Net ZEB Design Processes and Tools - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 193

model (e.g., rectangular building with a certain window-to-wall ratio
and a standard code-compliant HVAC system) and then export this
model for direct use and detailed modeling in EnergyPlus. This
approach normally provides inputs for many typical building
characteristics (e.g., standard occupancy and plug loads schedules for
schools) - a task that is otherwise time-consuming. A limitation of this
approach is that it restricts the modeler to use the simulation engine
that is behind the front end. Furthermore, this workflow is normally
unidirectional, meaning that once the model is modified in the detailed
tool, the user cannot return it to the front-end interface.
2. Interoperability between tools allows the same model to be saved and
opened by multiple design tools - ideally of different model resolution.
Recent advances in industry standards (e.g., Industry Foundation
Classes (IFC), and Green Building Extensible Markup Language
(gbXML)) have attempted to remove barriers between tools. However,
this remains a challenge rooted largely in the conflicting demands of
different tools and their intended audiences. For instance, building
information modeling (BIM) tools have a high degree of detail in
geometry, and to a lesser extent in building materials. Building energy
modeling tools, in contrast, require a high degree of detail in building
materials (e.g., thermo-optical properties), but do not require as high a
resolution for geometry (e.g., trim and other intricate detailing). In fact,
inclusion of such details results in excessively complex models that do
not yield significantly better accuracy (see Figure 4.10 ) , and may take
unacceptably long to detect bugs and simulate. BIM is recognized as a
process that has reinvented the building design industry, though
widespread adoption has not yet occurred for energy modeling.
Another method to simplify models is to decouple certain model aspects
(e.g., modeling renewable energy systems independently of the rest of the
building systems vs. a single integrated model). In order to avoid
overlooking any interactions, simulationists often try to integrate every
possible building element into a single model. However, efficiency at the
early design stage can be expedited if opportunities for decoupling are
exploited.
If two or more systems have minimal physical interactions, it may be
possible to decouple the models and even use two different tools to model a
singlebuilding.Forinstance, Figure4.11 showsaVenndiagramtorepresent