I'm redoing a shack in the woods and I'm planning to use wood construction. My approach is to layer everything as follows: external wood siding, then a vapor barrier, followed by insulation, another vapor barrier, and finally internal wood siding. My question is, do I need to tape both vapor barriers? I have mixed opinions from friends - one says yes and the other says no. Also, just to clarify, we're in a cold climate in Germany, so any advice specific to that would be appreciated!
3 Answers
Actually, in many cases, you might not even need a vapor barrier. If it's not placed correctly, it can cause more issues than it solves. A vapor retarder might be a better option instead. Plus, having two vapor barriers is typically seen as a bad idea because walls need to be able to dry out in at least one direction. You might want to research some common building practices in your area. Conditions and products can vary quite a bit by region!
For cold climates, it’s common to have a vapor barrier on the inside, right under the wall board, while an air barrier or diffusion membrane goes on the outside. Using products like SIGA Majvest on the exterior and SIGA Majpell on the interior can work well. Just remember, taping those vapor barriers is essential, otherwise, they won’t be effective at all!
There’s also the risk of mold if you don't design your house with the vapor barrier in mind. It was once common to put a plastic barrier in basements before drywall, but that often led to problems like black mold and wood rot. If you're considering membranes like Tyvek under your siding, they work differently since they allow moisture to escape but don’t let it in. Just some things to consider!
Thanks for the insight! I just updated my post to mention we're in Germany, which might affect the products available to us. It definitely makes me think about some additional questions!