Zero-energy buildings, also called net-zero buildings, are buildings that consume no electrical energy over the course of a year. Many critics believe net-zero homes and other buildings are the next wave of architecture, since they are free of heating bills, electric expenses, air conditioning costs and other energy uses. The following is a partial list of the basic elements that are typically used to make a house, office or other structure a net-zero building.
1. Solar Panels
Solar panels -- large panels of photovoltaic cells -- convert solar radiation from the sun to electrical energy. Zero-energy buildings generally require a suite of several solar panels to supply an adequate amount of energy for the building's uses, depending on whether it's a home, office, school or other building. Solar technology is constantly evolving with increased efficiencies and energy storage capabilities. Most zero-energy homes and buildings must remain connected to the local electrical grid (instead of going completely off-grid), and in the event of an area-wide electrical blackout, net-zero buildings also lose power.
2. Geothermal Heating and CoolingThe temperature underground is generally stable and moderate all year -- roughly 55 degrees F -- through icy winters and blazing hot summers, similar to a deep cave. Geothermal heat pumps take advantage of these stable temperatures to save energy on heating and cooling costs. In winter, geothermal heat pumps (or ground-source heat pumps) warm the air more efficiently than a typical heating system, which must heat up air that's much colder than 55 degrees F. In summer, these systems also save energy by cooling a zero-energy building's air by using air that's already quite cool. And because geothermal systems produce very few greenhouse gases compared to older heating and cooling systems, the EPA calls geothermal systems the most energy-efficient and environmentally safe technologies available today.
3. Insulated Wall Materials
Walls have been insulated for centuries, ever since animal skins were first hung on rock walls, or sod huts were crafted with thick dirt walls. Straw bale houses are also gaining favor among some home builders because of their insulation value. Many architects have started using structural insulated panels (SIPs) or modular, stacked insulating concrete forms (ICFs) to ensure a high insulation value, or R-value, of the walls in a zero-energy home or building. Though initially more expensive than typical wood construction, these newer insulating technologies are vastly superior and result in lower long-term costs.
4. Heat Recovery SystemsIf you're concerned about getting fresh air inside a zero-energy home or office with superior insulation -- you're not being paranoid. Radon gas, mold, mildew and other airborne impurities can create a dangerous indoor environment, sometimes known as sick building syndrome. But heat recovery systems in net-zero buildings, also called heat recovery ventilation systems, move fresh outdoor air into a building while also allowing improved climate control and reduced heating and cooling costs through the use of a heat exchanger that stabilizes the temperature of both incoming fresh air and circulating indoor air.
5. Insulated Windows
Windows that are just one pane of glass have very little insulation value, and don't do much to keep houses cool in summer or warm in winter. Years ago, people discovered that two panes of glass with air or argon gas sandwiched between the glass gives a window much better insulation. While most newer buildings have double-pane windows, zero-energy homes can enjoy better insulation with triple-pane windows, though they are more expensive and much heavier than double-pane windows.