I have a tub/shower with failing greenboard walls. I intend to replace walls with CBU, thinset, and tiles. Except for contractors using Schluter-Kerdi, the rest in my area say not to use a vapor-barrier (VB). My county permitting office stated it is better not to use a VB. I live in the mid-Atlantic region with winter temps in the single digits and summers over 100 occasionally. They say it's better to let airflow dry the wall cavity. This goes against most of what I read. Is this new thinking?