Passive house is a voluntary building performance standard for very high energy efficiency and thermal comfort that substantially reduces a building’s carbon footprint. Buildings certified to the standard are ultra-low energy and typically require very little energy for space heating or cooling. The approach is used for housing and for non-residential buildings such as offices, schools, kindergartens and healthcare facilities. Energy efficiency is integral to architectural design rather than an add-on. Although most common in new construction, the principles are also applied in deep renovations.