All attics — vented or unvented — should have an air barrier (a properly detailed airtight drywall ceiling, for example) regardless of climate. Omitting a ceiling vapor barrier by arguing that "you have to let the moisture escape" or "because the house has to breathe out the top" is actually correct, in a way. If you live in an area with sustained freezing temperatures, you should have a plastic vapor barrier between the drywall and the studs, wherever "warm meets cold" (exterior walls, top floor ceiling). The solution is a moisture barrier, called a vapor barrier, covering your exterior walls and ceiling. In most cases, insulation is first installed then covered with the barrier of choice. 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. 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.
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.
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.
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.
Homeowners rely on this type of insulation—which is usually made of polyurethane, polystyrene, or polyisocyanurate—for both exterior and interior wall sheathing. Foam boards work well to insulate everything from foundation walls and basement walls to unfinished floors and ceilings.
Vapor barriers are usually best installed on the side of the wall that experiences the hotter temperature and moister conditions: the inner surface in colder climates and the outer surface in hot, humid climates. In existing spaces, oil-based paints or vapor-barrier latex paints offer an effective moisture barrier.
It isn't important to insulate the ceiling between the attic and the garage because those areas are not affected by a home's heating and cooling system. It is important to insulate any walls that separate the garage from air-conditioned rooms in the house.
The vapor barrier is always installed facing the heated side of the wall or ceiling, because that's where the moisture is coming from.
Insulating Between Rafters You can use either faced or unfaced batting for this installation. When using insulation that has either paper or plastic facing, that moisture barrier faces outward, toward the attic space. Even if the attic space is unheated, it typically is warmer than the outside air in winter.
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.
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.
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.
A vapor barrier is an essential part of a building, but it's often installed incorrectly or omitted entirely. 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.
You will need a moisture barrier underlayment when installing: On a cement subfloor. On any subfloor that has a chance of moisture coming up and soaking into the flooring.