What is Free Cooling?
The term “free cooling” refers to a technique that has been known in southern Europe since time immemorial: the short-term temperature cycles created by the succession of day and night are used to balance the indoor climate. Early in the morning, the windows are opened wide, the air that has cooled down overnight flows into the rooms and extracts heat from the building structure; as soon as the outside temperature rises, the windows are closed and the cooled building mass ensures a balanced indoor climate during the day. This vernacular technology does not require any human energy or building services.
Today, this technology can be used very efficiently thanks to highly developed control technology, as the architects Baumschlager Eberle have shown in their extensively discussed project 2226 in Lustenau. The combination of vernacular technology with a “high-tech” control system can make optimal use of the shifts in the temperature cycles, so that the entire building does not use any energy for room temperature control over the entire year.
The requirements
A prerequisite for free cooling is the presence of sufficient storage mass in the building (storey ceilings, access cores). In addition, this storage mass must be in direct thermal exchange with the room air. This can lead to a conflict of objectives with room acoustics – similar to thermally activated building components: bare concrete ceilings are highly reflective, so that an unpleasant acoustic room climate is created, especially in large rooms.
