Cellulose Insulation Facts & Do-it-Yourself Guide

Homeowners have more choices than ever when deciding on the insulation for their homes.

Plastic foams, rock wool, cellulose and even cotton insulation are readily available. Insulation materials come in many forms. They are sprayed, stapled, blown, nailed or simply laid in place.

The choices can be difficult to sort through, but cellulose insulation is one of the most energy efficient and green solutions available for insulation.

Cellulose is “green.” It’s made of 80% post-consumer recycled newsprint. The fiber is chemically treated with non-toxic borate compounds (20% by weight) to resist fire, insects and mold.

The Cellulose Insulation Manufacturers Association (CIMA) claims that insulating a 1500 ft2 house with cellulose will recycle as much newspaper as an individual will consume in 40 years.

If all new homes were insulated with cellulose this would remove 3.2 million tons of newsprint from the nation’s waste stream each year. There’s room to grow. Fewer than 10% of the homes built today use cellulose.

Cellulose Wall Insulation

Cellulose earns “green” points because it requires less energy than fiberglass to manufacture. Disciples claim 200 times less petro-energy than fiberglass. More realistically, Environmental Building News reports that fiberglass requires approximately 8 times more energy to make when adjusted to reflect energy cost per installed R-value unit.

Choosing the right insulation material is important. However, the quality of the installation is critical. Efficient insulation systems need thoughtful preparation.

Armed with a trusty caulk gun and spray container of insulating foam, seal all penetrations in the structural envelope prior to insulation.

Seal all gaps in the wall sheathing and framing. Fill narrowly spaced studs and headers. Seal around window, electrical, and plumbing penetrations. Once all leakage points are sealed you are ready to install the cellulose insulation.

Blown Cellulose Insulation

Blown Cellulose

Blown cellulose can be installed in new or existing structures. It is popular in retrofit applications because existing wall finishes are not removed to install the insulation. It is favored in attic applications because you can blow unrestricted depths of fiber to achieve deep coverage with very little labor.

Blown cellulose is shredded newsprint that is installed with special equipment. Construction-savvy homeowners should be able to install blown cellulose in open attics; not walls or cathedral roofs, which should be left to serious DIY homeowners or professional insulation specialists.

You can use blowing machines from rental centers and building material dealers that sell cellulose insulation. But in general, this is a job for pros.

On paper the application is simple. Dry cellulose fiber is blown through a hose into open attics or into enclosed wall, floor or cathedral-roof framing cavities.

Two people are required to run the equipment. One person feeds dry fiber into a hopper; breaking up clumps of cellulose as it is passes into the blowing system.

The hopper and blower can be located inside or outside the house. The other person operates a hose that is attached to the blower and extends to the locations where insulation will be deposited.

The ratio of air to fiber is adjustable and with some experimentation the right balance is struck. A 3-inch diameter flexible hose is typically used to blow fiber into open attics.

If an attic floor is already installed, remove some of the boards or drill holes at strategic locations to fill the floor cavities with insulation. If the floor cavities are already filled, blow an additional layer of cellulose directly over the floor sheathing to improve the level of protection. The job is dusty and wearing a mask is required.

Blowing fiber into enclosed wall and cathedral framing cavities is different. Here a smaller 1- or 2-inch diameter fill tube is attached to the end of the larger hose. The fill tube is inserted into enclosed cavities through a series of strategically placed holes.

The general idea is to drill a series of 2-inch holes horizontally across the structural surface so that the holes are centered in each framing cavity. One or more holes per framing bay are required depending on the length of the framing cavity and the applicator’s fill technique.

Filling walls and cathedral roofs from the outside is the typical practice. Pieces of siding or roofing are removed, holes drilled and insulation fill tubes inserted. Air pressure is cranked up for cavity-fill applications to provide a more densely packed injection called dense-pack cellulose.

The narrow fill tube is inserted into the holes and pushed to within a foot of the far end of the enclosed cavity as the blowing begins. When the packed insulation becomes dense enough to stall the blower, the hose is backed out a bit. The blower gears up and filling resumes.

The process is repeated until the framing cavity is filled. Then jump over to the hole(s) in the adjacent cavity. The injected fiber compacts tightly around wires, plumbing, and other penetrations providing an airtight insulating blanket with a slightly elevated R-value approaching R-4 per inch. The holes are plugged and the siding and roof covering is patched or reinstalled when the blowing is completed.

Cellulose can be blown into wall or cathedral roof cavities from the inside as well. Remove interior trim, drill – or simply drill holes through the interior drywall surface – and blow.

Replace trim and patch the holes after the cavities are filled. In new construction, walls must be enclosed with fiber-reinforced plastic sheeting or drywall before cellulose can be blown into the framing. The plastic sheeting doubles as a vapor barrier. Choose whichever strategy makes the most sense for your situation.

If you have a home that was insulated years ago with inadequate levels of insulation, you are not out of luck. Skilled cellulose professionals can snake fill tubes into a wall already filled with fiberglass batting.

The installer fills the cavities with dense-pack cellulose in a way that crushes the existing insulation without balling up the batts, achieving a full uniform application of the new cellulose fiber. The goal on any application is to assure complete coverage that is installed at a density that will not settle over time.

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