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Aldo Leopold Legacy Center (Wisconsin, USA)

Credits: ©2009 Aldo Leopold Legacy Center

The Leopold Center utilizes green architecture to be a net zero energy green building, meeting all of its energy needs on site. Despite the contrasts of Wisconsin’s four-season climate, the Leopold Center uses 70 percent less energy than a building built just to code, and the center’s roof-mounted solar array is projected to meet 110 percent of the building’s energy needs on an annual basis. The Leopold Center helps us to envision how we can use energy more efficiently and develop positive relationships to other people and the planet. Through energy efficiency, renewable energy, and an ongoing commitment to land stewardship, the Leopold Center became one of the first carbon neutral buildings in the world—meaning annual operations account for no net gain in carbon dioxide emissions. (Scroll to bottom for additional resources.)


Aldo Leopold Center from Above

The Leopold Legacy Center is a carbon-neutral, ‘zero net energy’ building that produces more than110 percent of its annual building energy needs. ©2011 Kubala Washatko Architects

The initial carbon balance for the Leopold 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 been 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 Leopold Center’s carbon emissions and underestimate the amount of carbon offset or sequestered, meaning the Leopold Center’s projected carbon budget leaves a cushion for error. By operating within this carbon budget, the Leopold Center now meets the ambitious goals established by the 2030ºChallenge.

Zero Net Energy
To make the Leopold 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 Leopold 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 Leopold 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.

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 Leopold 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 Leopold 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 Leopold 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
The foundation'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 Leopold 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. Foundation 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 Leopold 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 Leopold 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 storing 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 Leopold Center.

The Future of Energy
The conversation about the future of energy in America has focused narrowly on developing new energy sources such as finding new reserves of fossil fuels and increasing the gallons of ethanol produced from corn. Energy conservation is a far more lucrative investment which pays many dividends, including economic returns for the investor.

On an annual basis, the Leopold Center is projected to produce 110% of the energy consumed on site. By focusing on energy conservation from the beginning of the design process, we are able to meet the bulk of our energy needs during the winter—and generate income during the summer by selling surplus electricity to the local utility.

Buildings account for 38% of our total energy use, including 71% of our electricity use. Considering that 75 percent of buildings standing today are likely to be replaced by 2035, smart construction has huge potential for reducing our energy needs.

Energy Conservation
The Leopold Center will use 70% less energy than a typical 12,000 square foot building built simply to code. This significant energy saving was realized through a combination of savvy design and scrutiny of building components.

Low tech solutions yield about half of our energy savings:

• Of the energy used by conventional buildings, half typically goes to heating, cooling, and lighting.

• Bringing in daylight reduces interior lighting needs.

• Higher than standard levels of insulation in the walls and ceiling keep the building cooler in the summer and warmer in the winter than typical insulation would.

• Promoting cross ventilation—and providing windows that open and close—allows air to flow freely and allows us to turn off the mechanical ventilation equipment.
• Overhangs allow the sun in during the winter yet block the hot sun during the summer.
• A “thermal flux zone” reduces heat flow between the main office and the outdoors.

• Altogether, savvy design reduces the work load on the mechanical systems, and the smallest, most-efficient equipment was selected to do the job.

Energy for heating and cooling is drawn from the ground beneath our feet. Solar panels capture the sunlight that falls on the roof, generating electricity and heating our water. Firewood comes from logging slash and carefully selected trees from our forests. By reducing our energy use and using renewable energy sources, we have substantially reduced our dependency on coal and natural gas, the two most common forms of energy for electrical production and heating.

- Buildings account for 38 percent of U.S. carbon dioxide emissions, and 10 percent of global carbon emissions. Burning these fossil fuels, we release carbon dioxide at an unnatural rate, driving global warming.
- The Leopold Center is also designed to be carbon neutral, in that no fossil carbon is added to the atmosphere as a result of occupancy.

In half an hour enough of the sun’s energy reaches the Earth’s surface to meet the World’s energy demand for a year!

Photovoltaic panels allow us to turn that sunlight into electricity. The Leopold Center has a 39.6 kilowatt (kW) solar electric (photovoltaic) system on its roof, the second largest in Wisconsin. Our PV array consists of 198 panels and can generate 60,000 - 70,000 kilowatt hours (kWh) of electricity per year. Each kWh equals the electricity used to keep a 100 watt light bulb lit for 10 hours.

The photovoltaic (PV) system is connected to the Adams Columbia Electric Co-op power grid. The extra electricity the panels produce during the summer months will be credited toward the electricity we may need to purchase during the winter. We expect to produce 110% of the energy we need to operate our building over the course of a year.

Earth Tubes
A particularly innovative component of the Leopold Center is a system of earth tubes designed to ventilate the building.

All commercial buildings are required to have a mechanical ventilation system capable of introducing a specific amount of outdoor air into the building while occupied. The air is heated or cooled, then circulated throughout the building. Heating and cooling is traditionally an expensive portion of the energy budget, especially in periods of temperature extremes. Earth tubes are designed to reduce this expenditure by moderating the temperature of the air before it enters the heating or cooling elements. In the Leopold Center, the incoming air will travel through a series of underground cement tubes, taking on the ambient temperature of the earth. Compared to the extreme outdoor temperatures ranging from –20º to 95º, the air in the earth tubes after traveling though the system will have a minimum temperature of 17º and a maximum temperature of 74º.

The earth tubes system contains 600 linear feet of 24” diameter cement pipe, very much like stormwater drainage pipe, laid over a 5,000 square foot area and buried about ten feet below the building. The sections are connected with a rubber gasket to prevent gases in the soil from leaching into the ventilation system. Permeability of the pipe allows evaporation of any water that condenses inside the tubes.

The pipes are connected at one end to a larger vertical pipe that extends above ground and serve as the air intake. At the other end, the air enters the basement of the building, where it goes through a UV filter to eliminate mold and bacteria before being circulated throughout the building.

Radiant Floor
The primary means of heating and cooling in the Leopold Center will come from a radiant floor system. In the United States, radiant floors are typically used only for heating; cooling requires that the relative humidity be monitored and the cooling turned off when it exceeds a threshold so that water does not condense on the floor. Air circulation from the earth tubes helps keep the relative humidity low in the Leopold Center.

The concrete floor of the main building houses tubing containing liquid that regulates the temperature. The system gains or loses heat through exchange with the earth itself: nineteen geothermal wells extend 220 feet below ground, absorbing heat from the ground in the winter and dissipating it in the summer, then regulating temperature in the building through a heat exchange pump. The whole system is composed of 8,400 linear feet of tubing!

Because of the mass of the system and concrete’s insulative qualities, once the slabs reach the desired temperature, it is easy to maintain the temperature without high inputs of heat.

Geothermal energy use currently ranks third among US renewable energies, following hydropower and biomass. The full potential for geothermal use may be realized through increased public awareness and more advanced technical support.

Wood Heat
Several fireplaces and wood stoves have been included in the design of the Leopold Center to reinforce the aesthetic connection with the Shack. The most auspicious of these is a large Rumford fireplace which will dominate the entry foyer. Characteristic of early American architecture, Rumford fireplaces are tall and shallow to reflect more heat out into the room, therefore heating more efficiently than other fireplaces. Fresh air piped to the fireplace and the thermal mass of the unit further improve the performance. The Rumford fireplace in the Leopold Center is an important component of the green building efforts. Wood heat serves not only an aesthetic purpose, it also is a key part of the energy budget – using wood heat will greatly reduce the need for energy input to the heating system during the winter months. Wood stoves and fireplaces throughout the building provide radiant heat sources where supplemental heat is most needed. Burning wood takes advantage of a renewable resource that is plentiful in our area.

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Aldo Leopold Center Case Study USGBC

Aldo Leopold Legacy Center (Wisconsin, USA)

Aldo Leopold Headquarters Article from GreenSource