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BEAM P
LUS FOR
N
EW
B
UILDINGS
I
NDOOR
E
NVIRONMENTAL
Q
UALITY
(I
EQ
)
V
ERSION
1.2
I
EQ
2 P
LUMBING AND
D
RAINAGE
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 146
refuse.
V
ENTILATION
Where mechanical ventilation in the form of extractor fan is provided,
such as in bathrooms and lavatories, care should be taken to ensure that
water seals are intact and operate according to the design intent [5].
Consideration should be given to the quality and quantity of air intake,
air-flow path and fan capacity.
The Environmental Health Team of the World Health Organisation
(WHO) has advised that the optimum volume for bathroom ventilation is
2 cfm/sq ft (10.2 l/s per sq. metre). WHO is of the view that a larger
volume does not add much on the comfort side and has the hidden risk
of building up negative pressure. Designers are advised to provide an
opening to bathrooms and lavatories for make-up air, such as an
undercut to the door or an opening with a louvre at the door or wall, in
order to minimise the build-up of negative pressure where an extractor
fan is used for ventilation. The airflow path created should avoid
circuiting of the ingress and exhaust air.
5
Buildings Department. Practice Note for Authorized Persons, Registered Structural Engineers and Registered
Geotechnical Engineers, PNAP No. ADV-25 Extractor Fans in Bathrooms and Lavatories in Domestic Buildings.
http://www.bd.gov.hk/english/documents/pnap/ADV/ADV025.pdf