Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You? -- Environmental Protection (2023)

Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You? -- Environmental Protection (1)

Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You?

As the insulation industry is taking strides toward sustainability, it's crucial to educate yourself on the eco-friendly merits and insulation credentials of each material.

  • Nov 21, 2017

Insulation greatly decreases the amount of energy we use, keeping our homes comfortable throughout the year. It’s a critical addition to protecting the environment in our daily lives. Here, we examine the three main types of insulation — fiberglass, cellulose, and foam — and weigh the pros and cons of each. We also look at some of the alternative insulation materials, including their "green" credentials compared to traditional materials.

Decode the R-values
Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You? -- Environmental Protection (2)R-values tell you how well a type of insulation prevents heat transfer. Typically, the thickness and density of the material determine the R-value. The higher the R-value, the better the material will insulate. The number is presented per inch, so an R-value of 3.1 at 12 inches would provide an overall value of R-38. The chart below offers guidelines for R-values based on where you live and what you are insulating. Whenever possible, choose the material with the highest R-value to get the most out of your insulation.

(The Regional R-Values chart is available here.)

Where to Insulate
The most vulnerable areas for heat loss in your home include the attic, outer walls, and crawl spaces. You might also consider insulating your hot water pipes to prevent freezing, or your water heaters and HVAC vent ducts to prevent energy loss. If these areas are already insulated, you can add extra layers or replace outdated materials to decrease your home's energy consumption.

Choose Your Material
Many factors will determine which type of insulation to choose, including your home’s construction and the type of insulation already in place. Here are some of the most popular options:

Fiberglass is a mineral fiber created from recycled glass, sand, and other materials. It is available in three types:

  • Blown-in. If you are insulating an attic or wall cavities, blowing the insulating material in using pneumatic equipment ensures maximum coverage. You can also apply it over existing insulation. Blown-in fiberglass has an R-value of 2.2 to 2.7 per inch.
  • Batts. Fiberglass batts and rolls are ideal for placement between framing during construction in floors, walls, attics, and ceilings. They’re denser than blown-in insulation, offering an R-value of up to 4.3 per inch.
  • Rolls. These can be precut to fit between studs and joists, making them great for attics and floors. You can also add a facing to the outward part of the material to act as a moisture barrier. Like batts, they offer an R-value of up to 4.3 per inch.

Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You? -- Environmental Protection (3)There has been some concern about the health effects of fiberglass, as the fibers can easily be inhaled. However, it is not classified as a carcinogen, and once it's installed safely behind Sheetrock and plaster, breathing it in is no longer an issue. If you're installing it yourself, be sure to wear pants, long sleeves, protective eye gear, work gloves, and a face mask to limit your exposure. Some manufacturers even offer plastic-wrapped rolls to cut down on dust during insulation and act as a vapor barrier once installed.

Additionally, manufacturers are now using as much as 30 percent recycled glass in their fiberglass and significantly reducing the number of volatile organic compounds (VOCs), such as formaldehyde, used in production. Fiberglass is increasingly becoming a greener option, and it’s one of the most affordable insulation materials available.

Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You? -- Environmental Protection (4)Cellulose is an alternative to blown-in fiberglass. It's a fiber made from around 80 to 85 percent recycled paper. Cellulose is denser than blown-in fiberglass, so it has a better R-value — about 3.2 to 3.8 per inch, however, it does settle and flatten over time, losing some of that insulating value. Because paper is flammable, cellulose insulation needs to be treated with borate and/or ammonium sulfate so that it can be used safely. Even though it’s a recycled material, the addition of chemicals counteracts some of its eco-friendly benefits.

Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You? -- Environmental Protection (5)Foam insulation comes in two forms: rigid panels and spray foam. Its R-values range from 4.0 to 6.5 per inch. Foam insulation expands, meaning it can seek out every nook and cranny that might be leaking air. When the foam seals, the R-value spikes to twice that of cellulose and fiberglass. Uniform thickness is the only way to guarantee optimal R-value. You’ll get the best results by hiring a professional to install it.

While foam insulation offers lots of insulating value, it contains polyurethane, which is a potent VOC. The EPA has stated it can cause or aggravate some respiratory problems. Keep your home well-ventilated during installation and allow the time required by the manufacturer for the VOCs to dissipate.

Alternative Options
Other insulation options could be considered "greener" than traditional materials, but it's important to weigh the eco-friendly payoff if they don't provide as much R-value.

Fiberglass, Cellulose, or Foam: Which Is the Right Insulation Material for You? -- Environmental Protection (6)An alternative to fiberglass batts and rolls is rock wool insulation (R-value 3 to 3.3 per inch). Rock wool usually contains 85 percent postindustrial recycled content, and it doesn't need additional chemicals to make it fire retardant.

Cotton insulation (R-value 3.4 per inch) — sometimes sold as denim insulation — is an increasingly popular alternative for batts and rolls. Look for a manufacturer that uses 80 percent or more recycled cotton, because although cotton is a renewable resource, it takes a lot of energy to produce. Sheep wool is another green option, though it needs chemical treatment to resist fire, pests, and mold.

As the insulation industry is taking strides toward sustainability, it's crucial to educate yourself on the eco-friendly merits and insulation credentials of each material.

An award-winning freelance journalist, Jennifer Tuohy has written for newspapers, magazines, marketing, and online content for more than 15 years. She covers a variety of subjects, but her passions lie in technology, sustainability, and the intersection of the two. She writes for The Home Depot, which carries a wide selection of insulation options to help your home be as energy efficient as possible.


What is the most environmentally friendly insulation? ›

What is the most environmentally friendly home insulation material? The most environmentally friendly and sustainable home insulation options include sheep's wool, aerogel, denim, cork, polystyrene, and cellulose. You can significantly lower your carbon footprint by using these insulation options.

Which is better insulation cellulose or fiberglass? ›

At 3.5 per inch of material, the R-value of blown-in cellulose is 23% better per inch than fiberglass batts! According to research done at the Oak Ridge National Lab, fiberglass loses up to 50% of its R-value in very cold conditions; making cellulose a better choice for homes in northern climates.

Which insulation is better fiberglass or foam? ›

When it comes to which is best in the spray foam insulation vs. fiberglass debate, spray foam wins, hands down. If you're a DIY-er, you may be used to installing fiberglass insulation. But if you're looking for something that will last a lifetime, let a professional install spray foam.

What are the disadvantages of cellulose insulation? ›

Disadvantages of Cellulose

It requires specialized equipment to install, so it's less DIY-friendly than its batt insulation counterparts. It's prone to settling and compression, which can decrease its R-value.

Is foam insulation better for the environment? ›

A key differentiator that makes spray foam insulation more environmentally friendly than other types of insulation is that it is incredibly energy efficient.

What is the healthiest insulation? ›

Real Wool, Mineral Wool, and Fiberglass Blown-In

Mineral wool and real wool blown-in are less common but are healthier choices.

Do mice like cellulose insulation? ›

Rodents generally are not drawn to cellulose insulation, either. This is because it's loose and tends to fall in on itself. It's not ideal for burrowing and building a nest. You can pretty easily install cellulose yourself, but you have to rent a special machine to blow it into the walls of your attic.

Should I replace cellulose insulation? ›

Because it is made primarily of recycled materials, however, cellulose insulation does degrade over time. The typical lifespan is 20 to 30 years, with degradation beginning as early as 15 years after installation. As with other types of insulation, severe weather or outside interference can reduce the lifespan.

What is the best insulation on the market? ›

Closed-cell foam is the most effective, with an insulation value of around R-6.2 per inch of thickness. Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture. Open-cell foam insulation value is around R-3.7 per inch of thickness.

What is the downside to foam insulation? ›

On the downside, spray foam insulation comes at a price that is considerably more expensive than fiberglass. Often times, spray foam is triple the price of fiberglass and sometimes it can be more. Applying spray foam insulation is also something that is not advised to do by yourself unless it is a very small job.

Can mold grow on spray foam insulation? ›

As a product, spray foam insulation does not attract mold. And unlike wood or metal, spray foam does not rot, rust or deteriorate. This means that an area properly sprayed with foam insulation will never become a food source or a hospitable environment for a mold colony.

What are the disadvantages of fiberglass insulation? ›

  • Fiberglass insulation is not that much effective when there is a significant difference between the outside temperature & inside temperature because it keeps the heat inside and becomes less effective.
  • If it becomes wet, it loses its insulation qualities, making it ineffective.
Sep 19, 2018

Why not to use cellulose insulation? ›

Cellulose insulation is heavy, and compacts any underlying insulation. Because cellulose insulation is paper, it absorbs moisture when it rains, and in areas of high humidity. Cellulose insulation degrades over time and has to be replaced. Cellulose insulation promotes the growth of mold & mildew in your attic.

Does cellulose insulation cause mold? ›

Mold growth sets in: Thanks to its chemical treatment, mold doesn't grow on cellulose insulation. However, water-soaked fibers sit right against wood studs and drywall, which are susceptible to mold growth.

Does cellulose insulation grow mold? ›

Although it is possible for mold to grow on cellulose insulation in extreme circumstances, this would only happen in conditions such as a leak or a flood. To put this another way is to say that mold will grow in cellulose insulation but only in situations where mold would be growing everywhere else as well.

Is foam insulation bad for the environment? ›

While it's true that some spray foams are better than others, all are more damaging to the environment than almost any other type of insulation. If spray foam is the best solution, consider using HFO-blown foam over the more common HFC foams.

What is the least toxic spray foam? ›

Icynene® is a non-toxic spray foam. It doesn't contain formaldehyde, HCFC, CFC or HFA so it produces no toxic emissions. And, unlike polyurethane foams, Icynene® foam cells are only filled with air.

What can I use instead of foam insulation? ›

Spray Foam Alternatives
  • Cellulose Insulation.
  • Mineral wool insulation.
  • Fiberglass batting or roll insulation.
Jan 31, 2022

What is the safest type of home insulation? ›

Compared to fiberglass insulation, any of the above options would be safer than insulating your home with tiny glass shards dipped in formaldehyde. However, the safest option of all is cellulose.

What is the most energy efficient home insulation? ›

The Five Most Efficient Insulation Materials
  • Fibreglass. Fibreglass is the most widely used insulating material these days. ...
  • Cellulose. Cellulose is made from recycled paper products and isn't just an efficient insulator, it's very environmentally friendly. ...
  • Mineral wool. ...
  • Polystyrene.
Sep 30, 2022

What insulation has highest R-value? ›

Vacuum insulated panels have the highest R-value, approximately R-45 (in U.S. units) per inch; aerogel has the next highest R-value (about R-10 to R-30 per inch), followed by polyurethane (PUR) and phenolic foam insulations with R-7 per inch.

Do termites eat cellulose insulation? ›

The answer is no—termites do not feed on cellulose insulation, and in fact, this material can actually repel termites. Cellulose insulation doesn't attract termites. It's treated with fire-retardant chemicals that insects are not drawn to.

Does cellulose insulation need a vapor barrier? ›

With Modern's Cellulose insulation, a vapor barrier is not recommended except in very cold weather or high moisture areas such as spas or pool buildings. However, many building codes do require an Air barrier or Vapor retarder to be installed. Check your local building codes for compliance.

Is cellulose insulation harmful for human body? ›

Cellulose insulation made of formaldehyde and small fibres are hazardous from environmental point of view. Individuals with preexisting skin disorders and asthma are allergic to cellulose, because of its itch inducing particles. The particles can be irritating to the eyes, skin, and lungs.

Is cellulose insulation a fire hazard? ›

Cellulose insulation

Products are largely made of newspaper, which is highly combustible. Even though it's heavily treated with fire-retardant chemicals prior to installation, it is a recognized fire hazard by the Consumer Product Safety Commission (CPSC).

Does cellulose insulation need ventilation? ›

If you have fiberglass or cellulose insulation already installed, then it is crucial that you have adequate and proper ventilation.

Does cellulose insulation rot? ›

Cellulose is non-corrosive to steel, copper and aluminum. Cellulose will not lose it's energy saving abilities over time. Cellulose will not rot, decay or mildew, and it does not support fungus or mold growth.

What is better spray foam or cellulose? ›

Spray foam is the better choice when it comes to long-term cost and thermal resistance. If you prefer using safer and eco-friendly materials that offer good sound control at an affordable price point, then you may prefer cellulose insulation.

What is the most common insulation used in homes? ›

Blanket insulation -- the most common and widely available type of insulation -- comes in the form of batts or rolls. It consists of flexible fibers, most commonly fiberglass. You also can find batts and rolls made from mineral (rock and slag) wool, plastic fibers, and natural fibers, such as cotton and sheep's wool.

What is the best insulation for warmth? ›

Fiberglass is the most common type of insulation used for residences because it is by far the best, particularly for hot climates. Here's why: Fire-retardant – Fiberglass insulation is fire-retardant, making it an ideal choice for homes in dry climates and areas prone to fire.

What type of insulation is the greenest? ›

Comprised primarily of post-consumer recycled paper, cellulose insulation products have some of the highest environmental ratings among insulation products on the market. The manufacturing process for cellulose insulation is up to 30 times less energy-intensive than making fiberglass or wool mineral insulation.

How can I insulate my house eco-friendly? ›

  1. Sheep's Wool. Sheep's wool is not only a sustainable natural resource, but it has some characteristics that make it a brilliant material for producing internal wall insulation. ...
  2. Recycled Insulation. ...
  3. Straw Bale. ...
  4. Hemp Insulation. ...
  5. Cork. ...
  6. Wood Fibre and Wool. ...
  7. Cellulose. ...
  8. Cotton.
Jan 14, 2022

Which insulation has the lowest embodied energy? ›

Blown cellulose had the lowest embodied carbon among all insulation materials analyzed. Project teams should explore the feasibility of using plant-based insulation, like blown cellulose – not only reduce embodied carbon but for its carbon-storing capacities.


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