Readers ask: Does unfaced insulation need a vapor barrier?

November 2022 · 4 minute read

Fiberglass Insulation In most climates, it needs a vapor barrier. Some builders rely on batts with attached kraft-paper facing to do that job, but Tom recommends unfaced batts, covered in plastic with all the seams taped shut.

Is it OK to use unfaced insulation in walls?

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.

What do you cover unfaced insulation with?

Cover the newly installed insulation with a layer of plastic sheeting or other vapor barrier only if there isn’t already a vapor barrier in place. If the insulation is installed over existing insulation, either faced or with a barrier over top, adding another vapor barrier will lead to structural problems.

Can you put plastic over unfaced 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.

Does insulation work without vapor barrier?

To work effectively, the vapour barrier also must be warm enough to stay above the dew point on the exterior side, which means sufficient insulation must be installed over the barrier to maintain the temperature no matter the weather outside. (Source: NRCA.) (Source: NRCA.)

Do I need to cover unfaced insulation?

Fiberglass Insulation In most climates, it needs a vapor barrier. Some builders rely on batts with attached kraft-paper facing to do that job, but Tom recommends unfaced batts, covered in plastic with all the seams taped shut.

Does unfaced insulation need to be stapled?

INSTALLING FACED INSULATION WITHOUT USING STAPLES The insulation must fit snugly at the sides and ends. Some CertainTeed products, such as SpeedyR, are prodcuced without stapling flanges specifically to be friction fit, and do not need to be stapled.

Is aluminum foil a vapor barrier?

This aluminum foil sauna vapor barrier will protect the building structure by preventing moisture from absorbing into the interior walls. This aluminum foil sauna vapor barrier is designed for high temperatures and assists by reflecting radiant heat back into sauna room.

Does vapor barrier go over insulation?

So one of your home’s most common vapor barriers — and one of the most important — is the one used over the insulation in your exterior walls. It’s designed to stop the moisture before it can enter the wall cavities.

Do you need vapor barrier behind drywall?

Normally interior walls do not require a vapor barrier, but there are some situations where it is highly recommended. The paint acts as a vapor barrier as well. A continuous plastic vapor barrier behind the drywall will protect the interior walls of these areas from water damage.

Can you use 4 mil plastic for vapor barrier?

Barricade’s 4-mil plastic sheeting is a multipurpose film perfect for a wide variety of construction or DIY projects. This medium-duty plastic sheeting is commonly used as a vapor barrier in between insulation and drywall, used as a drop cloth or a temporary cover for equipment and supplies.

What happens if you don’t use a vapor barrier?

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 know if you 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.

What happens if there is no vapor barrier?

Fiberglass is porous to air infiltration, and without the vapour barrier, the warm moist air in the room will migrate to the cold wall surface and moisture will condense. You want to insulate, and also stop the room air from getting to the wall.

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