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BEAM P
LUS FOR
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EW
B
UILDINGS
I
NDOOR
E
NVIRONMENTAL
Q
UALITY
(I
EQ
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V
ERSION
1.2
I
EQ
14 T
HERMAL
C
OMFORT IN
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ATURALLY
V
ENTILATED
P
REMISES
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 170
simulations for unoccupied premises are required.
Alternatively, compliance may be demonstrated under appropriate
summer and winter conditions through the measurement of temperature in
suitable locations in a sample of premises most exposed to external heat
gains.
The Client shall provide evidence in the form of a report prepared by a
suitably qualified person detailing any means used to control the external
(solar) heat gains, the specification and details of the thermal simulation
software used in the analysis, and the results of the simulations.
Where compliance is demonstrated by measurements the details of
measuring equipment, sampling locations, sampling time, time of
measurements, external temperature and prevailing weather conditions
shall be provided.
Where it can be demonstrated that the predicted indoor temperature lies
within the 80% acceptability limits given in ASHRAE 55-2004 a credit shall
be awarded.
Alternately, where it can be demonstrated that the Predicted Mean Vote
(PMV) in occupied/ habitable rooms is between –1 and +1, a credit shall
be awarded.
b) Performance with air-conditioning
The measurement locations shall include at least one representative
sample of each type of premises (occupied spaces) as defined by the type
of HVAC system used, design occupancy density, nature of usage,
zoning, etc. The measurements shall be undertaken in a normal occupied
period. The sensors used in the measurement survey shall have an
accuracy that complies with ISO 7726 [2] or equivalent. To earn credit the
results shall demonstrate compliance with the prescribed design criteria
within the prescribed limits, for a minimum of 90% of the prescribed
locations.
B
ACKGROUND
Thermal comfort standards such as ISO 7730 [ 3 ] and ASHRAE 55
establish relatively tight limits on recommended indoor thermal
environments, and do not distinguish between what would be considered
thermally acceptable in buildings conditioned with natural ventilation.
Derived from laboratory experiments using a thermal-balance model of the
human body these standards have attempted to provide an objective
criterion for thermal comfort, specifying combinations of personal and
environmental factors that will produce interior thermal environments
acceptable to at least 80% of a building's occupants. The heat-balance
models, on which the standards are based, were developed in tightly
controlled conditions. The people involved were considered passive
subjects of climate change in artificial settings, and little consideration was
given to the broad ways they might naturally adapt to a more wide ranging
thermal environments in realistic settings.
Field studies and research has demonstrated that occupants of buildings
with centralised HVAC systems become finely tuned to the very narrow
range of indoor temperatures provided, developing high expectations for
homogeneity and cool temperatures, and soon became critical if thermal
conditions do not match these expectations [4,5]. In contrast, occupants of
naturally ventilated buildings are more tolerant of a wider range of
2
International Standard Organization. ISO 7726, Ergonomics of the thermal environment — Instruments for measuring
physical quantities. 1998.
3
International Standard Organization. ISO 7730. Moderate thermal environments – Determination of the PMV and PPD
indices and specification of the conditions for thermal comfort.
4
de Dear R, Brager G S, Reardon J, Nicol F et al. Developing an adaptive model of thermal comfort and preference/
Discussion. ASHRAE Transactions. Vol. 104. 1998. pp 145-167.
5
Brager G S, de Dear R. A Standard for Natural Ventilation. ASHRAE Journal. October 2000. pp 21-28.