Insulation is required by code and is a critical component of any energy efficient residential or commercial building.
Photo Credit: Greenfiber

Insulation is very important for green building, because it lessens the amount of energy needed to heat or cool the space. Oak Ridge National Laboratory claims that heating and cooling make up 50-70% of energy use in the average U.S. household, which makes insulation a crucial component of energy efficiency.

The best type of insulation will depend on a range of factors, including the type of application, budget, and space restrictions. Insulation's effectiveness is measured by the R value, which is the ability of the material to resist the transmission of heat. Therefore, higher R values will be better at reducing heat loss in cold weather.

Cellulose Insulation

Cellulose insulation is made from at least 80% recycled paper, which helps to remove paper from landfills. In fact, the Cellulose Insulation Manufacturer’s Association reports that more than 38% of U.S. landfills are made up of paper products, which makes this insulation especially helpful in alleviating environmental impacts. Plus, it has a lower carbon footprint from transportation than fiberglass or foam insulation.

Due to both its high R-value and density, celluose insulation has excellent thermal properties.

The high R-value and density of cellulose insulation provides an excellent thermal barrier, particularly in climates with either hot summers or cold winters. Cellulose insulation has been shown to perform better than fiberglass when the difference between indoor and outdoor temperatures increases to over 80°F differential (constant cellulose performance of R-19 compared to a reduction to R-10 of fiberglass insulation).

Unlike some other insulation materials, cellulose insulation provides a barrier against air infiltration by filling gaps and voids in walls, attics and floors. This is due to the fact that its installation is ‘blown-in’ (dry) or ‘moisture-added’.

Installation for this material typically a two-person operation that requires one person to feed the insulation material into a blowing machine while the other directs the hose to where the cellulose is required. The air to fiber ratio can also be adjusted to ensure complete coverage.

Moisture-added installations are typically utilized for new construction, and involves essentially the same procedure as above. The difference is that as the insulation is sprayed through the hose, a small amount of water is added. This helps adhesion with the sprayed surface and helps ensure the application leaves no gaps or spaces. The cavity is filled until the material actually extends beyond the face of the studs or rafters, and then the extra is leveled off.

Usually, professionals should install cellulose insulation, especially for moisture-added installation. In any case, protective equipment should always be worn during the process.

Cellulose insulation can contribute to LEED, not only for energy performance and thermal comfort credits, but also for recycled content and/or regional materials credits due to its responsible material sourcing.

Despite its many benefits, cellulose insulation is flammable because it’s made mostly from paper. Flame-resistant chemicals can be added to the insulation, but these usually offgas VOCs, which are harmful for indoor air quality.

Spray Foam Insulation

Spray foam insulation is relatively new, only entering the market as it is currently known in the 1970s-80s. It is less popular than other types of insulation, but it is extremely versatile and suits many applications, including attic retrofits. Since it is applied as a spray, it can fit in many different types of areas of various shapes and sizes.

It has great thermal properties compared to many other types of insulation, with R values per 5 inches of material, as well as good acoustic properties. It creates an air barrier when applied, which reduces moisture, mold and mildew.

Spray foam insulation uses both polyurethane and polyisocyanurate (a variation of polyurethane). It is sprayed into the space as a liquid, but it rapidly expands into a foam and then dries as hard plastic.

Spray foam insulation may be either open-cell or closed-cell. Open-cell allows water vapor to move through, while closed-cell does not. Closed cell insulation has higher R values than open-cell.

Spray foam insulation should be applied by an experience professional.

Fiberglass Insulation

Fiberglass insulation is made from mineral substances like silica sand and recycled glass, processed from molten state to an incombustible fibrous form. The fibers are then collected into a matte to produce fiberglass insulation. Producing fiberglass insulation requires melting the materials in a fossil fuel–burning furnace, which consumes substantial amounts of energy, often producing a greater amount of air pollution than in manufacturing processes involving other insulation types.

Although the manufacturing process is very energy intensive, the resulting fiberglass insulation product can have high recycled content through the use of recycled glass. The U.S. Environmental Protection Agency (EPA) requires that 20 percent of fiberglass materials come from recycled sources, either post-consumer or post-industrial.

Although the Occupational Safety and Health Administration requires cancer warning labels on fiberglass insulation products, if installed properly there is little danger of inhaling fibers, which are throat, eye, and skin irritants. During the installation process, fiberglass insulation installers should wear skin protective equipment because the small fibers can cut skin.

Fiberglass has a high R Value and performs very well as a building insulator, though not necessarily as well as other types of insulation, such as spray foam insulation, or even cellulose, depending on the application. As the thickness of fiberglass insulation increases, so does its R Value.

Fiberglass insulation is inert, typically ages well, and is difficult to ignite, therefore does not require fire retardants. However once it has caught fire, like other insulation types, perhaps with the exception of pre-treated cellulose, it will burn fast, hot, and could emit toxic gases.

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