Good insulation lowers energy bills by trapping heat or cold air inside a building. While fiberglass insulation is easier to install and more common (used about 85% of the time), cellulose insulation is often considered more energy efficient.

Comparison chart

Cellulose Insulation versus Fiberglass Insulation comparison chart
Edit this comparison chartCellulose InsulationFiberglass Insulation
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Cellulose InsulationFiberglass Insulation
How it works Cellulose cells have natural insulating power. Traps air inside tiny glass fibers, slowing transfer of heat.
Cost Around $0.40 per square foot Around $0.40 per square foot
Air leakage Less Yes
Installation Fibers blown into gap in wall. Sheets placed in wall
Energy efficiency More efficient Less efficient
Flammability No, as heavily treated with boric acid Potentially, due to kraft paper on batts.
Extreme cold No difference Loses heat quickly
Floor insulation with blow-in recycled cellulose
Floor insulation with blow-in recycled cellulose

How it works

Cellulose insulation includes cellulose cells that have natural insulating power. It is made of shredded paper plus a fire retardant chemical known as a borate. The paper is broken down into cellular fibers that provide insulation.

Fiberglass insulation contains billions of tiny glass fibers, which contain trapped bubbles of air. These air bubbles slow the transfer of heat.

Pros and Cons

Fiberglass insulation is more common and can be installed more easily. However, it does not prevent air leakage and is potentially flammable. Fiberglass insulation loses heat quickly in extreme low temperatures.

Advantages of cellulose insulation include

The disadvantages of cellulose include:

In this video, a home inspector from central Texas gives his opinion and carefully compares the two types of insulation. It is slow but worth watching.

On the other hand, the following video is opinionated and argues in favor of cellulose insulation:

Energy efficiency

Cellulose insulation, like spray foam insulation, limits air movement. A study by the University of Colorado found that cellulose insulation reduced air leakage by 38%.

Fiberglass insulation cannot stop air from passing through it, meaning that more than 30% of heat or air conditioning can escape.

R value

A product’s r-value is its resistance to heat flow. A higher R-value prevents more heat from escaping through the insulation. Homes generally require insulation with an R-value of around 38. The R-value of cellulose insulation is approximately 3.8 per inch so you need about insulation that is about 10 inches thick to reach R-38. The R-value of fiberglass insulation is approximately 2.2 per inch so you need much thicker insulation to achieve the same R-value of 38.

Recommended levels of insulation in different parts of the U.S.


Both cellulose insulation and fiberglass insulation are low-cost and have a similar inch-for-inch price. However, as cellulose insulation often requires professional installation and specialized skills, it usually turns out to be more expensive.

Installation Process

Cellulose insulation is installed using an insulation blower. The fibers flow through a long hose and are blown or sprayed into the space. The machine can densely pack the fibers, creating an even layer of insulation that fills all gaps. It is usually installed by a professional.

Fiberglass insulation usually comes in batts or rolls. In order to be completely effective, fiberglass insulation must be cut carefully around obstacles such as power sockets. This can be incredibly time consuming. If an individual is willing to settle a less effective job, fiberglass can be easily installed without professional assistance.

Here's an informative video about overcoming 3 main problems in installing a fiber glass insulation.


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