[Equest-users] ASHRAE 90.1 Specific Question - How to Determine Lighted Facade Area

Nick Caton ncaton at smithboucher.com
Fri Oct 19 07:28:01 PDT 2012

Hi Omer,

Note there's a 90.1 glossary term for "façade 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.



Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617

-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Ömer Moltay
Sent: Tuesday, October 16, 2012 5:54 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] ASHRAE 90.1 Specific Question - How to Determine Lighted Facade Area

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?


Omer Moltay
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