The 2012 International Energy Conservation Code (IECC) is like a freight train barreling down the track. Starting January 1, 2015 – compliance will require new buildings to be at least 15% more efficient. This will require a tighter building envelope, more insulation that is installed more carefully, sealed ductwork, higher-end windows, and more efficient lighting.

• Blower-door testing is required, and tightness requirements have increased.
• Duct tightness must be measured, and the requirements are more rigorous.
• Homes within climate zones 3 to 8 (and some homes in zones 1 and 2) will be required to have whole-house mechanical ventilation.
• In certain climate zones, window glazing U-factor and solar heat gain coefficient (SHGC) requirements will need to meet new higher standards.
• Wall insulation requirements are higher in certain climate zones, and builders in colder climate zones will be required to install continuous exterior insulation to reduce heat loss from thermal bridging.
• The 2009 IECC required that 50% of lighting fixtures in a new home be CFLs, the 2012 IECC has raised this percentage to 75%.

For more detail, check out this presentation from the US Department of Energy: