Subject: Office lighting

From: [email-masked] (Gregg Mackell)
Date: 23 May 1995 12:32:05 -0400

Hi Everyone,

I received a call from someone yesterday who is working with the
lighting in a single-story office building.  The business is
illuminated with deep cell parabolics or possibly even egg-crate
louvers.  Recently, to cut down on solar gains, the company
applied a heavy tint to the windows.  Now, from the exterior, the
luminance of the luminaires is so low that the combination of
this and the tint make the office appear closed during the day.
My initial reaction was to tell her to add some luminance to the
space: wall sconces with a high luminance or possibly even a neon
OPEN sign, but something to allow a passer by to see that the
office is open.  This is not the first instance I've heard of
this type of problem.  I heard of a supermarket that added
specular reflectors to strip fixtures and created the same
"Closed Illusion".  They ended up cutting slits in the specular
reflectors so that the bare lamps were visible from the exterior
(and it worked).  There are probably more window film
manufacturers out there than there are reflector manufacturers.
Is this becoming a common problem, or are these just isolated
incidents?  Have any of you successfully solved these same type
problems?

Thanks,

Gregg Mackell
([email-masked])

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From: [email-masked] (Naomi Johnson Miller)
Date: 25 May 1995 18:35:59 -0400

In response to the question about making a building with window film
look "open", I would not suggest washing the inside of the glass
with light.  What makes an interior space look open is surface
luminance, and that means washing walls, ceilings, and vertical
surfaces with light.  Make sure the finishes are light in color,
then add some light to the surface through wallwashing, uplighting,
wall sconces, valances, pendants, etc. etc.  What won't work is
low-brightness downlights or recessed parabolics located so that
their light doesn't strike any vertical surfaces.

Washing the glass will not achieve surface brightness. Your watts
are better spent on the walls and ceiling.

Naomi Miller
Lighting Research Center