A low-energy house is characterized by an energy-efficient design and technical features which enable it to provide high living standards and comfort with low energy consumption and carbon emissions. Traditional heating and active cooling systems are absent, or their use is secondary. Low-energy buildings may be viewed as examples of sustainable architecture. Low-energy houses often have active and passive solar building design and components, which reduce the house's energy consumption and minimally impact the resident's lifestyle. Throughout the world, companies and non-profit organizations provide guidelines and issue certifications to guarantee the energy performance of buildings and their processes and materials. Certifications include passive house, BBC—Bâtiment Basse Consommation—Effinergie (France), zero-carbon house (UK), and Minergie (Switzerland). Buildings alone were responsible for 38% of all human Greenhouse gas emissions (GHG) as of 2008, with 20% attributed to residential buildings and 18% to commercial buildings. According to the Intergovernmental Panel on Climate Change (IPCC), buildings is the sector which presents the most cost effective opportunities for GHG reductions.
Background During the 1970s, research on low-energy buildings was done in Denmark, Sweden, Germany, Canada, and the United States. The implementation of standardized low-energy building concepts has developed differently in each country.
Canada In the late 1970s, the province of Saskatchewan contracted the Saskatchewan Research Council to design and build a passive solar house suitable for the extreme climate of the Canadian prairies, where winter temperatures can drop to negative 40 degrees Celsius (-40°F). The project resulted in the construction of the Saskatchewan Conservation House in Regina in 1977 by a team led by engineer Harold Orr. The project developed a heat recovery air exchanger (HRV), hot water recovery, and a blower-door apparatus to measure building air-tightness, techniques that became common in low-energy building in other parts of the world. Orr would go on to apply many of those techniques to retro-fitting existing buildings to improve energy efficiency.
Germany Triggered in the 1970s by the first energy crisis and growing environmental awareness, energy conservation became increasingly important in Germany. In 1977, the country's first energy-related building standard was enacted. The German Passivhaus Institute introduced the first certified passive house in 1990. The annual heating requirement was introduced as an important parameter by the third German Thermal Insulation Ordinance (1995). In 2013, however, there was no clear legal requirement for a low-energy building standard in Germany. According to Maria Panagiotidou and Robert J. Fuller, definitions, policies and construction activity of zero-energy buildings must be clear. The European Union's Energy Performance Directive requires that beginning in 2021, only low-energy buildings may be built.
United Kingdom Changes to national policies have occurred since May 2015 in the UK. One of the most significant has been the withdrawal of the Code for Sustainable Homes (CfSH) as a system for assessing and encouraging improvements in the environmental design of dwellings. This has abandoned the code's schematic which provided a framework of achievement levels and to which low-energy designers could aspire to meet or surpass. Although energy-conservation legislation still exists in the building regulations, there is a lack of suitable standards exceeding basic regulations. As a result, the Passive House Standard may expand its influence and impact on energy-efficient houses.
United States Interest in low-energy buildings has increased in the United States, primarily due to rising energy prices, decreasing costs for onsite renewable-energy systems, and increasing concern about climate change. California requires all new residential construction to be zero net energy by 2020.
Types Low-energy houses are broadly defined, but are generally known as houses with a lower energy demand than common buildings regulated by the national building code. The term "low-energy house" is used in some countries for a specific type of building. A low-energy house is a guideline rarely specified in actual values (heat load or space-heating minimum). A passive house is a standard, with specific recommendations to save heating energy. At one end of the spectrum are buildings with an ultra-low space-heating requirement which require low levels of imported energy (even in winter), approaching an autonomous building. At the opposite end are buildings where few attempts are made to reduce their space-heating requirement and which use high levels of imported energy in winter. Although this may be balanced by high levels of renewable-energy generation throughout the year, it imposes greater demands on the national energy infrastructure during winter.
National standards The term "low-energy houses" may refer to national building standards. These standards sometimes seek to limit the energy used for space heating, which is the largest energy consumer in many climate zones. Other energy uses may also be regulated. The history of passive solar building design provides an international view of one form of low-energy-building development and standards.
Europe Standards for low-energy buildings in Europe have proceeded differently in each country, and there is no common certification or legislation for low-energy buildings valid in all EU member states. As a movement towards reducing energy use and emissions, a common legislation concerning buildings’ energy performance, the Energy Performance of Buildings Directive (EPBD) was published in 2002 and became effective in January 2003.
Norway In NS 3700, the draft official standard, low-energy buildings are defined. About the buildings' energy performance, two alternatives for rating their primary energy use are under discussion:
A limit on a building's annual CO2 emissions, calculated by multiplying the annual supplied energy by a CO2 factor A percentage of its heating demand must be met with renewable energy.
Denmark Low-energy houses are defined in the National Building Regulation Building Regulations 08, and are divided into two classes. They are regulated in the regulations' chapter 7.2.4: Low-energy.
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