In July of 2013 the company that makes the fabric that the ZPacks Rain jacket uses made a change to their manufacturing process which resulted in a massive increase of MVTR of the fabric. I would encourage you to read this article that I wrote on the changes made to the fabric. Suffice to say, the jacket went from a rated 20,000-25,000 g/m2/24hrs range up to a range of 40,000-41,000 g/m2/24hrs. These are based on the JIS L 1099 testing method.
http://hikelighter.com/2013/11/07/zpacks-rain-jacket/