Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 444

Fig. 7.67 Winter design period performance, with VC on the original
daylighting window size

The data indicate that the size of the daylight window can be increased to
receivemoredaylightandpassivesolarheatgaintoreducethespaceheating
load. Hence, the size of the daylight window is increased to 2.5 times its
original size. The WWR of the daylighting window becomes 32%. To avoid
space overheating, the control strategy for the VC is if room temperature is
2 °C or more higher than the room heating setpoint (22 °C), then the VC
maximum transmittance multiplier, , will be set to

(7.10)

where the illuminance set point is set at 300 lux and is the average

illuminance level of the interior zone.

After enlarging the window size and applying the VC control strategy, the
space heating energy consumption is lowered to 5.11 kWh, a reduction of
11% for the 2-day period. Note that the space heating energy consumption
is slightly less than that spent on warming supply air. The VC control was
activated during the first day when the south zone temperature reached
24 °C to reduce the transmitted amount of solar radiation to avoid space