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Buildings and Cities

Net Zero Buildings

The Rocky Mountain Institute Innovation Center is a net zero building on the north shore of the Roaring Fork River in Basalt, Colorado. The two-story, 15,600-square-foot building was constructed using Integrated Project Delivery software and model, a replicable process that can be employed by commercial projects around the country of similar scale. Although located in one of the coldest climate zones in the United States, the insulated building envelope was built with R-50 walls and R-67 roof. It has an 83-kilowatt solar photovoltaic system on the roof that provides more energy than the building is designed to use. The building was designed to use less water than the rain and snow that fall upon the site. Although graywater use is not allowed as yet in Colorado, a graywater system was installed in anticipation of changes in state regulations. To save heating and air-conditioning energy, the Center focused on heating and cooling people, not the space. They addressed the six factors that affect human comfort, which are air temperature, wind speed, humidity, clothing level, activity level, and the temperature of surrounding surfaces. By zeroing in on these factors, the Center has a broader range of comfortable air temperature, from 67 to 82 degrees Fahrenheit compared to the conventional commercial building range of 70 to 76 degrees. This cut energy use by 50 percent, eliminated the air-conditioning system, and requires a small heating system only on the coldest days.

A net zero building is one that has zero net energy consumption, producing as much energy as it uses in a year. In some months it may generate excess electricity through distributed renewables; at other times it may require electricity from the grid. On balance, it is self-supporting. Net zero buildings are more resilient during disasters and blackouts, are more carefully designed by necessity, and generally have reduced operating costs.

Designing a net zero building means seeing a building as a system and addressing the sources of energy use. There are multiple ways to reduce a building’s energy loads, including:

  • Daylighting,
  • Maximum insulation,
  • Electrochromic glass,
  • Passive solar design, and
  • Advanced heating and cooling.

Net zero buildings were once a novelty, but are becoming more commonplace, as architects roll out extraordinary buildings across the world. There is now a Walgreens drugstore in Chicago that is a net zero building. Net zero neighborhoods, districts, and communities are also being designed and constructed. Newer net zero buildings push the margins further: zero water and zero waste. They harvest rainwater and process sewage on-site into compostable forms.

References

ventilation principles from…termite mounds: King, Hunter, Samuel Ocko, and Lakshminarayanan Mahadevan. “Termite Mounds Harness Diurnal Temperature Oscillations for Ventilation.” Proceedings of the National Academy of Sciences 112, no. 37 (2015): 11589-11593.

Kaupuni Village…in Hawaii: NREL. Kaupuni Village: A Closer Look at the First Net-Zero Energy Affordable Housing Community in Hawaii. Golden, CO: National Renewable Energy Laboratory, 2012.

Sonnenschiff…in Freiburg, Germany: Michler, Andrew. “Sonnenschiff: Solar City Produces 4X the Energy It Consumes.” Inhabitat. July 27, 2011.

Cambridge…net zero by 2040: City of Cambridge. “Net Zero Action Plan.” http://www.cambridgema.gov/cdd/projects/climate/netzerotaskforce.

California…net zero [goals]: Waltner, Meg. “New California Building Efficiency Standards Set the Stage for Zero Net Energy Homes by 2020.” Natural Resources Defense Council (blog). June 10, 2015.

Walgreens drugstore in Chicago: Jaspen, Bruce. “Close to Its Home, Walgreen Tests Energy-Saving Ideas.” New York Times. June 4, 2013.

U.S. building sector energy consumption: Architecture 2030. “U.S. Building Sector Emissions Down—The Driving Force: You!” January 4, 2017; EIA. Annual Energy Outlook 2017. Washington, D.C.: U.S. Energy Information Administration, 2017.

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