Question - Do I need a vapor barrier behind drywall?

Answered by: Steve Flores  |  Category: General  |  Last Updated: 17-06-2022  |  Views: 909  |  Total Questions: 11

Considerations. The standard installation of a plastic vapor barrier is between the studs and the drywall, but there are some exceptions to this. In exterior walls that are below-grade, like basement walls, plastic should not be used at all. Some applications require a different use of plastic vapor barriers. Installing a vapor barrier on the (warm) interior wall of your cement brick house will prevent condensation and reduce air leakage through your walls and insulation. Because no vapor barrier can be perfect, and some water may still get in, you must create a venting path for the water to get through the insulation. In many colder North American climates, vapour barriers are a required part of building construction. You may find that vapour barriers are often not required in warmer climates. And, if installed in the wrong climate or on the wrong side of building materials, a vapour barrier can cause more harm than good. The permeance of unpainted drywall is very high, generally between 20 and 90, so it's not a vapor retarder at all. Meanwhile, air leakage through a 1 square inch hole in a sheet of drywall allows 30 quarts of water vapor to pass through the drywall under the same conditions. If water vapor diffuses or infiltrates into the wall cavity and finds the cool surface, moisture problems can occur. Of course, you can have moisure problems here even without the exterior vapor barrier because of what Bill Rose calls the rule of material wetting.

https://www.garagejournal.com/forum/showthread.php?t=229283

Back years ago, it was always said to NOT put a plastic vapor barrier over the insulation before hanging drywall or whatever material you decide to hang, as it would cause the room or building to act like a greenhouse.

https://www.architectmagazine.com/technology/understanding-vapor-barriers_o

The original reason for using vapor barriers was a good one: to prevent wall and ceiling assemblies from getting wet. This can lead to significant moisture problems and mold; problems occur when walls get wet during construction or more often throughout the home's life.

https://www.inman.com/2012/02/01/vapor-barrier-tips-walls-floors/

In simple terms, a vapor barrier is a material that won't allow moisture to pass through it, such as plastic sheeting. It's designed to stop the moisture before it can enter the wall cavities. There are two basic types of vapor barriers used with exterior wall insulation. The most common is paper-faced insulation.

https://www.ecohome.net/guides/2316/the-difference-between-air-barriers-and-vapor-barriers/

In order to prevent condensation from forming, a vapor barrier should be placed on the warm side of your insulation to stop warm, moist air from condensing on a cold surface inside your wall. In cold climates like Canada, for most of the year the vapor barrier should be on the inside of the insulation.

https://en.wikipedia.org/wiki/Vapor_barrier

A vapor barrier (or vapour barrier) is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies of buildings to prevent interstitial condensation and of packaging.

https://www.wrmeadows.com/perminator-vapor-barrier-tape-overlap-seam/

PERMINATOR TAPE is a self-adhesive tape, used in conjunction with the application of PERMINATOR underslab vapor barrier. PERMINATOR TAPE is for use in sealing vapor barrier seams and attachment to footings, protrusions, etc.

https://www.greenhomeguide.com/askapro/question/i-have-a-home-with-exposed-fiberglass-insulation-in-

Fiberglass insulation will not degrade unless exposed to water. The fiber could become airborne if a vent is blowing on it or it is disturbed in some way. It can be covered with a plastic vapor barrier to protect your home air quality. The plastic can be bought at any big box store.

https://www.finehomebuilding.com/2016/11/29/drywall-repairs-vapor-barriers

Repairing a vapor barrier: If a vapor barrier is damaged during a drywall installation or repair, it may be patched with housewrap tape, but small holes only marginally impact effectiveness. When patching drywall on an exterior wall, it's almost impossible not to damage the vapor barrier.

https://www.dupont.com/knowledge/weather-barrier-faqs.html

No, DuPont™ Tyvek® is not a vapor barrier. It is made with unique material science to keep air and bulk water out while allowing moisture vapor inside walls to escape.

https://dengarden.com/basements/How-to-Finish-Your-Basement

Visqueen on Walls A common question people have when finishing a basement is: "Should I use visqueen or plastic sheeting on one side or the other of the framed basement walls? " The answer is no. Plastic will keep moisture from moving through the wall.

https://www.askthebuilder.com/house-wrap-vs-vapor-barrier/

The house wraps are designed to allow water vapor to pass through them, but stop liquid water. Vapor barriers are put on the inside face of wall studs in cold climates and they're put on the exterior of homes in hot and humid climates. You want the vapor barrier as far away from the cooler wall surface as possible.