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.
Blown in attic insulation without vapor barrier.
I install my vapor barrier in the middle of the wall system between the two walls.
The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.
The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.
If you do there is a chance that moisture that has slipped by the first vapor barrier will become trapped by the second vapor barrier decreasing the value of your insulation.
Thousands of houses have had insulation blown in without incident mostly because old houses are so leaky that there is little or no chance for water vapor to build up to cause the insulation to.
Such a location works both as a vapor barrier as well as an air barrier and eliminates the need for an external air barrier not a easy application on a multi storried building as well as any special electrical pans and their sealing.
Install siding over the insulation.
After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.
Attach 1 inch foam board insulation.
When adding additional insulation to an attic that is already insulated never use insulation with a vapor barrier.
Attic vapor barrier detail for cold climates the best approach for a vented attic in a cold climate is installing a layer of drywall with a good coat of latex paint the paint creates a semi permeable vapor barrier.
Handy homeowners can install blown in insulation in the attic.
Blowing insulation into walls is best left to the pros because it involves drilling into stud spaces that may contain electrical.
They come with or without a paper or foil facing that acts as a vapor barrier.
A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective.
Do not add a vapor barrier on top of the insulation in your attic since the paper facing on the existing insulation is the vapor barrier.
Caulk window trim and use weatherstripping to reduce air leaks.
If you ve tried everything else and are determined to insulate the walls of an old house follow these.
Apply a house wrap vapor barrier to exterior walls.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.