Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 428

design team to make changes to compensate, such as increasing the size and
changing the mounting height of the LightLouvers™.
Up to this point, the RADIANCE simulations were calculated at a single
point in time, noon on the equinox, for clear sky conditions. This was to
fulfill the simulation requirements for the LEED 2.2 IEQ 8.1 credit. Once
the daylighting design needed to be integrated with the electric lighting
design and the energy model, daylight modeling became more complex, as
described later.
Annual (hourly) illuminance distributions were required to aid in
optimizing the electric lighting control zones. For this work, Radmap was
used to prepare a “cumulative sky” for use in RADIANCE. However, no
luminous output description (photometric) files were available for the
LightLouver™ under such sky conditions. They were only available for a
clear sky at noon. Instead, the actual complex geometry of the
LightLouver™ was inserted into the 3D model for RADIANCE to use,
making the simulations more time intensive.
Furthermore, complex fenestration devices usually require forward
raytracing to properly characterize daylight transmission. Since RADIANCE
uses backward raytracing, the design team had to compensate by setting
very conservative simulation parameters to account for some solar flux that
may not be calculated accurately with this method.
Once the electric light control strategy was designed, yet another piece of
software, Sensor Placement and Optimization Tool (SPOT), was required to
translate these requirements into a lighting schedule in a form useable by
eQuest (Guglielmetti, Pless, and Torcellini, 2010).
7.4.2.12 Significance of the Early Design Stage
Generally speaking, the cost of design changes increases the later they occur
in the design and construction process. This is due to the nature of the
design and construction process that is normally linear. Design decisions
are funneled in a cumulative manner toward key milestones that are used
to evaluate a design's appropriateness in terms of performance and cost. As
a project passes through these key milestones, the building design becomes
fixed and complete.
Conversely, the degree of influence any building stakeholder has on the
final project decreases with time. The inertia built-up through the chain