ASHRAE 90.1-2007 has some additional requirements compared with 2004. Read through the standard for a complete update. The following are some samples. 

All exterior walls must be installed with rigid insulation of the spans across all floors. This can be accomplished by placing the insulation outside the air barrier. 
All exterior doors must be tested for maximum air leakage rate. 
All spaces must have independent lighting controls. 
Occupancy sensors must be installed in some spaces.
The minimum efficiency level of specific mechanical equipment has been raised.