How Long Does Fiberglass Insulation Last? A Contractor’s Guide

With how many options for insulation there are, your clients likely have plenty of questions, including what the lifespan of fiberglass insulation is. We’ll outline the answer for you and provide signs of wear and tear so you can best advise your clients.

How Long Does Fiberglass Insulation Last?

If the fiberglass insulation is of good quality, installed correctly, and not disturbed, you can expect it to have the same lifetime as the building itself — usually 60+ years. However, “disturbed” can mean several things that can impact the lifespan:


While mold won’t grow on fiberglass (it is not a food source for mold), it can become compromised if it comes into contact with water from any source. If you’re noticing fiberglass becoming matted by water, there is likely a bigger problem (like a leaky roof), and it’s important that the insulation be replaced when the leak is fixed.


Like water, moisture can break down fiberglass over time. Again, mold won’t grow, but if the building is in a humid or rapidly changing climate and the insulation has more direct contact with moisture (such as in attics or exterior walls), it should be inspected for damage.


The hope is that fiberglass insulation is installed correctly (held in place by blown-in fabric or netting if needed) so that it isn’t disturbed by wind. However, in places like attics and exterior walls, this may be difficult. If the insulation has been moved by wind, it should be inspected for damage.

Rodents and Insects:

The unfortunate reality is that rodents and/or insects may use insulation as a home or they could take some for their own nests. Especially if you have had an infestation, it’s important to check out the fiberglass insulation to make sure it has been undisturbed. If a client has suspicions that they’re dealing with rodents and/or insects, they should replace their fiberglass insulation before the 60-year lifespan. 

However, if any signs of wear and tear are present, it’s important to consider a replacement.

Signs That Fiberglass Insulation Needs to Be Replaced

If at any point the following are noticed, or if a client is uncertain when their fiberglass insulation was last replaced, they should seriously consider replacing the insulation:

  • Moisture damage, including looking matted
  • Compressed or flattened insulation
  • Appearing “slumped”
  • Signs of rodent or insect activity.
  • Appears to have been stepped on
  • There is a noticeable draft in the building or it is unable to hold heat/cool air like before.

If any of these signs are present, it’s important to recommend replacement to your client.

4 Tips for Replacing Fiberglass Insulation

If you determine that fiberglass insulation needs to be replaced, here are some tips to keep in mind:

1. Wear protective gear:

Fiberglass is made of thinly spun threads of glass. Although the concerns around fiberglass being dangerous have lessened over the years, it is still suggested that you use PPE such as: cut-resistant work gloves, a loose-fitting longsleeved shirt, safety glasses and a disposable mask. Respiratory protection is always advised during any insulation installation, but not necessary.

2. Remove all old insulation:

Fiberglass insulation should never be removed by hand. Instead, protect your team from unseen sharp objects by using the proper removal equipment. If your team is looking for training on fiberglass insulation removal, our training team is prepared to walk you through the process and what equipment is needed.

3. Choose the right type of insulation:

While fiberglass has been used for decades, there are many options to choose from, including open- and closed-cell spray foam insulation and eco-friendly spray foam. Depending on the need and building, fiberglass or spray foam insulation can be a great option. If you need help determining what to use, contact your local IDI representative to walk you through each.

4. Properly dispose of old insulation:

Old fiberglass insulation can’t be thrown in the dumpster. Make sure to properly dispose of any old insulation — no matter the amount — properly.

Frequently Asked Questions About Fiberglass Insulation

Can Fiberglass Insulation be Repaired?

Blown fiberglass can be re-blown into place as long as it hasn’t been disturbed and isn’t damaged. However, it is beneficial to replace the blow-in insulation completely. Batts can have additional insulation added to it, or the damaged section can be completely replaced. However, damaged insulation cannot be repaired.

Can Fiberglass Insulation Be Used in All Climates?

Fiberglass insulation can be used in any climate as it is water- and flame-resistant, making it ideal for wet and rainy climates as well as dry locations that experience wildfires.

Can Fiberglass Insulation be Used in Attics?

Fiberglass insulation can be used in attics. However, because attics have more susceptibility to common disturbances, it may need to be replaced more often.

At IDI, we partner with contractors around the country to provide the best equipment and bulk materials, including wholesale fiberglass insulation. For the latest in the insulation industry, we offer individual and group training. Contact us today to see how we can help your company grow.


Have a question on anything insulation, pricing, or want to place an order? With hundreds of products and countless services, our experts will help walk you through the process of getting ready for your next project. Get in contact with our team today for help and guidance on the right products and best techniques for you and your business.