Zero-energy homes require no input from nonrenewable off-site power sources, emit no net greenhouse gases into the atmosphere, and sometimes feed surplus energy back into the grid. Many combinations of passive and active gener- ation can be used for designing a zero-energy structure, depending on what’s appropriate for local climate, budget, site regulations, codes, and individual preferences.
Passive efficiency strategies are best implemented during the construction phase. These include things like orientation on the site for maximum southern sun exposure during winter months, natural ventilation systems, strategically placed windows and shade trees, and thermal mass that can absorb and retain heat. More active strategies include geothermal heat pumps that recover energy from ground sources, and wind turbines placed on site.