New Forest Ranger Station
KJWW provided engineering design and energy modeling for the administrative building of the U.S. Forest Service’s new Chippewa National Forest Ranger Station.
The 13,035-square-foot, two-story administrative facility is seeking LEED Silver certification. The project scope also included other buildings on site – an attached heated warehouse, unheated garage and a crew quarters. Energy modeling was not performed for these structures.
In accordance with the U.S. Department of Agriculture’s federal guidelines, the overall project was required to achieve a 30 percent reduction in energy in comparison to the ASHRAE-90.1-2007 baseline. The HVAC system efficiency for the administrative building was optimized to help achieve the overall energy reduction goal. Several HVAC system options were considered and then further defined using energy modeling. A bio-mass, 272-kBtu pellet-burning boiler ultimately was chosen for the heating system. A high-efficiency, propane-fired, condensing-style boiler also was installed to be used during low load and peak load conditions. The pellet boiler will provide the majority of the heat load for the building throughout the lengthy Minnesota winters. An on-site storage facility holds about a two-month supply of pellets.
During warmer months, an air-cooled condensing unit provides cooling for the administrative building.
A dedicated outside air handling unit with energy recovery provides ventilation air for the administration building. Demand control ventilation, using CO2 sensors, is used in high-occupant areas to limit the ventilation air when the rooms are not in use. To avoid mechanically cooling or heating the outside, end switches shut off the dedicated outside air unit whenever an operable window is open. Wall monitors light up green when windows can be opened in each room, allowing fresh air to circulate at suitable times for both optimal air quality and energy use. A variable air volume unit conditions individual spaces in the office area.
Lighting and controls are designed for minimal energy use and are LEED compliant. Occupancy sensors are used throughout for automatic shut-off, with daylight sensors controlling lights closest to windows. Areas such as conference rooms are provided with multi-level switching and dimming to allow for flexibility of room use and energy savings.
A propane-fired, semi-instantaneous water heater provides domestic hot water to the building. Low-flow fixtures and dual-flush water closets reduce water usage.
The project was modeled with Trane Trace and submitted to LEED for approval. Numerous reports were developed to show progress and updates during each of the required USFS review sets.
A metering system connected to a national Forest Service database allows the agency to track building performance and make adjustments.