What mil plastic over insulation?

Author: Trudie Daugherty  |  Last update: Monday, April 6, 2026

Insulation blankets are typically made of fiberglass, polyester, wool, polyurethane, or cotton batting. Vapor barriers are typically made of polyethylene plastic and start at a minimum of 6 mils thick.

What type of plastic to cover insulation?

What type of plastic sheeting can be used to cover ceiling insulation? The best solutions to use in these applications are either a Vapor Barrier or a Radiant Barrier. Most climates require a vapor barrier to cover ceiling insulation, but not all insulation requires a vapor barrier.

Can I use 4 mil plastic for vapor barrier?

To classify as a vapor barrier, a material must have a perm rating of 0.1 or below. Our vapor barriers that are 6 mils (0.06 perms) and thicker meet this bare minimum, but a thicker material provides a little extra protection along the way.

Is it OK 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.

Should I use a 6 mil or 10 mil vapor barrier?

By sticking with a thicker mil plastic, you'll have a dryer crawl space and better air quality. We recommend using a vapor barrier of 16 mil or higher.

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

What is 6 mil poly used for?

Agriculture: 6 mil plastic sheeting finds utility in agricultural settings for greenhouse coverings, mulching, or as a protective layer for hay or silage. Packaging: For lightweight items, 6 mil plastic sheeting can be utilized for packaging, wrapping, or protecting goods during transportation.

What is the difference between 10 mil and 15-mil vapor barrier?

15-mil vapor barriers are slightly thicker and more durable than 6-mil, 10-mil, and 12-mil liners. However, they are not comparable to the heavier, more robust 20-mil vapor barrier.

What is the best way to cover insulation?

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.

Is thick plastic a good insulator?

The short answer to the question “is plastic a good insulator” is yes, it is. Plastic conducts neither heat nor electricity, making it well-suited to electrical applications.

What can you put 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.

How thick should the plastic be over its insulation?

Insulation blankets are typically made of fiberglass, polyester, wool, polyurethane, or cotton batting. Vapor barriers are typically made of polyethylene plastic and start at a minimum of 6 mils thick.

What is the best mil thickness for a vapor barrier?

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.

Which is stronger, 4 mil or 6 mil?

4 MIL - Heavy duty protection when packaging nails, screws & heavy metal parts. 6 MIL - Extra heavy duty protection against punctures and tears on bulky items or items with sharp corners.

What is the R-value of 6 mil plastic?

A single layer of 6 mil polyethylene typically has an R-value of approximately 0.85, while a double poly cover (two layers of poly) has an approximate R-value of 1.25.

What type of vapor barrier for insulation?

Polyethylene plastic sheet. Asphalt-coated Kraft paper.

Why is plastic used for insulation?

Unlike metals, plastics do not have free electrons available for conduction mechanisms. Hence, they are poor conductors of heat.

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 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.

What is the best plastic for a vapor barrier?

The Top 5 Underlayments for Vapor Barriers
  • 8 Mil White/Black Dura-Skrim® Reinforced Plastic Sheeting.
  • 12 Mil White/Black Dura-Skrim® Reinforced Plastic Sheeting.
  • 20 Mil Dura Skrim® Reinforced Plastic Sheeting.
  • VaporBlock® Vapor Barrier.
  • PRO Crawl Barrier.
  • Vapor Barrier Tape.

What material is used to cover insulation?

Insulation Facings

Common facing materials include kraft paper, white vinyl sheeting, and aluminum foil.

What do you put on top of insulation?

Boards for loft flooring can be installed on top of insulation using plywood, wood, or plastics. Installing loft flooring and boarding over insulation helps save space, prevent heat loss, and increase home value.

What is the best way to layer insulation?

The first layer should have the facing against the drywall to act as a vapor barrier. (The general rule for insulation is that the facing always goes toward the conditioned space.) The second layer of insulation should be unfaced so that moisture doesn't collect between the layers.

Can I use 4 mil plastic as a vapor barrier?

Our 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.

Is 10 mil plastic thick?

How thick is 10 mil plastic sheeting? 10 MIL thickness = 0.010 inches thick. As a measuring unit of thickness, 1 mil = 1/1000 inches.

Can I use 6 mil plastic for vapor barrier?

6 mils is the minimum thickness for vapor barriers. Most vapor barriers may range from 6 to 20 mils in thickness. Although 6 mil is the minimum standard, the crawl space environment may require a thicker material to effectively block moisture and gases.

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