Low-energy house

This thermogram compares a traditional building (left) to one built to the German passive house standard (right)

Generically, a low-energy house is any type of house that uses less energy than a traditional house.

General usage

The meaning of the term 'low-energy house' has changed over time, but it generally refers to a house that uses around half of the German & Swiss low-energy standards mentioned below for space heating, typically in the range from 30 kWh/m²a to 20 kWh/m²a (9,500 Btu/ft²/yr to 6,300 Btu/ft²/yr). Below this the term 'ultra-low energy building' is often used.

The term could also refer to any house whose energy use is below the standards demanded by current building codes. Because national standards vary considerably, 'low energy' developments in one country may not meet 'normal practice' in another.

National standards

In some countries the term relates to a specific building standard. In particular these seek to limit the energy used for space heating, since in many climate zones it represents the largest energy use. Other energy use may also be regulated.

In Germany a "Low Energy House" (Niedrigenergiehaus) has a limit equivalent to 7 litres of heating oil for each square meter of room for space heating annually (50 kWh/m²a or 15,850 Btu/ft²/yr). In Switzerland the term is used in connection with the MINERGIE standard (42 kWh/m²a or 13,300 Btu/ft²/yr).

In comparison, the German Passivhaus ultra-low energy standard, currently undergoing adoption in some other European countries, has a maximum space heating requirement of 15 kWh/m²a or 4,755 Btu/ft²/yr.

In the United States, the ENERGY STAR program is the largest program defining low-energy homes. Homes earning ENERGY STAR certification use at least 15% less energy than standard new homes built to the International Residential Code, although homes typically achieve 20%-30% savings.^[1]

In addition, the US Department of Energy launched a program in 2008 with the goal of spreading zero-energy housing over the US. Currently, participating builders commit to constructing new homes that achieve 30% savings on a home energy rating scale.^[2]

Beyond ultra-low energy buildings

Beyond ultra-low energy buildings are those that use, on average over the course of a year, no imported energy (zero energy buildings), or even those that generate a surplus (energy plus houses), both of which are being built.

This can be achieved by a mixture of energy conservation technologies and the use of renewable energy sources. However, in the absence of recognized standards, the mix between these - and consequently the energy-use profile and environmental impact of the building - can vary significantly.

At one end of the spectrum are buildings with an ultra-low space heating requirement that therefore require low levels of imported energy, even in winter, approaching the concept of an autonomous building.

At the opposite end of the spectrum are buildings where few attempts are made to reduce the space heating requirement and which therefore use high levels of imported energy in winter. While this can be balanced by high levels of renewable energy generation throughout the year, it imposes greater demands on the traditional national energy infrastructure during the peak winter season.

Low energy technology

Low-energy buildings typically use high levels of insulation, energy efficient windows, low levels of air infiltration and heat recovery ventilation to lower heating and cooling energy. They may also use passive solar building design techniques or active solar technologies. These homes may use hot water heat recycling technologies to recover heat from showers and dishwashers. Lighting and miscellaneous energy use is allieviated with fluorescent lighting and efficient appliances. Weatherization provides more information on increasing building energy efficiency.

Zero energy buildings gives further detail about the general evolution of the low energy house.

References

See also

Energy portal

Sustainable development portal

• Energy audit
• List of low-energy building techniques
• Low-carbon economy
• Passive house
• Superinsulation
• Zero energy building

Building energy rating systems:

• Australia - House Energy Rating
• Canada - EnerGuide
• UK - National Home Energy Rating
• US - Home energy rating

External links

• Study on Energy Performance of buildings The European Parliament 2009
• Very Low Energy Houses - discussion paper - Nov 2006
• IEA Energy Conservation in Buildings and Community Systems Programme.
• Common Fire Foundation Comprehensive Overview of Green Building, plus info on the net zero energy "Greenest Building in the Eastern US" (non-profit)
• MINERGIE (official site)
• Residential & Commercial Energy Audits

This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations where appropriate. (February 2008)

Examples

• Minimum Energy houses in the Netherlands (1982-1983)
• rockenergy: low carbon houses, low energy houses, 5-litre houses
• photo from a low-energy house in Germany 1992
• low-energy house in Denmark
• low-energy, respective passive-houses in Norway
• low-energy houses in Norway
• Meet the Greenovate Hosts: Chris Prelitz