Sustainable towers: an enquiry for MEEDDAT

Commerzbank Tower, Germany - Architect: Lord Norman Foster

CSTB has drawn up an international inventory of « remarkable » office tower buildings in terms of sustainable development, and particularly energy performances, at the request of the Ministry of Ecology, Energy, Sustainable Development and Regional Development (MEEDDAT).  This study started in 2007 and was composed of two parts.  The first part consisted in listing international labels to characterise tertiary buildings for the two particular aspects mentioned above.  The second part focused on the carrying out of an inventory of high performance office towers.  The objectives were to create a state-of-the-art report of best practices in environmental engineering and to identify the most innovative technologies.

St Mary Axe, Great Britain - Architect: Lord Norman Foster

Approximately twenty towers were identified according to the study criteria, in Europe, America, Asia and even Africa.  Five of them were selected (Conde Nast Building, USA; Commerzbank Tower, Post Tower Bonn and Highlight Business Tower, Germany; St Mary Axe, UK) for a more detailed and thorough analysis of their environmental and energy performances in use.  "We contacted clients and design offices who supervised the construction of each of the five buildings, says Sophie Cuenot, in charge of both the studies and the project.  We sent them a questionnaire in order to obtain as much information as possible for each building.  We actually visited two of them and held direct discussions with the clients and design offices about their real performances."




An energy summary to be considered globally

Conde Nast Building, USA - Architects: Fox & Fowle

The study carried out provided very specific information.   "Due to their configurations and large floor areas, the towers can particularly be characterised by the high energy consumption related to air conditioning, ventilation and lighting, says Sophie Cuenot.  Energy needs for the operation of elevators are also high.  Secondly, the use of renewable energies is limited due to the small available surface areas available for installing equipment, for example such as photovoltaic panels."  Similarly, glazed facades are not ideal to quaranty thermal and visual comfort.  They are also a source of large energy losses.

Commerzbank Tower, Germany - Architect: Lord Norman Foster

As a consequence, would towers be incompatible with sustainable development and energy performance?  This is an important issue. Many possibilities for improvement deserve further study.  Firstly, integrated design of an office tower is essential, and can lead to energy savings up to 30%.  Secondly, it seems to be essential to partition office space to enable standalone and independent operation depending on the use made of them, resulting in large potential energy savings.  In order to do so, early cooperation (regarding integrated conception) between building final users and the project management team is necessary.  Furthermore, the choice of high performance offices equipment has a strong influence on reducing internal loads and energy use..

Finally, the study could be broadened to include other aspects of sustainable development that have not yet been taken sufficiently into consideration:  space management (densification), location of the tower in the town, and problematic of user transport and associated services, taking account of grey energy contained in materials, health impacts; all these parameters should be taken into account and put into parallel with the energy balance of high rise office buildings.