Aldo Leopold Legacy Center
The First Carbon Neutral Building
As the first building to be recognized by LEED as carbon neutral, the Aldo Leopold Legacy Center has helped to set the standard for carbon neutrality in green buildings for the future. The initial carbon balance for the Legacy Center is based on estimates of carbon flows: emissions from combustion, electricity generation and other foundation activities; projected offsets from renewable energies; and carbon sequestered by the foundation’s forested lands. Accounting procedures and measurement systems have be set in place to record actual carbon flows annually. Estimating conservatively, carbon flows are projected to be:
- Total emissions: 13.42 tonC/yr
- Offset from renewable energies: -6.24 tonC/yr
- Forest sequestration: -8.75 tonC/yr
- Net result: -1.57 tonC/yr
Energy modelers have chosen to use figures that should overestimate the Legacy Center’s carbon emissions and underestimate the amount of carbon offset or sequestered, meaning the Legacy Center’s projected carbon budget leaves a cushion for error. By operating within this carbon budget, the Legacy Center now meets the ambitious goals established by the 2030ºChallenge.
Zero Net Energy
To make the Aldo Leopold Legacy Center carbon neutral in its operation, it first needed to be built as a net zero energy building. The design team studied nine existing high performance buildings to develop performance standards for the Legacy Center. Net building energy demand is calculated as the difference between building energy use and solar energy produced; in a zero energy building, this number should be zero or less. The buildings reviewed are listed by net energy use from least to greatest. Based on the low energy demand of the Woods Hole Research Center, the design team set 5 kWh per square foot floor per year (17 kBtu per SF per yr) as an energy performance goal for the Aldo Leopold Legacy Center. Given that goal, roughly 3,000 square feet of photovoltaic panels would be needed to produce the energy the building would require, leading to a zero energy building.
Building Measured |
Building Energy Use (kWhr/SF/yr) |
Solar Energy Produced on Site (kWhr/SF/yr) |
Net Energy Use (kWhr/SF/yr) |
Woods Hole Research Center |
4.7 |
1.6 |
3.1 |
Lewis Center Oberlin College |
8.7 |
3.9 |
4.8 |
Zion NP Visitor's Center |
7.9 |
0.7 |
7.2 |
NREL Thermal Test Facility |
8.4 |
0.0 |
8.4 |
Schlitz Audubon Nature Center |
9.1 |
0.3 |
8.8 |
Cambria Office Building |
10.8 |
0.3 |
10.5 |
Urban Ecology Center |
14.6 |
3.2 |
11.4 |
Big Horn Building Materials |
11.6 |
0.1 |
11.5 |
Chesapeake Bay Foundation |
11.8 |
0.1 |
11.7 |
Aldo Leopold Legacy Center |
Projected: 5 |
Projected: 5.1 |
Projected: -0.1 |
Given the extremely low demand of the Woods Hole Research Center, the design team focused on design options that would reduce demand. Four guiding principles for the design team were:
- Design all occupied space as perimeter zones allowing daylight and natural ventilation
- Maximize the number of hours electric lighting can be turned off during occupancy
- Maximize the number of hours the HVAC system can be turned off during occupancy
- Minimize pumping power in all pipes and ducts
Carbon Neutral Analysis
The carbon neutral analysis for the Legacy Center took into account direct and indirect emissions, offsets, and sequestration occurring on the foundation’s forestlands.
Direct Carbon Emissions due to Combustion
Direct emissions of carbon include two sources: stationary combustion devices and fuel combusted in organization owned vehicles. Emissions from foundation vehicles are easy to track by monitoring fuel purchases; tracking emissions for stationary combustion devices requires a little more creativity. The Legacy Center has three wood burning stoves and one fireplace installed in the building. To estimate emissions, the Aldo Leopold Foundation staff will set aside two full cords of wood (approximately 5 tons), to be weighed when stacked) for the 2007 – 2008 heating season. Any wood remaining at the end of the heating season will be weighed again to determine the mass of wood combusted.
Indirect Carbon Emissions due to Electricity Generation
The Aldo Leopold Foundation Legacy Center is projected to generate 61,268 kilowatt hours (kWh) of electricity per year from the solar panel array. At night and on days when solar-generated electricity does not meet the building demand, electricity will be purchased from Adams-Columbia Electric Cooperative
To offset the emissions of the purchased electricity, the Aldo Leopold Foundation has contracted to purchase wind-generated electricity from the utility.
Indirect Carbon Emissions due to Other Organizational Activities
ALF’s long-term goal is to account for all possible carbon emissions due to organizational activities. Emissions due to employee commuting, employee business travel, water supply, sanitation, and solid waste removal are estimated as a part of this carbon balance. Emissions due to visitors traveling to the center will be included once an average visitation rate can be established. Practices such as employee carpooling have not been included in this analysis, but would further lower emissions.
Employee air travel was calculated at a rate of 10.0 lbs carbon per 100 passenger miles. With an estimate of 36,000 air travel miles per year, the annual carbon emissions for business air travel is projected to be 1.80 Tons carbon per year. The Aldo Leopold Foundation will track actual employee business travel (air and car) for a more accurate annual emissions report.
The Aldo Leopold Legacy Center pumps water from a well on site and uses an on-site septic field for sanitary waste removal. All energy used in the pumps, and, therefore, all carbon emissions due to water and sanitary systems is included in the electric energy consumption of the building.
Carbon emissions from solid waste removal have been derived by estimating the emissions generated per unit mass of material removed. ALF employees and visitors are asked to recycle as a standard practice; however, recyclables must still be hauled away from the site, contributing to total carbon emissions. The Aldo Leopold Foundation is assumed to generate 5,200 lb waste material per year (100 lb per week) contributing 0.92 Ton of carbon emissions per year.
Carbon Sequestration
The Aldo Leopold Foundation owns over 500 acres of forest. Prior to constructing the Legacy Center, the foundation certified 35 acres, including roughly twenty containing red and white pine planted by Aldo Leopold and his family, according to Forest Stewardship Council (FSC) rules. A selective harvest of these acres culled the smaller diameter trees to use as building materials in the Legacy Center. While mature trees have a slower rate of sequestration than rapidly growing saplings, they still are able to store more carbon each year due to their size. Prior to harvest, a percentage of the trees to remain were measured to set a baseline of the volume of wood in the forest. In the fall of 2007, those trees will be re-measured to determine their growth rate and estimate the growth rate of the forest; this measurement will be repeated every 6 years. For now, in absence of a measured sequestration rate, a conservative rate of 500 Lb carbon per acre will be assumed (a conservative estimate). The 35 acres of FSC-certified forest will then be stoing 8.75 tons of carbon per year. The rest of the foundation’s forested acres will not be included in the carbon neutral analysis of the Legacy Center.