2.10 Secondary Facades - External Ventilation Shafts

An alternative to secondary facades is to use external chimneys. This scheme uses very similar principles to that of a double facade; the difference being that the external chimneys are only used over the ventilation openings. This arrangement clearly has cost and space saving advantages over that of double façades.

A second architectural advantage is that it is possible to provide an animated facade. Forming the chimneys from glass or other translucent materials, allows interesting designs in the form of graphics to be incorporated within the chimneys, adding further interest to the facade of the building.

One of the drawbacks of this design is that acoustic treatment may be required within the chimneys to prevent the spread of sound along its length. This may be required to maintain the acoustic separation across floors. If this is the case, acoustic art work could be used to give the architectural design and also to provide the acoustic absorption within the chimneys.

2.11 External Spaces as Secondary Facades

Secondary Façade as a Functional Space
Often there is a need for spaces such as cloakrooms, changing areas, walkways, balconies and other non-acoustically sensitive spaces to be located adjacent to a building. By making these spaces external and unheated, i.e. open covered spaces, it is possible to use these areas as a secondary facade . If required, additional acoustic protection can be added by means of placing an attenuator within the secondary facade 1. This attenuator could be located under benches, cupboards, shelving areas, raised areas etc. This would be an ideal way of preventing noise break-in from low flying aircraft, nearby rail lines, or a large main road such as a motorway.

Acoustic screening and ventilating from under a building
Acoustic screening is an effective method of controlling noise break-in to a building.
Illustration 2 shows how a large, suspended, raised (play) area was used to accommodate the fall in the land across a school site. This play area provided a highly effective screen to aircraft noise and potentially other major noise sources. The acoustic attenuation is provided as the vents under the deck have little or no visibility to the noise sources affecting the development. In simple terms, providing an air inlet under the building prevented noise ingress into the building.