Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 368

1. Operational changes: existing hardware with changes to control
strategies, such as setpoints and logic for controls related to solar heat
collection and usage/storage;
2. Building envelope changes: either passive or active envelope
components to change how the house interacts with the environment;
and
3. Generation: active systems to offset energy use.
For redesign, the operational changes will be considered first because they
are noninvasive and have no material costs. The last two options - envelope
upgrades and generation - will be considered simultaneously. A fourth
category of upgrades could consider a modification to occupant behavior.
Nearly 40% of the electrical loads are related to appliances, lighting, and
plug loads. Furthermore, some of the heating and cooling can be attributed
to the fact that the occupants have the set points at values other than
anticipated during design. For instance, the daytime heating setpoint is
22.5 °C instead of 21 °C, resulting in a predicted 10% increase in heating
loads, according to the model. However, these social aspects are considered
beyond the scope of the current study. Making assumptions that could lead
to sacrifices in comfort and convenience would undermine the occupants'
values. While the designer cannot predict discretionary energy use to a
high degree of certainty, they can inform the occupants about their habits;
either informally or through the installation of an “energy dashboard” that
provides useful feedback. For example, the authors visited the occupants at
their home after several months of occupancy to show them a breakdown
of energy use. Upon informing the occupants that the electric resistance
heater in the garage was using nearly as much energy as the heat pump,
they reduced its use to negligible levels. Chetty, Tran, and Grinter (2008)
stated that real-time feedback of household energy consumption can lead
to 10% savings with minimal change in behavior. Further grid-side benefits
can be achieved through shifting non-time-sensitive loads, such as clothes
drying and dish washing. Such habits can be encouraged using different
time-of-use electricity rates.
The analysis of many of the upgrades described are made possible because
EnergyPlus is a detailed tool that has a powerful output facility with which
many low-level outputs (e.g., nodal temperatures and heat fluxes) are
available on the timestep level. Many earlier stage design/simulation tools,
such as HOT2000, use standard configurations. However, the creation of