No, you do not need to put plastic sheeting over faced insulation. The facing itself acts as a vapor and moisture retarder, and adding a plastic layer can actually cause problems.
In general, if you're using faced batt insulation, the kraft paper facing acts as a vapor barrier, making additional plastic sheeting unnecessary. However, if you're in a colder climate like the upper Midwest or Northeast, a vapor barrier might be recommended on the warm side of the walls and ceiling.
Faced insulation
Kraft and standard foil facings can burn and must not be left exposed.
The paper side of faced insulation is flammable and must not be left exposed. Cover it with a finishing material such as drywall.
No, you do not need an additional vapor barrier when installing Kraft-faced insulation. The Kraft paper itself acts as a built-in Class II vapor retarder (the only one required). Adding another plastic or foil vapor barrier can trap moisture inside the wall cavity, which leads to mold and wood rot.
Best Insulation Cover Options
Reinforced polyethylene products offer durability and moisture resistance for most jobsite conditions. Pro Crawl Anti-Mold Vapor Barrier with MPT™ meets ASTM E1745 and ASTM G21 standards. It resists moisture vapor and fungal growth, making it ideal for crawl spaces and enclosed areas.
Unfaced insulation is great for new construction, remodels, walls, floors, ceilings, basements, attics and crawlspaces. It's best used for interior wall applications that do not face the outside and also in rooms that don't need moisture control, like living rooms, dining rooms and studies.
While you can physically touch fiberglass insulation with bare hands, you should never do it intentionally. Fiberglass is made of spun glass fibers that break off easily. Touching them causes microscopic glass shards to embed themselves in your skin, leading to severe, irritating itching, and sometimes a rash.
No, standard Tyvek cannot be used as a traditional vapor barrier. Tyvek is a housewrap designed as an air and moisture barrier. It keeps bulk water out but is highly vapor-permeable, allowing moisture to escape the wall to prevent rot and mold.
Unfaced insulation is generally cheaper than faced insulation, as it lacks the extra vapor retarder material (kraft paper or foil).
Yes, you can install unfaced insulation over existing faced insulation. In fact, it is the standard and recommended method for adding a second layer of insulation.
Mice are curious and always searching for safe, snug, and warm nesting sites. Attics filled with blown-in insulation provide an excellent option–from the mice's point of view. As long as there is a ready food source. Mice are omnivorous and will eat and chew on almost anything including wood and electrical wires.
Because spray foam can trap moisture, hide the condition of the roof, make it difficult for surveyors to inspect, which means risks like timber decay, dry rot, and not forgetting increased fire risk. If you've got it or you're buying a property that does, this is something you need to know upfront.
Yes, mold can absolutely grow under a vapor barrier. While vapor barriers are designed to block moisture, any moisture that gets trapped beneath the barrier—due to a plumbing leak, groundwater seepage, or poor installation—will create a prime environment for mold to grow, out of sight.
Installing faced insulation is an effective way to improve your home's energy efficiency. The most golden rule: the paper or foil facing must always face the conditioned (heated or cooled) living space. In a wall, this means the facing touches the drywall/interior side.
Yes, mice can easily chew through foam insulation. Because mice have strong, continuously growing teeth, they will chew through soft materials like foam to create tunnels, sharpen their teeth, or gain access to a warm space.
Most building codes require vapor retarders in climate zones 5 and higher (colder regions). Faced insulation typically satisfies this requirement, but always verify local codes.
The ZIP System and Tyvek both act as weather-resistive barriers (WRBs), but they work very differently. ZIP replaces standard sheathing and housewrap with an all-in-one coated board and taped seams. Tyvek is a breathable housewrap layered over standard oriented strand board (OSB) or plywood.
Yes, you can install siding over plywood, and in fact, structural plywood or OSB is the standard and recommended base layer (sheathing) for almost all exterior walls. Plywood provides structural strength, wind resistance, and a solid nailing surface.
Yes, your lungs can get rid of fiberglass, but how effectively they do it depends on the size of the fibers and where they end up in your respiratory tract.
Insulation often contains fiberglass, a material made up of tiny, sharp fibers. When these fibers come into contact with your skin, they can cause small cuts and irritation, leading to itchiness. Wearing protective clothing can prevent this uncomfortable reaction when handling insulation.
Exposed insulation is generally not an emergency or highly toxic, but it does pose physical health risks if it is touched, disturbed, or located in primary living spaces. The danger largely depends on the type of insulation and how often you interact with it.
What time of year is Insulation cheapest?
The healthiest, non-toxic insulation for your home is natural sheep's wool or hemp insulation. These materials contain no chemical binders or formaldehyde, actively regulate indoor humidity to prevent mold, and do not off-gas.
“Faced insulation is typically used in exterior walls and ceilings where moisture control is a concern, while unfaced insulation is suitable for interior walls and areas where moisture is not a significant issue.