Where Does Vapor Barrier Go In Attic

Whether or not you need a vapor retarder hinges on three main factors.

Where does vapor barrier go in attic.

If you put it on the right side where the humidity is it s not much of a vapor retarder. Vapor barriers are also a cold climate artifact that have diffused into other climates more from ignorance than need. Not so asphalt saturated kraft paper. Attic vapor barrier detail for cold climates.

What role does a vapor barrier play. In any case the vapor barrier must point to the warm side. Some debate still occurs over how necessary vapor barriers are but a consensus is growing closer. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. Rose 1997 regales readers of this history. Over time this trapped moisture can rot the wood framing in your attic or cause mold and mildew to appear. In circumstances where conditions inside a home or office are much different than outdoor conditions water.

Also on the graph is the permeance of polyethylene. Joe says in the article plastic vapor barriers really are vapor barriers when things get wet. Warm humid air will move towards. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

It is frightening indeed that construction practices can be so dramatically. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. On the other hand an air barrier a properly detailed air tight drywall ceiling for example in the absence of a vapor barrier can be effective since it stops the flow of vapor laden air.

The history of cold climate vapor barriers itself is a story based more on personalities than physics. Even though we apply vapor barriers to exterior insulated walls in cold climates it s no longer recommended for ceilings floor of the attic. This essentially means that in the winter vapor inside your home will want to move into your attic where it is colder. The wetter it gets the better it dries.

A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective. In the summer the reverse occurs. Most authorities now agree that vapor barriers are important under certain conditions but not necessarily as a whole house solution for every home. Not every wall does.