Net ZEB Design Processes and Tools - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 169

a time, and revisited as the solutions are refined. In addition, as in all other
design stages, back-and-forth communication between the engineers and
architectsshouldexist.Typically,theengineerformulatesrecommendations
to the architect to allow the most efficient design and the architect may
integrate these recommendations into the design. This iterative process will
continue until the building is optimized. From the energy calculations, the
engineerwillthenpropose-whiletakingintoaccounttheRETs-theHVAC
systems to match the calculated load. In an efficient Net ZEB the design of
the RETs and the HVAC systems should be fully integrated.
4.2.5.1 Envelope and Thermal Inertia
In the design development phase, the building envelope composition is
further developed and the design and calculation of thermal mass elements
(thermal inertia) is refined. For example, if raised floors or false ceilings are
integrated in the design, other solutions have to be considered to integrate
thermal mass elements, such as incorporating thermal mass into the walls.
The refinement of these particular aspects of the building will allow a better
evaluation of the space heating and cooling energy consumption.
At this stage, some details should be specified to limit thermal bridges and
prevent the resulting condensation risk. In addition, thermal mass elements
should be designed in conjunction with wall compositions and natural
ventilation. In the concept design phase, thermal mass elements were
estimated using rules of thumb. In the design development phase, rules of
thumb can also be used at the beginning, but eventually, the evaluation will
require the use of complex energy simulation tools that can handle detailed
wall compositions, occupancy schedules, internal gains, solar gains, as well
as forced and natural ventilation. The simulation tools that can be used in
this case ideally permit a coupling between thermal and airflow networks so
that the thermal envelope, thermal inertia, and natural ventilation can be
efficiently studied.
It is not necessary to perform calculations for the whole building.
Calculations using detailed simulation tools can be limited to specific zones
to save time and focus efforts. Results from these critical zones are usually
sufficient to study the efficiency of the solution sets and to assess the impact
on the cooling and heating loads. Such calculations allow refining the
building design with regard to building envelope and thermal inertia until
the desired heating and cooling load profiles are obtained.