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New and Alternative Insulation Materials and Products

Many of the thermal insulation materials and products discussed below are intended as alternatives to more commonly used types. Manufacturer and product names have been intentionally omitted unless necessary to convey an adequate description of the material.

Fiberglass: Some manufacturers now produce medium and high-density fiberglass batt insulation products that have slightly higher R-values (ft2h° F/Btu) than previous varieties. The denser products are intended for insulating areas with limited cavity space, such as cathedral ceilings.

High-density fiberglass batts for a 2 x 4 inch (51 x 102 millimeter [mm]) stud-framed wall has an R-15 value, compared to R-11 for "low density" types. A medium-density batt offers R-13 for the same space. High-density batts for a 2 x 6 inch (51 x 152 mm) frame wall offer R-21. High-density batts for an 8.5 inch (216 mm) spaces offer about R-30. R-38 for 12 inch (304 mm) spaces are available too.

One manufacturer markets an unconventional fibrous insulation product. It is a combination of two types of glass that are fused together. As the two materials cool during manufacturing they form random curls of the material. This makes the material less irritating and possibly safer to work with and it requires no chemical binder to hold the batts together. It also comes in a perforated plastic sleeve to assist in handling.

There are also several variations of loose fiberglass intended for use with insulation blowing machines. Some products claim higher recycled material content, or some other marketing theme, that can make them stand out from the competition. However, they all provide similar thermal performance.

One significant variation is the Blown-In-Blanket (BIB.) This is similar to the more common "wet-spray" cellulose in that the material is mixed with a latex adhesive, misted with water to activate the glue, and blown into wall stud cavities. Tests have shown that walls insulated with a BIB system are significantly better filled than with other forms of fiberglass insulation, such as batts.

  • Mineral Wool: The term "mineral wool" refers to three types of insulation that are basically the same:
  • "glass wool," or "fiberglass," made from recycled glass;

  • "Rockwool," made from basalt, an igneous rock; and

  • "slag wool," made from steel-mill slag.

Most mineral wool made in the United States is actually slag wool. Most mineral wool is a brittle/ loose material. Mineral wool does not use additional chemicals to make it fire resistant.

Recently, a Canadian company began producing a softer, batt type mineral product. This batting is denser, fits standard wall cavities tighter, and is somewhat less prone to air convection thermal losses. Than standard fiberglass batt products. Its thermal resistance is approximately R-3.7 per inch, which is comparable with sprayed cellulose insulation or high-density fiberglass batts.

Plastic Fiber: Plastic fiber insulation is not readily available in most areas of the U.S. This material is made of mainly recycled plastic milk bottles (polyethylene terephthalate or PET.) The fibers are then formed into batt insulation similar to high-density fiberglass, and then treated with a fire retardant. R-values vary with batt density: R-3.8 per inch at 1.0 lb./ft3 density to R-4.3 per inch at 3.0 lb./ft3 density. Plastic fiber insulation is relatively non-irritating to work with and doesn't readily burn. It does, however, melt when exposed to flame. The batts are also reportedly difficult to handle and cut with standard job-site tools.

Polyurethane Foams: All closed-cell polyurethane foam insulation made today is produced with a non-CFC (chlorofluorocarbon) gas as the blowing agent. This gas doesn't insulate as well as insulation made with a CFC gas, however it is less destructive to our planet's ozone layer. Foams made in this way have an aged R-value of R-6.5 per inch thickness. Their density is generally 2.0 lb./ft3 (32.0 kilograms per cubic meter [kg/m3]). There are also low-density open-cell polyurethane foams (0.5 lb./ft3 [8 kg/m3]). These are similar to conventional polyurethane foams, but are more flexible. Some low-density varieties use carbon dioxide (CO2) as the blowing agent.

Low-density foams are sprayed into open wall cavities and rapidly expand to seal and fill the cavity. There is at least one manufacturer who offers a slow expanding foam. This type is intended for cavities in existing construction where there is no insulation. The liquid foam expands very slowly and thus reduces the chance of damaging the wall from over-expanding. The foam is water vapor permeable, remains flexible, and is resistant to wicking of moisture. It provides good air sealing and yields about R-3.6 per inch of thickness. It is also fire resistant and will not sustain a flame upon removal of the flame source.

Soy-based polyurethane foam products are also available. These products use a spray-in-place foam derived from soy beans. The cured R-value ranges from 3.8 per inch to 7. It can be applied with the same equipment as is used for petroleum-based polyurethane foam products.

Nitrogen-based Urea-Formaldehyde (UF) Foam: Urea-Formaldehyde (UF) foam was used in residential housing during the 1970's. However, after many health related court cases due to improper installation practices, it was removed from the residential market and is now used primarily for masonry walls in commercial/industrial buildings. This type of foam insulation uses compressed air as the expanding agent. Nitrogen-based, UF foam may take several weeks to cure completely. Unlike polyurethane insulation, this product does not expand as it cures and also allows water vapor to easily pass through it. UF foam also breaks down at prolonged temperatures above 190° F (88° C) and contains no fire retardant chemicals. This insulation has an R-value of about 4.6 per inch and costs are competitive with loose-fill or poured-in insulation.

Phenolic Foam: This type of foam was somewhat popular years ago as a rigid foam board insulation. It is currently available only as a foamed-in-place insulation. It has a R-4.8 value per inch of thickness and uses air as the blowing agent. One major disadvantage of phenolic foam that it can shrink up to 2% after curing. This makes it less popular today, since there are alternatives that do not have this disadvantage.

Cementitious Foam: Air-Krete is a magnesium silicate, cementitious (cement-based) insulation that is foamed and pumped into closed cavities. The initial consistency of the foam is similar to shaving cream and after curing is similar to a thick pudding. It is easily damaged by water since it is made from minerals extracted from seawater. It is non-toxic and doesn't burn. It has an R-value of about 3.9 per inch and costs about as much as polyurethane foam.

Foaming Insulation Vehicles: These are latex-based foamed adhesives that transport an insulating material (such as fiberglass) into a cavity. After the bubbles in the foam dissipates, it leaves the encapsulated insulation uniformly distributed in the cavity and it's R-value unchanged. It is intended for enclosed building cavities. It is not widely available in the U.S. Here are typical R-values attained for three types of insulation applied in this manner:

  • Fiberglass:   R-4.0 per inch

  • Mineral Wool:  R-3.8 per inch

  • Cellulose:  R-3.7 per inch

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