FIRST CARBON-NEUTRAL BUILDING
Original LinkOn October 18, the U.S. Green Building Council <http://www.usgbc.org/> certified the world's first carbon-neutral building. It is "the greenest building ever built," according to the organization's Leadership in Energy and Environmental Design (LEED) ranking system.
The 12,000 square foot structure produces 15% more energy than it consumes, thanks to its geothermal heating system and the 39.4 kilowatt photovoltaic solar array on its roof. Its heating and ventilation system is built around "earth tubes" that heat or cool air underground before it is sent into the building. The building also incorporates more conventional energy-saving features, such as maximizing insulation and capturing daylight and natural breezes.
The new structure houses the Aldo Leopold Foundation <http://www.aldoleopold.org/>, which sits on the 80 acres of "worn-out farmland" immortalized in Leopold's landmark conservation book, A Sand County Almanac. The building's columns and beams originate from native trees that Leopold and his family planted to improve their parcel of Wisconsin land.
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THE ALDO LEOPOLD LEGACY FOUNDATION
Original LinkKNOWING WHERE OUR ENERGY COMES FROM
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 Legacy Center is also designed to be carbon neutral, in that no fossil carbon is added to the atmosphere as a result of occupancy.
PHOTOVOLTAICS
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 Legacy 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 Legacy 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 Legacy 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 Legacy 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 Legacy 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 Aldo Leopold Legacy 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 Legacy 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.