Comfort Considerations in Net ZEBs: Theory and Design - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 123

criterion). And the 1992 version introduced the diagram to estimate the
temperature rise for comfort purposes as a function of air velocity produced
by devices under direct control of occupants.

The adaptive comfort model, as proposed in ASHRAE Standard 55 (ANSI/
ASHRAE, 2004, 2010), presents two acceptability classes: the 80%
acceptability class, which is normative, and the 90% acceptability class,
which is informative. Their ranges are reported in Table 3.3 .

Table 3.3 Acceptability classes in ASHRAE 55

ASHRAE
55 class

Scope PPD

(%)

Fanger
PMV

Adaptive
Δ T op (K)

90% To be used when a higher standard

of thermal comfort is desired

≤10 −0.5 ≤
PMV ≤
+0.5

±2.5

80% To be used for typical applications

and when other information is not
available

≤20 −0.85 ≤
PMV ≤
+0.85

±3.5

The target comfort class has to be chosen on the basis of the level of thermal
acceptability required in a building and whether very low variations of
indoor environmental variables are required (e.g., in the case of sensitive or
unhealthy occupants).

The model developed by Nicol and Humphreys (2002) has been more
recently included in the European standards EN 15251 (CEN, 2007); hence,
it is sometimes referred to as the European adaptive comfort model. EN
15251 proposes four comfort categories, which are called I, II, III, IV, and
are defined according to the ranges of PMV proposed by ISO 7730, but, in
this case, the standard provides a description of the scope for every category
( Table 3.4 ) .