and radiators for heating. An envelope upgrade along with a high-efficiency heat recovery ventilator reduced heating energy demand to about 50% of a typical code-compliant design, Heller reported.
Radiant heat in the floor comes from a wood pellet boiler manufactured in Europe that uses untreated wood pellets made from compressed waste sawdust. An automatic feed mechanism sends pellets into the burn chamber gradually.
HVAC contractors, the local forest service management, and maintenance personnel were hesitant about switching to a wood boiler since there had been an injury caused by one elsewhere in the state, Heller explained. Loading the hopper had also been done by hand.
“To overcome the local office’s reluctance, we designed the air-to-water backup heat pump system to provide system redundancy so the building can switch back and forth from pellets to highly efficient electricity depending on pellet availability and price,” Heller notes. “After the first year of operation, the pellet boiler has performed without incident.”
Harrigan Centennial Hall
Situated next to the public library, Harrigan Centennial Hall serves as a public gathering space and a welcome center for summertime tourists arriving by cruise ship.
“The original building was based on large 4-pipe fan coil air handlers with fixed outdoor air supply provided with hot water from an oil boiler and chilled water from an air-cooled chiller,” Heller explained.
A new system decoupled the ventilation from the heating and cooling. Now a zonal air-to-air VRF heat pump with low-fan-energy ductless ceiling cassettes in most zones provides heating and cooling.
Initially the heat pumps and refrigerant piping were installed in ways that generated loud vibrations. “One primary lesson learned at Harrigan Centennial Hall is that VRF equipment vibrations must be adequately isolated from the building structure to eliminate noise complaints,” the case study concluded.
Heller says that local incentives and rebates are helping Sitka transition from fuel oil to municipal electricity. “The city has seen a surge of demand for ductless heat pumps and has seen an improvement in local air quality from using less oil and wood heat,” he wrote.