Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 362

Total heating electricity (space heating and DHW) is only about one-third
of the total. This is in contrast to the existing housing stock, for which this
fraction is closer to 80% (NRCan, 2008). Three major reasons for this are
the decreasingly important impact of heating as envelopes become higher in
quality, the strong passive solar component, and the fact that a heat pump
was used, reducing the space heating and cooling energy by a factor of about
3.7. It should be noted that because of the desuperheater's assistance in
domestic hot water heating, the DHW load appears lower in the winter. This
is simply because the DHW load is measured based on auxiliary electric
water heating, not total DHW load.
TheHRVandaircleaneraccountforabout8%oftotalannualelectricityuse.
Future effort to optimize the controls to minimize ventilation when it is not
needed or when natural ventilation is sufficient would be beneficial.
The lighting, appliances, and plug loads account for over one-third of the
total energy use, yet this was given a disproportionately low level of
attention relative to other aspects of the design. While new high-efficiency
appliances were selected, the potential for real-time display of data in an
effort to impact occupant behavior was not examined. This result
emphasizes the importance that Net ZEB designers also examine
energy-conserving approaches to lighting and appliances.
The monthly PV performance showed reasonably good comparison to
modeled performance (based on RETScreen) during the summer months
(see Figure 7.14 ) . However, during the four coldest months - November
through February - generated electricity was only 20-40% as much as
expected. This is almost exclusively due to chronic snow accumulation.
Figure 7.15 shows a typical winter day after snowfall.