NEC 2008 Code changes

 http://www.iaei.org/subscriber/magazine/06_d/johnston.html

Also Part II
http://www.iaei.org/subscriber/magazine/06_e/johnston.html

note:
New Section: 310.15(B)(2)(c) Conductors Exposed to Sunlight on Rooftops and
Table 310.15(B)(2)(c)

Cheers