Net ZEB Design Processes and Tools - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 167

contraction and the friction losses into account), or equivalent. This
parameter is required in the calculation of the air flow going through an
opening. Assumptions have to be formulated with regards to zone
temperature, but nonetheless, this procedure provides a good estimate of
the required opening area. This aspect of the building will be refined later
during the design development stage.
The concepts of solar protection, thermal mass, and daylight use, even
though treated separately in this section, are all interrelated concepts. For
example, design decisions regarding shading devices will simultaneously
affect the solar gains, the effectiveness of the thermal mass and the amount
of daylight available in the space. Thus, it is important to analyze the effect
of every design decision on the building solar protection, daylight, natural
ventilation, and thermal mass activation.
4.2.4.5 Building Envelope Thermal Resistance
Building geometry (orientation, aspect ratio, etc.) and envelope thermal
resistance influence the space heating and cooling energy consumption. The
building form is normally known during the concept design stage but the
composition of the walls is not yet fully defined. The detailed characteristics
of walls and windows are difficult to predict at this stage, since the decisions
regarding the building envelope composition will be based on energy
calculations and functionality.
Considering that the details of the building envelope components are
unknown, their insulation thickness and type are sufficient to estimate their
overall heat transfer coefficient ( U -value). If respecting the level of
insulation previously determined, the U-value should not be affected
significantly by the detailing of the wall composition that will occur later
in the design process. For a given shape, when assuming heat transfer
coefficients for the walls, roofs, floors, and windows in conjunction with
other inputs like weather data, the building energy consumption can be
calculated and the shape and aspect ratio can be adjusted until the targeted
energy consumption is reached. The evaluation of the building energy
consumption for heating can be performed using simple tools that require a
limited number of inputs such as the U -value of the walls, floors, and roof
as well as the U -value and solar heat gain coefficient (SHGC) of the glazing
elements. At this point, the requirements of the opaque surfaces' insulation
and the windows' U -values and SHGC are selected. This will not guarantee