Choose cellulose if you want superior air-sealing, better energy efficiency, and high recycled content. Choose fiberglass if you need a budget-friendly, DIY-friendly option for open spaces, or are concerned about moisture.
Cellulose is generally considered better for thermal efficiency, air sealing, and eco-friendliness, while fiberglass is superior for moisture resistance, price, and DIY installation. Because "better" depends on your specific needs, compare the two materials below:
While cellulose insulation is an eco-friendly and highly effective thermal barrier, it comes with notable drawbacks. Its primary disadvantages include susceptibility to moisture damage, settling over time, heavy weight, and dust generation during installation.
The healthiest, non-toxic insulation for your home is natural sheep's wool or hemp insulation. These materials contain no chemical binders or formaldehyde, actively regulate indoor humidity to prevent mold, and do not off-gas.
Moisture Trapping
Although fiberglass does not absorb moisture, it can trap water if the insulation becomes damp. This trapped moisture can reduce the material's thermal resistance and promote mold and mildew growth, leading to potential health concerns.
Fiberglass insulation is generally not toxic or life-threatening, but it can be highly irritating. Because it is made of tiny woven glass fibers, direct contact causes severe itching and rashes, while breathing in the dust irritates your eyes, nose, throat, and lungs.
Non fiberglass insulation options include spray foam, blown-in cellulose, soy-based materials, and natural fiber batts that offer safer, more sustainable choices for your home.
This type of loose-fill insulation does not settle as much as other types and is made from recycled paper products, mainly newspaper. In terms of toxicity, cellulose insulation is considered non-toxic to humans and pets. However, it's important to address potential moisture issues.
Fiberglass particles typically stay in the lungs for a relatively short period, ranging from a few days to a few weeks. Unlike asbestos, modern fiberglass is engineered to dissolve or break down, allowing the body’s immune cells (macrophages) to digest and clear the fragments.
The Environmental Protection Agency banned spray-on asbestos insulation in 1973, certain types of pipe and block insulation in 1975 and new asbestos insulation products in 1989. In 2024, the EPA banned most uses of chrysotile asbestos products, including imports.
Yes, cellulose insulation significantly deters mice when compared to traditional materials like fiberglass. It acts as a physical and chemical barrier in a few key ways:
Yes, your lungs can get rid of fiberglass, but how effectively they do it depends on the size of the fibers and where they end up in your respiratory tract.
Additionally, old cellulose insulation may contain harmful chemicals from outdated fire retardants. Another concern is the potential for mold growth if the insulation becomes damp or wet. This can lead to poor indoor air quality, posing health risks for those living in the home.
Foam Board or Rigid Foam
They provide good thermal resistance (up to 2 times greater than most other insulating materials of the same thickness), and reduce heat conduction through structural elements, like wood and steel studs.
Cellulose insulation is a popular, eco-friendly choice, but it comes with notable drawbacks. Its primary disadvantages include susceptibility to moisture damage, long-term settling that reduces its insulating power, heavy weight that can strain older ceilings, and a high upfront cost.
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.
The best non-toxic insulation is either mineral wool or foam insulation inserts.
No, fiberglass is not as bad as asbestos. While both can cause temporary physical irritation, asbestos is a proven carcinogen that causes aggressive diseases like mesothelioma and asbestosis. Fiberglass is generally treated as a mechanical irritant and is considered significantly safer.
Yes, rockwool (mineral wool) is generally considered safer and healthier than fiberglass. Rockwool is made of natural stone and recycled slag, whereas fiberglass is spun from glass fibers. Rockwool does not contain asbestos and offers significant health, fire, and safety advantages.
No, cellulose insulation does not contain asbestos. It is a plant-based product primarily made from recycled paper materials (like old newspapers and cardboard) and treated with boric acid to make it fire and pest resistant.
Made from plant cellulose, the world's most abundant organic compound. Unlike other “biodegradable” plastics, this quickly degrades in salt water without leaving any microplastics behind. Scientists may have developed “perfect plastic”: Plant-based, fully saltwater degradable, zero microplastics.
Direct contact with fiberglass or breathing airborne dust containing fiberglass may irritate the skin, eyes, nose, and throat. The symptoms of irritation are often nonspecific, temporary, and may include itching, coughing, or wheezing.
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Mineral wool batts are a great choice when it comes to thermal performance. They beat the fiberglass batts with a 22–37% higher R-value per inch. Mineral wool wins with an R-value of up to R15 for a 3.5-inch material thickness.
No, fiberglass insulation should never be left uncovered. Why? Health Hazards: Exposed fiberglass can release fine particles and fibers into the air, which can cause respiratory irritation, skin rashes, and eye irritation. Long-term exposure can lead to more serious health problems.