Great River Energy Headquarters

Photo credit: Lucie Marusin

Energy

Whole-building energy modeling began early in the design process to inform design decisions and system selection. Energy modeling predicts that the facility will operate with a 47.5% energy cost savings compared to ASHRAE Standard 90.1-2004. The synergistic energy strategies include optimizing daylight harvesting with lighting controls and a high-efficiency mechanical system combining a water-source heat pump with under-floor displacement ventilation. The displacement ventilation system allows cool air delivered to conditioned spaces to be warmer than it would be in a conventional ducted system. This reduced cooling load, with a lower "delta T," allows the load to be met with water-side economizer coils in the spring and fall. Displacement ventilation combined with heat recovery means that additional fresh air is provided without any energy increase.

The building receives nearly 14% of its energy from on-site renewable resources: approximately 10% from wind and 3%–5% from the photovoltaic array. The wind turbine produces up to 200 kW at full output and the photovoltaic array produces 72 kW at full capacity. On-site renewable energy can power approximately 50 homes annually. When these sources are combined with Green Power, purchased from off-site wind generation facilities, 100% of the building’s electricity is renewable, surpassing the 2030 Challenge’s 2015 non-renewable energy reduction target of 75%.

Bioclimatic Design

Maple Grove, Minnesota, is an extreme environment with four distinct seasons. The long, cold, dry winters and hot, humid summers require buildings to accommodate a wide range of climate conditions. Temperatures range from -10 degrees F to a humid 90 degrees F. Heavy precipitation, winds, and storms develop any time of year. Periods of warm sunny days invite people outdoors through the fall and spring months.

Because hot, humid summers, site noise pollution, and cold weather infiltration reduce the effectiveness of operable windows, the GRE team focused on envelope design and innovative, efficient mechanical, electrical, and plumbing (MEP) systems to maximize fresh indoor air and comfort through all seasons. Individual occupant controls and a 30% increase of fresh air are the result.

Building orientation and daylight atria optimize thermal performance and daylighting. Daylight modeling and envelope analysis early in the process shaped a building that is oriented to the site's microclimate and responsive to the intense demands of the regional climate. The result is a comfortable, flexible, and interactive workplace. A unique problem presented by the extreme climate is the great potential for occupant discomfort near building perimeters due to summer heat gain and winter heat loss. The GRE headquarters solves this problem by placing circulation spaces near the perimeter, with all occupied workspaces located inboard.

Energy security

Approximately 14.5% of the building's electricity needs are met through onsite wind power and photovoltaics.

Data Sources & Reliability

Reliability
Simulation: DOE II with exceptional calculations for thermal displacement and water source heat pump; savings from heat pump deducted from heating energy use.

EPA source energy use reduction (no onsite renewable energy): Energy Star rating: 82 or 33.0%

EPA source energy use reduction (with onsite renewable energy): Energy Star rating: 90 or 44.0%

LEED NC 2.2: percent energy savings (LEED Cr EA1 energy calculation - ASHRAE 90.1 2004): energy cost savings 48.5%

LEED NC 2.2: percent onsite renewable energy generation (energy cost): 478,000 kWh/year or 14.5%

AIA 2030 neutral reductions

• 2030 efficiency & conservation: 57.5 Kbtu ft²/year or 47%
• 2030 onsite renewable energy 9.9 Kbtu ft²/year or 8%
• 2030 reportable grid supplied renewable energy (Green-e Certified): 24.5 Kbtu ft²/year or 20% (Actual 100%)

Gross reduction of non-renewable energy: 91.9 Kbtu ft²/year or 75%

Gross non-renewable energy demand (relative to national average): 30.6 Kbtu ft²/year or 25%

EPA national CO2 Eq emissions reduction (no off-site renewable energy): 1,532.2 metric tons/year or 44%

EPA national CO2 Eq emissions reduction (with off-site renewable energy): 2,114 metric tons/year or 60%

Green Strategies

• Ground-coupled Systems
  • Use ground-source heat pumps as a source for heating and cooling
  • Use surface water as a sink for mechanical cooling
• Solar Cooling Loads
  • Use light-colored exterior walls and roofs
• Daylighting for Energy Efficiency
  • Design an open floor plan to allow exterior daylighting to penetrate the interior
  • Use atrium for daylighting
  • Use large exterior windows and high ceilings to increase daylighting
• Cooling Systems
  • Use waterside economizers in chiller-based cooling systems
• Photovoltaics
  • Use building-integrated photovoltaics (PV) to generate electricity on-site
• Other Energy Sources
  • Use a wind turbine system to generate electricity
• Ventilation Systems
  • Use displacement ventilation
• HVAC Distribution Systems
  • Consider using an access floor system

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Our thanks to the ENERGY STAR program of the U.S. Environmental Protection Agency, and to the U.S. Department of Energy, and to BuildingGreen, Inc. for hosting the submission and judging forms.

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