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Can I Add New Insulation Over Old?

One of the most common questions we get is, “can you put new insulation over old insulation?” The answer is often “yes,” but there are some important exceptions you should know about beforehand.

Multiple areas of the home can benefit from retrofit insulation (i.e., adding insulation to an existing space). These include:

Those who are wondering can you put new insulation over old insulation will find answers below to some of the most common questions about installing and combining different types of home insulation. However, we strongly advise homeowners who are considering insulation upgrades to consult a qualified professional before going the DIY route.

The Big Question: Do I Need to Remove Old Insulation Before Installing New?

In the majority of cases, removal of old insulation is NOT necessary before adding new. Nonetheless, we recommend getting a comprehensive assessment by a home insulation professional to make sure there are no issues that could adversely affect the efficiency of the new material. 

Key considerations include:

Insulation removal and replacement can be laborious and time-consuming. However, such a step may be necessary to maximize the efficiency and longevity of any new insulation you install.

For example, you will need to remove and replace the damaged material instead of adding new insulation on top of the old if you have excess moisture in the walls or animals have made their home in the current insulation. In addition, some types of insulation are incompatible with others.

Below, we take a look at some of the most common scenarios when it comes to combining old and new insulation. The answer to the question can you put new insulation over old insulation often depends on (a) the specific kind of material and (b) the condition of your current home insulation.

Can You Put Blown-In Insulation Over Batt Insulation?

In 1978, Colorado adopted new building codes that required the use of insulation and other energy efficiency measures. Since that time, batt insulation (i.e., insulation that comes in long, flat rolls) has remained the most common type of insulation in both new homes and existing properties.

Fiberglass, mineral wool, and cellulose are among the most popular materials used in batt insulation. These are also the materials used for blown-in or loose-fill insulation, which is any material that is installed by blowing or pouring it into an opening inside the structure.

Provided the existing rolls are in good shape, you can absolutely retrofit batt insulation with blown-in insulation! Materials can even be mixed, such as blowing in cellulose insulation on top of fiberglass batts (or vice-versa).

Can You Put Rolled Insulation on Top of Blown Insulation?

Blown-in insulation is often installed in attics and other tightly enclosed spaces. If blown-in insulation was previously installed in one or more areas of your home, it is perfectly acceptable to also add rolled insulation.

There is one caveat, however. You need to avoid faced insulation. Faced insulation has a paper barrier that retards water vapor. When this layer rests on blown-in insulation, it can lead to moisture buildup. Only unfaced insulation should be used when adding rolls to blown insulation.

Can I Blow Insulation Over Existing Insulation?

The answer to this question depends on what kind of old and new insulation you’re considering. As discussed above, blown insulation can be added quite effectively to any type of insulation made from mineral or natural fibers. Spaces previously treated with spray foam may also be augmented with blown insulation—provided the spray foam is 100% dry and settled.

Read More: A Guide to Choosing the Proper Home Insulation

Can Insulation Be Blown Into Existing Walls?

One of the most common situations where people ask can you put new insulation over old insulation is when they want to upgrade insulation in the walls of the house. Although poorly insulated walls are a leading cause of energy loss, people are often reluctant to address the problem because they don’t want to have to tear out the walls to add new insulation.

Blown insulation is the perfect solution because it can be added by cutting a 1–2 incision into the wall. While this might seem easy, blowing the right amount of loose-fill insulation into the wall cavity can be difficult. Adding too little will result in ongoing issues with drafts and high energy bills, while adding too much insulation can restrict air flow, create ideal conditions for mold to grow, and even damage the wall.

Can You Put a Vapor Barrier Over Faced Insulation?

Faced insulation already has a vapor barrier. The facing, often made of kraft paper or foil, serves as a vapor barrier to help control moisture diffusion.

Ironically, combining the vapor barrier found on faced insulation with plastic sheeting or another kind of vapor barrier can lead to moisture problems. Moisture can become trapped between the two vapor barriers, potentially causing condensation, mold growth, and damage to the insulation and building materials. If you are concerned about moisture accumulating inside the walls, you should use unfaced insulation with a suitable vapor barrier.

Can You Spray Insulation Over Old Insulation?

Spray foam insulation is the Rolls-Royce of home insulation options. Its quality, efficiency, and durability are simply unmatched.

However, there are situations where spray foam insulation is not suitable. For example, you should NOT spray foam insulation over old insulation. Gaps can form when spray foam is applied to batts and rolls, reducing the effectiveness of the new insulation. 

Read More: Can Spray Foam Be Used in Existing Walls?

You may find a lot of information online saying it’s okay to combine spray insulation with older materials. However, we’re here to tell you that the efficiency, strength, and seal created by spray foam insulation suffers if the old insulation isn’t removed before the spray foam is applied.

Can You Put New Insulation Over Old Insulation? Find Out Today!

Retrofitting a home’s current insulation is always preferable to removing and replacing insulation. Adding new insulation to the old saves time and money, in addition to limiting disruptions to your home.

You can count on transparent pricing when you decide to hire REenergizeCO. We thoroughly evaluate your home’s insulation and provide targeted recommendations for lowering your monthly energy bill, making your home more comfortable, and optimizing your energy efficiency.

Contact REenergizeCO today to inquire about professional installation of new insulation over old. Our team serves customers in Denver, Fort Collins, and throughout the Colorado Front Range.