Does Faced Insulation Need A Vapor Barrier?

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Insulating your house is one great way to keep it warm and reduce the cost of heating. One common insulator is faced insulation. You may wonder if faced insulation needs a vapor barrier. In this article, we have scoured the internet to give you the definitive answer to the question.

Since vapor barriers are only additional protection and not required to finish faced insulation, they are not always necessary. In fact, in some parts of the United States, it is better to not add vapor barriers as they can do more damage than good to your insulation. This is because the type of barrier you use should depend on the type of weather your location experiences.

Interested to learn more things about faced insulation and vapor barriers? Continue reading below as we discuss these two in detail below. We will also tackle topics such as which insulation is better and if you can put the same insulation over the other.

Covering an insulation mineral wool with the use of hydro-vapor barrier material, Does Faced Insulation Need A Vapor Barrier?

Vapor barriers on faced insulation

The job of vapor barriers is to control the movement of water vapor in the insulation. They help protect the insulation from the build-up of mold that can post heath hazards and rot the insulation. The barrier's main job is to regulate air from interacting with the insulation, vapor barriers only control the moisture and nothing else.

Vapor barriers alone do not control air movement; instead, deal with moisture brought about by water vapor. In fact, they do not even serve as barriers but as a diffusion retarder. In simpler words - they are specifically designed to prevent moisture accumulation to preserve insulative materials.

On the topic of mineral wool, we have a previous article written about it: "How Long Does Mineral Wool Insulation Last?" Go ahead and check it out.

Covering insulation mineral wool with the use of hydro-vapor barrier material in the room of the country house

Which are better: vapor barriers or air barriers?

Vapor barriers and air barriers work similarly to one another. A well-installed vapor barrier can both regulate air and vapor simultaneously.

Their main difference is that vapor barriers are specifically designed for moisture brought by air. Since air also packs a significant amount of vapor in it, both of them can be easily mixed up when choosing what type of barrier you will install.

Choosing a Vapor Barrier for Your Climate

Back view of roofer builder worker installing vapor barrier around the skylight opening in attic of new house under construction

Experts recommend that you choose which barrier based on the climate of your location. You may refer to this guide on the different climate zones in the US.

Generally, if you are living in the southern United States, climate zones 1 through 3 will not need vapor retarders. While places in climate zones 4 and up may require vapor barriers, but not always. It is only those that experience extremely cold weather in climate zone 7 that will truly need vapor retarders on their insulation.

This is because, during winter, a lot of heating is produced inside the house. Activities like cooking and burning wood in a fireplace create vapor. This is more common in places in the northern part of the United States where the house's windows and doors are shut trapping heat inside the homes.

The southern states, however, experience much warmer weather throughout the year, and ventilation is much better. Using vapor barriers in hot places generally just traps the humidity in walls and stops it from escaping.

This is especially true in zones 1 and 2 as the climate is more humid and hot. Humidity can be trapped in the walls or within the insulation.

Excess humidity can damage your walls over time. This can cause early structural deterioration compared to what is expected from your walls and insulation.

So the suggested barrier for this type of climate zone is an air barrier. This is because when walls get wet, the amount of water that goes through caused by the vapor is smaller compared air caused humidity in walls. This is well explained in the video down below.

Can you put faced insulation over faced insulation?

No, you should not do this. As mentioned above, faced insulation that has a vapor barrier can easily trap moisture. If you put another faced insulation on top of face insulation, a significant amount of moisture can form inside your insulation and in your walls to damage them.

If you are planning to reinforce old insulation, it is better to have the old one stripped down and removed completely and then put in new, especially if old insulation has been wet. This will not only give you new insulation, but it can also serve as a check-up to see the conditions of your walls and attic spaces where the insulation is.

This can be a great opportunity to check for mold or damage and find out if your walls need replacing. Furthermore, detecting any repairs needed earlier on can help you save money in the long run as to not cause even more damage. This practice is called preventive maintenance.

Here is an article that can guide you when to know if your insulation already needs replacement: "How Long Does Insulation Last And When To Replace It?"

Cost of insulation installation

Work composed of mineral wool insulation in the floor

The national average cost of home insulation can be anywhere between $3,000 and $10,000 for a 2,000 square foot home or between $1.50 and $5.00 per square foot. Factors such as location and other preparations needed to be done before installation can influence the total cost.

You can DIY home insulation if you possess the skills and know-how to do it. Fiberglass batts and rolls in particular are fairly inexpensive. But if you don't feel comfortable with this project, we recommend that you hire professionals as it can be very technical, especially when it comes to choosing the barriers for your insulation.

The benefit of spending more on professional service will pay off as this also serves as an investment in creating more comfort in your house, especially during the cold season. This can also add value to your house as this is an additional amenity.

Faced insulation vs. unfaced insulation

Collage of a faced insulation and unfaced insulation

When it comes to choosing which insulation it all depends on where you need it to be. Faced insulation has paper. These types bode well in ceilings, floors, and especially crawl spaces.

While unfaced insulation bodes well in attics or places between floors with living spaces. They are also good for soundproofing.

You may choose to go with faced insulation as sometimes states require that vapor retarders be installed on walls for safety - even though we have discussed earlier that this is not necessary - this is true on commercial or apartment buildings.

One good thing about unfaced insulation is its non-combustible property, meaning it will not burn. This is because compared to faced insulation, it doesn't have paper in it. In some cases, they are also used as fire prevention features for some houses and buildings.

In summary

Faced insulation can go without a vapor barrier. But because of outdated state guidelines and inspections, you are sometimes required to have a vapor barrier if you are installing a faced installation. And improper installation of these barriers can actually cause your walls more harm than good.

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