Tommy Kleiven, SINTEF / Civil and Environmental Engineering Anne Grete Hestnes, NTNU / Faculty of Architecture and Fine Art

Natural ventilation in buildings relies on wind and thermal buoyancy as driving forces. Humankind has used these driving forces throughout history to create the desired thermal environment and to transport away undesired contaminants. The technique we take advantage of to control and adjust our indoor climate has grown ever more sophisticated. This technique has in the 20th century been dominated by mechanical ventilation and air conditioning. These technologies have developed into systems of great complexity with an increasing number of components, need for space, and use of energy. Despite this, many of the mechanical systems do not manage to deliver the desired indoor climate. Because of this contradiction, the focus has again been put on simpler, more robust, and less energy consuming solutions.

The driving pressures derived from wind and thermal buoyancy are low compared to those produced by fans in mechanical ventilation systems. It is therefore necessary to minimise the resistance in the airflow path through the building. Thus, the building itself, with its envelope, rooms, corridors, and stairways, rather than the ducts familiar from mechanical ventilation systems, is used as air path. A natural ventilation concept is therefore highly integrated in the building body and will consequently have influence on building design and architecture.

This paper examines the relationship between building design and the utilisation of natural ventilation in office and school buildings in Northern Europe. The main objectives of the work have been to identify and investigate the architectural consequences and the architectural possibilities of natural ventilation. Case studies and interviews with architects and HVAC consultants have been the most central “research instruments” in achieving this. The case buildings studied are the GSW Headquarters in Germany (solar chimney/double facade), the B&O Headquarters in Denmark and the Media Primary School in Norway (sunspace). The most important findings are that:

— Utilisation of natural ventilation in buildings has architectural consequences as well as possibilities.

— Natural ventilation primarily affects the facades, the roof/silhouette, and the layout and organisation of the interior spaces.

— The ventilation principle applied (single-sided, cross — or stack ventilation) together with the nature of the supply and extract paths, i. e. whether they are local or central, are of key importance for the architectural consequences and possibilities.

— Designing a naturally ventilated building is more difficult than designing a similar but mechanically ventilated building. An interdisciplinary approach from the initial stages of design is mandatory for achieving successful natural ventilation concepts.