In mixed climate areas the vapor barrier is optional depending on the total design of a building.
Do i need a vapor barrier in my garage attic.
The facing contains a thin layer of asphalt which acts as a vapor barrier to block moisture.
In hot dry climates your attic can be vented though like in hot humid climates you should not install any vapor retarder or barrier.
The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.
Whether or not you need a vapor retarder hinges on three main factors your climate your home and the location of the wall you re insulating.
In cold climates a vapor barrier is almost always needed.
No you don t need a vapor retarder class i or otherwise.
If you need a vapor barrier and your insulation is unfaced you must cover it with a polyethylene film.
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.
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.
The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.
The facing on faced insulation acts as a vapor retarder.
Since there seems to be only one long wall and very little framed cavity wall on the gable ends it would be advantageous to go ahead and finish the job by insulating and drywalling these walls.
A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective.
My other consideration would be insulating the exterior walls.
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.
It s important to use the right type of insulation to prevent moisture problems in your attic.
Not every wall does.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
Attic insulation is available with and without a paper facing.
After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.
By the time you paint the drywall though you ve brought it into the class iii vapor retarder range between 1 and 10 perms and even less water vapor will diffuse through.
Here s what you need to know about the facing on attic insulation.
