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. Sometimes, su ...

. Low-energy houses often have

active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * "Active" (song), a 2024 song by Asake and Travis Scott from Asake's album ''Lungu Boy'' * Active Records, a record label Ships * ''Active'' (ship), several com ...

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 France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

), zero-carbon house ( UK), and Minergie (

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

). Buildings alone were responsible for 38% of all human

Greenhouse gas emissions Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...

(GHG) as of 2008, with 20% attributed to residential buildings and 18% to commercial buildings. 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 "provide governments at all levels with scientific information that they can use to develop climate policies". The World Met ...

(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 Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, and the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. The implementation of standardized low-energy building concepts has developed differently in each country.

Canada

In the late 1970s, the province of

Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...

contracted the

Saskatchewan Research Council The Saskatchewan Research Council (SRC) is a provincial treasury board crown corporation engaged in research and technology development on behalf of the provincial government and private industry. It focuses on applied research and development proj ...

to design and build a passive solar house suitable for the extreme climate of the

Canadian prairies The Canadian Prairies (usually referred to as simply the Prairies in Canada) is a region in Western Canada. It includes the Canadian portion of the Great Plains and the Prairie provinces, namely Alberta, Saskatchewan, and Manitoba. These provin ...

, where winter temperatures can drop to negative 40 degrees Celsius (-40°F). The project resulted in the construction of the

Saskatchewan Conservation House The Saskatchewan Conservation House (211 Rink Ave, Regina, Saskatchewan, Canada) is an early exemplar of energy-efficient building construction that introduced best practices for addressing air leakage in houses. It was designed in response to the ...

in Regina in 1977 by a team led by engineer

Harold Orr Harold Walter Orr (born April 30, 1931) is a Canadian mechanical engineer known for his work on energy-efficient construction and air leakage in houses, in particular the prioritization of energy demand reduction over active systems through the ...

. 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 The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

'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.

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 that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

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 An autonomous building is a hypothetical building designed to be operated independently from infrastructure, infrastructural support services such as the electric power grid, gas grid, municipal water systems, sewage treatment systems, storm dr ...

. 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 A heating system is a mechanism designed to regulate and maintain a desired temperature within a space by utilizing thermal energy. It is a fundamental component of Heating, Ventilation, and Air Conditioning (HVAC) systems, providing warmth to resi ...

, 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 Greek ...

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 Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...

(EPBD) was published in 2002 and became effective in January 2003.European Commission,
DIRECTIVE 2002/91/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 16 December 2002 on the energy performance of buildings
, Official Journal of the European Communities, 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 Ventilation may refer to: * Ventilation (physiology), the movement of air between the environment and the lungs via inhalation and exhalation ** Mechanical ventilation, in medicine, using artificial methods to assist breathing *** Respirator, a ma ...

. Low-energy buildings may be certified by RAL-GZ 965 for planning or construction.

Switzerland

Low-energy buildings may receive the Minergie 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 The National Renewable Energy Laboratory (NREL) in the US specializes in the research and development of renewable energy, energy efficiency, energy systems integration, and sustainable transportation. NREL is a federally funded research and ...

(NREL). The

Energy Star Energy Star (trademarked ENERGY STAR) is an Efficient energy use, energy-efficiency program established in 1992. It is administered by the U.S. Environmental Protection Agency (EPA) in partnership with the U.S. Department of Energy (DOE). The EPA ...

program is the largest certifier of low-energy homes and

consumer product A final good or consumer good is a final product ready for sale that is used by the consumer to satisfy current wants or needs, unlike an intermediate good, which is used to produce other goods. A microwave oven or a bicycle is a final good. Whe ...

s 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 energy production, the research and development of nuclear power, the military's nuclear w ...

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 Can ...

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

Natural Resources Canada Natural Resources Canada (NRCan; ; )Natural Resources Canada is the applied title under the Federal Identity Program; the legal title is Department of Natural Resources (). is the department of the Government of Canada responsible for natural r ...

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

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

the above programs align with the BC Energy Step Code, a provincial regulation to incentivize (or require) a level of

energy efficiency Energy efficiency may refer to: * Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process ** Electrical efficiency, useful power output per electrical power consumed ** Mechanical efficiency, a rat ...

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.

Obstacles and issues

Energy efficient housing affects

indoor air quality Indoor air quality (IAQ) is the air quality within buildings and Nonbuilding structure, structures. Poor indoor air quality due to indoor air pollution is known to affect the health, comfort, and well-being of building occupants. It has also be ...

. Airtight houses will trap pollutants inside them, whether produced indoors or outdoors, and lead to an increase in human exposure and potential health issues. 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. 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 Resource efficiency is the maximising of the supply of money, materials, staff, and other assets that can be drawn on by a person or organization in order to function effectively, with minimum wasted (natural) resource expenses. It means using the ...

and reduce global

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

associated with the burning of

fossil fuel A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geolog ...

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 (also called green energy) is energy made from renewable resource, renewable natural resources that are replenished on a human lifetime, human timescale. The most widely used renewable energy types are solar energy, wind pow ...

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

building envelope A building envelope or building enclosure 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 ...

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 ...

or building-integrated photovoltaic,

wind turbine A wind turbine is a device that wind power, converts the kinetic energy of wind into electrical energy. , hundreds of thousands of list of most powerful wind turbines, large turbines, in installations known as wind farms, were generating over ...

s, solar thermal (solar water heaters),

heat pump A heat pump is a device that uses electricity to transfer heat from a colder place to a warmer place. Specifically, the heat pump transfers thermal energy using a heat pump and refrigeration cycle, cooling the cool space and warming the warm s ...

s, and

district heating District heating (also known as heat networks) 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 heater, space heating and w ...

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 1,0001,500 kg CO₂e/m² (around 500 kg CO₂e/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 An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process. Solar energy, burning a fossil fuel, waste heat from factories, and district heating systems are examples of heat sour ...

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 need ...

Earth cooling tubes A ground-coupled heat exchanger is an underground heat exchanger that can capture heat from and/or dissipate heat to the ground. They use the Earth's near constant subterranean temperature to warm or cool air or other fluids for residential, agri ...

Geothermal heat pump A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that use 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 a ventilation system that recovers energy by operating between two air sources at different temperatures. It is used to reduce the heating and cooling ...

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 vari ...

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 fro ...

Renewable heat Renewable heat is an application of renewable energy referring to the generation of heat from renewable sources; for example, feeding radiators with water warmed by focused solar radiation rather than by a fossil fuel boiler. Renewable heat techno ...

Seasonal thermal energy storage 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 need ...

(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 (sun ...

Solar hot water Solar water heating (SWH) is heating water by sunlight, using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and latitudes. SWHs are widely used for residential an ...

* Solar devices

Passive solar design and landscaping

Passive solar building design and

energy-efficient landscaping Energy-efficient landscaping is a type of landscaping designed for the purpose of conserving energy. There is a distinction between the embedded energy of materials and constructing the landscape, and the energy consumed by the maintenance and ope ...

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 the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

(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 by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

and north in the Southern Hemisphere) maximizes passive

solar gain Solar gain (also known as solar heat gain or passive solar gain) is the increase in thermal energy of a space, object or structure as it absorbs incident solar radiation. The amount of solar gain a space experiences is a function of the total i ...

. However, solar gain (especially in

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

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, e.g., including only woody plants with secondary growth, only ...

s, attached

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

s with

vine A vine 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 themselves, for instance, when used in wicker work.Jackson; Benjamin; Da ...

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 In building design, thermal mass is a property of the matter of a building that requires a flow of heat in order for it to change temperature. Not all writers agree on what physical property of matter "thermal mass" describes. Most writers use ...

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 Leaf, 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 Passive may refer to: * Passive voice, a grammatical voice common in many languages, see also Pseudopassive * Passive language, a language from which an interpreter works * Passivity (behavior), the condition of submitting to the influence of ...

and active daylighting 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 incan ...

s and

solid-state lighting Solid-state lighting (SSL) is a type of lighting that uses semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, ...

with

LED lamp An LED lamp or LED light is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps and fluorescent lamps. The most efficient commercial ...

OLED An organic light-emitting diode (OLED), also known as organic electroluminescent (organic EL) diode, is a type of light-emitting diode (LED) in which the emissive electroluminescent layer is an organic compound film that emits light in respon ...

s and polymer light-emitting diodes and low-voltage

incandescent light bulb An incandescent light bulb, also known as an incandescent lamp or incandescent light globe, is an electric light that produces illumination by Joule heating a #Filament, filament until it incandescence, glows. The filament is enclosed in a ...

s, compact metal halide,

xenon Xenon is a chemical element; it has 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 lamp A halogen lamp (also called tungsten halogen, quartz-halogen, and quartz iodine lamp) is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of an inert gas and a small ...

s) can be used. Solar-powered exterior security and

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

, with

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s on each fixture or connecting to a central

solar panel A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...

, 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 In physics, motion is when an object changes its position with respect to a reference point in a given time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed, and frame of reference to an obser ...

and daylighting operation sensors further reduce energy consumption and

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

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. The domestic application attached to ...

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 mark A certification mark on a commercial product or service is a registered Mark (sign), mark that enables its owner ("certification body") to certify that the goods or services of a particular provider (who is not the owner of the certification ...

s 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 a globally active nonprofit ecolabel for renewable energy (electricity, gas, and heat and cold). It is owned by the Finnish Association for Nature Conservation and managed in cooperation with other environmental NGOs. EKOenergy star ...

are other certification marks.

Background

Canada

Germany

United Kingdom

United States

Types

National standards

Europe

Norway

Denmark

Germany

Switzerland

North America

Obstacles and issues

Technology

Energy efficiency

Improvements

Passive solar design and landscaping

Lighting and electrical appliances

See also

References

Further reading

External links

Examples