Is there a technical problem if I install insulation with vapor barrier on both sides?

Question

Is there a technical problem if I install insulation with vapor barrier on both sides?

Asked by Felix

Answers

Danny Kelly's picture

Old building codes used to require a vapor barrier on the "warm in winter side" of the wall.

New building science now advises not to install a vapor barrier on either side and definitely not on both sides.

  • When your wall gets wet, you want it to be able to dry in both directions.
  • A vapor barrier on both sides of your insulation will trap moisture inside your wall.


For more information:

Read Tessa Smith's Q&A "In a passive house wall assembly, is the vapor barrier on the inside or outside?"