Should you put plastic over insulation in attic?

Author: Vella Torp V  |  Last update: Friday, May 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.

Should you cover attic insulation with plastic?

Definitely do not add a plastic barrier between insulation layers. And as suggested above, make every effort to seal any openings where warm moist house air can leak into the attic. Vents, chimneys, wiring holes, etc. And do not cut off attic ventilation during the winter.

Should you install plastic over insulation?

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.

Can you put a vapor barrier over insulation in an 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.

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

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.

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.

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.

What plastic to use to cover insulation?

The best insulation vapor barriers are made of polyethylene plastic and are reinforced to stand up against wear and tear. For extra protection, choose an insulation cover with mold and fire protection.

When not to use vapor barrier?

Don't: Put Vapor Barriers on the Bottom of the Floor Joist in the Crawl Space. Because vapor barriers are good at retaining moisture, putting plastic sheeting on the joists can cause moisture to build up under the floor.

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.

Does the vapor barrier go before or after 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 walk on attic insulation?

The Golden Rule of Attic Safety

These are the bones of your attic, offering the firm support needed to bear your weight. Ignoring this rule and stepping on the drywall or insulation is a fast track to an unplanned ceiling inspection from below, thanks to our unforgiving friend, gravity.

What protective gear is needed for attic insulation?

Long-sleeved shirt tucked into pants, gloves, safety glasses and bump hat are essential protective gear. If you don't have a bump hat, any hat is better than none. Wear a respirator. A disposable N95 respirator is the minimal protection you need from any airborne fibers in attics.

Do I need an attic insulation shield?

In attics, either use an Attic Insulation Shield (AIS or AIS-R) or enclose the chimney. The chimney must be protected against the known contact hazards of insulation or stored combustible materials - mat- tresses, clothing, etc.

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).

How much R-value is lost when compressing insulation?

When fiberglass batts are compressed, both the thickness and the R-value go down. The deeper the cavity, the more the R-value is reduced. 14 inch R-49 insulation is reduced to R-44 when compressed to fit an 11 ⅞ inch space. Further compression of 5/8 of an inch (11 ¼ inches) reduces the R-value to R-42.

Should I use r30 or r38 for attic?

If your attic has little or no existing insulation, you'll want to install an R-38 rated material. If your attic has 2-3″ of existing insulation, you'll want to install an R-30 to achieve a total of R-38. If your attic has 5-6″ of existing insulation, you'll want to install an R-19 to achieve a total of R-38.

Can I use plastic instead of Tyvek?

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 goes first, Tyvek or insulation?

Tyvek gets installed first, insulation goes on top

Installing the WRB directly to the sheathing allows for the best possible moisture seal around windows, doors, and other penetrations. Tyvek DrainWrap is the recommended WRB to use under any panelized product, including rigid insulation.

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.

Do I need a vapor barrier in attic insulation?

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.

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.

What are the symptoms of insulation sickness?

Insulation exposure can cause skin, eye, and respiratory irritation. Symptoms include itchiness, redness, coughing, and difficulty breathing. Prolonged exposure can lead to more severe health issues like lung disease or cancer.

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