As part of the DeAL research project, the Steinbeis Transfer Center for Energy, Building and Solar Engineering in Stuttgart analyzed ten buildings with decentralized ventilation systems built into the facade. They rated the buildings for comfort, user satisfaction, owner satisfaction and energy efficiency. The firm Transsolar Energietechnik and the Institute of Building Services and Energy Design at the Technical University of Braunschweig were partners in the project.
Office layout and equipment are increasingly expected to be flexible and space-saving – just one reason why ventilation systems built into facades are more and more in focus compared to traditional air conditioning systems. Modern systems like these draw air into each room through openings in the outer wall. Some also expel outgoing air in the same way. Air is conditioned locally in each individual device. The way these ventilation systems work is totally different to more commonly used centralized ventilation systems, which take in and condition air through a central device. They also contrast with systems which use decentralized induction devices to condition both fresh and recycled air, but which take in air through a central device using air channels.
Decentralized ventilation systems are a relatively new technology and the DeAL project was the first scientific study on how these systems work in practice. The team conducted a detailed analysis, which included assessing the current technology status of the systems, a cost analysis on the buildings, a survey of users and owners, and measuring energy consumption and comfort levels.
By analyzing different building facades, the team demonstrated that decentralized ventilation systems can be integrated in all common styles of building facade today. The buildings studied needed significantly less heat energy and tended to consume less electrical energy than modern office buildings of a similar standard with centralized ventilation. Short and long-term mea-surements as well as user surveys all pointed to high levels of comfort and optimal temperature control. Some buildings exceeded limits for workplace sound emissions. In some cases, this was caused by incorrectly set ventilation systems, insufficient sound insulation, or no sound insulation at all. Another strong argument in favor of decentralized ventilation is the more efficient use of space, as less equipment is needed than in conventional systems. The buildings showed a 5 to 15 per cent improvement of space efficiency.
The DeAL evaluation underlined the benefits of decentralized ventilation – namely, improved comfort and temperature control, and more efficient use of energy and space. In many cases, however, there was still potential for optimization. To make the most of decentralized ventilation systems and extract their maximum benefit, they should be planned in from the very beginning as part of an all-round approach to building design. In particular, the systems should be coordinated with facade planning, architecture and building services engineering.
Dr.-Ing. Boris Mahler
Monique Caspary-Weber
Steinbeis Transfer Center for Energy, Building and Solar Engineering (Stuttgart)
stz327@stw.de