Foamed-in-place insulation materials have become fairly popular in the commercial and residential building industry since the early 1970s. The technical data, however, can be as dizzying as high school chemistry because the benefits of the different materials are determined by more than just R-value alone. Cost, thoroughness of installation, and air and vapor retarder properties all are to be considered when selecting a foamed-in-place insulation product.
A plastic foam material consists of a gas phase dispersed in a solid plastic phase and derives its installed properties from both. The solid plastic component forms the matrix, whereas the gas phase is contained in voids or cells. It is often referred to as the blowing or foaming agent Although specific processes vary, foamed-in-place insulations start as a liquid that is sprayed through a nozzle into wall, ceiling, and floor cavities. The chemical reaction created by the mixing at the nozzle causes the material to expand while it is sprayed onto or into a wall cavity. The insulation is a cellular material with millions of tiny air-filled cells. The term cellular plastic, a synonym for plastic foam, is derived from the structure of the material.1
Foams are classified as open-cell or closed-cell. In open-cell foams, the individual cells are interconnected. These insulation materials are of low density and flexible, with a rigidity similar to that of a sponge or sponge rubber. Polyicynene, for example, uses water as a blowing agent and heat to create the open-cell structure that provides the thermal performance, and can be installed in any thickness.
In closed-cell foams, each cell (more or less spherical in shape) is completely enclosed by a thin wall or membrane of plastic. These foams comprise the high-density, rigid foams like polyurethane foam. The typical installation is only 2.5 to 3", not filling the cavity completely. Closed-cell foams also take longer to completely dry (cure), although spray polyurethane foam (SPF) typically rises and sets in between 5 and 15 seconds and is dry to the touch in less than a minute.
Foamed-in-place materials require special equipment to meter, mix, and spray into place. Installation of foamed-in-place insulation is always done by certified insulation installers. Spray-foam materials cost more than conventional blanket insulation but provide a more complete coverage and may perform as an air retarder. An approved 15-minute barrier, such as gypsum wallboard, must cover all foam materials on the inside of a building except where approved by building codes or local building code officials based on diversified fire tests specific to the application.
Foam systems provide good air leakage control, moisture control, and sound control, in addition to providing thermal insulation. In other words, many of these products in certain climates can serve as a one-step insulation, moisture/vapor barrier, and wind barrier system. The foam system can take the place of building wrap, fiberglass, polyethylene vapor barrier, tape, foam, and caulking and eliminates the labor-intensive work associated with airtightness detailing when insulating with conventional insulation products.2 Elimination of the air barrier may offset some of the additional costs.
Polyurethane foam insulation has come under scrutiny in the past two decades in the wake of growing environmental awareness. The public health concerns resulting from the use of formaldehyde in urea formaldehyde foam insulation (UFFI) may have been the catalyst for more public and scientific protests surrounding the environmental consequences of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) that are used in the blowing agents that create the foam’s insulating cells. (For a complete discussion of UFFI, see Chap. 16.)
A chlorofluorocarbon (CFC) is a compound consisting of chlorine, fluorine, and carbon. CFCs are very stable in the troposphere. They were developed in 1930 by DuPont and General Motors for use as safe refrigerant alternatives to sulfur dioxide and ammonia, which were corrosive and toxic. DuPont began selling CFCs under the trade name Freon for use in refrigerators (CFC-11) and air conditioners (CFC-12). Besides being used as refrigerants, CFCs were used as nontoxic and nonflammable blowing agents for making foam (CFC-11, CFC-12). During the early 1970s, scientists discovered that CFC molecules did not easily decompose in the lower atmosphere because of their chemical stability. Instead, they were drifting into the stratosphere and attacking the ozone layer, which shields the earth from harmful ultraviolet radiation.3 They are broken down by strong ultraviolet light in the stratosphere and release chlorine atoms that then deplete the ozone layer.4
A hydrochlorofluorocarbon (HCFC) is a compound consisting of hydrogen, chlorine, fluorine, and carbon. The HCFCs are one class of chemicals being used to replace the CFCs. They contain chlorine and thus deplete stratospheric ozone, but to a much lesser extent than CFCs.4
The initial hypothesis linking CFCs and depletion of the stratospheric ozone layer was first published in 1974. Between 1974 and 1987, scientists continued to research and understand atmospheric processes that were affecting stratospheric ozone.5
The ozone layer is the region of the stratosphere containing the bulk of atmospheric ozone that lies approximately 10 to 25 miles above the Earth’s surface. Depletion of this layer by ozone-depleting substances (ODS) will lead to higher ultraviolet radiation (UVB) levels, which in turn will cause increased skin cancers and cataracts and potential damage to some marine organisms, plants, and plastics.4
In 1987, an international team of scientists collected and analyzed evidence reportedly linking the Antarctic ozone hole to ozone – depleting chemicals. In response to this growing threat, the international community negotiated the Montreal Protocol, which led to the U. S. Congress passing the Clean Air Act Amendments of 1990. These amendments set into place restrictions on the production and consumption of ODS, a ban on nonessential products, requirements for approving the use of safe substitutes only, and a requirement for warning labels.5
A July 1992 ruling required producers of class I substances (CFCs, halons, carbon tetrachloride, and methyl chloroform) to gradually reduce their production of these chemicals and to phase them out completely as of January 1, 2000. As of 2003, there will not be any production and/or importing of HCFC-141b, the most common blowing agent of polyurethane products. An identical ban on HCFC-142b and HCFC-22 will be enforced in 2010. As of 2015, there will not be any production and/or importation of any HCFCs, except for use as refrigerants in certain equipment.
The scheduled phase-out of CFCs and HCFCs has played a role in the research and development of various spray-foam materials. (The switch by conventional polyurethane manufacturers from CFC-11 to HCFC-141b has greatly reduced the ozone-depletion impacts, but even HCFC depletes ozone to some extent.6) Polyurethane, once an industry leader, now has competition from Icynene, Air-Krete, Tripolymer Foam, and other products that have been developed without using CFCs or HCFCs for foaming agents.