Choosing the right insulation material is one of the most critical decisions when improving a building’s energy efficiency and acoustic performance. Two popular options on the market today are fiberglass and cellulose insulation, each with distinct characteristics and benefits. When it comes to comparing the two, it’s important to know what sets them apart.Â
Fiberglass insulation, made from spun glass fibers, has been an industry standard choice for decades due to its affordability and widespread availability. Its familiar pink or yellow batts can be found in walls and attics across America, making it the most commonly used insulation material.
Cellulose insulation, on the other hand, represents a more environmentally conscious choice, manufactured from recycled paper products treated with fire-retardants. This sustainable insulation option has gained significant traction recently as homeowners and builders increasingly prioritize performance and environmental responsibility.
While both materials serve the fundamental purpose of insulating structures to meet local building codes, cellulose offers several distinct advantages that make it particularly attractive for modern construction and retrofitting projects.
R-Value and Thermal Efficiency
Regarding thermal performance, cellulose insulation demonstrates superior efficiency with an R-value ranging from 3.2 to 3.8 per inch, compared to fiberglass, which on average typically achieves 2.2 to 2.7 per inch.
This higher R-value means cellulose provides better insulating properties per inch, making it a more efficient choice for spaces where depth might be considered.
Air Sealing Properties
Cellulose insulation creates a superior air barrier due to its dense, compact installation method and unique material properties. Cellulose achieves an impressive density of 3.5 pounds per cubic foot, effectively sealing cracks, crevices, and voids around pipes and irregular spaces. This thorough coverage significantly reduces air infiltration, which is responsible for up to 40% of a building’s heat loss.
Fiberglass batts, while common, often struggle to provide the same level of air-sealing effectiveness. The rigid nature of fiberglass batts can create gaps around obstacles and irregular spaces, leading to air leakage pathways. Even when properly installed, fiberglass batts typically allow up to 30% more air infiltration than cellulose insulation.
This difference becomes particularly noticeable in older homes with numerous penetrations and irregular framing, where cellulose’s ability to conform to spaces provides a distinct advantage in creating a more effective thermal envelope.
Acoustical Performance
Cellulose insulation demonstrates superior sound-dampening capabilities due to its dense composition and installation method. When professionally installed, cellulose achieves exceptional noise reduction by absorbing sound waves and converting them into minimal friction energy. In field testing comparing identical wall types, cellulose insulation reduced noise by 44 NIC points compared to fiberglass batts at 40 NIC points – a difference that translates to a 60% reduction in sound power transmission.
The key to cellulose’s acoustic superiority lies in its ability to fill cavities without gaps or voids completely. While fiberglass batts can leave spaces that allow sound to travel through walls, cellulose’s dense-pack installation creates a seamless sound barrier by filling all spaces around wiring, plumbing, and irregular framing.
This comprehensive coverage is particularly effective at reducing airborne noise like voices and music, though it’s important to note that both materials have limitations when it comes to impact noise transmission through structural elements. For optimal soundproofing results, cellulose insulation should be installed to a density of approximately 3.5 pounds per cubic foot, which not only maximizes acoustic performance but also prevents settling over time.
Fire Safety
While both insulation types offer fire protection, they achieve this through different mechanisms. Fiberglass is naturally non-combustible due to its inorganic glass composition, requiring no additional fire-retardant treatments. In fact, unfaced fiberglass is accepted as a fire block in wood frames, though it’s important to note that some fiberglass facings like kraft paper or foil are combustible.
Cellulose insulation takes a different approach to fire safety through comprehensive chemical treatment. While the base material is made from recycled paper products, it undergoes extensive treatment with boron-based fire retardants that become a permanent part of the material’s structure.
In real-world fire testing at the National Research Council of Canada, cellulose-insulated walls demonstrated up to 50% better fire resistance than fiberglass-insulated assemblies. This superior performance is attributed to cellulose’s dense structure and unique characteristics:
- It restricts oxygen availability in wall cavities, helping to suppress combustion
- Forms a char layer when exposed to fire, creating a protective barrier
- Maintains structural integrity rather than melting or collapsing
- Provides occupants more evacuation time and firefighters extended response windows
While both materials meet building code requirements for fire safety, it’s worth noting that cellulose is one of the few building materials specifically treated for fire resistance, with its fire retardants maintaining effectiveness throughout the product’s lifetime.
Environmental Impact & Sustainability
Cellulose insulation stands out as the more environmentally conscious choice, containing up to 86% recycled content primarily from post-consumer paper products that would otherwise end up in landfills. This high recycled content significantly reduces waste and aligns with circular economy principles, while fiberglass typically contains only 20-30% recycled materials.
The manufacturing process for cellulose insulation is notably more energy-efficient than fiberglass production. While fiberglass requires high-temperature melting of glass and sand, consuming substantial energy and producing greenhouse gas emissions, cellulose production involves a more straightforward process of shredding paper and adding fire retardants.
In fact, the total energy requirement to produce fiberglass insulation is estimated to be 8 to 10 times greater than that of cellulose insulation. Additionally, when it comes to installation, cellulose insulation has a zero waste process. All excess material is vacuumed up and reused for other applications. With fiberglass, leaving a jobsite with zero material waste is not always possible. Cellulose is a natural insulation product that provides many sustainable benefits that fiberglass simply can’t compete with.
Mold and Moisture Control
Cellulose insulation’s approach to moisture management offers distinct advantages through its unique hygroscopic properties. When properly treated with boron-based compounds, cellulose can absorb and redistribute moisture without compromising its structural integrity or insulating properties.
This moisture management system works through capillary action, which helps draw moisture away from damp surfaces and distributes it evenly, allowing for controlled drying rather than concentrated wet spots that could lead to mold growth. Borates also act as an EPA registered fungicide, which helps add additional resistance to the growth of mold and other fungi.
Takeaways
While both fiberglass and cellulose insulation have their place in modern construction, the advantages of cellulose become clear when examining key performance metrics. From superior R-values and sound dampening to exceptional fire resistance and environmental sustainability, cellulose insulation offers compelling benefits for both new construction and retrofit projects.
For homeowners and contractors seeking a versatile insulation solution that delivers on both performance and sustainability, Nu-Wool’s premium cellulose insulation products offer the best of both worlds. Whether you’re looking for dense-packed wall cavity insulation or blown-in attic coverage, Nu-Wool’s comprehensive range of cellulose solutions provides industry-leading thermal performance, superior air sealing, and environmental responsibility – all backed by decades of expertise in insulation technology.Â
Make the smart choice for your next project by choosing an insulation that works as hard as you do to create comfortable, energy-efficient spaces that stand the test of time.
This article was contributed by Eco-Building Products, a proud partner of Nu-Wool. See their Cellulose Insulation Guide for more resources and information about this fantastic product.
