Net ZEB Design Processes and Tools - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 153

site details, the functionality and occupancy level, as well as the economic,
energy, and environmental goals or requirements.
At the beginning of the concept design phase, some specific energy-saving
strategies should already be considered while ensuring thermal and visual
comfort and considering environmental impact. These strategies include
integratingpassivesolardesign,ahigh-performancebuildingenvelope,load
management, daylighting, and natural ventilation. Considering the
integrationofthesespecificelementsaswellastheircontrolstrategiesinthe
early design stage along with strategies for RETs increases the chances that
the net-zero energy objective remains attainable. The decisions made at this
stage are critical. For example, an insufficient window opening to wall ratio
could limit the potential for daylighting and natural ventilation, increase
the space cooling load and have important unrecoverable consequences on
the size and cost of the cooling equipment and RETs. At the end of the
concept design phase, the building designer provides a global sketch of the
building. In this phase, the overall heat transfer coefficients ( U -values) for
the envelope components are used because the details of the composition
of the opaque and glazing elements are usually unknown. Control strategies
and system concepts for HVAC are retained, but the specific details and
components remain undefined.
In the third phase, design development, decisions are made regarding the
integration of efficient HVAC systems and the refinement of RETs for
heating, cooling, and power. During this stage, the major elements of the
architectural concept including the composition of the building envelope
and the details of the HVAC system are developed.
In the fourth phase, the building details are finalized. At the fifth stage,
the building is constructed. Lastly, during the commissioning, operation,
andmonitoring phase,thebuildingoperation andperformance areassessed
to ensure that the building economic, energy, and environmental goals are
achieved and that the occupants are confirmed to be comfortable.
This section focuses on the building design stages: the concept design, the
design development, and the technical design stages. Table 4.1 shows
generally how the building design is refined as it advances from one stage
to the next. Even though these stages are shown in this table as linear and
well-defined, it is important to mention that the building design process
involves several iterations within each stage. Similarly, while the different
systems are shown as being separate, they are intertwined and must be