Existing Low-Energy Houses
High savings potential tapped with the modernisation of old buildings in a German Energy Agency project
- Project participants
- Detailed information
- Regional distribution
As part of the project "Existing Low-Energy Houses", a total of 143 buildings have been or are being modernised to an exemplary level of energy performance. These buildings modernised as "low-energy houses" are on average around 50 percent more energy-efficient than is required of comparable new buildings by the Energy Conservation Regulations (EnEV).
The modernisation draws on energy-efficient construction methods as well as urban planning experience with sustainable modernisation of residential buildings.
The pilot phase modernisations (2003 to 2005) produced very positive results according to the evaluation, and so over 100 participants will be involved in a 2nd project phase beginning in 2006.
Low-energy houses are new buildings or modernised older ones with a certain maximum energy requirement. These levels are set out in the Energy Conservation Regulations (EnEV). The pilot project "Existing Low-Energy Houses" aims to exploit savings potentials when modernising old buildings.
Particular priority is given to the following:
- Reduce energy needs
- Efficiently convert energy
- Integrate renewable energy resources
At least one pilot project is being implemented in each federal state to reduce the demand for primary energy according to the Energy Conservation Regulations (EnEV) to no more than 60 kWh/ m²·a. This is around 30 to 50 percent less than the EnEV requirements for new buildings.
Solutions from the field of energy-efficient construction used in the implementation of this project include the following:
- Innovative building insulation
- Triple glazing
- High-efficiency heating systems
- Avoidance of thermal bridges
- Implementation of ventilation technology and heat recovery
- Implementation of renewable energy resources, biomass
The modernisation projects were accompanied by extensive public education campaigns and public relations. This ensured a rapid transfer of expertise and accelerated the market launch of innovative technologies for improving the energy performance of buildings. The modernisation projects also serve as best practice case studies for economically viable modernisation recommendations.
As proposed by the Council for Sustainable Development, the federal government launched the "Existing Low-Energy Houses" project in 2002 as part of the national sustainability strategy.
The projects are implemented by the housing construction companies themselves, coordinated by the German Energy Agency (dena) and supported financially by the KfW-Förderbank (Development Loan Corporation) on behalf of the Federal Ministry of Transport, Building and Urban Development.
A total of 19 housing companies renovated around 880 apartments in 33 buildings as "low-energy homes" during the 1st project phase, sometimes using highly innovative passive house components which had previously been used mainly in new developments.
The pilot phase evaluation showed that transmission heat loss had been cut by 80 percent in the buildings tested. All of the prototype properties now boast thermal insulation which is 45 percent more effective than standard new EnEV buildings.
In concrete terms, this means an energy requirement of 3 litres of fuel oil per m²·a as against 7 litres of fuel oil per m²·a in standard new EnEV buildings and 20 litres of fuel oil per m²·a in normal older buildings.
Economic efficiency studies have shown that the innovative solutions were introduced into the economic sector by means of incentives.
In addition to multi-family homes, single-family and two-family homes as well as protected buildings are increasingly being included in the pilot promotion.
There is a huge potential for energy savings in this segment throughout Germany. Alternative modernisation technologies (e.g. the insulation of inner walls) can be applied here.
Around 2,230 housing units with an overall area of more than 138,000 m² are having their energy performance improved. Approximately 49 percent of the buildings are owned by the housing sector; the remaining 51 percent are privately owned (24 percent private owners of multi-family homes and 27 percent owners of single and two-family homes).
The construction phase is scientifically monitored and evaluated from beginning to end. It has already been demonstrated that energy-efficient forms of construction can cut energy requirements by an average of 80 percent.
Following modernisation, the buildings consume just 50 percent of the energy required to heat comparable new buildings. The modernisation projects also clearly demonstrate that energy-efficient construction and modernisation as well as sustainable energy use concepts are significant factors in ensuring that housing and real estate retain their value and attractiveness irrespective of rising energy costs.
Modernisation requirements differ greatly from project to project, allowing for a variety of creative solutions. Three priorities can be identified in all of the pilot projects:
Reducing the energy required
The building envelopes are markedly improved in all of the projects to reduce the heating energy requirements in the construction projects. Typically - as long as this is in accordance with regulations concerning the protection of historic buildings - the exterior walls are fitted with insulation approximately 20 centimetres thick. The energy performance of basement ceilings and of roofage or top-floor ceilings is increased. For the windows a minimum of double-glazing, and in most cases triple-glazing or passive house windows, is used.
Efficient energy conversion The resultant required energy, already reduced to a minimum following improvements to the building envelope, is provided by efficient installation engineering. Heat is mainly generated by gas condensing appliances, heat pumps and wood pellet boilers. Condensing appliances are extremely efficient, as they condense the water vapour contained in waste gases and use this for additional heating. Heat pumps exploit the higher temperature of the ground when outdoor temperatures are low, raising the ground temperature until it can be used for heating. Wood pellet boilers use renewable resources as sources of energy, providing heat with a minimum of CO2 emissions. In addition to district heating from centralised combined heat and power systems (CHP), small-scale combined heat and power systems are also used. Heat generation is complemented by efficient ventilation, in particular by controlled heat recovery ventilation.
Integrating renewable energy resources
In over half of the buildings, renewable energy resources are integrated into the supply concepts in order to reduce demand for fossil energy sources. In 48 percent of the buildings these are solar thermal installations which contribute to drinking water heating and, to some extent, space heating. Over one quarter of the buildings use biomass. In certain cases, further renewable components are integrated into the concept such as the use of a photovoltaic installation or of a geothermal heat exchanger to pre-condition the room air.
The following diagrams depict the regional distribution of the 33 pilot projects and the 110 second-phase projects.
National distribution of the construction projectsThe dark dots indicate the pilot phase projects, the lighter dots mark the second-phase projects. The map makes it clear that the "best practice" principle works - the pilot projects are cogent examples and act as multipliers.
The pilot project "Existing Low-Energy Houses" proves that existing buildings can be improved to a level of energy performance significantly below the requirements of the Energy Conservation Regulations (EnEV) - more so than new buildings.
From the over 140 construction projects, valuable experience regarding the improvement of energy performance can be gained and shared, and concepts for economically viable improvement of the energy performance of buildings can be developed.
Many of these findings will be able to be included in the new promotional programme of the Development Loan Corporation (KfW).
The dena project is expected to continue in 2007 and to be extended to include local buildings (schools, gymnasiums, etc.).