Low-Energy Houses and Passive Houses

Efficient heating systems in a low-energy house
Efficient heating systems in a low-energy house

Particularly energy-efficient buildings offer economic benefits in the face of rising energy prices, help combat climate change and provide a very pleasant room temperature.

In Germany, buildings that meet the low-energy house standard have an annual energy requirement of between 30 and 70 kilowatt hours per square metre. The term "passive house", meanwhile, refers to particularly efficient buildings that do not require an active heating system to achieve a comfortable room temperature. To meet this standard, the annual energy requirement per square metre for room heating must be reduced to less than 15 kilowatt hours, while the building must also be equipped with ultra-efficient ventilation and heat recovery systems.

To achieve these values, renovation of the building envelope and the heating and ventilation systems must be planned and executed by professional experts. Energy-efficient optimisation of the building envelope includes doors and windows, as well as insulation of the exterior walls and basement, roof, roofspace and floor slab. Thermal bridges, in particular around windows and in entrance areas, are to be avoided as far as possible. Savings can be made in the building's HVACR (heating, ventilation, air conditioning and refrigeration) through efficient heat generation and distribution, a large proportion of passive solar energy utilisation and sophisticated ventilation technology.

Ventilation system with heat recovery
Ventilation system with heat recovery
Due to the multitude of energy-efficient buildings that have already been constructed in Germany (including passive houses), German companies have had the opportunity to acquire extensive expertise in meeting specific challenges in relation to building construction and technology. Changes in consumer behaviour play a key role in this context because the active ventilation systems required (in passive houses in particular) render many old and particularly inefficient practices superfluous, for example, tilting windows to ventilate a room.

Breakdown of buildings in Germany according to average heating demand
Breakdown of buildings in Germany according to average heating demand
Knowledge gained from and technologies used in the construction of energy-efficient buildings (for example, passive new builds) can also be applied to the renovation of building stock, including the optimisation of heating technology to ensure low wastage, ventilation measures and the avoidance of thermal bridges. German companies can achieve savings of more than 80% in a typical old build.

The "Energy-Optimised Construction" (EnOB) programme of the Federal Ministry of Economics and Technology and the "Low Energy Standards for Existing Buildings" project of the German Energy Agency (dena) provide impressive demonstrations of how, through best practices in energy-efficient renovation, existing buildings can meet the same standards as a low-energy house (see www.enob.info).