Cellulose vs Fiberglass Insulation: Cost, R‑Value, and Real‑World Comfort
Picking the right insulation material is a big deal for comfort, noise, and energy bills. If you are weighing cellulose vs fiberglass insulation, you are not alone. Both can be the best insulation in the right spot, but they behave differently once they go into your home. Cellulose insulation leans eco‑friendly and dense, while fiberglass insulation brings broad availability and easy installs.
In 2025, homeowners care about cost, performance, and environmental impact. You might also care about soundproofing a bedroom, stopping heat loss in the attic, or avoiding mold growth. Some projects call for a pro install, especially when you need air sealing, dense-pack walls, or blower equipment. This guide breaks down how each type of insulation works, where it fits best, and what to expect on price, R-value, and safety so you can make a smart, comfortable choice.
What Is Cellulose vs. Fiberglass Insulation and How Do They Go In?
Cellulose insulation is made from recycled paper products, usually recycled newspaper, that are treated with fire-retardant borates. It is a loose-fill insulation material that gets blown into place. Fiberglass insulation is made from spun glass fibers, often with some recycled glass. It comes as batts for easy placement or as loose-fill fiberglass for blown-in insulation.
Both materials are common for home insulation upgrades and new builds. The right pick often depends on the space. Attic insulation responds well to blown-in coverage that blankets every corner, while new framing is a natural fit for fiberglass batts. Walls can go either way, but dense-pack cellulose in wall cavities can boost thermal performance by limiting air flow within the cavity.
Installation affects results more than most people think. Any voids or gaps drop thermal resistance and allow air infiltration. Blown-in cellulose or blown-in fiberglass can help fill odd shapes. Batts excel in simple, open bays when cut and fitted with care. For blowing or dense-pack, expect pro-grade equipment and trained installers.
Cellulose basics: recycled paper, fire-treated, blown-in, or dense-pack
Cellulose starts as recycled paper products with high recycled content. Borates are added for fire resistance and to deter pests. In attics, installers blow in loose-fill cellulose to reach the target depth and R-value. In walls, dense-pack cellulose is installed to a specific density that limits air movement and settling. It excels at filling irregular spaces and around wires, which is why it is popular in older homes and retrofit projects. Cellulose also adds a bit of sound dampening, which can make the living space quieter.
Fiberglass basics: glass fibers in batts or loose-fill
Fiberglass uses glass fibers bound into blankets called fiberglass batts or supplied as loose-fill for blowing. Batts slide between studs and joists, which makes them a common choice for new construction and straightforward attic bays. Installers place the facing side correctly based on local guidance, then trim to fit snugly without compressing. Blown-in fiberglass works like cellulose in attics, where it can blanket large areas quickly with even coverage.
Install methods compared: batts, blown-in, and dense-pack
- Batts: Great for new framing and simple bays. The risk is gaps or compression, which lowers the R-value. A careful fit is key.
- Blown-in: Both cellulose and loose-fill fiberglass work well in attics. They cover odd shapes, wires, and small voids without lots of cutting.
- Dense-pack: Cellulose is the go-to for dense-pack walls. It reduces air movement inside cavities and improves thermal performance and soundproofing. It requires professional equipment and technique.
Best places to use each in 2025: attics, walls, retrofits, and new builds
- Cellulose shines in attic top-offs and dense-pack wall retrofits. It reduces air flow in cavities and often improves soundproofing.
- Fiberglass batts fit new builds with open framing and consistent spacing. They are a practical, budget-friendly option for simple layouts.
- Blown-in fiberglass can be cost-effective for large attics when you want quick, even coverage.
- Many homeowners are shifting toward eco-friendly choices with higher recycled materials, which keeps cellulose front and center in 2025.
Cost, R-Value, Noise, and Safety: How They Compare
Both insulation types can meet building codes when installed correctly, but they reach that goal differently. Think of fiberglass as the reliable, widely available option, and cellulose as the dense blanket that cuts air movement and noise.
Cellulose insulation typically carries higher installed costs than fiberglass, especially if you go dense-pack. In return, you often get fewer voids and better sound dampening. Fiberglass batts usually win on upfront price and speed of install, which helps on large or simple projects.
On health and safety, fiberglass can irritate skin and lungs during installation, so masks, gloves, and long sleeves matter. Cellulose uses borates as a fire-retardant and to resist pests, and both materials depend on good moisture management to avoid mildew or mold growth. Neither is an air barrier on its own, so air sealing is still needed.
If you want a manufacturer’s perspective on fiberglass performance and R-values in walls, see Knauf’s overview: Cellulose vs Fiberglass Insulation: Which is Best?.
R-value per inch and real-world performance
R-value is a measure of thermal resistance. Both cellulose and fiberglass can deliver a higher R-value when you install enough depth and avoid gaps. Dense-pack cellulose often performs well in walls because it limits internal air flow and fills tiny spaces. Fiberglass batts can lose performance if they are compressed or cut poorly. In attics, code targets vary by climate zone, and total depth matters more than the material alone.
Upfront cost, lifespan, and potential rebates
Fiberglass batts are typically cheaper upfront. Blown-in fiberglass often lands in a similar range. Blown-in cellulose may cost more, and dense-pack can add labor, but coverage and sound control can improve comfort. When kept dry, both materials offer long service life. In 2025, some rebates or tax credits may be available for energy efficiency upgrades or higher R-values under current energy programs, which can offset costs.
Health, fire safety, moisture, and pests
During installation, fiberglass particles can irritate, so protective gear is smart. Cellulose is treated with borates for fire resistance and pest resistance. Both materials need proper air sealing and moisture control, since wet insulation loses insulating properties and can invite mildew. Good attic ventilation, air barriers where required, and vapor control guided by local building codes reduce risk.
Environmental impact and sustainability
Cellulose uses recycled content, often from recycled newspaper and other paper products, which keeps its environmental impact low. Fiberglass uses glass fibers and resin, with many brands adding recycled glass to improve sustainability. If eco-friendly choices matter to you, cellulose is often the greener pick. That said, modern fiberglass also offers strong performance with growing recycled content options.
FAQs: Quick Answers on Cellulose vs Fiberglass Insulation
Scott – HVAC Project Manager
Reviewed by Scott, Bryant-Certified HVAC Project Manager – 17 Years of Experience
Scott brings 17 years of HVAC experience to his role as Project Manager at Superior Service. He is Bryant Certified and specializes in designing and overseeing heating and cooling solutions that keep homes efficient and comfortable year-round. Customers appreciate Scott’s ability to guide projects smoothly from start to finish.
Contact Superior Service
Both cellulose and fiberglass can deliver strong thermal performance when installed well. Choose based on space, budget, and your goals for comfort, noise, and sustainability. If you want better soundproofing and recycled content, cellulose is a great insulation solution. If you want simple, fast installs in new framing, fiberglass batts make sense. Ready to dial in the right R-value and cut energy bills with the best insulation for your home? Get expert advice, clean installation, and local code guidance from a trusted team. For a quick quote or inspection with a satisfaction guarantee from Superior Service, call today.
"*" indicates required fields
