Attention to detail during installation is necessary in order to realize the benefits of any type of insulation. Small voids in areas that should have insulation allow for unnecessary energy losses. One US Army study found that insulation voids in just 4% of the outside area of a structure equate to a 50% loss in energy. Spray-in insulations provide an advantage in that they completely seal the area to which they are applied, in effect creating an air barrier.
Thermal bridges are paths through which heat transfer occurs in areas that are not directly insulated, such as wall studs. Steel-framed structures are especially prone to energy losses due to thermal bridging. Thermal bridges can be reduced through the introduction of thermal breaks, obstructions to these paths, which can be created by directly insulating the framing of a structure. Conventional insulating techniques insulate only in-between the stud framing of a house. Such insulating techniques leave thermal bridges throughout a wall, typically resulting in a wall that was insulated with R-13 insulation having a whole wall average insulating value of only R-10. An effective method for creating thermal breaks is the installation of rigid foam insulation board on either the interior or exterior of a structure. One manufacturer, US Building Technology, offers rigid foam board in strips that are the same width as studs, and adhere to the studs by friction. Directly insulating the framing using these strips greatly reduces the use of rigid insulation board material. Another advantage of this product is that it extends the width of the walls, allowing more insulation to be installed in-between the studs.
Rigid Foam Insulation Boards are often manufactured using chlorine-based chemicals that destroy the earth's protective ozone layer. Depending on the manufacturer and type of insulation board produced, recycled content can range from 0 to 50 percent. Until recently, chlorofluorocarbons (CFCs) were used as in manufacturing extruded polystyrene (XPS), polyurethane, polyisocyanurate, and phenolic foam insulation boards. All but one manufacturer currently make their XPS foam insulation boards with hydrochlorofluorocarbons (HCFCs). HCFCs are far less destructive to the ozone layer than CFCs, but damaging nonetheless. The severity of the ozone depletion situation has led to the recommendation to avoid both types of insulation blowing agents. Most rigid foam insulation boards are available in a wide range of thicknesses, from a fraction of an inch to several feet.
Dow Chemical now offers an XPS insulation board that does not use ozone depleting HCFCs or CFCs. This product, High Performance Underlayment, uses HFC-152a, a non-ozone-depleting substance. It is sold in fan fold sections, and is available only in 3/8 and 1/4 inch thicknesses, with R-values of 1.5 and 1, respectively. All other XPS insulation boards made in the United States by Dow use HCFCs.
Other alternatives in rigid board insulation are available that do not use CFCs or HCFCs. Expanded polystyrene (EPS), polyicynene and a few polyurethane foam insulations do not use CFCs or HCFCs (See the Engineered Sheet Products section of this Sourcebook ). EPS is made by expanding the polystyrene beads with pentane, a hydrocarbon gas that contributes to smog, but is not linked to ozone depletion or global warming. Several manufacturers now capture up to 95 percent of the pentane used in production.
In the past, the public has been misled with the idea that EPS insulation board should not be used below grade. However, a recent study performed by Canada's Institute of Research in Construction has shown EPS to retain its initial performance characteristics throughout a 2 year test in a below grade environment. The only rigid insulation board of any material type that is approved for below grade exterior use in the South is Perform Guard, manufactured by AFM R-Control Corp. Perform Guard is an EPS board that is manufactured with borates for protection against termites, which are problematic in the South. Borates, derived from the mineral boron, are natural substances that can be used as fire retardants and insect repellents in various applications.
One concern associated with XPS, polyurethane, and polyisocyanurate insulation materials is the degradation of R-value over time. The HCFCs used to make these materials slowly escapes over time, often resulting in an insulation material with a substantially lower R-value than the advertised R-value in just a few years.
Cellulose insulation is the best example of recycled material used in insulation. It is made from approximately 80 percent post-consumer recycled newspaper and treated with fire retardants and insect protection. Some chemical additives often used to treat cellulose are not thoroughly understood from an indoor air quality standpoint. Cellulose insulation that is treated with borates is preferred. Recycled newsprint that contains printer's inks can possibly outgas formaldehyde into a home. If there is any outgassing from inks, it should fall well below levels irritating most persons. However, a person with acute chemical sensitivity should be careful in selecting all building materials including insulation. Insulation made from non-inked paper is available to eliminate any outgassing from inks. Cellulose can also be bound as a wet spray and installed by a professional in open wall cavities resulting is entire walls that are effectively sealed. A long-term performance concern is possible loss of fire-retardant chemicals.
Mineral Wool insulation is making a comeback after losing its market share to fiberglass in the 1960s and 1970s. "Mineral wool" actually refers to two different materials: slag wool and rock wool. Slag wool is an industrial waste product produced from iron ore blast furnace slag. Rock wool is produced from natural rocks of basalt and diabase. Slag wool accounts for approximately 80 percent of the mineral wool insulation industry and contains 70-90 percent post-industrial recycled content. It is available as blow-on wall insulation (a starch binder is used), as loose blow-in attic insulation, and as batts. It offers very good energy performance, will not burn, and is chemically inert. Mineral wool fibers are similar to fiberglass in their ability to become airborne and be inhaled.
Fiberglass insulation is available as loose-fill and in batts. Traditional fiberglass is considered a risk by some because of the insulation fiber's ability to become airborne and be inhaled, similar to asbestos. There are also some concerns about the glues used to hold together the fiberglass. Most fiberglass insulation is produced using a phenol formaldehyde (PF) binder to hold the fibers together. Most of the binder dissipates during the manufacturing process and is captured with pollution prevention equipment. The remaining binder is slowly released into the building cavity in which the insulation is installed and may affect persons with chemical sensitivity. Several new fiberglass products have been introduced which use either an acrylic binder or no binder at all. All of the major fiberglass insulation manufacturers use at least 20 percent recycled glass cullet in their products. Newer forms of fiberglass insulation, which are fused and spun to create a 'steel wool" type of form, are considered less harmful than traditional fiberglass because of the reduced tendency to become airborne, reduced amount of glue required to hold the material together, and reduced skin irritation. Owens Corning Miraflex fiberglass is a new product introduced to address health concerns about glass fibers. The fibers are stronger and less brittle and contain no chemical binders or dyes, so there should be no offgassing. Grid-SHIELD Rx, made by Schuller International, Inc. is a new commercial fiberglass batt insulation that is produced with an acrylic binder and does not offgas formaldehyde either during manufacturer or in use. Grid-SHIELD Rx is encapsulated with polyethylene, which keeps the fibers out of the airstream, and makes it easier to install with no itching.
Spray in foam insulations that are currently available can be divided into two categories, those that use HCFCs, and those that do not. Polyisocyanurate and polyurethane foams both use HCFCs as a blowing agent. Polyicynene and Tripolymer are both spray-on insulations made of proprietary substances that do not use CFCs or HCFCs. All spray in foam insulations must be installed by a trained professional contractor.
Cementitious Foam insulation is made from magnesium oxide that is derived from sea water and blown in place with air. No CFCs or HCFCs are used. Because of its inorganic composition, it has very low VOC emissions, is totally inert, and non-combustible. Cementitious foam insulation is available commercially in one product: Air-Krete . There is one installer of this type of insulation in our region. This type of insulation is considered the most benign from an indoor air quality standpoint; it is also more costly.
Perlite insulation is made from a naturally occurring volcanic mineral and is often used as loose fill insulation in concrete block cavities. Perlite can be bound into other materials and used in sheet form. It is commonly used in commercial roofing material and can be used as an aggregate in concrete. It is non-flammable, lightweight, and chemically inert. |