Does Cellulose Insulation Lose R-Value Over Time?

If you are installing cellulose insulation for the first time, you may be wondering if it loses its R-value at some point. Over the years, cellulose insulation, similar to rolled and batt insulation, can settle and lose its thickness due to age and environmental factors. But does this affect the R-value of insulation? We have researched the answer to this question, and in this post, we will answer it for you.

Most cellulose insulation will begin to settle at some point during its lifetime. Unfortunately, this settling creates aeration within the material that will cause the R-value to decrease by 15-20%. And if the insulation becomes disrupted due to moisture, constructional damage, or pests, it's likely to lose more R-value. Often, contractors will recommend blowing about 15-20% more insulation than is necessary to account for this.

Cellulose insulation is at its highest R-value when it is loose-fitting and not decompressed. However, this doesn't mean that you can't simply add more insulation on top of it when it does settle. Continue to learn more about making your cellulose insulation last longer and how to remove it if you need to.

Spraying cellulose insulation in the attic of a house, Does Cellulose Insulation Lose R-Value Over Time?

Cellulose Insulation and R-value

As mentioned previously, cellulose insulation can settle by anywhere from 15% to 20% depending on how well it was installed. However, when this occurs, it can create gaps in your attic or wall cavities. If the insulation is installed between floor joists, it could leave a space between the joist and the floor, creating drafty areas in the room.

This is why hiring a professional contractor to install insulation for you may be ideal if you have never worked with insulation before. A contractor can prevent many of the problems caused by settling, and they can instruct you on how to best care for the insulation so that it lasts as long as possible.

Does cellulose insulation degrade over time?

Cellulose insulation applied in the wooden framing of a house, Does Cellulose Insulation Come In Rolls?

Yes. Cellulose can degrade over time, as it will naturally decompress at some point. This tends to be around the 15 to 20-year mark. However, different factors can affect the total lifespan of cellulose insulation. You can minimize this by ensuring that the insulation is installed correctly and that you are using the best type for your home's areas.

How long will cellulose insulation last?

On average, cellulose insulation can last anywhere from 20 to 30 years. The length of time that the insulation lasts will depend on a few different factors. The most important two are how well the insulation was installed and the environmental factors within your home that promote its longevity. Let's take a look at a few things that can cause the insulation to age prematurely.


Cellulose insulation has the highest decompression rate of any type of insulation. The settling will begin slightly after the installation has been installed, and then it will continue over the months and years. If the settling becomes extensive, it can cause a severe decline in the insulation's energy efficiency, especially if it is not addressed or re-filled.

This is the quickest and easiest way to remedy the issue. You can add cellulose insulation over old insulation to maintain the R-value of the total insulation needed for your home. However, before doing this, you'll want to ensure that the insulation is free of moisture or pests, which can also contribute to the insulation losing its R-value.

Unnoticed air leaks

If there are any direct air leaks where the cellulose insulation is installed, it can affect its ability to regulate heat transfer. This means that you may notice gaps and drafty areas where the insulation is installed.

Frequently this may present itself as hot and cold spots in one room and none in an adjacent room. It's important to note that these air leaks may be very difficult to detect after the installation has already been installed.

This is why a thorough inspection of the area in which the insulation will be installed is crucial to ensuring that the insulation will be effective once applied. If you notice any air leaks before the insulation install, be sure to seal them properly or have a contractor come out to perform this job for you.

Humidity and moisture issues

Cellulose insulation is made mostly from recycled newspapers and other similar materials. This means that it's typically more susceptible to damage from moisture and humidity.

For example, if you have a leak in your attic from a busted water tank or frozen pipes, it can seriously affect the installation's ability to perform. Note that cellulose insulation is typically water-resistant. However, if the insulation is exposed to large amounts of water over an extended period of time without drying out, it can develop mold issues.

Pest issues

Though cellulose insulation is typically sprayed with pesticides to keep pests out, some pests can find their way into your insulation after a few years. This is especially true for insulation that has become degraded, decompressed, or damaged in some way. The most common pests include termites, rodents, ants, and spiders.

While rodents may not necessarily harbor inside cellulose insulation (as it's too airy and light for them to nest), they may eat through it to find food and water resources. However, other household pests and insects may nest within the insulation, laying eggs and causing further damage.

If you suspect that your cellulose insulation has developed a pest issue, it's best to contact a professional exterminator as soon as possible. The situation will only get worse over time.

Does cellulose insulation lose R-value when compressed?

A cellulose insulation panel

Yes. Cellulose insulation does lose its R-value when it is compressed. The amount of loss depends on how much insulation is decompressed but typically ranges anywhere from 15% to 20% of its initial value.

Signs That It's Time To Remove Cellulose Insulation

There are situations when removing old cellulose insulation is necessary. Sometimes this is when the insulation has become damaged in some way. Let's take a closer look at a handful of situations in which replacement can be imminent:

  • There is significant water damage to your basement or roof due to weather, blown off roof shingles, busted pipes, or broken water heaters.
  • If there is mold growing inside the insulation. It can cause the insulation to decompress prematurely and lose its R-value.
  • The insulation has been punctured by home reconstruction, furniture moves, or by pests.
  • The insulation begins to appear dusty or dirty--this is especially true for insulation located in places where wood dust may be common such as attics, basements, and crawl areas.
  • If your home is older and the building has small air leaks that were not detectable before the insulation was installed

Signs Your Cellulose Insulation Should Be Replaced

If you are unsure whether or not the cellulose insulation in your home needs to be replaced, here are a few signs to look out for:

  • The temperature in specific rooms of the home starts to feel uneven. For example, you may notice hot and cold areas in certain parts of the house.
  • It seems that the thermostat has a hard time keeping the house at the right temperature, and it appears to fluctuate randomly.
  • Your home suddenly feels more drafty than before.
  • The insulation looks decompressed, wet, or old.
  • You notice that your energy bill is starting to climb more than it did in the previous years.
  • You or someone else in your home begins to suffer from respiratory-related illnesses or sudden allergies.
  • Your home starts to develop excessive condensation, seemingly random leaks (particularly in the attic, basement, or beneath the floors), or other moisture-related issues.
  • You're having issues with pests, including rodents, squirrels, insects, or raccoons.

Does cellulose insulation get mold?

Cellulose insulation is unlikely to grow mold as it's sprayed with chemicals to prevent mold and mildew from forming on it. However, it can grow mold if it's exposed to excessive amounts of water or humidity over an extended time.

Wrapping Things Up

Spraying cellulose insulation in the attic of a house, Does Cellulose Insulation Lose R-Value Over Time?

We hope that this post has helped explain how cellulose insulation can lose its R-value over time. Remember, the better you maintain the environment in which your insulation is located, the longer it may last. Cellulose insulation should be replaced when it shows signs of degradation, severe decompression, wetness, or other significant damage.

If you've never installed this type of blow-in insulation before, it's best to have an HVAC professional come to install it properly. Not only will this help ensure its effectiveness, but the technician can also alert you to any other HVAC-related issues prior to the install.

Before you go, be sure to check out some of our other posts:

How To Insulate Laminate Flooring [3 Best Underlayment Options]

How To Keep Mosquitoes Away From An Evaporative Cooler

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