Should you put plastic over insulation in an attic?

Author: Albertha Larson II  |  Last update: Monday, April 7, 2025

Even if the attic space is unheated, it's typically warmer than the outside air in winter. If you have chosen unfaced batting insulation for your rafters, you should staple sheets of plastic over the batting to accomplish a moisture barrier.

Should you put plastic over insulation in a ceiling?

Big no-no! Plastic traps moisture, which can cause mold in your attic. Insulation needs to breathe. Think of it like a sweaty sweater under plastic - not comfy!

Can you put a vapor barrier over insulation in an attic?

In colder climates, where the home's heating system sees more use, the vapor barrier should typically be installed on the insulation's interior side. In warmer climates, where the home is often kept cooler, the vapor barrier should usually be installed on the exterior side.

Is it OK to cover attic insulation with plywood?

Hey there! 🙌 Yeah, you can totally put plywood planks on top of your insulation in the attic. Just make sure it's not compressing the insulation too much, ya know? 😅 You want to keep that air flow going and not mess up the R-value.

What do you put on top of insulation?

In general, either batt or rolled insulation or blown loose-fill insulation (fiberglass or cellulose) can be installed on top of old insulation.

You're Using Vapor Barriers Wrong | What You NEED To Know

Can you put plastic on top of insulation?

Yes, covering your insulation with a vapor barrier plastic before installing drywall is crucial. It prevents moisture buildup that can lead to mold, rot, and even structural damage. A polyethylene vapor barrier also adds a layer of fire protection, making your home safer.

What is the plastic called that goes over insulation?

After the insulation is in place you will want to add a vapor retarder, sometimes called a vapor barrier, if you need one. Not every wall does. A vapor retarder is a material used to prevent water vapor from diffusing into the wall, ceiling or floor during the cold winter.

Does attic insulation need to be covered?

If you have exposed fiberglass insulation, it's best to cover it to prevent the fibers from spreading in the occupied areas of your home. Unoccupied or low-traffic areas of your home, like a closed attic, don't necessarily need to have covered insulation.

What protective gear is needed for attic insulation?

Long-sleeved shirt tucked into pants, gloves, safety glasses and bump hat are essential protective gear. If you don't have a bump hat, any hat is better than none. Wear a respirator. A disposable N95 respirator is the minimal protection you need from any airborne fibers in attics.

What do you cover insulation board with?

In case you can't cover your insulation foam boards with plaster cover, you are able to paint them by following these steps: To have a smooth finish, you should cover the insulation boards' edges with some sandpaper.

Can you put too much insulation in attic?

While loft insulation is an effective way to improve energy efficiency and reduce heating costs, over-insulating can lead to several potential issues. Firstly, over-insulation can lead to poor ventilation in the attic, which can cause moisture buildup and increase the risk of mould growth.

Where should you not put insulation in the attic?

Also, when laying down additional insulation, work from the perimeter toward the attic opening. Never lay insulation over recessed light fixtures or soffit vents. Keep all insulation at least 3 inches away from recessed "can" lights, unless they are rated IC (Insulated Ceiling).

Can you put boards over insulation in attic?

When you're ready to install your loft boards, you should position them above your insulation using Loft Leg supports designed for this purpose. This will avoid compressing the insulation and ensure it is working to its maximum potential.

When should you not use a vapor barrier?

Because a vapor barrier is a low permeable barrier, it keeps moisture from passing through. This is beneficial to keep moisture away from a dry surface but will trap moisture behind it if installed on a water-damaged concrete wall, causing the wall to fail further.

Can I just use plastic as a vapor barrier?

You can use plastic if you put polyethylene between your drywall and the wall studs. This way, you should get a tighter wall without trapping moisture inside the exterior walls. If you are framing out a below-grade basement, however, do not use plastic as a vapor barrier.

Do I need a vapor barrier over fiberglass insulation?

Being an inert material, it is a non-viable food source for mold and will not support mold growth. Fiberglass insulation cannot fight the battle against moisture intrusion alone, however. Vapor barriers applied over the face of the insulation provide additional benefits in the fight against moisture.

Do I need an attic insulation shield?

In attics, either use an Attic Insulation Shield (AIS or AIS-R) or enclose the chimney. The chimney must be protected against the known contact hazards of insulation or stored combustible materials - mat- tresses, clothing, etc.

What is the recommendation for attic insulation?

The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.

How can I cover exposed insulation in my attic?

The good solution for this is a house wrap material (often referred to by the popular commercial brand Tyvek) which allows vapor to pass through while blocking water itself on the outside of the home. You can also put up a thin board, plywood, or even drywall, if the goal is simply to prevent accidental contact.

Should you put plastic over insulation in attic?

Even if the attic space is unheated, it's typically warmer than the outside air in winter. If you have chosen unfaced batting insulation for your rafters, you should staple sheets of plastic over the batting to accomplish a moisture barrier.

How do you tell if your attic is properly insulated?

Looking across your attic, if the insulation is level with or below the attic floor joists, you probably need to add more insulation. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough, and adding more insulation may not be cost-effective.

Can you put Tyvek over insulation?

Yes. DuPont Tyvek® is compatible, and can be installed with foam insulation products.

Should you cover insulation?

If the insulation is ever disturbed, it can cause many health problems that are otherwise easily avoided. Breathing in fiberglass particles can irritate your eyes, lungs, and skin. This health risk is probably the best reason you want to cover your fiberglass insulation.

Why is insulation wrapped in plastic?

Encapsulated fiberglass batt insulation is a popular thermal and acoustical insulation solution for all types of construction and any climate zone across the U.S. It is easy to install and is wrapped in plastic to provide a comfortable, itch-free and dust-free installation.

What material is installed over insulation to prevent moisture from entering?

A vapour barrier (sometimes referred to as vapour retarder) is typically a plastic or foil sheet used for damp proofing to prevent interstitial condensation from forming in various building assemblies such as walls, roofs, foundations and floors.

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