Net ZEB Design Processes and Tools - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 202

For early-stage design, when passive strategies (e.g., building form,
insulation level, window size, type, and placement, and thermal mass) are
being evaluated, idealized HVAC systems are normally adequate. Such
systems are modeled to deliver heating and cooling as needed to maintain
simplifiedcomfortconditions(e.g.,basedonairtemperatureandhumidity).
Idealized methods become less accurate when issues such as HVAC
capacity, distribution energy (fans, pumps), and controls are established
in the design. For Net ZEBs, these details can be significant because
distribution (fan or pump) energy can be relatively high and controls are
often advanced.
The sheer number of available HVAC configurations and components
means that HVAC systems are among the most difficult to model. This has
been resolved in many BPS tools and interfaces (e.g., eQUEST, EnergyPlus,
and Example File Generator) using templates in which several common
HVAC configurations are provided to the user. For the frequent occurrence
in which the designed HVAC configuration is not represented by one of the
built-in templates, a common workflow strategy is to use the template as a
starting point and then modify it, as needed, to represent the configuration
of interest. In the context of Net ZEBs, the vast number of HVAC
configurations is further complicated by the fact that renewable energy
systems are often integrated into the building, systems, and/or plant, as
shown in Figure 4.17 . Thus, in order to accurately model these integrated
systems, a detailed coupled model is necessary.
Fig. 4.17 Data flow in decoupled ( ____________ ) and coupled (- - - - -)
building-HVAC modeling approaches for Net ZEBs
TheÉcoTerrahouse,whichhasanovelBIPV/Tcollectorthatisintegratedto
anactivelychargedventilatedconcreteslab,facedthechallengeofhavingno
readily available models for such a system during design (Chen, Athienitis,