Vapor Barrier Paint

I’m working on improving the insulation and air sealing of an existing home. I’ve heard there are paints that can be used as a vapor barrier. Is that true? What are they?
- John, Detroit

Yes, some paints can be used as vapor barriers. To be effective, of course, you have to first make sure all regular air leaks are sealed in the wall using caulk, socket sealers, etc. The paint needs to have a low perm rating – specifically a 1 or lower. See this article from the excellent EERE website for more technical info on this.  Also, here’s a nice overview of some additional considerations including potential problems and solutions with vapor barriers from the Natural Handyman site.

Many standard paint manufacturers make a vapor barrier paint, but you may have to special order it, depending on your local store’s stock. Sherwin Williams has Preprite SF-1, Ace has the Royal Touch Undercoat, Benjamin Moore has the Super Spec Vapor Barrier Primer, and so on… Not all brands carry them though (for example, I found nothing at first look for Behr or Glidden).

Of course, I’d most like to recommend a vapor barrier paint that is also a low-voc paint (especially key if this is a retrofit with people living in it) — but I’m not currently aware of any. Anyone else found one?