How to seal penetrations in a vapor barrier

[Mats Bengtsson]

Well, it's lucky we don't live in Texas. There, they apparently recommend vapor barriers on both the inside and outside:

Where humidity is high in the summer and air conditioning is used, a vapor barrier is recommended on the exterior wall (warm side). During the winter, the interior vapor barrier prevents water vapor from penetrating the insulation and condensing on a cold surface. During the summer, the exterior vapor barrier can prevent water vapor from penetrating the insulation from the outside and condensing on a cold air conditioned surface on the inside of the wall.

Maybe that could be the solution to all the discussions about having a moisture barrier or not?

If you have both the inside and the outside, then once the building material has dried, it should be difficult to find situations where the moisture barriers could cause problems.

--- Mats ---

 

[jon_h]

If one of the moisture barriers is not absolutely tight, the consequences of a small moisture leak somewhere will be catastrophic, the moisture will not be able to diffuse out of the construction. It would probably work violently poorly.

 

[Mats Bengtsson]

If one of the moisture barriers is not completely sealed, the consequences of a small moisture leak somewhere will be catastrophic, as the moisture will not be able to diffuse out of the construction. It would probably work incredibly poorly.

Darn, there it fell as well.

--- Mats ---

 

[jon_h]

Yep. The best thing would be to skip the diff lock entirely if the circumstances are as they write in Texas. And perhaps build stone houses preferably.

 

[klaskarlsson]

Yep. The best thing must be to skip the diff lock entirely if the circumstances are as they write in Texas. And maybe build stone houses predominantly.

Even in Sweden, I think we might get such situations with very isolated houses.
The advantage we have is that we have relatively dry air, so even with air conditioning inside and upwards of 30 degrees outside, there isn't much condensation.

Otherwise, I don't believe at all in this thing about blocking moisture here and there. It's really hard to get everything completely tight—and it shows over and over again that we fail (in 5-10 year intervals when different construction techniques that were "good" are ruled out).

Better to have durable materials and let the houses breathe, I think, and seal locally in places where there is extreme moisture (wet rooms, saunas, etc.)...

/K

 

[jon_h]

I completely agree. The margins are as large as possible in stone houses, and quite small when building with lightweight construction techniques using organic materials.