Is it OK to put plastic over insulation?

Author: Chad Swift  |  Last update: Sunday, October 12, 2025

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.

Can you put plastic over insulation?

Yes, it is possible to put plastic over insulation in an attic, but it is not always recommended or necessary.

What can I cover exposed insulation with?

One quick and effective way to cover exposed insulation is by using plastic sheeting. This method is simple and can be done with materials readily available at stores like Home Depot.

Can you put plastic on top of insulation in an 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.

Why do they put plastic over insulation in walls?

Vapor barriers are installed along, in, or around walls, ceilings, and floors. Of course this is done to prevent moisture from spreading and potentially causing water damage.

How Vapor Barriers Work

Should I cover fiberglass insulation with plastic?

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.

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.

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.

Is it OK to cover attic insulation with plywood?

Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.

Should you remove old insulation?

Absolutely, unless you fancy your home's underbelly doubling as a dusty museum. As a rule of thumb, if you are planning on adding spray foam insulation to the crawl space, then all of the old insulation needs to be removed so the foam has a clean surface to be sprayed onto.

How to cover insulation cheaply?

Fabric panels are a cost-effective way to cover exposed insulation. They're an alternative to traditional wall materials and can help improve the acoustics in a room. Any kind of permeable fabric will work and they're easy to install. Stretch fabric over a wooden frame or directly on the wall surface.

What plastic is best for insulation?

Good Electrical Insulation
  • Acetal. High strength, stiff, low friction engineering plastic with good wear properties.
  • DuPont™ Vespel® Polyimide. Extremely high temperature creep resistant plastic with excellent friction and wear characteristics.
  • ECTFE. ...
  • ETFE. ...
  • FEP. ...
  • G10/FR-4 Glass Epoxy. ...
  • GPO-3 Thermoset. ...
  • LE Linen Phenolic.

Can I use Tyvek to cover insulation?

Don't worry about that one. But with that strong air stream, breaking up of fiberglass strands and moving them around is a cause for concern. So, buy Tyvek, and use it to cover the insulation; staple it to framework. It is not a vapor barrier, so it is OK to put over the insulation.

Does plastic help insulate?

According to Energy.gov, plastic window insulation can save you 10%–30% on heating and cooling costs. While plastic window sheeting may have some downsides, it is reasonably effective as a wintertime insulator.

Can you put stuff on top of insulation?

Boarding over your loft insulation can be a great upgrade for your home when done correctly, so your insulation is not compromised. It can provide you with usable storage, or even extra living space, which will only enhance the value of your property.

What mil plastic over insulation?

The thicker the vapor barrier, the more durable it tends to be. For instance, a 6 mil plastic sheeting may be suitable for a basic level of moisture protection, but a 12 mil or 20 mil vapor barrier would offer superior resistance to punctures and tears.

What can you cover insulation board with?

While there are no UV rays to destroy the foam board's insulative properties, interior exposure can create a fire hazard. Therefore, to qualify a building for an occupancy permit, most jurisdictions in North America demand that a thermal barrier, like drywall, cover the foam board.

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.

Does attic insulation need to breathe?

In order for insulation to do its job, sufficient airflow to the outside surfaces is required. Good ventilation in your attic will allow the moisture to get out. An attic that is well ventilated will reduce the roof surface temperature and eliminate moisture.

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.

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.

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.

Will mold grow under a vapor barrier?

However, if not installed correctly or if damaged, vapor barriers can actually contribute to mold growth.

Should you put plastic over insulation in a ceiling?

Exposed insulation is at risk of catching fire if not covered properly because it is extremely flammable. Installing a fire retardant plastic sheeting over insulation slows the fire damage rate in the case of an adverse event.

Is Tyvek a vapor barrier?

Is DuPont Tyvek® a vapor barrier? 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.

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