Cellulose Insulation – The ABCs of Green Building Materials

Made from consumer paper products, cellulose insulation typically contains about 85 percent recycled content. Using this green building material can effectively lower the carbon footprint of your home or business property. Essentially, this is because cellulose insulation is plant cell matter that is still storing the carbon sequestered when it was alive.

Responsible management of the US forestry industry has led to a sustainable supply of planted trees, which are a highly renewable resource for both building and paper products. Combining this with the huge success enjoyed by the US recycling industry, makes cellulose insulation one of the top green building materials on the market today.

Dry loose-fill blow in cellulose insulation. Credit: Energy.gov

Cost-Effective, Easy, and Efficient Energy Savings

Adding extra insulation up in an attic is one of the easiest and most cost-effective ways to improve a home’s energy efficiency. Insulating power of up to R-49 can be achieved in an attic with additional cellulose insulation blown in. This is the best place to start when looking for an inexpensive but significant energy savings, since a building loses most of its energy through the roof.

Cellulose is treated with a borate product that is a Class I fire-retardant. The retardant can cause irritation to the lungs, but is perhaps less noxious than many other chemical flame retardants. It makes it highly undesirable to bugs and rodents, as well as resistant to mold and fire. And, although the job is dusty, installing this insulation is not difficult, even for the average homeowner.

There is virtually no waste or excess material left over from an installation job, either, because it is fully recoverable. The unused and swept up material is simply returned to the bag.


Thomas Jefferson was the First Architect to use Insulation

The word cellulose combines the French words, “cellule,” meaning “living cell,” and “glucose,” meaning sugar. Cellulose is one of the oldest insulation materials. The European Cellulose Insulation Association (ECIA) quips, “In its simplest form, insulation began when the first cavemen shielded themselves from the elements.”

Cotton, straw, hemp, corncob, sawdust, cardboard, and newspaper are all cellulosic materials that can be used for insulation. “In the United States,” reports ECIA, “the first architect who used insulation was Thomas Jefferson in his design of Monticello. And the insulation he used was cellulose.”

Thomas Jefferson's Monticello Plantation. Credit: Wikipedia commons

Thomas Jefferson was the third US president. In 1769, at age 26, Jefferson inherited 5,000 acres near Charlottesville, Virginia, and began building his famous Monticello Plantation on this beautiful estate.

Among the earliest cellulose materials used in the US for insulation was called “balsa wool,” or “balsa batt” — sawdust wrapped in paper packages. ECIA notes, “To this day, balsa wool insulation can be found in old, historic houses in the Northeast.”

Excellent Insulating Properties

Cellulose has excellent insulating properties. It is especially good at filling up walls tightly, increasing energy efficiency by reducing air pockets. It’s a good choice for many areas, such as pipes and wiring, that are difficult to insulate with other products.

While any type of insulation can improve a building’s energy efficiency, using cellulose insulation can contribute to obtaining LEED certification credits from the US Green Building Council.

Click on the image for a more comprehensive R-Value map via CIMA
Click on the image for a more comprehensive DOE R-Value map via CIMA
Zone 1: R-30 to R-49 Zone 4: R-38 to R-60 Zone 7: R-49 to R-60
Zone 2: R-30 to R-60 Zone 5: R-38 to R-60 Zone 8: R-49 to R-60
Zone 3  R-30 to R-60 Zone 6: R-49 to R-60

Cellulose Insulation has the Lowest Embodied Energy

The manufacturing process of any product requires energy. This is what is meant by “embodied energy.” More embodied energy in a product means that product is likely contributing significantly to global warming.

As an extremely energy-efficient product, cellulose insulation has far less embodied energy than foam insulation. The Cellulose Insulation Manufacturers Association (CIMA) claims that  “Foam insulations contain approximately 60 times as much embodied energy as cellulose insulation because they are made mostly from petroleum.”



The Various Types of Cellulose Insulation

Cellulose insulation is available in a wide variety of formats, including loose-fill, batt, and blanket forms. Loose-fill can be applied as a moisture-added spray into open wall framing, dry dense-packed into enclosed framing cavities, and dry blown into open attics.

Although the moisture-added method needs training and special equipment, loose-fill blown-in attic applications are possible to do it yourself with a little help and the correct equipment.

The following is a brief overview of the three application methods:

Credit: CIMA

• Dry Blown Loose-Fill Cellulose — This method requires a two-person team, with one person feeding dry, loose-fill insulation into a blowing machine. The machine blows the cellulose through a long hose controlled at the point of application by the second person. The packaging will indicate the depth of insulation that should uniformly cover the area to achieve the desired R-Value. The blower is commonly available for rent at home improvement stores, tool rental centers, and some specialty lumber yards. It may even be rented for free when purchasing the insulation at the same location. Don’t forget dust masks and goggles, as blown-in cellulose can be dusty.

Dry, Dense-Packed cellulose installation. Credit: CIMA
Dry, Dense-Packed cellulose installation. Credit: CIMA

• Dry, Dense-Packed Cellulose — This method of installation, commonly used to insulate enclosed walls, is more specialized. Additional wall hoses are needed, as well as a blowing machine producing at least 2.9 psi pressure from the hose outlet. The CIMA “does not recommend that the typical homeowner attempt a job of this scope.” This is because, as CIMA states, retrofitting cellulose into existing buildings “frequently involves work performed from ladders or staging around significant and potentially life-threatening hazards such as plumbing and the home’s electrical service and hidden wiring.”

Sprayed cellulose installation with moisture added. Credit: CIMA
Sprayed cellulose installation with moisture added. Credit: CIMA

• Sprayed (Moisture-Added) Cellulose — This method is commonly used in new construction before drywall is installed. Wall and ceiling cavities are still open, offering a convenient opportunity to spray in the cellulose. A small amount of water is added as dry cellulose is blown from the applicator hose. This activates natural starch adhesive properties in the cellulose, allowing it to adhere tightly to surfaces within the wall cavities. The spaces between the studs and against the exterior sheathing are filled in completely, leaving no gaps or voids through which air can pass. Excess material is scraped off flush with the face of the studs and recycled back into the blowing machine. The moisture typically dries within 1-2 days and then can be drywalled over.

Ready for a Cellulose Insulation Workshop?

Here’s how to do the attic yourself (Check out his smart tip for doing it solo):


And here’s how the sprayed wet cellulose is installed:


Don’t forget – watch for new posts every week in our new series, “The ABCs of Green Building Materials.” And if you’d like to give a shoutout for a project highlighting great green building materials, please add a comment below!

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