No, you should not do this. As mentioned above, faced insulation that has a vapor barrier can easily trap moisture. If you put another faced insulation on top of face insulation, a significant amount of moisture can form inside your insulation and in your walls to damage them.

Do you need vapor barrier with Kraft faced insulation?

Vapor Blockers

Vapor barriers—sheets of plastic or kraft paper—keep water vapor out of the wall cavity, so the insulation stays dry. Not every type of insulation needs a vapor barrier. But if it does, the barrier should face inside in northern, heating climates, and outside in humid southern climates.

Do I need to Poly over Kraft faced insulation?





More than likely, installing an additional layer of poly over kraft facing won’t cause any problems — it’s no more risky than if the wall had only unfaced batts and poly — and the risk of using poly on the interior is relatively low in a cold climate like New York’s.