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Loose-Fill Insulation
Types of Loose Fill Insulation | Vermiculite and Perlite | Fiberglass and Mineral Wool | Cellulose | Applications for Loose-Fill Insulation | Wall Insulation | Attic Insulation | Wet Installation | Dry InstallationQuick Facts
- Older homes may have asbestos containing vermiculite or perlite pellets
- Cellulose or fiberglass fibers are easy to install and provide better sealing than fiberglass batts which often leave gaps, lowering insulation value
- Should be installed in conjunction with air sealing
- Can be a non-invasive way of adding insulation to existing walls
- Can be added to attic insulation once air leaks have been sealed
Types of Loose-Fill Insulation
There are three main types of loose-fill insulation which can be found in houses.
- Vermiculite and Perlite: small grey or brown pellets which may contain asbestos and are no longer used but which may be found in older homes
- Fiberglass and Mineral Wool: small fibers which are blown into place and eliminate more air gaps than batt insulation; fiberglass can be made from recycled materials, but may contain formaldehyde
- Cellulose: small fibers which are blown into place and eliminate more air gaps than batt insulation; non toxic and made from recycled materials
Vermiculite and Perlite
This type of insulation is made by heating rock pellets until they pop, forming small, lightweight pellets. The pellets are installed by pouring them into open cavities and were commonly used to insulate homes before 1950. This types of insulation is no longer used because it is expensive, has a relatively low R-value per inch (R-2.4, compared to nearly R-4 for open-cell spray foam and fiberglass), and can sometimes contain asbestos (which also comes from rock). Any retrofitting efforts of homes with vermiculite or perlite insulation should take the risk of asbestos into account.
Fiberglass and Mineral Wool
Loose fill fiberglass or mineral wool can be made of recycled or new fibers. It is usually installed by using a blowing machine to blow the fibers into a cavity (such as a wall cavity) or an open space such as an attic floor. However, just like fiberglass batts, loose-fill fiberglass contains formaldehyde. Mineral wool does not contain formaldehyde.
This type of insulation is easier to install properly than fiberglass batts since it is simply blown in and doesn’t need to be cut to size, unlike batts. This also means that it tends to have a higher effective R-value than batt insulation, since it is less susceptible to leaving large gaps which lowers insulation value by allow air movement. The small fibers create somewhat of an air seal (compared to batts) by filling small gaps and cracks; this effect is increased when using a wet installation.
Manufacturers include:
Cellulose
Cellulose is generally made of recycled newspaper. It is treated only with non-toxic boric acid (with a toxicity comparable to that of table salt) making it a green building material. The boric acid makes the cellulose much more resistant to fire and to pest infestation. However, being made of paper, cellulose is more susceptible to water absorption than other forms of insulation such as fiberglass and spray foam. If the cellulose is exposed to humidity, it can absorb and trap moisture which can cause damage to surrounding wood joists. Water can also wash away the fire retardant boric acid.
Cellulose fibers are easier to install properly than fiberglass batts since it it simply blown in and doesn’t need to be cut to size, unlike batts. This also means that it tends to have a higher effective R-value than batt insulation, since it is less susceptible to leaving large gaps; large gaps lower insulation value by allow air movement. Small cellulose fibers create somewhat of an air seal (compared to batts) by filling small gaps and cracks; this effect is increased when using a wet installation.
Manufacturers include:
Applications for Loose-Fill Insulation
Although loose-fill can be used in many applications, it is most useful when used in:
There are two main installation technique for loose-fill fibers, each with its advantages and disadvantages:
Wall Insulation
Most houses lack sufficient insulation, including in their walls. Unfortunately it is more difficult to add insulation to walls than to an attic because the wall cavity is not generally accessible. Loose-fill insulation can be added to a wall by making easily repairable holes in the dry wall, instead of completely removing it as would be necessary to install batt insulation.
Attic Insulation
Once air leaks in the attic floor have been thoroughly detected and air sealed, loose-fill insulation can be blown in over existing insulation. If it is applied thickly and densely enough to cover ceiling joists and other thermal bridges (paths for heat to escape from the interior of the home), it adds insulation value as well as makes the existing insulation more effective.
Dry Installation
Blown in insulation settles a little over time, decreasing its R-value by creating air spaces which allow convective movement of heat through the wall cavity. It is important that blown insulation is installed densely enough to limit settling and loss of R-value over time.
Wet Installation
Fiberglass or cellulose fibers may also be mixed with water and adhesive as they are installed. This helps prevent settling and permits the insulation to stick to the wall and any gaps, creating a tighter seal. However, since the insulation must fully dry after installation, this method is not usually used for wall retrofits since the enclosed space will impede full drying.