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BEAM P
LUS FOR
E
XISTING
B
UILDINGS
I
NDOOR
E
NVIRONMENTAL
Q
UALITY
(I
EQ
)
V
ERSION
1.2
I
EQ
15 T
HERMAL
C
OMFORT IN
N
ATURALLY
V
ENTILATED
P
REMISES
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 135
standard. Consequently, for the BEAM assessment, months for which
the mean monthly outdoor temperatures are outside these limits can be
discounted.
When air-conditioning is likely to be installed the type, rating and
installation of units should be such as to provide for control over thermal
comfort conditions over the range of thermal loads that are likely to arise.
The Predicted Mean Vote (PMV) refers to a thermal scale that runs from
Cold (-3) to Hot (+3), originally developed by Fanger and later adopted
as an ISO standard. The original data was collected by subjecting a large
number of people (reputedly many thousands of Isreali soldiers) to
different conditions within a climate chamber and having them select a
position on the scale the best described their comfort sensation. A
mathematical model of the relationship between all the environmental
and physiological factors considered was then derived from the data.
From the PMV, the Predicted Percentage of Dissatisfied people (PPD)
can be determined. As PMV moves away from neutral (PMV=0) in either
direction, PPD increases. The maximum number of people dissatisfied
with their comfort conditions is 100% and, as you can never please all of
the people all of the time, the minimum number even in what would be
considered perfectly comfortable conditions is 5%.