Cellulose vs Fiberglass Insulation: Which One Is Better?

Comparison Between Cellulose And Fiberglass Insulation

When homeowners or builders choose insulation, the decision has lasting effects on comfort, energy use, and utility bills. Simply put, it’s not only about filling cavities. The debate between cellulose vs fiberglass insulation is common among homeowners because both materials have distinct advantages and trade-offs.

At Pure Eco Inc., we help homeowners make informed and affordable choices that boost comfort, reduce noise, and cut energy waste year-round. In this guide, we’ll compare cellulose and fiberglass side by side, by analyzing R-value, fire and moisture behavior, durability, environmental impact, and cost. This way, you will be able to decide which best fits your home and climate.

Key Takeaway

• This comparison reveals the main performance differences between cellulose and fiberglass insulation, showing how each behaves under real-world conditions rather than just in laboratory tests.
• It explains the environmental and practical factors, including moisture exposure, fire safety, settling, and installation quality, that have the greatest impact on efficiency and longevity.
• Readers will see where cellulose offers advantages, particularly in older or drafty homes that benefit from its density, and where fiberglass performs best, especially in dry climates or when cost and effectiveness matter most.
• The guide helps identify which insulation type suits specific building designs, ages, and regional climates, offering a clear framework for decision-making.
• Finally, it outlines the trade-offs in cost, health, and maintenance that determine which option provides the best long-term value for your property.

Pure Eco Tip: Even the best insulation material can underperform if not installed properly. According to Energy.gov, proper air sealing and density control can boost effective R-value by up to 25%.

What Is Fiberglass Insulation?

Fiberglass insulation is made from molten glass spun into thin, flexible fibers, which are then bonded together with a resin binder to create mats, rolls, or loose-fill materials. According to Energy.gov, modern fiberglass products often contain 20–40% recycled glass, reducing the environmental impact compared to older formulations.

As one of the most widely used insulation materials in homes and commercial buildings, fiberglass is valued for its affordability, noncombustibility, and ease of installation. It insulates by trapping pockets of air between fibers, which slows down heat and sound transfer through walls, ceilings, and floors.

Fiberglass insulation comes in three main forms:

• Batts and rolls — pre-cut sheets intended for standard wall, floor, or ceiling cavities, ideal for new construction or unfinished basements.
  
• Loose-fill insulation (blown) — small, lightweight fibers installed with a blowing machine, perfect for attics and irregular cavity shapes.
  
• High-density batts — used where space is limited, such as cathedral ceilings or 2×6 wall framing.

Its biggest benefits lie in cost and accessibility. Fiberglass can be found at nearly every home improvement retailer, and according to the Insulation Institute, it remains one of the most cost-effective ways to meet building code R-values.

However, installation quality can make or break performance. Studies show that air gaps, compression, or poor fitting can reduce fiberglass’s effective R-value by up to 25%, especially around wiring or framing. The EPA’s Energy Star program also notes that air sealing combined with proper insulation can save homeowners up to 15% on heating and cooling costs.

That’s why Pure Eco Inc. combines fiberglass insulation with thermal imaging and precision air sealing. To verify that every cavity is fully insulated and free from hidden leaks. Our team ensures you get the efficiency promised on paper and feel it in every room.

Beni, Senior Technician at Pure Eco Inc:

“At Pure Eco Inc., we don’t stop at insulation. We seal, test, and verify for lasting comfort and measurable energy savings.”

What Is Cellulose Insulation?

Cellulose insulation is primarily made from recycled paper fibers, often reclaimed newspaper material, that is treated with borate compounds for resistance to fire, mold, and pests. The treatment makes the material both non-corrosive and safe, while the recycled paper products give it one of the lowest environmental footprints of any insulation on the market.

Installed using blowing machines or dense-pack techniques, cellulose can fill wall cavities, attics, and ceilings with minimal gaps, creating a tight, continuous thermal blanket. Its dense texture naturally reduces air movement, which limits drafts, improves temperature stability, and often reduces energy loss beyond its nominal R-value.

Because it conforms around wiring, pipes, and irregular framing, cellulose is particularly effective for retrofits and older homes where wall cavities may not be uniform. In attics, its loose-fill form provides deep coverage that resists convective looping, helping stabilize indoor temperatures in both winter and summer.

Installation methods include:

• Loose-fill cellulose for attics, floors, and ceilings
• Dense-pack cellulose for existing walls
• Wet-spray or stabilized cellulose for sloped or vertical surfaces

What makes cellulose stand out is its density and ability to block the air from entering, reducing drafts and convective air movement.

Pure Eco Inc. specializes in cellulose installation for energy-efficient retrofits and older homes, achieving seamless coverage that reduces air leakage and improves sound control.

Key Differences Between Cellulose and Fiberglass

Which Insulation Should You Choose?

Choose cellulose if:

You’re improving an older or drafty home, want stronger soundproofing, or value sustainable, recycled materials. Its dense structure fills irregular cavities, blocks air leaks, and provides superior acoustic comfort. For retrofits and energy-efficient upgrades, cellulose often delivers the best long-term performance.

Choose fiberglass if:

You’re working on new construction, have a limited budget, or live in a dry climate where moisture control is less of a concern. Fiberglass is widely available, DIY-friendly, and offers dependable results at a lower upfront cost when properly installed.

Note, though, regardless of the material itself, installation quality matters more. Even high-R insulation can underperform if gaps, compression, or air leaks are left untreated.

Why Homeowners Trust Pure Eco Inc.

At Pure Eco Inc., we see insulation as a means to transform homes into healthy, quiet, and efficient spaces.

We bring:

• BPI-certified installation professionals who are trained in air-sealing and thermal diagnostics.
• More than 15 years of experience, more than 15 years of effectiveness.
• Eco-conscious materials from trusted U.S. manufacturers.
• Complete attic cleaning, insulation removal, and ventilation upgrades.
• Free energy audits to pinpoint inefficiencies before work begins.

“Pure Eco’s team replaced our old fiberglass with cellulose insulation, and the difference in temperature and noise was immediate. Our energy bills dropped by 30%.” — Homeowner in Los Angeles

Are You Ready to Insulate Smarter?

Pure Eco Inc. guarantees that every insulation project is done right, code-compliant, and built to last, from start to finish, whether you choose fiberglass or cellulose insulation.

Comfort, sustainability, energy efficiency, and savings should last for decades. That’s the Pure Eco Inc. promise.

Call (877) 870-7998 for more information about our services or to request a free energy audit today.

Frequently Asked Questions

What is the main difference between cellulose and fiberglass insulation?

Cellulose is made from recycled paper treated with fire-resistant chemicals, while fiberglass is made from fine glass fibers. Cellulose is denser and eco-friendly, while fiberglass is lighter and more moisture-resistant.

How long does insulation last?

Both fiberglass and cellulose can last 20–30 years or more when kept dry. A CPUC study found both retained 97% of their R-value after 30 years.

Is cellulose safe?

Yes. It’s treated with borates for fire and pest resistance, and contains no fiberglass fibers or formaldehyde binders.

Which insulation type is better for soundproofing?

Because cellulose is a very dense material, this makes it the superior choice for acoustic insulation, especially between floors or along walls that face the street.

Can I combine both materials?

Of course. Hybrid systems consisting of cellulose in attics and fiberglass in walls are common. Pure Eco Inc. designs layered solutions to balance cost and efficiency.

Which insulation has a higher R-value?

Both materials have similar R-values, but cellulose typically offers slightly better thermal performance per inch (around R-3.6 to R-3.8) compared to fiberglass (around R-2.9 to R-3.4).

Can I install cellulose or fiberglass myself?

Fiberglass batts can be installed by homeowners, but cellulose usually requires professional blowing equipment for proper coverage and performance.

Which insulation is better for my attic?

Cellulose is often preferred for attics because it fills gaps more effectively and provides better air sealing, but fiberglass works well in dry, ventilated spaces.

Resources:

1. https://www.energy.gov/energysaver/insulation-materials#:~:text=Cellulose%20insulation%20is%20made%20from%20recycled%20paper,product%20that%20packs%20tightly%20into%20building%20cavities.
2. https://www.umass.edu/bct/publications/articles/cellulose-insulation-a-smart-choice/#:~:text=Air%20pressure%20is%20cranked%20up,the%20framing%20cavity%20is%20filled.
3. https://www.energy.gov/energysaver/insulation-materials#:~:text=High%2Ddensity%20fiberglass%20batts%20for,mm)%20spaces%20are%20also%20available.
4. https://pda.energydataweb.com/api/view/3903/CPUC%20Group%20A%202023%20Residential%20Insulation%20EUL%20Study%20Final%20Report.pdf
5. https://insulationinstitute.org/wp-content/uploads/2016/01/BI473.pdf