Cellulose vs. Fiberglass Insulation – A Comparative Analysis

A home’s insulation is often an unsung hero, working quietly behind the scenes to keep the home’s occupants comfortable and safe from the elements. But no two heroes are created equal. When it comes to cellulose vs. fiberglass insulation, it’s a battle of performance, sustainability, and value. Below, BuildLabs, a leader in precision-built sustainable homes,  breaks down the pros and cons of each to help you choose the right champion for your home.  

What is Cellulose Insulation? 

Cellulose insulation is a fibrous material made from recycled plant materials like wood and paper and is then treated with non-toxic borate for flame resistance and protection against pests and mold. It comes in two forms: loose-fill and dense-pack.

• Loose-Fill: Lightweight and blown into open spaces like attics, it conforms to irregular surfaces, providing thorough coverage. Its loose structure makes it ideal for areas where gravity keeps it in place, such as flat or sloped attic floors.
• Dense-Pack: Installed under high pressure, it forms a tight, dense barrier that minimizes settling. This makes it highly effective in enclosed spaces like walls and ceilings, creating a solid thermal seal.

What is Fiberglass Insulation? 

Fiberglass insulation is made from fine glass fibers, typically derived from sand and recycled glass. These fibers are woven together and often bonded with a resin to create a lightweight, flexible material. It’s available in three main forms: batts, rolls, and loose-fill.

• Batts and Rolls: Pre-cut panels or long sheets of fiberglass, designed to fit snugly between wall studs, joists, and rafters. They are relatively easy to handle and install, making them a popular choice for DIY projects.
• Loose-Fill: Made of loose fiberglass particles, it’s blown into open spaces like attics using specialized equipment. It fills gaps, but is less dense than cellulose and may settle over time, potentially reducing its effectiveness. Additionally, fiberglass requires careful handling during installation to avoid irritation from the glass fibers.

Cellulose vs. Fiberglass Insulation: A Comparison

To help you choose the best insulation for your home, let’s compare cellulose and fiberglass in terms of sustainability, performance, health, and more. Remember, quality matters – even within the same material type. Always opt for high-quality products from trusted brands. The comparisons below assume top-tier options for both cellulose and fiberglass.

Sustainability

‍The material’s environmental impact, including its recycled content, energy use during production, and ability to be recycled or repurposed at the end of its lifespan.

• Cellulose: Made from up to 85% recycled materials, cellulose insulation is a sustainable choice that reduces landfill waste. Its production requires relatively less energy and the product can be recycled as fertilizer after its useful life as insulation is complete. 
• Fiberglass: Can be made from up to 50% recycled glass. However; fiberglass also relies on non-renewable resources like sand. Additionally, fiberglass manufacture is an energy-intensive process. 

Thermal Performance

‍How well the insulation keeps heat in (or out), measured by its R-value. This is an important factor as it highly influences the energy efficiency and overall comfort of a home. 

• Cellulose: Known for its higher R-value per inch, cellulose provides excellent thermal performance and air sealing, which can lead to lower energy bills.
• Fiberglass: While effective, fiberglass has a lower R-value and is more prone to air leaks, which can reduce its overall efficiency.

Health and Safety

‍Whether the material is safe to handle and live around, avoiding harmful chemicals, off-gassing, or irritants. Note that neither type of insulation acts as an air barrier, which is good as they allow air to circulate through the material. 

• Cellulose: Non-toxic and free from harmful chemicals, cellulose insulation is safe for both installers and homeowners. It also helps reduce mold growth and improves indoor air quality.
• Fiberglass: In 1994, fiberglass was classified as a possible carcinogen, but once installed and sealed behind walls, it poses no risk to home occupants. However, during installation, loose glass fibers can irritate the skin, eyes, and lungs if inhaled or touched, requiring proper protective gear.

Fire Resistance

‍No insulation is completely fireproof, but fire resistance measures how well it resists or slows flames and smoke. Both cellulose and fiberglass insulation have a Class A (or Class 1) fire rating – the highest possible – though their performance in real-world conditions may differ.

• Cellulose: Though inherently made of flammable material like newspaper and cardboard, cellulose is treated with non-toxic borates, which slow the spread of flames and smoke, making the insulation highly fire-resistant.
• Fiberglass: Fiberglass is naturally non-flammable, but it lacks the fire-retardant properties of borate. Additionally, fire tests typically exclude the craft paper backing used in batts, which can ignite if the fibers warm and melt during a fire.

Soundproofing

How effectively the material reduces noise from outside or between rooms.

• Cellulose: Its dense composition makes it an excellent sound barrier, effectively reducing noise pollution.
• Fiberglass: While it provides some soundproofing, it is less effective than cellulose due to its being less dense.

Durability

Moisture & Pest Resistance: How well the insulation manages moisture, which can lead to mold, rot, or pest issues.

• Cellulose: Treated with borates to resist rot, decay, and pests like rodents and insects. However, prolonged exposure to moisture can still lead to mold or mildew over time.
• Fiberglass: Does not rot, decay, or promote mold growth, and it is naturally resistant to pests. However, excessive moisture can cause it to compress, reducing its R-value and effectiveness over time.

Installation

‍How easy or complex it is to install, including whether professional help or specialized equipment is needed.

• Cellulose: Can be blown into walls and attics, filling gaps and voids more effectively than fiberglass. However, it typically requires professional installation for optimal performance.
• Fiberglass: Easier to install as batts or rolls, but it often leaves gaps that can compromise insulation efficiency.

Cost

‍The upfront price of the material and installation, as well as long-term savings. Costs vary depending on material quality, form (blown-in loose-fill or rolls and batts), and installation method.

• Cellulose: Typically installed as blown-in loose-fill by professionals, which, though labor-intensive, offers thorough coverage even in irregular and hard-to-reach spaces. The cost of professional installation for blown-in cellulose is often comparable to blown-in fiberglass. However, cellulose is not commonly available and cheaper DIY-friendly batts or rolls.
• Fiberglass: Available in both blown-in loose-fill and DIY-friendly batts or rolls. While blown-in fiberglass installation costs are similar to cellulose, fiberglass batts and rolls are often cheaper and easier to install yourself, making it a more budget-friendly option for DIY projects.

Lifespan

‍How long the insulation lasts before needing replacement or losing effectiveness. The lifespan of any insulation depends on proper installation, the quality of the material, and environmental conditions such as humidity, temperature fluctuations, and exposure to pests.

• Cellulose: Typically lasts 20 to 30 years. Over time, it may settle or degrade, especially if exposed to moisture, which can reduce its effectiveness. However, once cellulose is no longer effective as insulation, it can be recycled and repurposed as fertilizer, extending its useful life beyond its primary role. 
• Fiberglass: Can last 50 to 100 years, depending on exposure to environmental factors like moisture or physical damage.

Conclusion

The best insulation choice depends on your home and priorities. If sustainability, health, and thermal performance matter most, cellulose insulation emerges as a strong contender in the battle for your home’s comfort and efficiency. If cost and ease of installation are key, fiberglass may still hold its ground. By weighing these factors, you can choose the insulation that aligns with your values and home needs. Understanding the differences ensures your home is equipped with the right champion for long-term comfort, efficiency, and safety.

If cellulose insulation aligns with your goals, explore BuildLabs Organic Cellulose – a premium, eco-friendly option designed for exceptional performance and sustainability. No matter which insulation you choose, trust the experts at BuildLabs to guide your decision and ensure a seamless installation. Contact BuildLabs today to create a more comfortable, efficient, and sustainable home.