Should I put plastic sheeting over insulation?

Author: Prof. Jaycee Mueller  |  Last update: Wednesday, September 10, 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.

Is it okay to put plastic over insulation?

Yes you can install the plastic film (sheeting) over the faced insulation. The plastic sheeting will act as an air barrier and the faced insulation will be your vapor barrier. The reason why you can in this situation has to deal with Psychrometrics. This explains how moisture behaves at different temperatures.

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.

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.

Should I cover fiberglass 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.

How Vapor Barriers Work

What should I use to cover fiberglass insulation?

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.

Do I need a vapor barrier 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.

Can I put plywood over insulation?

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.

What can I put over 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.

Should I cover insulation?

Safety and Health. Properly covering and maintaining your insulation can significantly reduce health risks. It keeps harmful fibers out of the air and prevents fire hazards.

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 use plastic sheeting as a moisture 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.

Does house wrap help with insulation?

House wrap acts as a barrier between your home and the outside elements, helping to keep air out during winter months and heat out during summer months. This helps improve energy efficiency by keeping conditioned air from escaping through the walls of your home or building. This means improved insulation all year long.

What should you not do when installing insulation?

Leaving Too Many Gaps

One of the biggest problems DIY homeowners face is leaving too many gaps in their insulation. Gaps or insulation that isn't secured correctly can leave the building structure open to air and moisture leaks. Spray foam insulation is best for reaching into small cracks and any areas left open.

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.

Can you use too much insulation?

In fact, adding too much insulation to your walls can lead to problems such as poor ventilation, mould growth, and condensation. This is because thicker insulation can block airflow and trap moisture, leading to indoor air quality issues and even structural damage.

Do vapor barriers cause mold?

Install a New Vapor Barrier

If your vapor barrier was damaged or not installed correctly, it's important to replace it with a new one. This will help prevent moisture from seeping into your crawl space and creating the perfect environment for mold growth.

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.

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.

Can insulation touch roof sheeting?

If the insulation is installed properly, there should be a 2" air space above the insulation to the sheathing. In all practical purposes, this is should be easy to do if the rafters are 10" deep and the insulation is only 8". If that is the case, the random touching of the insulation buckling up will not matter.

What to put over insulation?

Installing foil on top of the insulation acts like the windproof shell on a jacket. The SuperPerf foil helps minimize convective looping within the insulation.

Does sheathing help with insulation?

Sheathing is commonly added to floors, ceilings and exterior walls. There are 2 types of sheathing, one adding structural strength to the framing-known as Structural Sheathing, and Non-Structural Sheathing, used for insulation.

Can I use plastic sheeting as a vapor barrier?

For crawl space projecs that require a vapor barrier installed within walls, builders commonly use a thinner plastic sheeting option such as 6 mil, but for the best durability in the crawl space, our vapor barrier experts instead recommend choosing 8 mil plastic sheeting.

Do you need a air gap behind insulation?

It provides an additional layer of insulation by trapping air and helps to prevent moisture buildup by allowing for ventilation. So, it's always recommended to leave an air gap when installing insulation, whether it's in your walls, roof, or floors.

Can you put plastic over 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.

Previous article
What is the folklore about clocks?
Next article
How much does it cost to remove an old bathtub?