Do you need a vapor barrier with foam board insulation?

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 foam board insulation need to be covered?

Tests have shown that these laminated boards can withstand UV ray damage for a reasonably long time. That said, it's still advisable to cover any foam board insulation exposed to the Sun within 30-60 days at the most. On most projects, that's more than enough time to finish the exterior walls.

Does Foamular need a vapor barrier?

The answer is, no. Walls must be assessed for vapor performance. The perception is, 1) liquid water runs off of foam plastic insulation, therefore, 2) it must be water impermeable, and, the misconception, 3) therefore it must be a vapor barrier.

Can you install insulation without vapor barrier?

Because this climate is dry and therefore less prone to water damage, vapor barriers are not necessarily required or needed. However, if a vapor barrier is required for the building, the general rule is to put it on the interior.

Should you put plastic between insulation and drywall?

Without poly beneath the drywall, water vapor hits the drywall and diffuses through to the drier (in summer) indoor air. By installing a sheet of poly there, you cut off that drying mechanism and water that finds its way into walls can stay there longer and do more damage.

Vapor Barriers: Need one or not?

Is moisture barrier necessary?

When moisture penetrates your flooring, it can cause mold, mildew, and the potential for water damage. A moisture barrier helps control the water vapor's movement to help protect your floors. Therefore, if you're installing floors in an area that sees moisture, even a little, a vapor barrier is needed.

Does foam board work as a vapor barrier?

Rigid foam board, especially foil-faced polyisocyanurate, creates a vapor-impermeable barrier, so the wall would have limited drying potential. Even more permeable types of insulation, such as expanded polystyrene, are vapor barriers when the installation is thick enough.

Is foam board vapor permeable?

The vapor permeability of foam varies from Class 1 vapor retarders: 0.0 perms for foil faced polyiso, to 0.5 perms for 2" thick XPS. EPS permeability varies but is approximately: 1" = 3.5 perms, 2" = 1.75 perms, 3" = 0.875 perms, 4" = 0.5 perms etc...

Is foam board breathable?

EPS - Expanded Polystyrene Foam Insulation Boards:

Rated at R4 per inch; EPS foam insulation boards are more permeable to air and moisture than XPS, but it doesn't retain moisture to the same extent because of it's more closed cell structure and it's breathability which lets it dry out.

Can exterior foam insulation cause mold and moisture problems?

The benefit of foam insulation in the exterior wall when it comes to moisture is it doesn't provide a favorable material for mold to grow in and most foam products contain no food value for mold. Foam insulation also creates a needed air seal that will keep your home comfortable and energy-efficient.

How do you cover rigid foam insulation?

The most common approach is to apply a stucco-like “parged” finish with a surface-bonding cement. These finishes range from a thin paint-on coating to a thick acrylic-modified mortar applied over hardware cloth or metal or fiberglass lath. The thin paint-on coatings are easily chipped and prone to peeling.

Which side of foam board insulation faces out?

The reflective side of the board should be oriented to the exterior and the non- reflective white side should be oriented to the interior. EXCEPTION: If vinyl siding is to be installed over AP™ Foil- Faced sheathing, install foam boards with the white nonreflective side toward the vinyl siding.

Do you put Tyvek over insulation board?

DuPont™ Tyvek® wraps can be installed UNDER or OVER exterior foam insulation. The DuPont™ Tyvek® wrap should be installed on the same plane as the window flanges to allow for the most effective installation.

Is foam insulation board waterproof?

Is Rigid Foam Board Waterproof? Technically, EPS and XPS rigid foam board insulation are considered to be water-resistant. A product branded as waterproof means that it offers complete impermeability, even if permanently immersed in water.

Can you put rigid foam insulation between studs?

Even with its flaws—namely, its inability to perfectly mold to the bays between the studs—rigid foam insulation will be a better bet than no insulation. Using low-expanding spray foam sealant to seal those gaps further increases rigid foam's insulating properties between studs.

What goes first house wrap or foam board?

Simplifying the decision

If you are installing “innie” windows, your housewrap should go under the foam. If you are installing “outie” windows, your housewrap should go over the foam.

Is foam board insulation mold resistant?

Foam building insulation, in both spray foam and foam board products, is resistant to mold growth but as we will explain here it is not absolutely mold-roof, and on occasion we do find mold growth on the surface of even closed-cell foam, in open-celled foam (rare), and on th surface of EPS and other foam insulating ...

What happens if foam insulation gets wet?

Wet insulation is prone to pests, mold, mildew, and eventually, it can cause damage to your house. It can change the air quality of the home, efficiency of the insulation, and the structure, which can lead to more costs.

What is the R-value of rigid foam board?

Extruded polystyrene: Extruded polystyrene (XPS) rigid foam is usually blue or pink in color, with a smooth plastic surface. XPS panels typically aren't faced with other material. The R-value is about R-5.

How do I know if I need a vapor barrier?

If you live in a mixed climate – hot and humid with several heating months in the winter, you probably need a vapor retarder. Specifically, if you live in climate zones 4C (marine), 5, 6, 7 and 8.

Can you put vapor barrier on both sides of insulation?

Avoid installing vapor barriers on both sides of a structure. Walls and ceiling cavities should ideally have the ability to dry out in one direction if the other side is constructed to prevent moisture penetration. Seal all wall cracks and holes in the wall being vapor-proofed to block air gaps.

Is it OK to cover insulation with plastic?

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.