Can you put plastic over insulation in an attic?

Author: Samantha O'Connell PhD  |  Last update: Saturday, August 2, 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.

Can you put plastic on top of insulation in an attic?

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.

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.

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.

Can you cover fiberglass insulation 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!

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

What can I put over fiberglass insulation?

PIB (Polyisobutylene) can also be used over fiberglass insulation. PIB is a type of vapor barrier that is designed to prevent moisture from penetrating through walls, ceilings, and floors.

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.

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 a vapor barrier over insulation in 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.

Can you put Tyvek over insulation?

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

Can plastic wrap insulate?

Savings in Energy and Money

They can also eliminate air leaks around the window if they extend over the woodwork, and this extra layer of plastic adds another layer of insulating air to reduce heat loss through the window.

Can you use plastic instead of Tyvek?

Plastic Degrades When Exposed to Repeated Heat

This is especially true of plastic sheeting installed under siding on south-facing walls. It's likely to become brittle in just a few years.

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.

Is it possible to over insulate an attic?

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

Should attic insulation face up or down?

Please note that the proper way to install it is to have it installed facing outward or towards the person installing it. Attic specialists look to install it facing downward on your ceiling. Meanwhile, when you're installing it in your crawl spaces, install the insulation facing upward.

What is the air gap for attic insulation?

Does Insulation Count as an Air Space? Typically we suggest you have an air gap between 1/2″ and 3/4″ for the radiant barrier to work. Air gaps larger than this work well too – they promote ventilation on the foil and help keep the air dry and the air temps lower.

Can I cover attic insulation with plastic?

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.

Is it OK to compress attic insulation?

What Happens If You Compress Blown-In Insulation? Like batts, compressing blown-in fiberglass insulation improves the R-value per square inch while diminishing the overall R-value. Also like fiberglass batts, some amount of compression is OK if the cavity is completely filled.

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.

How do you cover exposed insulation in an attic?

Here's how to do it:
  1. Get the Materials: Buy a roll of plastic sheeting and some painter's tape. ...
  2. Measure and Cut: Measure the area with the exposed insulation and cut the plastic sheeting to fit.
  3. Secure the Sheeting: Use painter's tape to secure the plastic sheeting over the insulation.

Can you put boards over insulation in an 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.

Does attic insulation need a moisture 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. Blown-in is primarily used on the attic floor, and vapor barriers are not a concern for attics in our climate zone.

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.

Can I put foam board over insulation?

Yes, foam board insulation is an excellent complement to batt insulation. Foam board insulation can add insulation and eliminate thermal bridging when used in wall and ceiling assemblies insulated with batts. It can potentially replace the vapor barrier and house wrap as well.

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).

Previous article
Is Tide with bleach safe to use?
Next article
Can you mix Dawn and baking soda together?