Do you put plastic over or under insulation? (2024)

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Do you put plastic over or under insulation?

Standard Installation Practices

Install the plastic sheeting only after the insulation, wiring and plumbing have been completed. Stretch the plastic sheet tightly across the top of the wall and staple it to the studs and plates with a hammer-tacker, a tool designed to install staples quickly and efficiently.

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(IDI Distributors)
Should vapor barrier go over or under foam insulation?

vapor barrier is located on top of the rigid insulation between the rigid insulation and the bottom surface of the concrete—in direct contact with the concrete. Do not, and I repeat, do not locate the [vapor barrier] under the insulation as it will keep the insulation wet.

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Can you put plastic on top of insulation?

People can, but people shouldn't. Plastic over insulation will trap vapor which will condense into water and leave your attic a wet mold mess.

(Video) When to Use Faced or Unfaced Insulation
(Today's Homeowner with Danny Lipford)
Should you put plastic over insulation in attic?

Plastic vapor barriers should only be installed in vented attics in climates with more than 8,000 heating degree days. You can forego the plastic and use a vapor retarder (kraft-faced insulation or latex ceiling paint) in all other climates except hot-humid or hot-dry climates.

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What is the correct way to face insulation?

Regardless of whether fiberglass insulation is installed in a wall, attic, or crawlspace; the paper facing should always face toward the inside of the home. That's because the paper contains a layer of asphalt adhesive which prevents water vapor from passing through it.

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Where do you put vapor barrier with insulation?

Vapor barrier materials are installed on the warm side of the insulation in a building assembly, as determined by climatic conditions. In warm climates, it will be on the exterior and in cold climates, it will be on the interior.

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(Home RenoVision DIY)
Does vapor barrier go on inside of insulation?

A vapour barrier is a sheet, typically made of polythene, placed on the warm side of a structure, between the cavity insulation and inner masonry skin. The vapour barrier prevents the warm air or water vapour from penetrating through the wall to where it might reach its dew point.

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(The Bearded Builder)
Can you insulate with a plastic vapor barrier?

Vapor Blockers

Vapor barriers—sheets of plastic or kraft paper—keep water vapor out of the wall cavity, so the insulation stays dry. Not every type of insulation needs a vapor barrier. But if it does, the barrier should face inside in northern, heating climates, and outside in humid southern climates.

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(Ecobob)
What should insulation be covered with?

However, rigid foam insulation must be covered with a fire-rated material when used on the interior of a building. Half-inch drywall is usually sufficient, but check with local building officials before installing.

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Does house wrap go over or under rigid insulation?

If you are installing “innie” windows, your housewrap should go under the foam. If you are installing “outie” windows, your housewrap should go over the foam.

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Can you put too much insulation in attic?

Can you add too much attic insulation? No, you can't add too much insulation. Of course, that assumes all other things are equal, meaning you're not doing anything stupid with your insulation like blocking the soffit vents or piling the insulation right up to the roof decking.

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(Building Science Corporation)
Can you install too much insulation in an attic?

Excess insulation in the attic can make a house too tightly sealed and block vents. If airflow is blocked, moisture can't escape. If moisture accumulates in the attic and comes into contact with warm air, that can allow mold to grow, which can result in serious respiratory problems in people.

Do you put plastic over or under insulation? (2024)
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.

Does it matter if insulation is faced?

Faced insulation is best for locations prone to moisture, while unfaced insulation is best for dry, interior locations. Unfaced insulation is more sound-proof and cost-friendly. Faced insulation is more fire-resistant and costly. Inspect your insulation annually to make sure it hasn't fallen.

Does the paper on insulation go in or out?

Kraft-faced insulation includes a paper vapor retarder, which helps prevent mold and mildew. Kraft-faced insulation should be installed in exterior walls, exterior basem*nt walls, and attic ceilings by pressing the product into the wall cavity with the paper side facing outward, towards the installer.

What is the 1 3 or 2 3 insulation rule?

Vapour barriers are important, as is their location. The 1/3 - 2/3 rule of thumb is close to the limit for acceptable positions (i.e. the vapour barrier can be up to 1/3 the way through the wall as measured by R- values, with 2/3 of the insulation value on the outside).

What is the best insulation for an attic ceiling?

Fiberglass batt is considered to be the best insulation for attics. Compared to other insulation materials, it is the cheapest and easiest to install. Fiberglass batt is also incredibly energy efficient, as it helps to slow the spread of hot and cold air.

Can you install insulation without vapor barrier?

Not every type of insulation needs a vapor barrier. But if it does, the barrier should face inside in northern, heating climates, and outside in humid southern climates.

When should you not use a vapor barrier?

You may find that vapour barriers are often not required in warmer climates. And, if installed in the wrong climate or on the wrong side of building materials, a vapour barrier can cause more harm than good. This circ*mstance may prevent water vapour from drying, which in turn can cause rot and mold.

Can you cover fiberglass insulation with plastic?

Fiberglass insulation will not degrade unless exposed to water. The fiber could become airborne if a vent is blowing on it or it is disturbed in some way. It can be covered with a plastic vapor barrier to protect your home air quality.

What is the proper installation of vapor barrier?

How to Install a Vapor Barrier
  1. Locate the Crawl Space Entrance. The entry hatch to a crawl space is not always obvious. ...
  2. Dry out the Crawl Space. It is best to begin with a crawl space that is as dry as possible. ...
  3. Clean the Crawl Space. ...
  4. Roll Out and Cut Plastic Sheets. ...
  5. Attach Sheeting to Walls and Piers. ...
  6. Improve Ventilation.
Nov 25, 2022

Which side of insulation goes against the wall?

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.

Will mold grow under vapor barrier?

Vapor barriers do not cause mold, provided they are installed correctly with no gaps or holes. Moisture will only become trapped if the vapor barrier is installed incorrectly, creating ideal mold growth conditions. Mold requires food, water, oxygen, and warmth to grow and thrive.

How thick should plastic sheeting be for vapor barrier?

Mils: Polyethylene sheeting is measured in 'mils. ' A mil is equal to 0.001 inches of thickness. Codes for residential applications often cite a 6 mil (0.006-inch thick) minimum vapor barrier. However, we recommend a 10 mil or higher for crawl space applications.

Can you use black plastic for vapor barrier?

Black Plastic Sheeting is suitable for construction and DIY projects. It is made of recycled polyethylene to ensure long-term use. This sheeting can be used as a temporary cover for equipment and supplies. You can also create a vapor barrier or cover crawl spaces thanks to its multipurpose design.

Are vapor barriers a good thing right?

There are many benefits to installing a vapor barrier in your wall or ceiling—it can help prevent moisture damage, increase energy efficiency and even lower the risk of mold and bacteria-related health issues. However, depending on factors like climate, building material and layout, the need can vary.

Can you install insulation wrong?

You could do it wrong

If you aren't a trained insulation installation professional, there is a good chance that you could end up installing your insulation incorrectly. A substantial problem when people try to install their own insulation is gaps in the insulation. Such gaps make the insulation highly ineffective.

Does insulation need room to breathe?

The insulation needs to “breathe” to do its job, so there must be a flow of air to the outside surfaces of the insulation. Paradoxically, insulation also needs to be sealed off on the inside surfaces. Walls or ceilings must be lined with a vapor barrier, a layer of a watertight material.

What happens if insulation is installed wrong?

By Topic. Installing insulation poorly, like leaving gaps or compressing the product, can affect the overall performance and cause energy loss in the home.

Can you use 4 mil plastic for vapor barrier?

We recommend using a vapor barrier of 16 mil or higher. This translates into a permeance rate of only . 0015 This is considered impermeable in American building codes.

Can you put vapor barrier on both sides of insulation?

Do You Need Vapor Barrier on Both Sides of Insulation? Vapor barriers are not required on both sides of insulation. They only need to be installed on the side of the insulation that faces the exterior. A vapor barrier provides a way to protect the integrity of your home.

How do I know if I have enough insulation?

Walls, floors and ceilings should feel warm and dry to the touch in your home. An indication that there is not enough insulation can be drywall or paneling feeling damp or cold. Conversely, the walls outside of your home should feel cold because insulation stops the heat from escaping.

Do you need plastic sheeting 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.

Should insulation be packed tight?

Insulate windows and doors

Stuff skinny strips of batting into spaces around windows and doors with a 3-in. wide putty knife. The insulation should fit snugly, but don't pack it.

Do you tape all house wrap seams?

All of the seams for the product should be taped according to manufacturer's instructions. Most house wrap manufacturer installation instructions have minimum horizontal overlaps of 4-6 inches and minimum vertical overlaps of 6 -12 inches. Most also require or recommend 1 in. plastic or metal cap fasteners.

How many inches of insulation is good in the attic?

The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.

How do I know if my attic has enough insulation?

Looking across your attic, if the insulation is level with or below the attic floor joists, you probably need to add more insulation. Assumes R-3/inch. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough, and adding more insulation may not be cost-effective.

What is the lifespan of attic insulation?

Proper attic insulation can help keep your home cool in the summer and warm in the winter and minimize drafts and noise pollution. Attic insulation lifespan typically lasts about 10-15 years, but its lifespan can be affected by several factors, including your home's climate, ventilation, and pests.

Should I remove old insulation or just add more?

If your insulation is wet or damaged, we strongly recommend replacing it before applying a new layer. Otherwise, the problem will spread throughout the new insulation and could significantly damage roofing structures. If the insulation is in good condition, then a new layer can be placed on top without difficulty.

Is it OK to double up insulation?

Thicker is better

The thermal barrier of a home should consist of a continuous layer of insulation on all sides—including the lowest floor, the exterior walls, and the ceiling or roof. Doubling the thickness of insulation will double the insulation's R-value, cutting heat loss in half.

Can you put new insulation on top of old insulation?

In general, either batt or rolled insulation or blown loose-fill insulation (fiberglass or cellulose) can be installed on top of old insulation. If you need to add new insulation on top of old insulation please note the following: Draftproofing should be completed prior to the addition of more insulation.

Can you touch insulation with bare hands?

While touching fiberglass doesn't usually lead to long-term effects on your health, exposure to it may cause intense itching, redness, or a rash. So, it's important to remove fiberglass from your skin as soon as possible so it doesn't come in contact with your eyes, nose, or throat.

Should attic insulation be on the floor or on the ceiling?

roof insulation is no-contest. The floor wins every time. Insulating the floor is standard practice for an unfinished attic space. The exception to this rule takes place when families opt to convert an unfinished attic space into something usable or livable.

Do you need plastic vapor barrier over faced insulation?

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 house wrap go over insulation board?

If you choose to install house wrap with rigid foam, generally, it should go under the insulation, not around it. However, you can rely on the advice of your contractor to make your final decision, since not every professional agrees on this order.

Should you put plastic over spray foam insulation?

Cold climates should use polyethylene plastic vapor barriers between the wall and insulation. Vapor barriers are often installed in basem*nts and crawl spaces to prevent ground moisture from leaking in. In houses with spray foam insulation, however, vapor barriers are not necessary.

Can you leave insulation exposed?

"Fiberglass insulation should never be left exposed in an occupied area, according to the American Lung Association," says ALA's Godfrey. "Exposed fiberglass insulation, once in the air, does cause respiratory reactions, such as dry, scratchy throat and coughing, as well as acting as a skin and eye irritant.

Does my insulation need to be faced?

Unfaced insulation is great for new construction, remodels, walls, floors, ceilings, basem*nts, attics and crawlspaces. It's best used for interior wall applications that do not face the outside and also in rooms that don't need moisture control, like living rooms, dining rooms and studies.

Do you need membrane under insulation?

When insulating a building from the inside, you will always need a vapour barrier. The only exception to this is when your insulation of choice already has a vapour resistant layer. In this case, you should seal the gaps and seams with vapour tape to ensure that the vapour still can't get through.

Can I use plastic sheeting as a vapor barrier?

Reinforced polyethylene plastic sheeting (poly) comes in a variety of thicknesses and strengths. A 6 mil thick poly is commonly used as a vapor barrier and offers short-term savings to the homeowner.

Should vapor barrier go up walls?

If doing an encapsulation (including the crawlspace in the building envelope and making it conditioned space) the experts agree that the vapor barrier should extend up the wall, stopping four to six inches below the sill plate to allow for an unobstructed pest control inspection area.

What do you cover insulation board with?

Most interior XPS boards must be covered with an accepted thermal barrier. Some XPS products have passed the NFPA 286 testing and don't require a thermal barrier; check with your manufacturer to see which XPS products are exempt.

Does insulation board go foil side in or out?

If you are wondering how to install the foil backed insulation on your walls here you have few tips to consider. if it is hot outside, the reflective part of your foil insulation must face outside. if it is freezing outside, the best orientation of the reflective part is inside.

Can I cover insulation with Tyvek?

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. If you add any more insulation, take the Tyvek off and put down batts of Polywrap, 8-inch-thick fiberglass insulation wrapped in perforated polyethylene.

Do you need air gap with spray foam insulation?

Believe it or not, attic ventilation for spray foam insulation is not needed. The simple reason is that spray foam is applied to the attic ceiling and not the attic flooring.

What do you put over foam insulation?

Drywall, either Standard or Fireguard, is normally used for this purpose because of its low cost and fire-resistant qualities. Other wall coverings may be available that will meet the criteria for fire protection but they will likely be more costly and sometimes more difficult to install.

What do you cover spray foam insulation with?

A thermal barrier is required to cover spray foam in all applications and is what separates the spray foam insulation from occupants and the interior of a living space. It's typical for drywall, plywood, or gypsum board to be the materials used as barriers for your room walls and ceilings.

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