Last Updated: Jul 21, 2021
Almost half of the energy that homeowners use is dedicated to heating and cooling our house interiors. Unfortunately, most of that energy is thrown out the window (or doors, walls, attics, etc.) due to a lack of effective and efficient insulation. The North American Insulation Manufacturers Association (NAIMA) estimates that roughly 90 percent of US homes are under-insulated. This fact essentially means that a considerable portion of the electricity, natural gas, or heating oil we use to heat and cool our homes (and the corresponding greenhouse gas emissions) is lost through heat transfer.
You can check out Rise's complete, three-part guide to insulation here. In this article, however, we will look at the pros and cons of cellulose blown-in insulation. This insulation option is growing in popularity worldwide due to its significant insulation properties and sustainable origins.
Cellulose insulation is a type of loose insulation made from post-consumer recycled paper content. Using recycled and reclaimed building materials is critical for a sustainable home, and blown-in cellulose insulation is often sourced from shredded recycled paper, cardboard boxes, and other commonly discarded waste paper products.
In the United States alone, there are roughly 62 million newspapers printed every day. Of those, almost 44 million are discarded in landfills. This waste amounts to about half a million trees thrown away after a quick, 15-minute read during our morning coffee. If we could recycle just 10 percent of those discarded newspapers, we could save an estimated 25 million trees each year. Of course, we can recycle old newspapers into new paper products. But, alternatively, they can be shredded and turned into high-efficiency cellulose insulation products that will spend dozens of years keeping our homes protected from the outside temperatures.
The US Department of Energy says that one of the benefits of blown-in cellulose insulation is that it generally does not require an extra moisture barrier. (Note: a vapor barrier is necessary for frigid climates and, of course, where building codes require one.) This feature reduces overall installation costs, making cellulose one of the most cost-competitive options for renovating an under-insulated home. When installed at the necessary density, there is a very low possibility that cellulose insulation will settle. Settling often happens with the more commonly used fiberglass insulation, leading to reduced R-values and low-insulation areas in roofs and walls where heat transfer occurs.
Another benefit of cellulose insulation is that you can install it in different thickness applications. This characteristic allows it to fit well in tight spaces between walls, ductwork, and electrical wires.
Cellulose insulation is made from roughly 75 to 85 percent recycled paper fiber. We mentioned newspaper above, but other post-consumer recycled paper content is used as well. With e-commerce continually growing to new heights, the amount of cardboard boxes we collectively consume is staggering. According to one estimate, about 100 billion cardboard boxes are manufactured and used each year in the United States. Fortunately, around 75 percent of these boxes are recycled each year. However, the remaining 25 percent still constitutes an enormous amount of cardboard waste that often ends up in landfills, contributing vast amounts of methane emissions, contributing to global warming.
The rest of the 15 to 25 percent of cellulose insulation content consists of fire retardants such as boric acid or ammonium sulfate. Dry paper in your walls is a significant fire threat, thus requiring the use of fire retardants by code. These flame retardants are generally considered to be less toxic alternatives to the traditional PBDE flame retardants.
Among all the different insulation materials available, blown-in cellulose insulation and cotton batt insulation are insulation materials with the highest recycled content.
The most obvious environmental benefit of cellulose insulation is that homeowners can reuse and recycle materials that would otherwise end up discarded in landfills. The foundation of the circular economy is to design waste and pollution out of our economic systems. This type of economy aims to keep products and materials in use, thus reducing raw material extraction and leading to natural ecosystems' regeneration. Cellulose insulation fits into this type of economy.
Fiberglass insulation, for example, is made from plastic reinforced by tiny fibers of glass. The average fiberglass insulation product only contains between 20 and 40 percent recycled content, with many manufacturers not using any recycled content at all. Neglecting to use recycled content requires more plastic manufacturing, increasing demand for petrochemicals sourced from the oil industry. Not exactly what we need to be doing, given the current reality of global warming.
In terms of interior air quality, cellulose insulation has shallow VOC levels. A Healthy Building Science report finds that blown-in cellulose insulation has a total VOC (TVOC) level of under 101 µg/m3 and a total formaldehyde level of 12.7 µg/m3. This amount is significantly lower than what Greenguard certification requires for their low-VOC insulation products.
Another environmental advantage associated with cellulose insulation is that it is naturally biodegradable. After its helpful lifespan (typically between 20 and 30 years), cellulose insulation will naturally decompose. Whereas fiberglass insulation and foam insulations will persist in landfills for hundreds of years, cellulose insulation will quickly start the natural decomposition process.
If your cellulose insulation uses boric acid as a fire retardant, you might even be able to use your old cellulose insulation. You could put it to use as mulch around your plants, or at least as a material to add to your backyard compost pile or vermicomposting bin. Recycled newspaper content is a favorite "food source" for worms and other microorganisms that thrive in healthy soil. In addition, boron (the main element in boric acid) is needed for healthy plant growth.
The answer to this question depends on what you are looking for as a homeowner. However, cellulose insulation is generally considered much "greener" than fiberglass due to its biodegradability and recycled nature. In addition, because this type of insulation is blown-in during installation, it is often easier to install in areas with tight spaces. Cellulose insulation generally outperforms fiberglass batts in terms of efficiency. These benefits, however, do tend to come with an added price tag. Cellulose insulation has an average price of $0.90 to 1.50 per square foot, whereas fiberglass insulation costs around $0.91 per square foot. However, it is possible to find cellulose insulation products that are even cheaper than fiberglass.
In general, cellulose insulation has a higher insulation capacity (R-value) than fiberglass. The Washington State University Energy Program reports that the R-value of loose-fill cellulose is R-3.2 to 3.8 per inch. In comparison, loose-fill fiberglass only has an R-value of R-2.2 to 2.7 per inch. The actual R-value of any insulation will depend on both the depth of the insulation and its density. In almost every climate, however, cellulose insulation has a higher R-Value than fiberglass.
Cellulose insulation is much denser than other types of insulation. For this reason, it can be an excellent solution for improving your home's soundproofing. If you live near train tracks, a busy highway, or have neighbors who have parties late into the night, installing thick cellulose insulation can be a part of a broader acoustic solution for a quieter home.
Anyone who has started a campfire probably knows that some old, dry newspaper is the best thing to help get the fire roaring. Cellulose insulation, made mostly from recycled newspaper and cardboard, would be a significant fire hazard if it weren't treated with fire retardants. Fortunately, almost all building codes across the country require fire retardants to be used with cellulose insulation. The most commonly used fire retardant is Boric acid, an excellent natural and non-toxic fire retardant that can keep your home safe from fire without filling your home with dangerous, toxic fumes.
Though cellulose insulation is almost always treated with different preservatives and chemicals to improve its water resistance, continual water exposure can lead to severe problems as it is not waterproof. Fortunately, high humidity levels in homes will generally not cause any issues with this type of insulation. So, it is ideal for families in regions that experience high humidity levels.
However, a burst pipe or a leaky roof will undoubtedly cause problems with cellulose insulation. With exposure to water, settling will tend to occur, thus reducing the R-value of your insulation.
Long-term exposure to water via roof leaks or leaky pipes can allow mold growth to set in, but only when the cellulose insulation is packed tightly next to wooden beams or plywood. Cellulose insulation treatment generally means that mold will not grow on the insulation itself. However, moisture and wood are a recipe for mold growth. The settling of cellulose insulation due to a burst pipe, for example, can hold moisture for long periods, thus facilitating the growth of mold on wooden surfaces.
After several decades of keeping your home cooled and warmed efficiently, cellulose insulation will eventually need to be discarded. Unfortunately, the fire retardant chemicals in cellulose insulation (such as boric acid) mean that cellulose insulation cannot be recycled into new insulation products. However, cellulose insulation is entirely degradable. Instead of sending it to a landfill, consider mixing cellulose with a truckload of wood chips (often given for free by telephone and utility companies) and topsoil for a fantastic mulch around your garden.
Cellulose insulation is a natural insulation product that allows homeowners to incorporate recycled materials into their homes. This feature makes it an environmentally friendly option while still offering high-performance insulating properties.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.