A low energy building is any type of building that uses less energy than a regular building, it is generally considered to be one that uses 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.
In many countries the term “low energy building” relates to a specific standard. In particular these seek to limit the energy used for heating, since it represents the largest energy use.
In the United States, the ENERGY STAR program is defining low-energy buildings. Houses earning ENERGY STAR certification use at least 15% less energy than standard new houses built to the International Residential Code.
Low energy house combines and optimizes the comfort of living, quality of construction works, energy and financial efficiency and environmental protection. They provide thermal comfort, accurate air flow, high quality humidity (controlled ventilation to ensure constant supply of fresh air), dust free living conditions and lighting (greater windows to secure enough interior lighting)
Usually the efforts to reduce home energy demand leads to higher investment costs. In principle, the reduction of heat necessary by 50 % causes additional costs of investments only 10-15%.
The increase in investment costs compared with the normal construction:
1. design phase
- higher demands for pre-project design
2. feasibility stage
- building construction (more thermal insulation, better glazing)
- new technologies (eg ventilation device with heat recovery, heat storage)
- requirements for professional and high quality design details
The functioning and quality of the low energy building is a key concept chosen. When the concept is missing, the object may be only a collection of components and materials without logical connections, so different measures may even compete.
Seven principles for designing low-energy house
Together with architects and experts, individual professionals we recommend to abide by these principles:
- Design a building in accordance with the surrounding environment – choose a compact building form, place the building with respect to local climate, configuration of the terrain, vegetation, orientation to the world and how the canyon.
- Take advantage of sunlight – design a reasonably large south-oriented windows, use transparent thermal insulation. An important measure is the accompanying accumulation of passive energy gains and summer heat protection (shielding) against overheating of the building.
- Increase the thermal protection of the building – go for a high heat insulating standard and avoid the creation of thermal bridges.
- Use controlled ventilation and air-make packaging structures – controlled ventilation provides the necessary flow of fresh air in the required quality with minimal energy losses because of heat dissipated air can be re-used. To prevent energy loss is important to producing airtight walls and roofs.
- Select the optimal resource to meet the needs of the residual heat – Take advantage of renewable heat. Low energy houses have low power consumption and heat to run out with the installations with less power (eg heat pumps) or with a small amount of fuel (eg wood).
- Choose low temperature heating system for heat distribution, choose energy-efficient hot water production – low temperature heating of the media leading to less heat loss, it pays to prepare for the distribution of heat. Use active solar installations (solar collectors), or heat pumps.
- Learn how to “use” your house. Use energy-efficient appliances – for optimum performance it is necessary to correctly set the technical facilities for day and night operations, and for different seasons.