How does eQuest know initial FootcandlesforDaylighting Calc?

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Does this mean that there is some "baseline" fc that is provided by the
electrical lighting? That is to say, eQuest will determine how many fc
daylight provides and satisfy the rest with some fraction of the
installed LPD? This implies that there is a relationship between LPD
and fc, is that true and if so what is it or where could I find it?

Luka Matutinovic, B.A.Sc., LEED(r) AP

Matutinovic, Luka's picture
Joined: 2011-09-30
Reputation: 0


That was my hope, but eQuest isn't that smart. As I was so directed by an "unimpeachable source", there IS no footcandle level until you set it in the Daylighting mode. eQuest then assumes that this is the level 100% of the lights emit. Then when you allow the Daylighting mode to run, eQuest lowers the % lighting based on how much you can gain from the skylights, side daylighting, etc.

Crude but straight forward.

Others can add or correct..

John R. Aulbach, PE, CEM

John Aulbach's picture
Joined: 2011-09-30
Reputation: 1

Here is an alternate method to eQUEST's daylighting strategies:

eQUEST does not model daylighting with much accuracy. I believe that the
best method to handle daylighting is to run models on independent
software (DAYSIM is free) and insert the results into lighting
schedules. My general practice with lighting schedules is to force 100%
of the lights to be on when the room is occupied and during the same
occupied times, create a new schedule that shows the fraction of lights
on from the DAYSIM output.

This method gives the modeler more control and flexibility with the
model and daylighting strategies. Many times we have 3 rows of lights in
a classroom and we typically force the row furthest from the window
always on when occupied so the minimum percentage of lights on during
daylighting is 33% (1/3).

Otto Schwieterman's picture
Joined: 2011-09-30
Reputation: 200

The newer versions of eQUEST have an illuminance method to define your
lighting data where you set your desired footcandle level that might be
what you are looking for. I haven't used it yet, but it allows you to
set up a lighting system and footcandle level, and calculates the
lighting power from that. It is slightly different from what you are
talking about in the sense that it doesn't calculate the footcandles
from a designed scheme, but goes the other way.

Vikram Sami's picture
Joined: 2011-09-30
Reputation: 0