Net ZEB Design Processes and Tools - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 209

Electric lighting simulation is considerably simpler than daylight analysis
because of the static nature of electric lights (Hensen and Lamberts, 2012).
Unlike the uncertainty of sky conditions, luminance output from luminaires
can be obtained from manufacturers in the Illuminating Engineering
Society (IES) format. Normally, if a software tool is used for luminaire
selectionandlayout,alightlossfactor(LLF)isusedtoaccountforallfactors
that depreciate the lumen output of luminaires from their rated values.
For coupling of lighting and daylighting models, a one-way data flow path
is generally acceptable. The following steps are performed manually or
automatically, depending on the BPS tool:
1. A daylighting simulation is performed and the necessary level of
supplementary electric lighting is calculated and passed to Step 2.
2. The electric lighting schedule profile is used to activate electric lights, as
needed to supplement daylighting, in the main building model. The
resulting heat gains and power consumption are incorporated into the
simulation.
This sequence is acceptable because the illuminance levels from daylight
and electric lights are additive and can be superimposed on any surface. The
advantage to this sequential approach is that detailed daylight analysis tools
can be integrated into the design process. However, the major shortcoming
of the sequential approach is that it is less suitable for dynamic shading
devices (e.g., roller shades or electrochromic windows) that are controlled
forbothvisualandthermalcomfort(e.g.,forstochasticoccupantmodeling).
Moveable window shading systems offer control of solar gains and visual
discomfortsothatabuildingcanadapttovaryingclimaticconditions.These
systems are ideally positioned on the exterior and light colored to maximize
the ability to prevent solar gains. However, interior movable shades in
colderclimates,especiallyinNorthAmerica,aremuchmorecommon;likely
because of concerns of ice and snow build-up and cost. Published results of
combined optical and thermal properties of complex fenestration systems
(i.e., windows and movable shading systems) are still quite sparse, despite
their significant effect on building performance (Newsham, 1994;
Tzempelikos and Athienitis, 2007). Lawrence Berkeley National
Laboratory's WINDOW software can provide the effective thermal and
optical properties of complex fenestration systems.