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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
12 V
ENTILATION IN
C
OMMON
A
REAS
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 166
context of environmental hygiene. Designers are recommended to
consider the provision of ventilation to common areas, such as corridors,
lift lobbies, entrance lobbies, etc. [6]. Where design constraints render
the provision of natural ventilation not feasible, mechanical ventilation
should be provided to improve the indoor environment. Good practices
when designing mechanical ventilation in public areas require:
the ventilation system to be capable of providing sufficient fresh air
taking into account the anticipated population;
intake and exhaust points be properly designed to prevent
contamination of fresh air supply and avoid short-circuiting; and
the ventilation system and its associated ductwork, where provided,
should be conveniently accessible for maintenance.
Ventilation for bathrooms, kitchens, refuse rooms, etc., as covered
elsewhere in BEAM, may be sources of pollution affecting common
areas.
Cross ventilation of common and circulation areas not provided with
mechanical cooling or ventilation is important to control temperatures
and to dilute pollutants and odours. Recommended practice is to place
ventilation openings so that cross ventilation can occur. However, wind
driven cross ventilation can only happen when there is a reliable higher
pressure on one side of openings than on the other. For an isolated
building this may be easily achieved by simple consideration of prevailing
winds and the building form. For buildings within dense groupings,
however, local wind direction may be less apparent, turbulence high, and
cross-ventilation decreased. A more sophisticated analysis of the
behaviour of the wind is necessary to ensure beneficial cross flows.
M
EASUREMENT
A
PPROACH
A suitable commissioning test may be performed. The test should be
carried out in representative sample, including worst case spaces as
defined above and performed under average wind conditions. In the case
of naturally ventilated spaces, measurements should be made under
conditions when windows are closed and purpose designed ventilators
are open.
M
ODELLING
A
PPROACH
Boundary layer wind tunnel modelling may be used for wind pressure
analysis. Wind pressure coefficients at inlet/outlet areas for common
areas shall be measured for at least one representative floor, including
worst case, for each type of occupied premise in the assessed building.
These may be site specific depending on the building’s height in relation
to nearby buildings and local terrain. The measurements will be taken for
at least the prevailing wind conditions which are likely to be site specific
and therefore should be determined case by case.
The modelling technique shall show a boundary layer as appropriate for
the site, and the model will include any significant buildings and site
obstructions within a distance of approximately 2 building heights. The
pressure data will be used with standard calculation procedures to
estimate flows through the common areas, arising from an average wind
condition. Buoyancy or turbulence driven flows need not be considered.
ASTM 2267 [4] states that building ventilation rates can be predicted
using approaches that range in complexity from simple single zone
models to elaborate multi-zone models. The underlying principles of
model operation are discussed in the ASHRAE Handbook [5]. The
modelling should take into account average wind speed conditions. In
6
Buildings Department. Practice Note for Authorized Persons, Registered Structural Engineers and Registered
Geotechnical Engineers, PNAP No. ADV-26 Ventilation of Common Corridors and Lift Lobbies in Buildings.
http://www.bd.gov.hk/english/documents/pnap/ADV/ADV026.pdf