Germany

Heating energy in buildings represents a significant proportion of the total global energy consumption. Uncontrolled airflow through the building envelope contributes significantly to its energy losses.  

The trend in European countries, such as Belgium, France and Germany is that the quality of the airtightness of the building envelope is getting better and better. This is true for small, airtight apartments, Passive houses and some large buildings with an excellent airtightness due to special requirements, e.g. oxygen reduction or fire protection.

Guaranteeing high indoor air quality and high degree of user satisfaction at the same time is one of the challenges when improving the energy efficiency of a building. Current non-residential buildings mainly use mechanical ventilation systems to ensure high air quality. Mechanical ventilation systems are known for minimising heat losses but at the same time lead to higher installation, operating and maintenance costs. Furthermore, mechanically conditioned rooms may lead to the sick building syndrome caused by the lack of operable windows.

The current type of construction preferred for new high energy efficient buildings in Germany, featuring highly insulated building components and an almost completely airtight building shell, raises several new challenges with regard to design, construction and use of these buildings. Cooling, in particular, is an issue that gains importance also in the residential sector, in connection with rising temperatures induced by the climate change.

It has already been proven that a large portion of the energy consumption gap between simulations and reality is due to the occupant behaviour in buildings. The improving airtightness of buildings makes that Indoor Air Quality (IAQ) can no longer rely on air renewal through infiltrations, bringing the need of ventilation systems. Within this frame, an ongoing dissertation focuses on the relationship between occupancy behaviour and ventilation systems in low energy buildings.

This study presents a comparison of three ventilation systems; automated Natural Ventilation (NV), balanced Mechanical Ventilation (MV) with heat recovery and Hybrid Ventilation (HV) with heat recovery for a new build office building.
The energy demand for heating and electricity as well as the indoor climate of the building were simulated using IESVE. Three key European cities were selected (Copenhagen, Munich and London) in order to investigate the applicability of the principles to different climatic conditions in Europe.