An energy-plus building (also called: plus-energy house, efficiency-plus house) produces more energy from renewable energy sources, over the course of a year, than it imports from external sources. This is achieved using a combination of

microgeneration Microgeneration is the small-scale production of heat or electric power from a "low carbon source," as an alternative or supplement to traditional centralized grid-connected power. Microgeneration technologies include small-scale wind turbin ...

technology and

low-energy building 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 ...

techniques, such as:

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 ...

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 ...

and careful site selection and placement. A reduction of modern conveniences can also contribute to

energy savings Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less energy for continuous service) or changing one's behavior to use less service (f ...

, however many energy-plus houses are almost indistinguishable from a traditional home, preferring instead to use highly energy-efficient appliances, fixtures, etc., throughout the house. "Plusenergihuset" (the plus energy house) was the Danish term used by

Jean Fischer Jean-Baptiste Fischer was an early twentieth century French road racing cyclist who won the 1901 Paris–Tours and participated in the 1903 Tour de France in 1903, where he finished fifth. Palmarès ;1901 : Paris–Tours :Bordeaux- Paris ...

in his publication from 1982 about his own energy-plus house. PlusEnergy is a brand name, used by

Rolf Disch Rolf Disch is a German architect, solar energy pioneer and environmental activist. Born in Freiburg im Breisgau, Germany, Disch has dedicated particular focus to regional renewable and sustainable energy. As head of his own architecture firm, ...

, to describe a structure that produces more energy than it uses. The term was coined by Disch in 1994 when building his private residence, the Heliotrope as the first PlusEnergy house in the world. Disch then went on to refine the concepts involved with several more projects built by his company, Rolf Disch Solar Architecture, in order to promote PlusEnergy for wider adoption in residential, commercial and retail spaces. Disch maintains that PlusEnergy is more than just a method of producing environmentally-friendly housing, but also an integrated ecological and architectural concept. As such, PlusEnergy is intended to be superior to low-energy or zero-energy designs such as those of Passivhaus.

Technical approach

The PlusEnergy approach uses a variety of techniques to produce a building that generates more energy than it consumes. A typical example is to capture heat during the day in order to reduce the need to generate heat over night. This is achieved using large North and South facing window areas to allow sunlight to penetrate the structure, reducing the need for energy use from light bulbs. Triple-pane or quadruple-pane windows (

U-value In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference pe ...

= 0.4 – 0.7 W(m²K)) trap this heat inside, and the addition of heavy insulation then means the structure is already warm in the evening and therefore needs less heating. In the Sun Ship, a commercial, retail and residential PlusEnergy structure, techniques such as phase changing materials in the walls and vacuum insulation are also used. This permits maximum availability of floor space without compromising efficient insulation.

Social and community aspects

An important part of the PlusEnergy approach that differentiates it from similar concepts is that the owner or tenant of a PlusEnergy building should be able to live and work comfortably in it without sacrificing lifestyle or normal living standards. For example, solar panels are made aesthetically pleasing so that they are integrated into the façade of the structure. This reflects PlusEnergy's emphasis on community planning and integration, with aspects of transportation, water management and communication also being seen as part of the design. PlusEnergy design also emphasises the importance of sustainable development on communities in general. An energy-efficient community is seen as generating positive identification and community pride. Rolf Disch says he attracts a "high quality of tenant", innovative undertakings and creative work places through his designs. Ecological urban planning techniques like traffic management with wide, attractive walkways, bicycle routes and connections to public transportation are all part of the PlusEnergy ideal. At the Solar Settlement for example, tenants and owners incorporate bicycle and car-sharing, and the neighborhood has an extensive car-free zone with many public transportation connections.

Example projects

Heliotrope

Built in 1994 as the private residence and special project of

Freiburg Freiburg im Breisgau (; abbreviated as Freiburg i. Br. or Freiburg i. B.; Low Alemannic: ''Friburg im Brisgau''), commonly referred to as Freiburg, is an independent city in Baden-Württemberg, Germany. With a population of about 230,000 (as o ...

, the Heliotrope is claimed by its designer to be the first building in the world to create more energy than it uses, being reliant on entirely renewable power, and being emissions free and CO₂ neutral. The structure rotates to track the sun, which allows it to use a large amount of natural sunlight and warmth during the day. After the success of Freiburg’s Heliotrope,

Hansgrohe Hansgrohe SE is a German sanitary fittings manufacturer. It was founded by Hans Grohe in 1901, in Schiltach, Baden Wuerttemberg, Germany. Hansgrohe is one of the world's largest shower head, hand shower and tap suppliers, next to competitors such ...

contracted Rolf Disch Solar Architecture to design and built another Heliotrope to be used as a visitors' center and showroom in

Offenburg Offenburg ("open borough" - coat of arms showing open gates; Low Alemmanic: ''Offäburg'') is a city located in the state of Baden-Württemberg, Germany. With nearly 60,000 inhabitants (2019), it is the largest city and the administrative capital ...

, Germany. A third Heliotrope was then built in Hilpoltstein,

Bavaria Bavaria ( ; ), officially the Free State of Bavaria (german: Freistaat Bayern, link=no ), is a state in the south-east of Germany. With an area of , Bavaria is the largest German state by land area, comprising roughly a fifth of the total lan ...

to be used as a technical dental laboratory. File: Heliotrop_Freiburg.jpg, Heliotrope in Freiburg File: LuftHeliotrop.JPG, Bird's eye view of the Heliotrope in Freiburg File: Heliotrophotel_ansicht.jpg, Heliotrope-Hotel Schloss Waretenstein

Solar Settlement

With the success of the Heliotrope, Rolf Disch Solar Architecture applied their PlusEnergy concept to mass residential production in the form of a community development of 50 PlusEnergy houses. The project, called Solar Settlement, won 2002 House of the Year, 2002 Residential PV Solar Integration Award, and Germany’s Most Beautiful Housing Community, 2006. Built between 2000 and 2005 in the Vauban quarter of

, the Solar Settlement is intended as an example of Disch’s vision of a “fundamental environmental imperative”. As of 2011, the homes have had more than 8 years of full occupancy and each produced more than 5,000 Euros ($5,600) of surplus energy a year, from which the owners of the houses have benefitted.

Sun Ship

The Sun Ship, located next to the Solar Settlement in Freiburg, uses its for retail, commercial and residential space. The Sun Ship houses a supermarket, convenience store and café on the first floor, offices and work spaces on the 2nd and 4th floors, and 9 penthouses on its roof. Notable aspects of the building are its vacuum insulated walls, ventilation with 95% heat recovery, triple paned windows, and solar-panelled façade.

Other projects

* Heliotrope,

Vauban, Freiburg Vauban () is a neighbourhood (''Stadtteil'') to the south of the town centre in Freiburg, Germany. It was built as "a sustainable model district" on the site of a former French military base named after Sébastien Le Prestre de Vauban, the 17th c ...

, 1994 * Heliotrope,

, 1994 * Heliotrope, Hilpoltstein, 1995 * Solar Settlement,

, 2002 * Sun Ship,

, 2004 File:Heliotrop Freiburg.jpg, Heliotrope in

, 1994 File:Heliotrop Nacht.jpg, Heliotrope built for

, 1994 File:SSHaus.jpg, A PlusEnergy home designed by Rolf Disch, 2000 File:LuftSS.jpg, 59 PlusEnergy Homes - the Solar Settlement in

, 2002 File:SoSchiff_Ansicht.jpg, The PlusEnergy Sun Ship in

, 2004

Literature

*Voss, Karsten and Musall, Eike: Net zero energy buildings - International projects of

carbon neutrality Carbon neutrality is a state of net-zero carbon dioxide emissions. This can be achieved by balancing emissions of carbon dioxide with its removal (often through carbon offsetting) or by eliminating emissions from society (the transition to the "p ...

in buildings 2nd edition, November 2012, Institut für internationale Architektur-Dokumentation GmbH & Co. KG, München,