Building a new home in climate zone 5. We have R-23 Comfort bat going in the walls with R-3 Zip wall going on the outside. Do we need a vapor retarder? thanks for the input.
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I have the same question, and a similar situation. What did you end up doing?
It depends on the structure of your house but I would be more concerned about air leaks than water vapor seeping through the walls. Contact a local contractor to give you some advice if need be.
In Zone 5, the paint on your walls is probably all the VR you need. Check out this piece by Martin Holliday for more detailed info. https://www.finehomebuilding.com/project-guides/insulation/energy-nerd-need-vapor-retarder