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 Sustainable architecture is architecture that seeks to minimize the negative environmental impact of buildings through improved efficiency and moderation in the use of materials, energy, development space and the ecosystem at large. Sustainable ...

. Low-energy houses often have active and

passive solar building design In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...

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 Minergie is a registered quality label for new and refurbished low-energy-consumption buildings. This label is mutually supported by the Swiss Confederation, the Swiss Cantons and the Principality of Liechtenstein along with Trade and Industry. T ...

(

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

Background

During the 1970s, experimental initiatives for low-energy buildings were made in

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of Denmark ...

, the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, and

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

. The German Passivhaus Institute introduced the first passive house in 1990. The implementation of standardized low-energy building concepts has developed differently in each country. Buildings alone are responsible for 38% of all human GHG emissions (20% residential, 18% commercial) as of 2008. According to the

Intergovernmental Panel on Climate Change The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to advance scientific knowledge about climate change caused by human activities. The World Meteorological Organization (WMO) a ...

(IPCC), buildings is the sector which presents the most cost effective opportunities for GHG reductions.

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 California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

requires all new residential construction to be zero net energy by 2020.

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 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 The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...

'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 The Code for Sustainable Homes was an environmental assessment method for rating and certifying the performance of new homes in United Kingdom. First introduced in 2006, it is a national standard for use in the design and construction of new 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.

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 The passive solar design of buildings includes consideration of their orientation to the sun and their thermal mass, factors which have been incorporated to a greater or lesser extent in vernacular architecture for thousands of years. Ancient Greeks ...

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.

Germany

Low-energy houses certified by RAL-GZ 965 have 30 percent less heat losses than regulated in the EnEV, a national building code. Other criteria affect

insulation Insulation may refer to: Thermal * Thermal insulation, use of materials to reduce rates of heat transfer ** List of insulation materials ** Building insulation, thermal insulation added to buildings for comfort and energy efficiency *** Insulated ...

, air tightness and ventilation. Low-energy buildings may be certified by RAL-GZ 965 for planning or construction.

Switzerland

Low-energy buildings may receive the

certification, a "quality label for new and refurbished buildings". The Minergie standard requires that buildings do not exceed 75 percent of average building energy consumption and fossil-fuel consumption must not exceed 50 percent of the average.

North America

The European Union directive has clarified low-energy houses in Europe, and a large portion of the discussions on zero-energy building in North America derives from the U.S. National Renewable Energy Laboratory (NREL). The Energy Star program is the largest certifier of low-energy homes and consumer products in the U.S. Although certified Energy Star homes use at least 15 percent less energy than standard new homes built in accordance with the International Residential Code, they typically achieve a 20- to 30-percent savings. The

United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...

introduced a program in 2008 to distribute zero-energy housing across the country. Canadian builders may use a range of standards, labels, and certification programs to demonstrate a high level of energy performance in a given project. These include: *Net Zero Home and Net Zero Ready Home certifications, administered by the

Canadian Home Builders' Association The Canadian Home Builders' Association (CHBA) is a not-for-profit organization representing residential construction and related industry firms in Canada. It was founded in 1943, following closely the adoption of the National Building Code of Cana ...

*Built Green labels, administered by Built Green Canada *Energy Star for Homes, administered by

Natural Resources Canada Natural Resources Canada (NRCan; french: Ressources naturelles Canada; french: RNCan, label=none)Natural Resources Canada is the applied title under the Federal Identity Program; the legal title is Department of Natural Resources (). is the depa ...

*The Canadian Passive House standard, administered by the Canadian Passive House Institute In

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

the above programs align with the

BC Energy Step Code The BC Energy Step Code is a provincial regulation that local governments in British Columbia, Canada, may use, if they wish, to incentivize or require a level of energy efficiency in new construction that goes above and beyond the requirements of ...

, a provincial regulation to incentivize (or require) a level of energy efficiency in new construction beyond the base building code. The code was designed as a technical road map to help the province reach its target of all new net-zero-energy-ready buildings by 2032.

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.

Obstacles and opportunities

Energy-efficient design often relies on new technologies and techniques. These may create technical obstacles in addition to social, cultural, and economic non-technical obstacles. Despite these obstacles, opportunities exist for skilled, knowledgeable professions to create cost-efficient solutions for energy efficiency in buildings. Buildings designed for good energy efficiency do not always live up to the design goals; various reasons lead to this performance gap.

Technology

Low-energy building design is considered important to encourage resource efficiency and reduce global

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

associated with the burning of

fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...

s. Design involves two general strategies: minimizing the need for energy use in buildings (especially for heating and cooling) through energy-efficient measures (EEMs) and adopting

renewable energy Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most renewable energy ...

and other technologies (RETs) to meet remaining energy needs. EEMs include

building envelope A building envelope is the physical separator between the conditioned and unconditioned environment of a building including the resistance to air, water, heat, light, and noiseSyed, Asif. ''Advanced building technologies for sustainability''. Hoboke ...

s, internal conditions, and building-services systems; RETs include

photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...

or building-integrated photovoltaic,

wind turbine A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year. ...

s, solar thermal (solar water heaters),

heat pump A heat pump is a device that can heat a building (or part of a building) by transferring thermal energy from the outside using a refrigeration cycle. Many heat pumps can also operate in the opposite direction, cooling the building by removing h ...

s, and

district heating District heating (also known as heat networks or teleheating) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating a ...

and cooling. Impacts include life-cycle costs, environmental impacts, and climate-change and social-policy issues. The best low-energy designs offer occupants a better environment and more stable, controlled thermal comfort in addition to reduced energy costs. GHG emissions associated with buildings construction are mainly coming from: # Materials manufacturing (e.g., concrete) # Materials transport # Demolition wastes transport # Demolition wastes treatment The construction, renovation, and deconstruction of a typical building is on average responsible for the emissions of 1,000-1,500 kgCO2e/m2 (around 500 kgCO2e/m2 for construction only). Strategies adopted by low-carbon buildings to reduce GHG emissions during construction include: # Reduce quantity of materials used # Select materials with low emissions factors associated (e.g., recycled materials) # Select materials suppliers as close as possible to the construction. # Divert demolition wastes to recycling instead of landfills or incineration

Energy efficiency

Reduction of energy consumption is more environmentally and financially advantageous than increasing onsite production to reach a low-energy goal. The less a home consumes, the smaller renewable-energy system it requires to reach net zero. Energy efficiency should always be the primary design strategy of a low-energy house.

Improvements

* Absorption refrigerator *

Annualized geo solar Seasonal thermal energy storage (STES), also known as inter-seasonal thermal energy storage, is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever nee ...

* Earth cooling tubes *

Geothermal heat pump A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that uses a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through ...

Heat recovery ventilation Heat recovery ventilation (HRV), also known as mechanical ventilation heat recovery (MVHR), is an energy recovery ventilation system which works between two air sources at different temperatures. Heat recovery is a method which is used to reduce ...

Water heat recycling Water heat recycling (also known as drain water heat recovery, waste water heat recovery, greywater heat recovery, or sometimes shower water heat recovery) is the use of a heat exchanger to recover energy and reuse heat from drain water from vario ...

Passive cooling Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. This approach works either by preventing heat from ...

* Renewable heat * Seasonal thermal energy storage (STES) *

Solar air conditioning Solar air conditioning, or "solar-powered air conditioning", refers to any air conditioning (cooling) system that uses solar power. This can be done through passive solar design, solar thermal energy conversion, and photovoltaic conversion (sunli ...

Solar hot water Solar water heating (SWH) is heating water by sunlight, using a solar thermal collector A solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, bu ...

* Solar devices

Passive solar design and landscaping

Passive solar building design In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...

and energy-efficient landscaping support the low-energy house in conservation and can integrate it into a neighborhood and environment. Following passive solar building techniques, where buildings are compact in shape to reduce surface area and principal windows oriented towards the

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...

(south in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

and north in the Southern Hemisphere) maximizes passive solar gain. However, solar gain (especially in

temperate climate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

s) is secondary to minimizing the overall house-energy requirements. In hot temperatures, excess heat can create uncomfortable indoor conditions. Passive alternatives to air-conditioning systems, such as temperature-dependent venting, have been shown to be effective in regions with cooling needs.Reda, F., Tuominen, P., Hedman, Å., Ibrahim, M.G.E.: "Low-energy residential buildings in New Borg El Arab: Simulation and survey based energy assessment". ''Energy and Buildings'', Volume 93, 15 April 2015, pp. 65-82. Other techniques to reduce excess solar heat include brise-soleils,

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

s, attached

pergola A pergola is most commonly an outdoor garden feature forming a shaded walkway, passageway, or sitting area of vertical posts or pillars that usually support cross-beams and a sturdy open lattice, often upon which woody vines are trained. The ...

s with

vine A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners themselv ...

s, vertical gardens, and

green roof A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage ...

s. Although low-energy houses can be constructed from dense or lightweight materials, internal thermal mass is normally incorporated to reduce summer peak temperatures, maintain stable winter temperatures, and prevent possible overheating in spring or autumn before the higher sun angle "shades" midday wall exposure and window penetration. Exterior wall color (when the surface allows choice) reflection or absorption depends on the predominant year-round outdoor temperature. The use of

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

trees and wall trellised (or self-attaching) vines can assist in temperate climates.

Lighting and electrical appliances

To minimize total primary energy consumption, passive and

active daylighting Daylighting is the practice of placing windows, skylights, other openings, and reflective surfaces so that sunlight (direct or indirect) can provide effective internal lighting. Particular attention is given to daylighting while designing a b ...

are the first daytime solutions to employ. For low-light days, non-daylight spaces and nighttime, sustainable lighting design with low-energy sources (such as standard-voltage

compact fluorescent lamp A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for inca ...

s and solid-state lighting with

LED lamp An LED lamp or LED light bulb is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps and can be significantly more efficient than mos ...

s, OLEDs and polymer light-emitting diodes and low-voltage

incandescent light bulb An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxida ...

s, compact metal halide,

xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

and halogen lamps) can be used. Solar-powered exterior security and

landscape lighting Landscape lighting or garden lighting refers to the use of outdoor illumination of private gardens and public landscapes; for the enhancement and purposes of safety, nighttime aesthetics, accessibility, security, recreation and sports, and socia ...

, with

solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

s on each fixture or connecting to a central

solar panel A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a photo ...

, are available for gardens and outdoor needs. Low-voltage systems can be used for more controlled (or independent) illumination, using less electricity than conventional fixtures and lamps. Timers,

motion detection Motion detection is the process of detecting a change in the position of an object relative to its surroundings or a change in the surroundings relative to an object. It can be achieved by either mechanical or electronic methods. When it is done by ...

and

daylighting Daylighting is the practice of placing windows, skylights, other openings, and Reflective surfaces (climate engineering), reflective surfaces so that sunlight (direct or indirect) can provide effective internal lighting. Particular attention is ...

operation sensors further reduce energy consumption and

light pollution Light pollution is the presence of unwanted, inappropriate, or excessive use of artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting, during the day ...

Home appliance A home appliance, also referred to as a domestic appliance, an electric appliance or a household appliance, is a machine which assists in household functions such as cooking, cleaning and food preservation. Appliances are divided into three ty ...

s meeting independent energy-efficiency testing and receiving

Ecolabel Ecolabels (also "Eco-Labels") and Green Stickers are labeling systems for food and consumer products. The use of ecolabels is voluntary, whereas green stickers are mandated by law; for example, in North America major appliances and automobiles us ...

certification marks for reduced electrical and natural-gas consumption and product-manufacturing

carbon emission label A carbon emission label or carbon label describes the carbon dioxide emissions created as a by-product of manufacturing, transporting, or disposing of a consumer product. This information is important to consumers wishing to minimize their ecologic ...

s are preferred for low-energy houses. Energy Star and

EKOenergy EKOenergy is an ecolabel for electricity. It is a not-for-profit initiative of the EKOenergy Network, a group of more than 40 environmental organizations from 30 countries. EKOenergy started in 2013 in Europe. Its secretariat is based in Helsinki. ...

are other certification marks.

References

External links

bigEE - Your guide to energy efficiency in buildings

IEA research program "Net Zero Energy Solar Buildings"

IEA Energy Conservation in Buildings and Community Systems Programme.

Common Fire Foundation
overview of green building and information on the net-zero-energy Greenest Building in the Eastern US
Article on Low-Energy Housing

Examples

World Map of international known Net Zero Energy BuildingsBuilding of low energy houses with Insulating Concrete Forms
{{Authority control Low-energy building Sustainable architecture Sustainable building Energy conservation Building House types Sustainable urban planning

Background

United States

Germany

United Kingdom

National standards

Europe

Norway

Denmark

Germany

Switzerland

North America

Types

Obstacles and opportunities

Technology

Energy efficiency

Improvements

Passive solar design and landscaping

Lighting and electrical appliances

See also

References

Further reading

External links

Examples