FAQ: Should You Put Plastic Behind 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.

Is a vapor barrier necessary behind drywall?

No, you don’t need a vapor retarder, Class I or otherwise. By the time you paint the drywall, though, you’ve brought it into the Class III vapor retarder range (between 1 and 10 perms), and even less water vapor will diffuse through.

Is an interior vapor barrier necessary?

Vapor barriers protect against mold and rot inside structures by preventing condensation and moisture from building up and damaging building materials. If a home is being built in a very humid climate, a vapor barrier can be an essential source of protection from problems caused by excess moisture.

Where should vapor barrier 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.

Do you need plastic over faced insulation?

More than likely, installing an additional layer of poly over kraft facing won’t cause any problems — it’s no more risky than if the wall had only unfaced batts and poly — and the risk of using poly on the interior is relatively low in a cold climate like New York’s.

Do vapor barriers cause mold?

The Problem With Vapor Barriers 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.

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Can I use plastic sheeting as a vapor barrier?

In simple terms, a vapor barrier is a material that won’t allow moisture to pass through it, such as plastic sheeting. A very simple experiment to show how a vapor barrier works is to lay a plastic garbage bag down on some damp soil. There are two basic types of vapor barriers used with exterior wall insulation.

Should a ceiling have a vapor barrier?

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.

How can I cover insulation without drywall?

Many of today’s houses use drywalls for their interior wall covering.

  1. Wood Planks. Wood planks will be a fantastic option to consider for anyone who would like to achieve a rustic look.
  2. Plastic Panels.
  3. Plywood.
  4. Veneer Plaster.
  5. Pegboard.
  6. Lath and Plaster.
  7. Wahoo Walls.
  8. Textured Wall Panels.

What happens without vapor barrier?

Cold Weather If water vapor diffuses or infiltrates into the wall cavity and finds the cool surface, moisture problems can occur. Of course, you can have moisture problems here even without the exterior vapor barrier because of what Bill Rose calls the rule of material wetting.

How do you secure a vapor barrier to the wall?

Stick the vapor barrier material to the foundation seal tape and then use mechanical fasteners to hold it forever. Drill holes through the plastic and through the seal tape into the block. If you drill through the seal tape you will prevent the plastic from peeling off when you remove the drill.

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Can you put plastic over insulation in attic?

Once you talked about stapling down sheets of plastic over rolls of insulation. In any case, a vapor barrier always faces the heated side, so it would never be put on top of batt insulation in an attic.