Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 367

Fig. 7.18 Comparison between measured heat pump electricity and
modeled values
Unlike for heating, which is tightly controlled, the occupants had the option
of overriding mechanical cooling by merely switching it off. Consequently,
the model overpredicted cooling energy. There was anecdotal evidence from
the owners that natural ventilation was used as a means for cooling and
increasing air movement. While this was coarsely modeled, other
discrepancies could occur from a high tolerance for high temperatures or
significant periods of absence during summer vacation.
Anotherinterestingpeculiarityisthatthemodelconsistentlyunder-predicts
heating energy from January to March and overpredicts heating energy in
November and December. Possible explanations are shading from trees,
ground reflectance variability (from snow) or simply, a change in occupant
behavior (e.g., greater internal gains or a changed heating setpoint).
7.2.4.6 Implementation of Redesign Strategies
This section outlines the redesign study that was performed. The
fundamental question being asked is how could ÉcoTerra and other similar
low-energy houses have been designed to achieve net-zero energy status?
The EnergyPlus model was used to assess each upgrade for energy
performance. There are three major categories of possible upgrades: