Dear All,
For baseline exterior lighting power, ASHRAE 90.1 instructs us to accept
0.2 W/ft2 for each illuminated wall or surface.
If we have a glass curtain walled office building with lighting provided
by luminaires mounted on facade spandrels, what is the definition of
illuminated wall? Spandrels + glass, or just spandrels?
Thanks,
Omer Moltay
Hi Omer,
Note there's a 90.1 glossary term for "fa?ade area." Read strictly, you shouldn't count any horizontal surfaces illuminated for that area.
That said, intuitively if the spandrel structures are intentionally illuminated and significant in area, I would probably count them in addition to any vertical surfaces illuminated. I can only caution that glossary term may give you a headache later if your reviewer is feeling saucy.
Note LEED requires (in distinction from 90.1) your baseline should model no more than the installed (proposed) watts for a nontradable surface - see your project-specific EAp2 spreadsheet (they've been changing of late) for guiding language on this. Also be aware the current templates enforce addendum i for 90.1-2007 for SSc8, which re-wrote everything regarding allowable exterior watts... as such 0.2 may be an incorrect number.
~Nick
NICK CATON, P.E.