Attic insulation and vapor barriers aren’t a safe combination for everyone to use safely within their homes. The reason why this is debatable is because vapor barriers can in some cases become a problem instead of a solution.
Having moisture within your house walls can lead to some serious problems. In theory, the purpose of vapor barriers is to keep the moisture away from your insulation. The mixture between moist and insulation can lead to rot and lose of R-value which will eventually lead to a faulty insulation with a lower R-value. The actual problem isn’t moist but the condense that creates within your walls. The condensed water inside your walls will in the best case scenario freeze and stay like that, worst case scenario you’ll end up with a stained ceiling or wall.
Attic insulations usually come pre-equipped with vapor barriers to keep the moisture out, however this doesn’t mean it’s fail proof and leakages can occur where the facings meet. One of the most problematic things with attic insulation and vapor barriers is how to properly combine them and leave out the moisture.
The phenomenon that usually occurs is that during the winters, you’re going to have a constant flow of hot air inside your house. The hot air will rise and it’s a good practice to let some of the moisture into your attic. As we know it hot air means moisture, moisture leads to rot and rot leads to faulty attic insulation which isn’t a really good thing.
Attic insulation and vapor barriers aren’t really necessary although useful in some cases - it mostly depends on the area you live in. If you’re living in an area with an average temperature of above 0 degrees Celsius the combination of attic insulation and vapor barriers isn’t necessary.