Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 482

performed nearly as well if the opportunity to exploit the local climate
had not been incorporated early into design.
- All design processes involved numerous experts throughout,
including both architects and engineers.
- All of the designers paid particular attention to the lighting,
equipment, and plug loads. With near-optimal envelopes and HVAC
systems, these loads represent both significant energy use and a
substantial opportunity for energy savings. While plug loads might
normally be neglected or downplayed, they are part of the energy
balance for Net ZEB design.
- Most design processes used common BPS tools that were either
commercial or government-developed. They were typically selected for
a balance of ease of use and available features, sometimes at the cost of
accuracy and integrated models.
- Since Net ZEBs tend to use new and custom technologies or design
and operational strategies many of the design teams had difficulty in
creating models in existing tools that were accurate representations of
the buildings as a whole. This issue was addressed by using multiple
tools and often creating simplified spreadsheet or customized tools.
- Parametric analysis and formal optimization were used for several of
the buildings. One common technique was to examine the predicted
performance of short sequences of representative days rather than
full-year simulations.
- The design processes revealed that there is a need for at least two
categories of design tools: simple tools that facilitate efficient
exploratory design in the early design stages and integrated tools that
have a greater number of technologies with accurate representations of
physics (e.g., thermal mass or solar radiation distribution in rooms).
Ideally, these tools are interoperable such that a common model can
evolve when using a range of tools from simple to advanced. Because
Net ZEBs tend to use advanced and/or custom technologies and other
features, ease and flexibility to incorporate new models is important.
- All of the Net ZEB case studies demonstrated the importance of
commissioning all buildings. In most cases, the buildings had minor
operational issues that resulted in higher energy consumption than
predicted. However, these were mostly very straightforward to resolve.