Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 477

Fig. 7.81 Thermal sensation votes by temperature ranges
Figure 7.81 shows that up to a temperature of 30 °C, at least 80% of the
people surveyed express a sensation of comfort. This limit is higher than the
level that is generally accepted in comfort standards and used by building
designers to assess thermal comfort.
Two main conclusions were drawn from this survey:
1. Thermal comfort can be reached when the operative temperature is up
to 30 °C assuming that natural and mechanical ventilation (openings
and ceiling fans) are properly sized; and
2. Based on the recorded values (13 to 21 g water /kg air ), the humidity level
has little effect on thermal comfort. High humidity levels (21
g water /kg air ) are not contradictory with thermal comfort and they are
much higher than the upper humidity limit of 12 g water /kg dryair
recommended by ASHRAE Standard 55 (ASHRAE, 2010).
7.5.12.3 A Comparison between the Experimental Data and the Givoni
Comfort Zones
Based on the thermal comfort surveys presented, it is possible to compare
the answers given by the occupant of the building with the comfort zones
proposed by Givoni on the psychometric chart.
The standard EN 7730 (EN, 2005) gives the relationship between the
predicted mean vote (PMV) and the predicted percentage dissatisfied
(PPD). When the PMV is between −0.5 and 0.5, the PPD is less than 10%.
For a PPD of 20%, the PMV would be 0.85. As a comfort zone is defined
for a maximum percentage of discomfort of 20%, the experimental data
represented in Figure 7.81 can be divided into four categories, as shown in
Figure 7.82 .