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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
14 T
HERMAL
C
OMFORT IN
N
ATURALLY
V
ENTILATED
P
REMISES
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 169
6
IEQ
6.5
T
HERMAL
C
OMFORT
I
EQ
14 T
HERMAL
C
OMFORT IN
N
ATURALLY
V
ENTILATED
P
REMISES
E
XCLUSIONS
Buildings that are not designed to utilise natural ventilation.
O
BJECTIVE
Promote the application of measures that reduce elevated temperatures
caused by external heat gains, and ensure installed air-conditioning units
can provide adequate control of indoor temperature.
C
REDITS ATTAINABLE
2
P
REREQUISITES
None.
C
REDIT REQUIREMENT
a) Performance with natural ventilation
1 credit for demonstrating indoor operative temperatures in
occupied/habitable rooms meet the 80% acceptability limits.
Alternatively,
1 credit for demonstrating the predicted Mean Vote (PMV) in
occupied/habitable rooms is between –1 and +1.
Alternatively,
1 credit for demonstrating that, the thermal performance, and the internal
wind speeds, of the occupied/habitable rooms fall within the 80%
acceptability range for the tropical climate conditions of Hong Kong.
b)
Performance with air-conditioning
1 credit for sustaining the air temperature at the design value within
±1.5°C when the air-conditioning unit is operating at steady state under
normal occupied periods.
A
SSESSMENT
a) Performance with natural ventilation
The assessment establishes the extent to which the design of the building
envelope can mitigate the effects of external heat gains. Based on the
output from a suitable thermal simulation model of the building the
predicted indoor operative temperature shall be compared with the criteria
given in ASHRAE 55 [ 1 ] under the ‘Optional Method for Determining
Acceptable Thermal Conditions in Naturally Conditioned Spaces’.
Assessment may be confined to the scenarios with the highest mean
monthly temperature of the hottest month or higher radiation heat gain of
whichever is higher, i.e., for those normally occupied areas of the building
most susceptible to external heat gains and/or which do not benefit from
the prevailing climatic conditions.
The spaces in question must be equipped with operable windows that can
be readily opened and adjusted by the occupants. Mechanical cooling for
the space shall not be provided, although mechanical ventilation with
unconditioned air may be utilised.
The thermal analysis shall be undertaken using dynamic thermal
modelling software. The thermal performance within the occupied or
habitable space of each type of premises most affected by solar gains
shall be determined. The modelling shall include full annual simulation
using standard Hong Kong weather data. The modelling will include the
effect of installed solar control features, e.g. glazing, internal or external
shading components, fabric and infiltration specifications, and site
obstructions. The modelling needs not include any internal gains, i.e.,
1
American Society of Heating, Refrigeration and Air-conditioning Engineers. ASHRAE 55-2004: Thermal Environmental
Conditions for Human Occupancy. Atlanta 2004.