Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 471

summer seasons, the air-conditioning in the offices was not used at all. It
shows that the hypothesis of the Givoni comfort zones for the assessment of
thermal comfort was not completely accurate. Therefore, an extensive field
study on thermal comfort was conducted on the ENERPOS building and is
presented in Section 7.5.12.
The purpose of the two split system units (one of 1780 W and the second
one of 700 W) was to cool the two technical rooms equipped with computer
hardware. In fact, only one technical room houses switchgear cubicles, thus
only one split system (700 W) is turned on for cooling purposes.
During the design phase, it was proposed to set up an uninterruptible power
supply (UPS), particularly for the two computer rooms. Nevertheless, at
the current time, there is no UPS in the building. Moreover, up to August
2012, the two computer rooms were not equipped with desktop computers.
Students came to the building with their own laptops. The computer rooms
are now equipped only with screens, keyboards, and mice. All central units
are located in the air-conditioned technical room. With regard to the offices,
the use of laptops and netbooks, instead of desktops, has been encouraged,
whichpartiallydecreasestheenergyuseforplugloads.Thischangebetween
thedesignphaseandthecurrentsituationexplainsthesignificantdifference
in the energy consumption of the plug loads (20 kWh/m 2 /yr rather than
approximately 6-7 kWh/m 2 /yr for the measurements).
To conclude, the difference between the model predictions and the
measurements for the energy use of ENERPOS is not a result of model
inaccuracy, but is due to the fact that the actual building operation differs
from that expected during design.
7.5.11.2 Thermal Comfort
During the design phase, a dynamic thermal model of the building was
undertaken using the DesignBuilder simulation tool. Figure 7.79 shows the
annual temperature profile of an office in ENERPOS. Based on the seasonal
variations in the temperature of the office, it was possible to predict the
different operational periods of natural ventilation, ceiling fans, or
air-conditioning, throughout the year. The transition from natural
ventilation to ceiling fans was carried out partly based on the experience
and knowledge of the site and climate by the design office team, but also
on the basis of a maximum average effective room temperature above 28