Can cross-battens ASV save energy in winter?

I have looked through you faq and you state that in winter it can help reduce you heating, or Therma Vent can ask as ventilation during the winter.  The study that was done by Oak Ridge National Lab in 2006 did in fact state that it helped, but can you give me more info or help me under stand why, also about a metal roof vs. asphalt with a Therma Vent Install? Is one better than the other.