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

Asked by Felix
Laredo, TX


Danny Kelly

Answered by Danny Kelly

Charlotte, NC

Kelly McArdle Construction

January 7, 2011

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?"

Tagged In: vapor barrier

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