The International Code Council (ICC) recently published the 2012 International Residential Code (IRC) that includes improved code requirements for balanced intake and exhaust for ventilated attics, and helps ensure that attic ventilators work as intended. The Roof Assembly Ventilation Coalition (RAVC) participated in the development of the code.
(http://www.ravcoalition.org/pdf/RAVC-IRC%20Press%20Release.pdf)
Improved Code Requirements for Attic Ventilation