When putting insulation in your home, there’s many different types of material you can choose from. Everyone knows the most common types, but did you know there are other alternatives? Read on to learn more about these products before you begin insulating your home.
Note: Manufacturer and product names have been intentionally omitted unless necessary to convey an adequate description of the material.
Glass Fiber (Fiberglass)
Some manufacturers now produce medium and high-density fiberglass batt insulation products that have slightly higher R-values (ft 2 h° F/Btu) than previous varieties. These denser products are intended for insulating areas with limited cavity space, such as cathedral ceilings.
High-density fiberglass batts for a 2x4 (51x102 millimeter) stud-framed wall have 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 2x6 (51x152 mm) frame wall offer R-21. High-density batts for an 8.5-inch (216 mm) spaces offer about R-30, but R-38 batts 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. 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, to 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.
The term "mineral wool" refers to three types of insulation that are basically the same: "glass wool," or "fiberglass," made from recycled glass, "rock wool," 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, 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 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./ft 3 density to R-4.3 per inch at 3.0 lb/ft 3 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.
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/ft 3 (32.0 kilograms per cubic meter [kg/m3]). There are also low-density, open-cell polyurethane foams (0.5 lb/ft 3 [ 8 kg/m3 ] ). These are similar to conventional polyurethane foams, but are more flexible. Some low-density varieties use carbon dioxide (CO 2 ) 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.
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.
This type of foam was somewhat popular years ago as rigid foamboard insulation, but 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 problem.
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, but 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 dissipate, it leaves the encapsulated insulation uniformly distributed in the cavity and it's R-value unchanged. It is intended for enclosed building cavities; however, t 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, and cellulose, R-3.7 per inch
Structural Insulating Panels (SIP)
Structural insulating panels (SIP) often consist of a foamboard core sheathed on one or both sides with plywood, oriented strand board (OSB), or gypsum board (drywall). The insulation is usually polystyrene or isocyanurate, but foam-straw composites are sometimes used as well. Panels range in size, but are most common in 4x8 foot to 4x10 foot (1.2x2.4 meter to 1.2x3.04 meter).
Because of their structural strength, SIPs reduce the need for structural lumber and minimize opportunities for air leaks and installation errors common with stud frame (stick-built) construction. It is also faster to build SIP wall assemblies than many other construction methods. Most comparison studies between stick-built and SIP houses show significant energy savings with the SIPs. Because these panels also reduce sound transmission, some designers use them for interior partitions too.
SIP roof panels sometimes have a nail-able layer only on one side. Its purpose is as a retrofit over an existing roof where additional insulation is desired but no attic exists under the roof deck. The insulated roof panels are also available with air channels just under the exterior sheathing for ventilated roof designs.
Insulating Concrete Forms (ICF)
An ICF system consists of interlocking foam board and, occasionally, hollow-core foam blocks. The foamboard forms are held vertical and parallel to each other by plastic or steel rods and ties. After adding the appropriate reinforcing steel rods (rebar) and poured concrete, the result is a very strong and insulated concrete wall. Such a building can be made from foundation to roofline. Some innovative builders make the roof of ICF as well.
Because of its flammability, any ICF exposed to the occupied space must be covered with an appropriate fire-resistant material. Most codes find half-inch (12.7mm) drywall acceptable. Then, the exterior of the building can be finished with anything the designer finds desirable.
Other systems use the rigid insulation board in the center of the concrete wall. These are often referred to as "tilt-wall" construction. The walls are poured in a form on a flat deck and after curing are tilted upright into position by a crane. Because the insulation board is inside the wall it reduces problems relating to fire and insect infestation.
Insulation block systems are typically hollow core polystyrene blocks that interlock to create the ICF wall system. Steel reinforcing rods are often used inside the block cavities to strengthen the wall. One draw-back of stacked block ICFs is that the foam webbing around the concrete filled cores provides easy access for insects and ground water to enter the building. To minimize these problems, some manufacturers make insecticide treated forms and often promote a waterproofing method for the foam blocks.
Concrete Block Insulations
Insulated concrete blocks take on many different shapes and compositions. The better concrete masonry units reduce the area of connecting webs as much as possible. The cores are filled with insulation—poured-in, blown-in, or foamed-in—except for those cells requiring structural steel reinforcing and concrete infill. This raises the average wall R-value.
Some block makers coat polystyrene beads with a thin film of concrete. The concrete serves to bond the polystyrene while providing limited structural integrity. Expanded polystyrene mixed with Portland cement, sand, and chemical additives is the most common group of ingredients. These make surface bonded wall assemblies with a wall R-value of R-1 per inch thickness. Polystyrene inserts placed in the block cores increase the unit thermal resistance to about R-2 per inch.
Hollow-core units made with a mix of concrete and wood chips are also available. They are installed by stacking the units without using mortar (dry-stacking). Structural stability comes from the concrete fill and appropriate rebar throughout for structural walls. One detracting point of this type is that the wood component is subject to the effects of moisture and insects.
Two varieties of solid, precast autoclaved concrete masonry units are now available in the U.S: autoclaved aerated concrete (AAC), and autoclaved cellular concrete (ACC). This class of material has been commonly used in European construction since the late 1940s. Air makes up 80% (by volume) of the material. It has ten times the insulating value of conventional concrete. The R-1.1 per inch blocks are large, light, and have a flat surface that looks like a hard, fine sponge. Mastic or a thin mortar is used to construct a wall, and then it often gets a layer of stucco as the finish. Autoclaved concrete is easily sawn, nailed, and shaped with ordinary tools. Since the material absorbs water readily, it requires protection from moisture.
Precast autoclaved cellular concrete uses fly ash instead of high-silica sand as its distinguishing component. Fly ash is a waste ash produced from burning coal in electric power plants. This ash is the material that differentiates ACC from AAC.
A wide variety of rigid insulation inserts are available to fill many critical locations in the insulated envelope of houses. Some examples are using inserts as air chutes, insulation dams, concrete block fillers, and ice dam retarders. Expanding foams efficiently seal and weatherize homes. Devices as simple as cardboard can be used to provide an insulation dam to help keep loose-fill insulating material around attic ductwork.
Several natural fibers are being analyzed for their potential insulating properties. The most notable of these include cotton, wool, hemp, and straw.
Cotton thermal insulation is no longer produced in the United States; however, you may still be able to find small quantities in some areas. Cotton-based insulation consists of recycled cotton and plastic fibers that have been treated with the same flame retardant and insect/rodent repellent as cellulose insulation. It meets the same Class I standards for fire resistance as fiberglass insulation. Cotton insulation also has thermal properties similar to fiberglass and cellulose insulation (R-3 or so per inch of thickness). Some chemically sensitive consumers feel that this type of insulation is "healthier" to use than other types, but field studies have proven that this is generally not the case. Other sources of indoor air pollution are a greater cause for concern than the type of insulation.
Wool and hemp insulation are relatively unknown in the U.S., but have been in use in other, less industrialized countries. Both products offer similar R-values to other fibrous insulation types (about R-3.5 per inch of thickness).
Straw bale construction, popular 150 years ago on the Great Plains of the United States, is receiving renewed interest. Straw bales tested by the Oak Ridge National Laboratory yielded R-values of R-2.4 to R-3.0 per inch. But at least one straw bale expert claims R-2.4 per inch is more representative of typical straw bale construction due to the many gaps between the stacked bales.
The process of fusing straw into boards without adhesives was developed in the 1930s. Panels are usually two to four inches (51-102 mm) thick and faced with heavyweight Kraft paper on each side. Although manufacturers’ claims vary, R-values realistically range from about R-1.4 to R-2 per inch. They also make effective sound-absorbing panels for interior partitions. Some manufacturers have developed SIPs from multiple-layered, compressed-straw panels.
Many types of insulation products are rapidly becoming incorporated into conventional construction. They may provide a convenient or sometimes a healthier approach to increasing the energy efficiency of a building. However, it is important to note that because some materials have been on the market for only a short time they may not be widely available, and performance and durability of some of these materials may not be well-documented. Always carefully research material characteristics to see if any are suitable for your purposes.
Conversion Factors for English (Imperial) R-values to Metric International System Units (SI)
Thermal Resistance (R)
RSI (m 2° C/W)
R (ft 2 h°F/Btu)
Insulation R/unit thickness
Note: The standard unit of measurement in the United States is the Imperial unit. To differentiate it from the metric system, the term 'SI' is used. For example, RSI refers to the R-value in International System (SI) or metric units.
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