Blown Attic Insulation Vapor Barrier

Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.

Blown attic insulation vapor barrier.

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. A vapor barrier basically helps to prevent moisture from entering your home through the ceiling floor or the walls. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

Moisture moves by two transport mechanism. A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective. 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. Cima does not recommend the use of vapor barriers with cellulose insulation except in circumstances of exceptionally high moisture levels such as an indoor pool facility or very cold climates.

It is a known fact that moisture in the air can trigger certain disorders and aggravate particular medical conditions such as hay fever asthma etc. A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days. To install blown in insulation in existing walls holes are drilled at the top of each stud space usually on the exterior and material is blown in via a long flexible hose. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Foam blocks airflow needs no vapor barrier and has a higher r value per inch than loose fill or batts so you ll get more protection with less depth. The hole is then. If your climate does not meet these conditions a vapor retarder like latex ceiling paint will work well for your house if you are in all other climates except the hot dry and hot humid. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case.

Then cover the foam with drywall as required for fire safety. But in some cases water vapor builds up in tight houses until it forces its way through the inside wall surface the vapor barrier and insulation hitting the back of the cool sheathing then. Not every wall does. That s because cellulose is the only insulation that actually manages moisture.