Comparing the Pros and Cons of Cellulose and Fiberglass Insulation

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Cellulose insulation costs more per square foot than fiberglass. It’s only available as blown-in insulation, which requires special equipment to blow or pour into an enclosed existing wall or open new wall cavities, unfinished attic floors, and other hard-to-reach places. However, it doesn’t degrade, and its R-value doesn’t lessen in extreme cold or when it’s compressed.

Compression occurs when insulation is improperly installed, has boxes or heavy items stored on it (think about all the junk stored in your attic), it gets walked over regularly, it gets moisture damage, or it has compressed upon itself due to age and placement.

Fiberglass Insulation

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Fiberglass insulation is the more affordable option, but its R-value decreases in extreme cold or with rapid temperature fluctuations. You’ll typically see fiberglass insulation in loose-fill form or blanket (batt) insulation, which is easily fitted between studs, joists, and beams. It’s a solid, cost-effective choice but isn’t considered environmentally friendly. Fiberglass is resistant to rot and mold but does lose R-value when compressed.

Cellulose vs. Fiberglass Insulation: Which is Better?

R-Value

Best for Resisting Flow of Heat: Cellulose

R-value is the rating that expresses how effective a material is at resisting the flow of heat. The higher the R-value, the more effective the material is as an insulator.

Both cellulose and fiberglass have similar R-values, but how they perform differs considerably, and these differences make cellulose the winner in this category.

Cost

Most Affordable: Fiberglass

While the cost isn’t the most important factor when insulating a home, it’s still a significant consideration for most. These insulation materials have similar prices for blown-in installation, which costs $1 to $1.50 per square foot. However, cellulose is only available as blown-in insulation. So, in this category, fiberglass wins as it’s also available as batting. Fiberglass batt insulation costs $0.30 to $1.50 per square foot.

Installation

Professional Installation: Tie

Both fiberglass and cellulose are reasonably easy to install, but it’s best to leave it to a local insulation pro who can offer you a product with the right density and R-value for your home. While installation isn’t difficult, installing it well is a challenge if you don’t have the right experience. Plus, if you’re installing blown-in, you’ll need to hire the necessary equipment. And, if you go with fiberglass, there are associated health risks from inhaling the tiny glass fibers.

Air Flow

Best for Controlling Airflow: Cellulose

Cellulose and fiberglass insulations will not act as airflow barriers. Instead, cellulose will slow down the flow of air, and fiberglass will trap air between its fine fibers as part of the insulation process. If it settles, thermal bridges can appear in the gaps. A thermal bridge is a space, such as in a wall cavity, where the lack of effective insulation allows hot or cold air to move freely in or out.

Environmental Friendliness

The Greener Choice: Cellulose

Installing new insulation is a great opportunity to make your home more eco-friendly. Cellulose insulation is made from a mostly recycled organic material. And, because it’s less likely to settle, there’ll be fewer thermal bridges, so it’s more effective in trapping air and limiting energy waste.

Which Insulation is Best for Your Home?

Which is Best for Cold Climates?

Cellulose insulation is the best option for cold climates because it handles temperature extremes and fluctuations more effectively than fiberglass. Once outdoor temperatures fall below freezing, fiberglass loses R-value because of the way it insulates. Fiberglass creates small air pockets, which aren’t conducive to handling the difference in interior and exterior temperatures. Cellulose insulation does not break down or lose its R-value in extreme cold, which makes it better insulation in cold climate areas.

Which is Best for Retrofitting Exterior Walls in Existing Properties?

Cellulose insulation is best for upgrading insulation in the exterior walls of old properties. Installers can blow it into wall cavities without having to remove drywall. It’s more environmentally friendly, too, particularly if you choose insulation with a high percentage of recycled material. Cellulose is designed for dense-pack situations such as retrofitting exterior walls and flows around objects and impediments, such as wiring or beams inside the cavities, significantly reducing the likelihood of thermal gaps.

Cellulose vs. Fiberglass vs. Foam Insulation

If you waste a lot of energy to keep your house comfortably cool or warm, then you’ve got an air leakage problem. Fiberglass and cellulose are ineffective at mitigating drafts and cold spots because they do not perform as airflow barriers.

However, foam insulation does stop air leakage when it is properly installed. Foam insulation costs more than fiberglass and cellulose (about $0.44 to $1.50 per board) but does help to improve a home’s carbon footprint by reducing heat transfer and energy waste. Whether you’re insulating an attic or wall cavities, foam insulation is a good option for energy efficiency.

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