Once you decide that blown-in insulation is the right choice for your attic, there is another important question to answer: fiberglass or cellulose?
Both materials are commonly used in attics, and both can improve your home’s energy efficiency when installed correctly. However, Minnesota homes face bitterly cold winters, humid summers, and major temperature swings throughout the year. Understanding how each material performs over time can help you make a more informed decision.
At Midwest Attic Solutions, we have helped homeowners throughout the Twin Cities improve their comfort and reduce energy loss with professional blown-in insulation. We use fiberglass because of its durability, moisture resistance, safety, and long-term performance.
Here is how fiberglass and cellulose compare.
What Is Blown-In Fiberglass Insulation?
Blown-in fiberglass insulation is made from fine glass fibers that are installed using specialized equipment. The loose material fills gaps and irregular spaces, creating a consistent blanket of insulation across the attic floor.
Unlike rectangular fiberglass batts, blown-in fiberglass can reach around wiring, pipes, framing, and other obstructions. This helps reduce the gaps and thin areas that can limit insulation performance.
At Midwest Attic Solutions, we install the Owens Corning® AttiCat® Expanding Blown-In Insulation System. This system provides even coverage, produces minimal dust during installation, and is designed not to settle over time.
What Is Cellulose Insulation?
Cellulose insulation is made primarily from recycled paper products treated with fire-retardant chemicals. Like fiberglass, it is blown into the attic to create a continuous layer of insulation.
Cellulose has been used successfully in homes for many years and can provide good thermal performance when installed to the proper depth. However, homeowners should understand how its weight, moisture response, settling, and material composition differ from fiberglass.
Fiberglass vs. Cellulose: Key Differences
Thermal Performance
Both fiberglass and cellulose can help an attic reach the recommended insulation level when installed correctly.
R-value measures how well insulation resists heat flow. While the two materials may offer similar initial R-values at the appropriate installed depth, long-term performance also depends on whether the insulation maintains that depth.
The Owens Corning® AttiCat® fiberglass insulation installed by Midwest Attic Solutions is designed not to settle. Cellulose can gradually settle over time, which may reduce its thickness and effective R-value unless additional insulation is added later.
Moisture Resistance
Moisture is a major concern in Minnesota attics. During the winter, warm indoor air can rise through ceiling gaps and enter the attic, where it meets cold roof surfaces. In the summer, heat and humidity can also place stress on the attic system.
Fiberglass is non-absorbent and does not retain moisture in the same way paper-based materials can. Cellulose may take on and hold moisture when exposed to ongoing humidity, condensation, or roof leaks. If it remains damp, its insulating performance may be reduced.
No insulation material can perform at its best when moisture problems are present. Proper air sealing and attic ventilation are essential for managing temperature and humidity while protecting your insulation and roof structure.
Settling
Settling occurs when insulation compresses and loses some of its original installed depth.
Cellulose is often installed at a greater initial depth to account for expected settling. If it settles more than anticipated, its effective R-value may decrease.
The AttiCat® fiberglass system we install is designed to maintain its loft and insulating performance without settling, helping provide consistent coverage over time.
Weight
Cellulose is considerably heavier than fiberglass.
Most properly constructed attics can support either material when it is installed correctly. However, fiberglass places less weight on the attic floor while still allowing the attic to reach a high insulation level.
Its lighter weight can be especially beneficial when adding insulation to an existing attic.
Fire Resistance
Both fiberglass and cellulose insulation products are manufactured to meet applicable safety standards.
Fiberglass is naturally noncombustible because it is made from glass fibers. Cellulose relies on added chemical treatments to improve its fire resistance.
Mold Resistance
Fiberglass does not provide a food source for mold. Cellulose contains recycled paper fibers, so persistent moisture may create greater concerns if the insulation remains damp.
However, mold is primarily a moisture problem rather than an insulation problem. Roof leaks, air leakage, blocked soffits, disconnected exhaust ducts, and insufficient ventilation should be corrected as part of a complete attic improvement plan.
Why Midwest Attic Solutions Uses Fiberglass
For many Minnesota homes, blown-in fiberglass provides the combination of performance and reliability we want for our customers.
Its benefits include:
- Long-term energy efficiency
- Minimal settling
- Strong moisture resistance
- Lightweight installation
- Naturally noncombustible materials
- Consistent performance over time
When paired with professional air sealing and proper attic ventilation, blown-in fiberglass can help reduce winter heat loss, improve summer comfort, and lower the workload on your heating and cooling system.
The right solution still depends on your home’s existing insulation, ventilation, air leakage, and overall attic condition. That is why every project at Midwest Attic Solutions begins with a free comprehensive 12-point attic inspection.
Our team measures the existing insulation, evaluates intake and exhaust ventilation, checks for moisture and mold concerns, inspects common air-leakage points, and uses thermal imaging to identify hidden areas of energy loss.
Is Fiberglass or Cellulose Better for Your Attic?
Both fiberglass and cellulose can be significant improvements over an under-insulated attic.
However, Midwest Attic Solutions recommends blown-in fiberglass for homeowners looking for durable, low-maintenance insulation that resists moisture, maintains its installed depth, and provides consistent performance for years to come.
The material itself is only one part of the decision. Proper installation, air sealing, ventilation, and moisture control all play an important role in how well your attic performs.
Schedule a Free Attic Inspection
Not sure what type of insulation is currently in your attic or whether you have enough?
Midwest Attic Solutions can evaluate your insulation levels, attic ventilation, air leakage, moisture conditions, and potential energy-loss areas before recommending the right solution for your home.
Learn more about our blown-in insulation services, explore available financing and rebate options, or schedule your free comprehensive attic inspection today.