Attic insulation is one of the most effective ways of preventing air from escaping your house. Insulating your attic offers many benefits, such as protecting the attic wall from heat and moisture-related damages. It also saves you a few bucks off your electricity bill. But, like every other building material, attic insulation doesn’t last forever, and it is bound to be replaced after a while. 

The life span of attic insulation depends on the material type, exposure to moisture, and other factors that we will discuss later in this article. Nevertheless, attic insulation should last for at least 15 years after installation.

Asides from the fact that attic insulation is energy efficient and eco-friendly, it helps improve the comfort of your home, prolong the lifespan of your roof, and improves the overall air quality in your home.

The most common types of attic insulation are:

  • Fiberglass Batts
  • Cellulose
  • Fiberglass Loose Fill
  • Spray Foam 

In this article, we will compare the four most common types of attic insulation, highlighting their respective lifespan, source materials, advantages, and disadvantages.

Attic Insulation Longevity Comparison Chart

Type of Attic InsulationAverage lifespan (years)Factors that affect longevityR-value
Fiberglass Batts20 -100 yearsMold infestation. Dirt, debris, and dust. Puncture or damage. Water leaks 3.1 to 3.4 per inch of thickness
CelluloseUp to 30 yearsWater leaks. Dirt, debris, and dust3.2 to 3.8 per inch
Fiberglass Loose FillUp to 100 yearsWater leaks. Dirt, debris, and dust2.2 to 4.3 per inch of thickness
Spray Foam80 – 100 yearsInstallation Mistakes. Applying the wrong thickness of the foam. Failure to remove all of the old insulation before adding spray foam. Not cleaning the substrates and/or not allowing the substrate to fully dry before installation. Spraying foam insulation over the top of old insulation. Leaving holes and gaps in the space being insulated. Installing spray foam on a surface that is too hot (over 80 degrees Fahrenheit) or too cold (below 60 degrees Fahrenheit)About 3.8 per inch of thickness

How Long Does Fiberglass Batts Attic Insulation Last?

Fiberglass batts are one of the most widely used insulation materials in the United States. It is made of plastic reinforced by tiny glass fibers. It is popular because of its fire redundant and thermal insulation properties, not to mention its aesthetic look. 

Considering the material and process in which it is made, fiberglass insulation can last up to 80 -100 years. Irrespective of this fact, studies show that fiberglass insulation may start breaking merely 20 years after installation. Several factors may affect efficiency over time. Some of them include:

  • Mold infestation
  • Dirt, debris, and dust
  • Puncture or damage
  • Water leaks
  • Damage (e.g. from storing things in the loft)

Fortunately, it is pretty easy to know when fiberglass batt ages. You can tell if the fiberglass is bad when you notice spots such as dirt, dust, or even icicles during winter. Increased noise due to loss of soundproofing ability is also one way of detecting a fault. In some cases, the attic insulation itself may start to break apart, shift, or get wet. 

How Long Does Fiberglass Loose Fill Attic Insulation Last?

Fiberglass loose fill is another popular choice, and it is made up of small fiber, foam, or other material particles. These tiny particles combine to create an insulating material that can fit into any space without affecting finishes or structural elements.

Fiberglass loose-fill insulation is non-combustible and inorganic. It also does not rot or absorb moisture nor support the growth of mold, fungus, or mildew. Interestingly, fiberglass loose-fill insulation can last for up to 100 years. While this might seem like a long time, it is barely up to four generations, and homeowners often neglect the history of their homes. 

The following factors may affect the long-term efficiency of fiberglass loose fill:

  • Mold infestation
  • Severe weather forces
  • Water leaks
  • Damage when storing things in the loft

Studies have shown that loose-fill fiberglass showed a significant reduction in R-value, and its resistance to heat-flow can reduce by up to 40% as it ages.

How Long Does Cellulose Attic Insulation Last?

Cellulose is one the most pocket-friendly and popular insulation materials used in the ceiling and walls of modern houses. It is also one of the oldest materials used for insulation to date. Cellulose, however, only became popular in the 1950s when chemicals like ammonium sulfate and boric acid were included in the materials.

Cellulose insulation is made mainly from recycled newsprint and denim, making it one of the most eco-friendly insulation materials. Its production can help remove over three million tons of discarded newsprint from the country’s yearly waste stream.  

Unlike fiberglass, cellulose insulation can last about 30 years under controlled conditions. However, it does start degrading about 15 years after installation. The following factors may really affect the effectiveness and overall longevity of the insulation over time.

  • Mold infestation
  • Severe weather forces
  • Puncture or damage
  • Chemical contamination
  • Water leaks
  • Human manipulation when storing things in the loft.

Some signs of cellulose deterioration include a reduced R-value, tear, mold growth(if wet), and discoloration.

How Long Does Spray Foam Attic Insulation Last?

Spray foam insulation is a liquid foam sprayed into position and set into an insulating layer. It has been in use for over 30 years and is now becoming increasingly popular as it’s an effective insulator and can also stop air leakage. 

In terms of longevity, spray foam insulation can last anywhere from 80 years to 100 years, with closed-cell spray foam having a slight edge in terms of durability. The issue with spray foam is its installation process, which could seriously affect its lifespan. Some examples of common mistakes when installing spray foam include:

  • Using the wrong foam thickness
  • Failure to remove all of the old insulation before adding spray foam
  • Not cleaning the substrates or not allowing the substrate to fully dry before installation
  • Spraying foam insulation over the top of old insulation
  • Leaving holes and gaps in the space being insulated
  • Installing spray foam on a surface that is too hot (over 80 degrees Fahrenheit) or too cold (below 60 degrees Fahrenheit)

How To Prolong Your Attic Insulation Lifetime?

Insulating a new attic can cost you about $1,500 – $4,000, depending on your roof size. So, it is prudent to find ways to maintain and prolong the lifespan of the current installation.

Highlighted below are some valuable tips to lengthen the lifespan of your attic:

  • Clear debris from time to time 

When debris such as twigs, branches, and leaves pile up and accumulate on your roof, it can prevent water from draining. When this happens, mold and mildew may start to develop, thus shortening the lifespan of your attic. 

  • Beware of vents 

When insulating an attic, be careful not to put any insulation over the vents, which will block airflow and cause trouble. Be especially careful when using loose-fill insulation, which can easily be accidentally pushed or blown over vents.

  • Look out for water leaks 

Water leakages may also develop mold and mildew, which can affect the quality of your health. Leaks can shorten attic insulation lifespan by almost 50%. Thus, it is essential to do routine maintenance on the house to check and repair water leakages. 

How Often Should Ideally Attic Insulation Be Replaced?

The fact is that the attic plays a significant role in the overall insulation of the home. A well-insulated attic can help maintain the temperature inside the home by keeping the cold air from the air conditioning system and preventing the hot air from entering.

The frequency at which attic insulation should be replaced depends on different factors. Experts suggest that the attic insulation should be replaced every 15 years. The attic in most homes serves as a storage area, so having it checked regularly may not be so easy. Nevertheless, you should become weary when you detect sudden changes in temperature, growth of molds, mildew, or usual electricity bills. Sometimes, a replacement may be necessary if the property is old.

Does Attic Insulation Lose R Value Over Time?

Sadly, yes. An insulating substance’s ability to resist heat flow is measured by its R-value. Thus, the higher the R-value, the better it is for insulation. The R-value is assigned based on several factors, including the type of material, the thickness, and its density.

For instance, spray foam insulation loses some R-value over a period of time, and the current R values on products are called “adjusted” or “aged” R values for that reason. The loss is an interesting curve —more R-value is lost in hot climates than in the cold, and the loss is smaller in places with moderate climates. 

If the foam insulation is foamed into an air-tight enclosure like a sealed metal panel, then there will be minimal change to the R-value. The same rule applies to fiberglass, cellulose, and spray foam attic insulation.

If the material is insulated under the proper condition, then the R-value should remain for many decades, if not a century or more. 


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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