Design of Balcony for Mitigating Traffic Noise and Improving Ventilation  

Project Title: Design of Balcony for Mitigating Traffic Noise and Improving Ventilation

Applicant: City University of Hong Kong

Total Approved Grant: $149,113.00

Duration: 1/12/2001 - 31/5/2002

Project Status/Remarks: Completed

Scope:

To demonstrate the ability of balcony in building design to reduce traffic noise and enhance ventilation and lighting. The project team will develop a computer prediction method to design balcony and verify the design using laboratory test and site measurement. The project results could be used by Government to establish design guidelines for balconies. The project team will organize a seminar and submit publications to technical journals to publicize the findings and demonstrate the method to design balcony with enhanced environmental performance.

Summary of the Findings/Outcomes :

Traffic noise at a residential unit can be mitigated not only by direct mitigation measures such as barriers or enclosures, but a good design of balcony with some architectural features such as vertical fins, which can be considered as a noise mitigation measure.


From previous studies, the noise reduction of a balcony is usually less than 5dB(A). Even there is no reflective building facade in surrounding, the balcony is extended to 1.5m width and the receiver is located at a large angle of incidence (figure 4.4a), the noise reduction is only around 6dB(A). It is due to the traffic noise leakage from the sidewall of the balcony and the reflection effect.

From the theoretical results, we have identified that the reflective noise mainly comes from the bottom surface of the balcony. If a titled surface or absorption material is used, a noticeable noise reduction could be achieved. The most effective measure to reduce traffic noise is to install a vertical fin on the balcony side to increase the path difference between the source and receiver and to eliminate noise leakage. This measure must be designed with a consideration of a proper building orientation. From the site measurement results, about 10dB(A) noise reduction could be achieved by adopting the new balcony design in a more complicated and reverberant condition. In conclusion, the recommendations to achieve a high noise reduction for a barrier design are listed below

- Increase the length of balcony

- Use the inclined ceiling and add the absorption material on it

- Mount a vertical fin on the balcony side to increase the barrier effect

A natural lighting and ventilation assessment on the assessed facades with balcony has also been conducted. The results indicated that the lighting level and natural air ventilation at the facade is raised when balconies with larger open space.

Finally, it can be concluded that the new balcony design can effectively improve the acoustic environment for residential buildings while it does not adversely affect the ventilation and lighting.