Should I put plastic over attic insulation?

Author: Chadrick McDermott II  |  Last update: Saturday, May 3, 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 insulation be covered with plastic?

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!

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.

Should you put a vapor barrier over insulation?

If you use faced insulation and staple the flanges to the studs, you do not need a vapor barrier. The vapor barrier is used when you use un-faced batts (without the paper). Insulation is best installed before you move into the shop and start placing tools, cabinets, etc on the walls.

Does attic insulation need a vapor barrier?

In Most Cases, Attic Insulation Does Not Need To Provide A Vapor Barrier. The good news is that blown-in insulation should not need a vapor barrier.

Insulating Attic Ceilings & Cathedral Ceilings (Phillips Vision: Episode - 63)

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.

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.

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.

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.

What goes first vapor barrier or insulation?

The sequence of construction steps is up for interpretation and may vary depending on your contractor or construction manager. Some builders swear by installing the vapor barrier first, while others claim that laying the vapor barrier over the insulation is better. Both may be correct.

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.

Can you put Tyvek over insulation?

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

Can you have too much insulation in your attic?

Yes, it is possible to put too much insulation in a loft or attic.

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.

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.

Is it safe to leave insulation uncovered?

Exposed insulation can irritate your skin, eyes, and lungs. It can also be a fire hazard, especially in areas like the attic, basement, or garage. Plus, it can lead to mold and mildew growth, which can cause even more health issues.

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.

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.

What is a vapor barrier for attic insulation?

A vapor barrier is a kind of material that's used to resist moisture from entering through the wall, ceiling, and even the floor. Water-water resistant materials come in sheets and are installed as per manufacturers' instructions.

Should I put plastic over my 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.

Will mold grow under a vapor barrier?

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

What are the disadvantages of a vapor barrier?

The Cons of Vapor Barrier Installation

Although vapor barriers aim to prevent moisture from entering the structure, they can also trap moisture inside. If not properly installed or upheld, this could result in the proliferation of mold and other issues related to moisture.

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).

Is yellow or pink insulation better?

In general, the color of insulation doesn't equal better performance over another color. Whether it's pink, white, brown, or yellow—color doesn't influence dependability, reliability, or the products effectiveness.

Is blowing in insulation in attic a good idea?

Blown-in attic insulation is one of the most effective ways to enhance your home's thermal performance and reduce energy bills.

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