The answers to this question, depends on your location, Canada has a stricter code issue than the US does . And with good reasons. The Canadian council issues are raised in another site, not affiliated with this one. Try www.jlconline.com
and go to the forums area under building science. Check out what all us professionals are talking about regarding this issue. It is a professionals only forum, you will not be able to ask questions, but come on back to here and tell us what you found out...to help others with similar situations.
I wish it was easy, but this is my passion...educating folks on how to do it best.