Does rock wool insulation need a vapor barrier?

Asked By: Fredric Imukov | Last Updated: 29th May, 2020
Category: home and garden indoor environmental quality
4.5/5 (2,048 Views . 27 Votes)
Note that rock-wool insulation only comes un-faced, meaning there's no kraft-paper or foil barrier. Depending on the situation, you may need to install an independent permeable membrane to serve as a vapor barrier.

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Moreover, should I use a vapor barrier with Roxul insulation?

roxul Comfortbatt is an unfaced semi-rigid batt insulation and a vapor retarder may be required by building code depending on the geographic location of the building. The use of a vapor retarder will limit the amount of water vapor that will move to the outside wall – reducing condensation in the wall assembly.

Beside above, is Rockwool mold resistant? ROCKWOOL products are inorganic which provide no food source for mold to grow. ROCKWOOL products are tested to ASTM C1338 – A Standard Test for Determining Fungi Resistance – and passes with zero fungal growth.

Keeping this in view, do you need a vapor barrier with foam board insulation?

5 Answers. Rigid foam insulation is usually a qualified vapor barrier. However, an installation between the studs can pose a challenge. To complete the vapor barrier you would want to foam-seal or tape all the sides where the rigid meets timber, because these gaps will facilitate vapor flow.

Is rock wool insulation itchy?

Like fiberglass, mineral wool contact can make you itch or even cause a mild rash.

39 Related Question Answers Found

Is Rockwool bad for your lungs?

Not only is rockwool unfriendly to the environment – it's also potentially harmful to your health. New blocks can contain a lot of dust and loose fibers that can get in your eyes, mouth, skin and lungs. If you're using rockwool, you should be using a mask, goggles and gloves when you work with it to protect yourself.

Should you put plastic over insulation?

Condensation occurs whenever warm air meets cold air. Without a vapor barrier in place, condensation inside the walls could ruin the insulation and promote the growth of harmful mold and bacteria. Plastic, specifically 6-mil polyethylene plastic, is the most commonly used vapor barrier.

Should you vapor barrier a bathroom?

The vapor barrier should be on the "inside" (between the insulation and drywall). There is no need to vapor barrier the non-exterior walls. If the tub shares this exterior wall I would put vapor barrier behind it (if you can) as the plastic tub surround will not give you a "vapor barrier" (I don't think).

Where should vapor barrier be installed?

Vapor barriers are usually best installed on the side of the wall that experiences the hotter temperature and moister conditions: the inner surface in colder climates and the outer surface in hot, humid climates. In existing spaces, oil-based paints or vapor-barrier latex paints offer an effective moisture barrier.

Does a vapor barrier prevent mold?


The original reason for using vapor barriers was a good one: to prevent wall and ceiling assemblies from getting wet. This can lead to significant moisture problems and mold; problems occur when walls get wet during construction or more often throughout the home's life.

Is Rockwool insulation better than fiberglass?

Fiberglass has an R-value of approximately 2.2 to 2.7 per inch of thickness. Mineral wool has a slightly higher R-value, ranging between 3.0 and 3.3 per inch. Fiberglass insulation typically contains 20 to 30 percent recycled content. Cost: Fiberglass insulation costs 25 to 50 percent less than mineral wool.

Is Rockwool the same as asbestos?

Rockwool fibers are single monofilament strands and do not separate into thin fibrils such as asbestos and will not penetrate the cell walls within the body. This is why rockwool is not as harmful to breathe in as asbestos. Because rockwool fibers are short and thick, the body can easily expel them.

Do interior walls need vapor barrier?

A vapor barrier is an essential part of a building, but it's often installed incorrectly or omitted entirely. Installing a vapor barrier on the (warm) interior wall of your cement brick house will prevent condensation and reduce air leakage through your walls and insulation.

Is foam board insulation mold resistant?

Pros: Spray foam insulation doesn't retain water, so it also doesn't promote mold or mildew growth. Spray foam creates an air seal that will keep the outside air from getting inside, thus also reducing drafts near your floor boards.

Does foam board insulation mold?


Closed cell spray foam insulation works as an incredible vapor barrier and has the highest resistance value on the market. Closed-cell spray foam insulation is completely waterproof and moisture resistant. In addition, the chemical makeup of the material leaves no food value for bacteria or mold to grow.

Does foam insulation cause mold?

As a product, spray foam insulation does not attract mold. And unlike wood or metal, spray foam does not rot, rust or deteriorate. This means that an area properly sprayed with foam insulation will never become a food source or a hospitable environment for a mold colony.

What is the difference between pink and blue foam board?

Both pink and blue foam boards are rigid insulation panels made from extruded polystyrene. The chemical composition, manufacturing process and insulating capability of the two products are similar; the principal difference between them is that they are manufactured by two different companies.

Can I use plastic sheeting as a vapor barrier?

In simple terms, a vapor barrier is a material that won't allow moisture to pass through it, such as plastic sheeting. It's designed to stop the moisture before it can enter the wall cavities. There are two basic types of vapor barriers used with exterior wall insulation. The most common is paper-faced insulation.

Does rigid insulation need to be covered?

Rigid foam insulation, whether it is expanded or extruded polystyrene, does have to be covered if it is installed in the interior of a building. This wall covering must have a minimum fire rating to protect the insulation from quick combustion during a fire.

What is the best exterior wall insulation?


What Insulation is Best for Exterior Walls?
  • Fiberglass has been used as a home insulation material for decades. It's affordable and effective, making it the go-to choice for many homebuilders and contractors.
  • Cellulose is a great choice for insulating an enclosed existing wall with minimal demolition.
  • Spray foam is applied wet and expands into thick, hard foam.

How thick should foam board insulation be?

Foam board insulation is easy to use and is a great DIY way to add some insulation. It comes in standard-size 4×8 sheets, and smaller sizes, in many different thicknesses from 1/4 inch to 2 inches. Some types of thicker foam board insulation are available, but they may need to be special ordered.

Which foam board insulation is best?

Choose the right type of rigid foam for your needs
  • Polyisocyanurate: Known as polyiso for short, polyisocyanurate foam has the highest R-value per inch (R-6.5 to R-6.8) of any rigid insulation.
  • Extruded polystyrene: Extruded polystyrene (XPS) rigid foam is usually blue or pink in color, with a smooth plastic surface.