Low-Energy House
Generically, a low-energy house is any type of house that uses less energy than a regular house.
How best to heat a house is a question that is often hotly debated. On one side, it is a purely personal choice affecting our daily life and personal comfort and productivity. But on the other side, given the enormous amount of heating energy the global built environment is consuming, it is also an important topic in the sphere of social responsibility. Residential heating is an area with great potential for carbon emission reductions.
A new trend due to the widespread discussions regarding climate change mitigation is the design and construction of low-energy houses. What importance does electric heating hold in this new market environment? Electric heating used to be seen as evil by environment-conscious consumers.
General usage
In general use, the meaning of the term ‘low-energy house’ has changed over time, and will certainly change in the future. Right now, it is generally considered to be one 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 (8,000 Btu/ft²/yr to 6,000 Btu/ft²/yr). Below this the term ‘ultra-low energy building’ is often used.
Other uses, for example to mean any reduction in energy use below the standards demanded by current building codes, are also frequently encountered. 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.
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. They may also use passive solar building design techniques or active solar technologies. To reduce energy needs for domestic hot water these homes may also use hot water heat recycling technologies to recover heat from showers and dishwashers.
For further detail about the general evolution of the low energy house, see zero energy building.
Sources:http://en.wikipedia.org/wiki/Low-energy_building