When selecting the best insulation for your home, there are some important factors you need to consider as a homeowner. One such factor is the changes in the condition of your insulation over time. 

Fiberglass insulation tends to lose its R-value over time, which is one downside most insulation methods shares. It is primarily caused by factors like the material and condition of the insulation and secondary factors like UV radiation, moisture, and maintenance issues.

In this case, how can you maintain your fiberglass insulation to last longer? Are there preventive measures to take to avoid this scenario? Is it inevitable for fiberglass insulations to lose their value over time?

This article explores some possible solutions to ensure the longevity of your fiberglass insulation. 

How Does Time Affect Fiberglass R Value?

Time takes its toll on almost everything, and your fiberglass insulation is no exception. Although there isn’t a defined number of years typical fiberglass should last as it depends on many factors, fiberglass insulation lasts for 25 to 100 years on average.

However, you are more likely to see some fiberglass batts falling after 10 to 20 years. The type of fiberglass insulation plays a part in how long it lasts.

Fiberglass Batts: Fiberglass insulation degrades as time passes, including the batts and blow-in types. The fiberglass batt insulation comes in standard sizes that must fit your desired space. However, the R-value of your insulation can be affected if the batt insulation boards do not accurately fit into this desired space. As time increases, insulation can fall out or deform, leaving cracks and leaks that decrease the overall R-value.  

Fiberglass Loose Fill: The loose fiberglass is no different, as its R-value decreases with time. It has a lower R-value when compared to batt, which is affected by the thickness and consistency of the loose coverings. Areas covered thinly will have lower R-values, affecting the entire home and the areas with higher R-values.

In general, time is a major influence on your fiberglass insulation as the slow degradation of the material and cracks negatively affect your home’s R-value.

Does Fiberglass Degrade Over Time On Its Own?

The answer to the question this section poses is yes and no

Yes! Fiberglass degrades on its own over time due to several primary and secondary factors we will discuss later, but you are assured of decades of use before replacement. 

No! Well-installed fiberglass insulation can last up to 100 years with proper use. However, there needs to be some form of maintenance during these years as the material begins to show signs of degradation as they approach 15 to 30 years.

What Other Factors Affect Fiberglass R-Value? 

Although the slow decline of the insulation material affects the R-value, other factors contribute actively to the fiberglass degrading and the corresponding reduced R-value. These factors include UV radiation, mold growth, constant human contact, rain or moisture, poor fiberglass materials, and/or poor installation and maintenance technique.


Among the many factors that affect fiberglass’s R-Value is temperature. Fiberglass insulation can lose up to 40% of its insulating capacity when outside temperatures dip below 20°F. When this occurs, your R-19 fiberglass insulation performs as if it were only R-9, costing you money in the long run.


Water or moisture is another factor affecting your fiberglass R-value. Once the insulation becomes damp due to leaks in your home’s wall, the insulating properties you enjoy get slashed into halves. A 1.5% increase in your fiberglass moisture content leads to a 50% reduction in its R-value.


High moisture content can also lead to mold growth, which leads to high repair costs and also exposes you to numerous health risks. Although fiberglass is resistant to mold growth as its sharp and ground glass can puncture any mold spores attached to it, mold still can develop on different parts of fiberglass insulation. It primarily grows and spreads from the insulating material’s facing.

Poor Installation

Poor fiberglass insulation installation can also contribute to the fiberglass’s R-Value. Installing fiberglass insulation requires you to create a substantial space between the insulating fiberglass material and the wall to avoid the growth of mildew and mold. However, certain professionals disregard this, allowing for mold and mildew growth.

Do Fiberglass Batts Degrade Slower Than Loose Fill Fiberglass?

It is difficult to ascertain whether batts fiberglass insulation lasts longer than loose-fill fiberglass as the lifespan of both kinds of insulation depends on several factors mentioned above. Some resources swear that batts fiberglass insulation degrades slower as loose-fill insulation gets compacted easily and thus has no value. In contrast, others claim that blow-in insulation is better as batts insulation loses its R-value in extreme cold and extreme temperature changes.

Since batts and loose-fill insulation are used in different home areas, the lifespan of both insulation installations largely will depend on circumstances. In areas where there is little to no human contact or disturbance, the insulation is bound to last longer in places with frequent human contact. 

So, there is no definite answer to which insulation will last better than the other.

How To Ensure Your Fiberglass Insulation Lasts Longer?

When your basement or ceiling was installed, you were promised decades of use as the home renovation professional shook your hands in a mutual agreement. Despite these promises, you must take certain actions to help your fiberglass insulation last better. 

Ensure Your Fiberglass Insulation Isn’t Compacted: One major factor that reduces fiberglass insulation’s lifespan is settling or compaction. Fiberglass insulation must always maintain its fluffy and foamy shape as originally installed to ensure maximum insulating properties. Hence, homeowners must do everything possible to ensure their fiberglass insulation does not get compacted.

Don’t Put Heavy Objects on the Fiberglass Insulation: Avoid putting heavy objects like boxes on the fiberglass insulation as they may compact. 

Watch out for Moisture Prone Places: Also, ensure you avoid moisture saturation from wall or roof leaks on the fiberglass insulation, as it can cause it to contract permanently.

Add a Protective Cover: You can seal the entire fiberglass insulation by stapling a poly-membrane sheet over it, installing a paneling, or/and working with an insulation expert.


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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