Plastic vapor barriers should only be installed in vented attics in climates with more than 8,000 heating degree days. You can forego the plastic and use a vapor retarder (kraft-faced insulation or latex ceiling paint) in all other climates except hot-humid or hot-dry climates.
What is the purpose of installing a vapor barrier?
What is the purpose of installing a vapor barrier? This is generally referred to as installing vapour barrier because the main function is to stop the warm moist air in your home from entering the cold interior space inside of your wall cavity. This will cause condensation inside the wall cavity which can cause deterioration of building ...
What is the proper attic insulation vapor barrier orientation?
Whether using loose fill or batts, put the vapor barrier closest to the warm side of your installation, where hot, moist air would get in—facing the house's interior in cold climates (beneath floor insulation) and the attic's interior in hot climates (on top of floor insulation). Some regions don't require a vapor barrier.
Should I remove old vapor barrier?
Why would the vapor barrier need to be replaced?
- Outdated protection. Years ago, builders used to install clear plastic under homes and other structures as protection. ...
- Damage to the vapor barrier. In order for your vapor barrier to perform at its best, it is necessary for it to achieve 100% soil coverage.
- Rodent infestation. ...
Should I install a vapor barrier on the ceiling?
For your ceiling a plastic vapor barrier should only be installed in vented attics in climates with more than 8,000 heating degree days. In Nebraska, heating degree days for a normal year is 6322.
Where should attic vapor barrier be placed?
The vapor barrier is always installed facing the heated side of the wall or ceiling, because that's where the moisture is coming from.
Why is there no vapor barrier in the attic?
Even though we apply vapor barriers to exterior insulated walls in cold climates it's no longer recommended for ceilings (floor of the attic). Because it's nearly impossible to seal penetrations in the ceiling, the reality is water vapor will get into the attic.
Is a vapor barrier necessary in ceiling?
A vapour barrier is an important component in building construction. Its purpose is to help prevent water vapour from reaching building walls, ceilings, attics, crawlspaces or roofs, where it can condense and cause building materials to rot or grow mould.
Can you put plastic over insulation in attic?
Plastic isn't recommended in this situation because it would create a second vapor barrier that can trap moisture and result in condensation and mold. Craft paper would have the same problem, this is what is most likely on the other side of the insulation for the vapor barrier you want.
How do you install attic vapor barrier?
There are five options for installing an air barrier system in an unfinished attic:concentrate on air sealing.install polyethylene over top of the joists.install polyethylene between the joists.spray foam between the joists (hire a contractor)spray foam under the roof to create a conditioned attic (hire a contractor)
Should you insulate the underside of your roof?
roof insulation is no-contest. The floor wins every time. Insulating the floor is standard practice for an unfinished attic space. The exception to this rule takes place when families opt to convert an unfinished attic space into something usable or livable.
Do vapor barriers cause mold?
One of the more common problems with crawl spaces that do not have a crawl space vapor barrier system is that they create high moisture levels, which may result in mold growth – as dampness creates the ideal environment for mold growth.
Where do you place a vapor barrier on a ceiling?
In order to avoid problems like these, the installation of a vapour barrier is crucial. This barrier must be applied onto the inner side of the heated zone, in order to prevent damp air from penetrating the insulation.
Does insulation need a vapor barrier?
Because it is mostly hot and very humid outside the building, the vapor barrier should be installed on the exterior of the insulation. This is recommended to keep the outside moisture from getting into the less humid, cooler interiors and damaging the building's structure.
Does blown in fiberglass insulation need a vapor barrier?
Fiberglass Insulation Like other batt-type insulation, fiberglass has a predictable R-value if not compressed but is difficult to fit around obstacles without leaving gaps. In most climates, it needs a vapor barrier.
Is it a good idea to put plastic over insulation?
Without a vapor barrier in place, condensation inside the walls could ruin the insulation and promote the growth of harmful mold and bacteria. Plastic, specifically 6-mil polyethylene plastic, is the most commonly used vapor barrier.
Does foam board insulation need a vapor barrier?
Foam insulation usually does not require a vapor barrier. For some foam insulation types, such as closed-cell spray foam and foam board insulation, the insulation itself stops the movement of most water vapor.
Does blown in insulation need a vapor barrier?
A common misconception is that vapor barriers are required in all insulation installations. With Modern's Cellulose insulation, a vapor barrier is not recommended except in very cold weather or high moisture areas such as spas or pool buildings.
Should you put plastic over insulation?
Standard Installation Practices Install the plastic sheeting only after the insulation, wiring and plumbing have been completed. Stretch the plastic sheet tightly across the top of the wall and staple it to the studs and plates with a hammer-tacker, a tool designed to install staples quickly and efficiently.
Should attic insulation be faced?
Attic Floor Insulation If you install batting between your attic floor joists, the material should be faced. Since the attic floor is the ceiling of the living space below, the facing installs against the top of the ceiling drywall or plaster.
How do you vapor barrier a ceiling?
0:053:41Interior Air Barrier Installation (1/3) Ceiling - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe first step of installation is carrying a roll to the room. And then rolling it out then cuts theMoreThe first step of installation is carrying a roll to the room. And then rolling it out then cuts the sheet with scissors.
Where is the air leak in a drywall box?
There can be air leaks in the crack between the drywall (or plaster) and the electrical box, and there can also be leaks at the holes in the back of the box where the electrical cable enters the box. These leaks can either be addressed from above or below -- whatever approach is easier.
Can you air seal a chimney?
Temporarily removing the floor boards is a good idea. Once the floor boards have been removed, you can air seal around the chimney, according to the advice in the "Air Sealing an Attic" article. You can definitely get air leaks through ceiling-mounted fixtures.
Can you put batts on top of a ceiling?
If you can roll housewrap or something over the existing floor and joists and detail the edges to make it air tight you can probably put the batts on top of that with little risk, but it's more permanent and less risky to air-seal at the ceiling plane.
Can you add insulation without sealing air leaks?
I don't recommend your idea of adding insulation without sealing air leaks. This violates all the rules of attic insulation and weatherization. You have to do this work in the correct order: first, seal the air leaks; then improve the insulation layer.
What happens if you add a second vapor barrier?
Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. Over time this trapped moisture can rot the wood framing in your attic or cause mold and mildew to appear. If you add more insulation on top of what is already there, be sure to use unfaced batts which do not have ...
What to do if you add more insulation to your attic?
If you add more insulation on top of what is already there, be sure to use unfaced batts which do not have a paper backing, or have another layer of insulation blown into your attic on top of the existing insulation. Good luck with your project,
What is paper facing insulation?
The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. Attic insulation should always be installed with the paper backing facing toward the living space (the ceiling in this case). This acts as a barrier to keep heated, moist air from rising up into the attic during cold weather.
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What is smart vapor retarder?
A smart vapor retarder is a vapor retarder material with the unique ability to react to changes in relative humidity by altering its physical structure.
Do you need a vapor retarder?
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.
Can a vapor retarder be used in a wall?
In certain climates vapor retarders can be a vital part of the wall construction. However incorrect use can lead to additional moisture problems. Consult an insulation professional in your area if you are unsure where or how to install a vapor retarder or consider a vapor retarder that provides some degree of additional flexibility, like a smart vapor retarder. A smart vapor retarder is able to adapt its permeability to allow the wall to dry should moisture get trapped in the wall cavity.
Why ventilate attic with outside air?
That’s because attic ventilation requires heat loss to remove moisture from attics. Cold air can’t hold much moisture. So ventilating a heavily insulated attic with outside air when it is really cold does not remove moisture. We do not want any moisture to get into an attic in a severely cold climate for this reason.
How does vapor move through a building?
There’s one other important qualification: Vapor moves in two ways, by diffusion through materials, and by air leakage through gaps and holes in building assemblies. Between the two, air leakage moves far more moisture than vapor diffusion. 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. You can’t just install plastic in a ceiling and assume it is also an air barrier. For plastic to be an air barrier, it needs to be continuous, meaning all joints and penetrations must be taped or caulked.
Can a vapor retarder be vented?
In hot-humid climates, attics should not be vented and vapor retarders should not be installed on the interior of assemblies. In hot-dry climates a vapor retarder should also not be installed, but attics can be vented. All attics — vented or unvented — should have an air barrier (a properly detailed airtight drywall ceiling, ...
Can you use plastic vapor barriers in attics?
Plastic vapor barriers should only be installed in vented attics in climates with more than 8,000 heating degree days. You can forego the plastic and use a vapor retarder (kraft-faced insulation or latex ceiling paint) in all other climates except hot-humid or hot-dry climates.
Is a vapor barrier effective in the attic?
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.
Can you put plastic in a ceiling?
You can’t just install plastic in a ceiling and assume it is also an air barrier. For plastic to be an air barrier, it needs to be continuous, meaning all joints and penetrations must be taped or caulked.
Can you use a vapor barrier in a cold climate?
As you move south into regions where it is not so miserably cold, this changes: Hence, the recommendation for a vapor barrier in a severely cold climate but only a vapor retarder in most other locations. In the old days in severely cold climates, where attics were poorly insulated, it was okay to omit a plastic ceiling vapor barrier.
Where should vapor barriers be installed?
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.
Why are vapor barriers important?
In circumstances where conditions inside a home or office are much different than outdoor conditions, water vapor is likely to move through wall cavities and can get trapped inside, and a well-installed vapor barrier is recommended. Vapor barriers can also be important for certain rooms where moisture levels are especially high.
Why should a wall be permeable?
The exterior face of the wall or floor cavity should remain permeable in order to allow dissipation of any moisture that does enter the wall cavity. Very hot and humid climates may benefit from an exterior vapor barrier that keeps outside humidity from penetrating into walls.
What was the purpose of sealing walls and ceilings with a vapor barrier?
During the energy crisis of the 1970s, a prevailing belief took root where it was thought that tightly sealing walls and ceilings with a vapor barrier was essential to blocking heat transference and reducing energy costs.
How does moisture move through a building?
Water vapor can pass through building materials in several ways, including direct transmission, and by heat transfer, but studies suggest that fully 98 percent of the moisture transfer through walls occurs through air gaps, including cracks around electrical fixtures and outlets, and gaps along baseboards. ...
What is the ASHRAE standard for ventilation?
Buildings should meet ASHRAE standards 62.2 or 62.1 for proper ventilation before being sealed by complete vapor barriers. Modern homes or offices that are tightly sealed in order to be highly energy efficient should also have air-to-air heat exchangers or other methods of ensuring a good exchange of fresh air.
Is polyethylene plastic good for insulation?
In very cold climates , the use of polyethylene plastic vapor barriers between insulation and interior wallboard may be beneficial, provided all air gaps into any wall and ceiling cavities are also blocked. The exterior face of the wall or floor cavity should remain permeable in order to allow dissipation of any moisture that does enter the wall cavity.
