How Long Does Insulation Last? (Spray Foam, Fiberglass, Cellulose, Mineral Wool)

“How long does home insulation last?” Perhaps you ask this question because you are wondering whether it’s time to replace your home’s current insulation. Or perhaps you don’t have insulation in your home and wonder whether insulation is a good investment. Whatever the reason, it’s a good question!

Home insulation is designed to last for several decades. Most modern batt insulation will have a warranty of between 50 to 70 years. Certain materials can last for up to 100 years or even more. But it depends to a large extent on the environment the insulation is being used in. The same material could last for 100 years in an outside wall, but only 10 years in a leaking attic. 

In this article, we’ll discuss what the lifespan of commonly used insulation material is, and the influence on the lifespan by the place where the insulation is applied. We’ll end by giving some tips on how to “listen” to your house when it “tells” you that your insulation needs attention.

The lifespan of commonly used insulation

Let’s look at the most commonly used insulation materials when it comes to house insulation and determine their average, normal lifespan. 

Type of Insulation Expected Lifespan Pros Cons
Spray foam Up to 100 years Durable Air-tight Reliable Mold resistant Does not absorb moisture Won’t move once set No important cons
Fiberglass 80 to 100 years Cost-effective Easy to work with Effective at blocking air and heat movement Needs to stay light and fluffy Absorbs water, and can breed mold Not effective anymore when compressed
Cellulose 20 to 30 years Eco-friendly Made from recycled materials Only has about one-quarter of the life expectancy of other materials. Once cellulose insulation is wet, you have to replace it.
Mineral wool Up to 80 years Durable Available in rolls, batts, or blown-in varieties.
Prone to moisture damage and mold growth Once the insulation has become wet, it needs replacement regardless of age.
The lifespan of commonly used insulations

Spray Foam Insulation

spray foam insulation
Spray foam insulation

Spray foam insulation can last a lifetime as it does not absorb moisture and is mold resistant. It is safe to say that the spray foam insulation in your house will last up to 100 years. The long lifespan can also be contributed to the specific characteristic that the installed foam won’t move when once settled unless you cut it.  Thus, the possibility of tears or other damage to the insulation is small. Nowadays spray foam is very popular in newly constructed homes, because of its durability. 

Fiberglass Insulation

If fiberglass insulation is not damaged by moisture or mold it can last 80 to 100 years. This is also a very popular insulation material because it is cost-effective and you can work with it easily. It is available as blown or batt insulation. 

fiberglass insulation
fiberglass insulation

The problem with fiberglass insulation is that it must stay light and fluffy to be effective. Unfortunately, if fiberglass insulation becomes wet from a roof or pipe leak, you have to replace it regardless of age. As it absorbs water easily and keeps it for a long time, it loses most of its effectiveness when wet.

If you compress fiberglass it is not fluffy anymore and the insulation is not effective. You might unintentionally compress the fiberglass insulation by stacking heavy articles on it in your attic for example. By doing this you’ve shortened the lifespan of the insulation.

Cellulose Insulation

Cellulose insulation has roughly a quarter of the lifespan of most other insulation materials and will start degrading naturally after about 15 years. It is, however, eco-friendly insulation because it is made from recycled materials. It provides very effective air and heat blocking. Air and heat cannot move through the cellulose insulation. 

cellulose insulation
cellulose insulation

Cellulose is loose-fill insulation to be used in attics. It is ideal as secondary insulation when you blow it over fiberglass batt or other longer life insulations. Like most other common types of insulation, cellulose also needs replacement regardless of age when it has become wet. 

Mineral Wool Insulation

Mineral wool insulation lasts from 30 to 80 years. The lifespan depends on the base material used, such as rock wool, glass wool, or slag wool.

mineral wool insulation
mineral wool insulation

Mineral wool is available in rolls, batts, or blown-in varieties, and is very durable insulation. But as with most other types of insulation, once the insulation has become wet, it needs replacement regardless of age.

Lifespan depends on where the insulation is applied

Although the lifespan of insulation material is important, you must remember that the same materials used in different places in the house can have shorter lifespans when used in specific “problem” places. There might, for instance, be a difference between the lifespan of material used in the attic and an interior wall.  

Crawl space and basements

A crawl space is an unoccupied, and mostly even unfinished, narrow space between the ground and the first floor. It is called the “crawl space” because there is typically only enough room to crawl rather than stand. These spaces are often damp and even wet for long periods.

As this space can have a great influence on the air and heat flow in and out of your home, it should be insulated. But as a result of the wet conditions in the crawl spaces, the insulation installed inside crawl spaces only lasts about 10 to 40 years – roughly about half the lifespan that the same material will have in other areas of your home. According to insulation companies, you’ll most probably have to replace the crawl space insulation every 10 years, especially if you live in a rather humid and wet environment. 

Your basement insulation should normally last for 30 to 50 years. But in principle, basements have the same problem as a crawl space – it can become wet and damp and the lifespan of the insulation can then be reduced with many years. But because it is less likely to suffer from such severe damages as in the crawl space, you probably only have to replace your basement insulation after about 20 years. 

Attic

Although the materials used for attic insulation under normal conditions can last 40 to 80 years roof leaks, as well as pests and small animals and rodents might damage the attic insulation. These extremes can cause the insulation to become ineffective after 10 to 15 years. 

Heavy storms and rain and large infestations can severely damage the attic insulation at any time and thus reduce the lifespan drastically. 

You or any other member of your family can also contribute to the reduction of the lifespan of your attic’s insulation. When fluffy material has been used for the insulation, you can compress the fluff and damage the insulation by putting large boxes on the material, or placing wood on the material to enable someone to walk in the attic.

If you are aware of the possible problems in an attic and ensure that the insulation is not compressed and frequently make sure that no small animals can get into the attic, the lifespan of your attic insulation will be much longer   

Exterior walls

We include exterior walls here because many people think that exterior wall insulation will also reduce the lifespan of the insulation. But on the contrary, wall insulation tends to last longer and in many cases is effective much longer than what the manufacturer even predicts. 

This is because the insulation is concealed inside the wall and protected from moisture and other factors leading to ineffectiveness. Theoretically, the insulation in your walls’ cavities should last for as long as the wall stays in place. 

How Often Do You Need To Replace Insulation?

It is difficult to exactly predict what your insulation’s life expectancy is, as it can differ from section to section.  But it will give you peace of mind to know that experts in this field agree that home insulation normally lasts for at least 4 or 5 decades. 

The International Association of Certified Home Inspectors

According to “The International Association of Certified Home Inspectors” insulation material such as spray foam, wrap tape and house wrap insulation can last for more than 80 years. 

Loose-fill, foam board, loose-fill and rock wool insulation can, according to them, even last up to 100 years if correctly installed. Cellulose has the shortest lifespan and even this is at least 15 years.

Unforeseen circumstances

But what always must be remembered is that unforeseen circumstances influence the lifespan of insulation. If, for instance, your attic or basement is flooded as a result of unexpected heavy rains, or a pipe has burst and your lounge’s ceiling has been wet for days, it is always good to inspect the insulation for any damage. There is a possibility that the insulation has been damaged to such an extent that all or part of it has to be replaced. 

Signs

Your house will also “tell” you when you have to inspect your insulation and perhaps replace certain parts of it.  Some signs will signal to you that it is time for you to inspect your insulation. We’ll also discuss this in this article.

Signs telling you that there might be insulation problems

  • You should replace insulation when it is not functioning on an acceptable level anymore.  Some of the signs indicating that there might be a problem with your insulation include the following: 
  • The indoor temperature in your home starts to fluctuate without you making any setting changes on the thermostat.
  • During summer and warm days, your air conditioner cannot keep the house cool even if it is working without stopping and at the lowest possible temperature.
  • During winter and cool days, your heater or furnace can’t get you’re your house’s temperature up to a comfortable level even when it is providing maximum heat. 
  • You suddenly get higher electricity bills without using extra appliances. 

Reasons why the insulation could have gone bad

There are various reasons why insulation can go bad.  We’ll list and discuss some of the common reasons.

Insulation shifting/moving 

If insulation hasn’t been fastened and installed properly it may over a period of time shift and move from its original place. This might expose certain areas and cause air draughts because if air can flow, unwanted heat will be able to escape or come into your home. Thus, the effectiveness of your insulation has been compromised. Therefore it is good to inspect your insulation at least once a year and repair where necessary to keep the insulation working. 

Dirt and Dust on the insulation material

When the roof insulation batts become dusty or dirty the effectiveness of the insulation can reduce.  Dirt and grime on reflective foil backed insulation can also reduce the reflective surface. The result is that its ability to reflect radiant heat away from your home is reduced.  If you clean the insulation from time to time you will also have longer effective use of the insulation. 

Moisture damage, including mold growth 

Water leaks and even condensation can damage your insulation. And it can lead to mold growth.  The water leaks can be a result of leaking pipes or damage to the roof during a heavy storm.  If repaired in time the insulation might be salvaged.

Tears in the insulation

Tears in the insulation leave gaps in the insulation which reduces its performance. Gaps allow air and heat to flow through. 

Pest infestation 

If insulation is infested by rodents or other pests, the insulation might rip and leave gaps for air and heat to flow through.

Conclusion

We hope that this article has given you peace of mind that home insulation is a long-term investment in your house.  Not only will good insulation helps to keep a comfortable temperature in your home for many decades, but it will also enhance the value of your property. 

If no devastating event like a severe storm occurs, your home insulation will last for at least 10 to 15 years in places like your attic and basement, but in general, it should last for 80 years and more. 

Charles John

A novice DIYer who learns about home ventilation. I am a mechanical engineer and have a basic knowledge of HVAC systems but I learn continuously to make myself the best blogger in that space.

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