The Lighting Controls Association has published an article I wrote on the topic of the major lighting changes in the 2009 version of the International Energy Conservation Code (IECC) related to commercial buildings.
One of the most controversial changes isn’t directly related to lighting, but it could have a significant impact on lighting design. Previous versions of IECC allowed various construction disciplines—lighting, mechanical, envelope—to be able to comply with either the applicable version of IECC or designated version of ASHRAE 90.1. IECC 2009 changes that, forcing all disciplines to comply with one code. Because IECC does not include the Space by Space Method contained in ASHRAE 90.1, this could affect design flexibility.
Other significant provisions include:
IECC 2009 now addresses daylighting control, albeit gently, as only separate control zoning is required (via separate circuiting) and no specific method of control is mandated. Manual switching, dimming and automatic controls can be used. IECC 2009 contains additional retail power allowances that are significantly lower than 90.1-2007. And the Code addresses exterior lighting power allowances using a system of four Lighting Zones.
Check out descriptions of these changes along with others here.