Blown-In Cellulose Insulation

Blown-In Insulation Products

Four major types of loose-fill cellulose products have been developed under a variety of brand names. These are generally characterized as dry cellulose, spray applied cellulose, stabilized cellulose, and low dust cellulose. These types are used in different parts of a building and for different reasons.

Dry Cellulose (Loose Fill)

Dry cellulose is used in retrofitting old homes by blowing the cellulose into holes drilled into the tops of the walls. It can also be blown into a new wall construction by using temporary retainers or netting that is clamped in place then removed once the cellulose has reached the appropriate density. This form of application does settle as much as 20% but the stated R-value of the cellulose is accurate after settling occurs. In addition, a dense-pack option can be used to reduce settling and further minimize air gaps. Dense-pack places pressure on the cavity, and should be done by an experienced installer.

Spray Applied Cellulose (Wet-Spray)

Spray applied cellulose is used for applying cellulose to new wall construction. The differences are the addition of water to the cellulose while spraying as well as adding some kind of moisture retardant such as chlorine to prevent mold cultures. In some cases the insulation might also mix in a very small percentage of adhesive or activate a dry adhesive present in the cellulose. Wet-spray allows application without the need for a temporary retainer. In addition, wet-spray allows for an even better seal of the insulated cavity against air infiltration and eliminates settling problems. Wet-spray installation requires that the wall be allowed to dry for a minimum of 24 hours (or until maximum of 25% moisture is reached) before being covered.

Stabilized Cellulose

Stabilized cellulose is used most often in attic/roof insulation. It is applied with a very small amount of water to activate an adhesive of some kind. This reduces settling and decreases the amount of cellulose needed. This can prove advantageous at reducing the overall weight of the product on the ceiling drywall helping prevent possible sag. This application is ideal for sloped roofs and has been approved for 5:12 (41.66%) slopes.

Low-Dust Cellulose

The last major type of cellulose insulation on the market is low dust variety. Nuisance levels of dust are created during application of most types of dry insulation causing the need for simple dust masks to be worn during installation. This kind of cellulose has a small percentage of oil or similar dust dampener added. This may also be appropriate to homes where people are sensitive to newsprint or paper dust (though new dust will not be created after installation).

Advantages Of a Warm, Insulated House

Thermal Performance

The thermal performance of loose filled cellulose compares favorably to other types of insulation. The thermal conductivity of loose-fill cellulose is approximately 40 mW/m·K (an R-value of 3.8 per inch) which is about the same as or slightly better than glass wool or rock wool. This doesn’t represent the whole picture of thermal performance. Other important aspects are how well the building envelope is sealed from air infiltration, convective air flows, and thermal bridging.

Cellulose is very good at fitting around items in walls like pipes and wiring leaving few air pockets that can reduce the overall efficiency of the wall. It also seals walls from air infiltration while providing the density to limit convection. The University of Colorado School of Architecture and Planning did a study that compared two seemingly identical test structures, one with cellulose and the other with fiberglass. The cellulose structure had used 26.4% less energy to heat. It also was shown to tighten the structure more than 30%. Subsequent real world surveys have cellulose performing 20-30% better at reducing energy used for heating than fiberglass.

Long-Term Cost Savings

Cellulose’s insulation qualities “can save homeowners 20 to 50 percent on their utility bills”, which is more than enough to justify the higher cost of spray foam insulation.

Sound Insulation

Noise reduction is achieved in three ways with cellulose. The first is that cellulose completely fills cavities leaving few air pockets for sound to travel in. The second is the cellulose materials ability to trap air. The significant difference between noise reduction with cellulose and fiberglass is its density. Cellulose is approximately three times denser then fiberglass. This helps deaden the sound through walls and between floor levels.

Mold and Pest Control

The borates in cellulose insulation provide superior control against mold, insects, and pests such as rodents. Installations have shown that even several months of water-saturation and improper installation did not result in mold.

Fire Retardation

The borate treatment also gives cellulose the highest (Class I) fire safety rating. Many cellulose companies use a blend of ammonium sulfate and borate. Although ammonium sulfate is normally odorless, unexplained emission of ammonia and a resulting ammonia smell has been found in some cases.

Vapor Barrier

A vapor barrier may not be needed with cellulose insulation. For example, recent studies have shown that air movement is the primary method by which excessive moisture can accumulate in mild marine climate such as Portland, OR, USA. An insulation that fills the wall cavity completely (such as cellulose or foam) can help prevent moisture problems. Recommendations against using vapor barriers with cellulose insulation are supported by studies, even though they classify cellulose as vapor permeable.

In addition, cellulose acts to distribute moisture throughout the cavity, preventing the buildup of moisture in one area and helping to dry the moisture more quickly. Cellulose manufacturers do not recommend the installation of a vapor barrier with cellulose.

Recycled Content

Cellulose is composed of 75-85% recycled paper fiber, usually post-consumer waste newsprint. The other 15% is a fire retardant such as boric acid or ammonium sulphate. Cellulose has the highest recycled content of any insulation available. By example, fiberglass has a maximum amount of 30% recycled content.

Low-Toxicity and Environmental Impact of Raw Materials

The non-recycled components of cellulose insulation are still environmentally preferable to the raw materials of most other insulation types, which are often petrochemical-based (this includes fiberglass). Unlike fiberglass, cellulose does not use formaldehyde-based glues, which present a continuing hazard after installation due to off-gassing of formaldehyde.

Cellulose has great advantages for industrial health and worker safety. Toxicity of the raw materials of most insulation types is typically highest during manufacture or installation. Neither is an issue with cellulose.

The sole hazard for cellulose is categorization by OSHA as a dust nuisance, requiring a simple dust mask during installation. This compares very favorably to the potential NIOSH cancer risk of fiberglass

Insulation is Green

All insulation helps make buildings more energy efficient. Using cellulose insulation can contribute to obtaining LEED credits in the US Green Building Council certification program. It can earn credit in two categories: the energy and atmosphere energy performance category and the materials and resources recycled content category.

Product Safety

Cellulose insulation can be very dusty during insulation and it is recommended that a standard dust mask be worn while working. The fire retardant boric acid is about as dangerous as table salt. There is a slight concern over the off-gassing of ink from the newspapers but the material is sealed behind walls, and no studies have shown this as an issue.

The Truth About R-Values

What’s An R-Value?

R-Value is the measure of the ability of insulation material to resist heat transfer. The R-Value is determined by placing carefully prepared test specimens between two plates in a laboratory apparatus and measuring heat flow through the insulation.

R-Value is a very accurate and reliable expression of how insulation materials perform with regard to conduction of energy in a laboratory apparatus. But people don’t live in laboratories or only deal with the conduction of energy. They live in homes with real walls and ceilings, and in the real world of buildings R-Value is only one factor which determines the actual performance of insulated building assemblies.

R-Values tell only part of the story.

R-Value is a laboratory measurement that measures conduction, but it does not effectively measure the other two methods of heat transfer: convection and radiation.

The truth is… not all insulation services effectively combat all three kinds of heat transfer.

R-Value Of Cellulose Insulation

Properly installed blown cellulose insulation has a typical R-Value of 3.2 - 3.8 per inch. To achieve a desired R-value both the depth and the density of the insulation much be monitored and maintained during installation.

Unlike other insulation services, cellulose insulation effectively combats all three kinds of heat transfer. Cellulose insulation can be installed as a dense monolithic block in walls and as a blanket in the attic which significantly reduces air infiltration and acts as an effective barrier to heat transfer.

Whether your home was built a century ago or completed yesterday, it’s not too late for you to enjoy the benefits of cellulose insulation.

Covering the loose-fill fiberglass in your attic with more of the same stuff “fails to restore the lost R-Value” that naturally occurs with fiberglass. But researchers at Oak Ridge found that when you “cap” your loose-fill fiberglass with cellulose, it not only adds R-Value, it actually restores the effective R-Value that fiberglass loses during cold weather.

Many older homes were built with little or no insulation in the sidewalls. Your local trained cellulose professional can add cellulose insulation to your existing home’s sidewalls, making your home more energy-efficient — saving you money!

So R-Value is only telling 1/3 of the story of how well your home will be insulated in real-world conditions.

R-Value is important, but building scientists know that focusing on R-Value to the exclusion of all other factors can result in disappointment. It’s known, for instance, that thermal bridging can reduce the actual energy efficiency of a wall by up to 50 percent. U.S. scientists have proven that convective flows in very light density attic insulation can reduce its performance by more than 40 percent under winter conditions.

Extensive and expensive air sealing measures must be used for fiber glass buildings to approach the tightness of buildings insulated with cellulose. The extra expense may yield few benefits. In a Massachusetts survey the cellulose insulated building still consumed 32% less energy for heating than buildings insulated with fiberglass, even after extensive air sealing of all the buildings was done.

What R-Value should I have in my house?

How much cellulose insulation you should have in your home will vary based on what type of climate you live in, the construction of your home, what heating equipment you are using and what type of fuel your heating system uses. The U.S. Department of Energy has put together some recommendations for minimum R-Values based on where you live in the United States.