An air barrier stops bulk air (and the moisture it carries) from moving through your walls, saving energy and preventing drafts. A vapor barrier restricts moisture from slowly seeping through wall materials (vapor diffusion). While an air barrier must be continuous, vapor barriers are strictly climate-dependent.
Code compliant air barriers prevent moisture infiltration into a wall system much more effectively than vapor barriers, which only stop moisture transported by vapor diffusion. However, some colder climate zones also require vapor barriers to prevent vapor diffusion into the wall systems during the winter months.
water molecules are smaller than air molecules so they can pass through membranes more easily than air. thats why you can have an air barrier membrane that allowed water vapour transfer, but not a vapour barrier that allows air transfer.
TYVEK HomeWrap® Air Barrier is a proven performer, not only for reducing Winter Heat Loss, but also Summer Cooling energy needs. TYVEK HomeWrap® allows moisture vapour to escape wall cavity, but provides resis- tance to water penetration thereby protecting structures from rain and snow during construction.
Can mold grow under a vapor barrier? Yes. If moisture becomes trapped beneath an improperly sealed or damaged barrier, mold can grow on the ground or on organic materials underneath it. Proper installation and regular inspection are essential.
Don't Install a Vapor Barrier Over Pre-Existing Mold or Standing Water. Active mold and standing water require remediation before installation. A vapor barrier traps existing moisture — which accelerates mold growth and worsens water problems.
What can I use as a vapor barrier?
Tyvek from DuPont: You've likely seen it before. Tyvek is a non-woven housewrap that's cost-effective, breathable (perm rating of 54), and quick to install using staples or nails. It's been a popular solution for many years—and for good reason. It's a proven, reliable product that's been in use since 1955.
Gypsum board drywall is, itself, a suitable air barrier material. The taping of drywall seams results in a plane of airtightness at the field of the wall. However, several steps must be taken to use this material property to create a continuous and complete air barrier system.
Foam Board or Rigid Foam
Foam boards -- rigid panels of insulation -- can be used to insulate almost any part of your home, from the roof down to the foundation. They are very effective in exterior wall sheathing, interior sheathing for basement walls, and special applications such as attic hatches.
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.
Can I use duct tape for a vapor barrier? No. Duct tape does not hold up in moisture or adhere well to polyethylene.
Installing Vapor Retarders for New Construction
They perform best when installed closest to the warm side of a structural assembly -- toward the interior of the building in cold climates and toward the exterior in hot/wet climates.
Here are the best vapor barriers for walls, handpicked by our team:
Some people add a small amount of dish soap to drywall mud to reduce surface tension, which helps release air bubbles and create a smoother, more even finish, especially when applying the final "skim coat"; however, this practice is not recommended by professionals as it can potentially weaken the adhesion of the mud ...
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.
Interior walls are frequently left uninsulated during construction because the energy efficiency benefits aren't as great as insulating exterior walls, floors and ceilings.
DuPont™ Tyvek® HomeWrap® is the original house wrap, leveraging advanced material science to keep air and water out while allowing water vapor to escape. This contributes to enhanced building durability by protecting homes from damaging wind and rain that can penetrate exterior cladding.
ZIP System® tape is prone to stress and tears at inside corners, creating yet another place for air and water to get into the wall. Tyvek® HomeWrap® folds easily into corners—forming a continuous barrier against air and water infiltration.
Yes, in cold climates, it's essential to install a vapour barrier on the interior side of insulation. This placement helps prevent warm indoor air from meeting cold surfaces, which can lead to condensation and moisture-related problems.
Fiberglass is probably the most common material. It's budget friendly and newer products don't irritate the skin and lungs. Fiberglass insulation is manufactured to slow airflow through the material. Cellulose is made of recycled paper and is treated for fire resistance.
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.
Placing the plastic vapor barrier between the insulation and interior wallboard in cold climates will help prevent air leaks and create a thermal barrier. In our experience, it's worth taking a moment to actually estimate the insulation needed for your walls before you start - it makes planning far smoother.