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BEAM P
LUS FOR
N
EW
B
UILDINGS
S
ITE
A
SPECTS
(S
A
)
V
ERSION
1.2
S
A
8 M
ICROCLIMATE
A
ROUND
B
UILDINGS
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 47
Appropriately numbered and suitably located test points should be
positioned in and outside the project site within the assessment
area. Particular attention should be paid to building corners, gaps
between buildings and building voids;
The annual wind rose (wind probability table) of the site should be
used;
At least 8 of the prevailing wind directions (out of 16) should be
tested;
The average “hourly mean wind speed” of the test points to be
reported;
No test point reported should exceed an average “hourly mean wind
speed” of 4 m/s.
b) Elevated temperatures
The Client shall submit a report detailing strategies and design solutions
to mitigate elevated temperatures in exposed public areas. This should
demonstrate the effectiveness of reducing temperatures by:
i) providing shade on at least 50% of non-roof impervious surfaces on
the site (parking, walkways, plazas) using light coloured high-albedo
materials (albedo of at least 0.4); or
ii) providing roof material with the Solar Reflectance Index (SRI) higher
than 78 covering at least 50% of the total roof area; or provide
vegetation covering at least 50% of the total roof area.
Area of exemption for the roof with material of high SRI or vegetation
would include areas occupied by mechanical systems.
c) Air ventilation assessment
The HPLB and ETWB have formulated the methodology for Air
Ventilation Assessment. The Client shall follow the prevailing technical
circular as described and demonstrate the effects and impacts on the
pedestrian wind environment.
The Client shall submit evidence in the form of a report prepared by a
suitably qualified person which follows the reporting requirement listed in
the prevailing technical circular.
B
ACKGROUND
The microclimate around buildings can suffer as a result of the restricted
natural ventilation from winds and breezes, leading to stagnant areas of
pollution and elevated temperatures. Conversely, the topology can lead
to significant amplification of wind at pedestrian level, leading to
discomfort and fatigue for pedestrians, damage to plant life,
accumulation of debris, and in more extreme cases, danger from
impeded walking and flying objects.
Wind flow around a site can be accelerated or decelerated due to the
building form, typically 2 to 3 times greater than for open ground.
Localised areas of accelerated wind around corners and between narrow
channels are of particular concern.
The following table [1] indicates that mechanical discomfort sets in at
wind speeds of about 5 ms
-1
, with speeds above 8 ms
-1
being very
uncomfortable and speeds above 20 ms
-1
being dangerous. Conversely,
some areas may receive relatively low wind flow with free airflow being
obstructed by buildings.
1
British Building Research Station, Wind Environment Around Tall Buildings. Digest 141, May 1972.