Carpeting, Indoor Air Quality, and the Environment
Our look at carpets addresses the indoor air quality (IAQ) concerns and also some broader environmental questions.
Carpeting has become ubiquitous in North America, covering more floors in homes, businesses, and institutions than all other floorcoverings combined. We love it for its softness, dirt-hiding ability, acoustic muffling, and low cost. Recently, however, carpets have come under fire for their potential role in indoor air quality problems, and they’ve been questioned for their typically short service life. Carpets have come to have two strongly contrasting images in our culture: they represent the warmth and comfort of home, but also the worst of our fossil-fuel based, disposable society.
Carpets have been gradually increasing their share of the floorcovering world for the last few decades. Once a luxury reserved for the very rich, carpets and rugs now cover 70% of the floors in the United States. In 1993 Americans purchased 5.5 square yards of carpet per person, or nearly 1.5 billion square yards total—enough to cover nearly 40% of Rhode Island. Between 1960 and 1993, carpet purchases grew by 654%, while the average cost of carpets in real dollars dropped dramatically. Cheap fossil fuels and mass production have made very inexpensive carpet possible. Our look at carpets addresses the indoor air quality (IAQ) concerns and also some broader environmental questions.
In 1988 the installation of new carpeting at EPA headquarters in Washington, D.C. led to a rash of health problems and complaints from the staff. This incident became the first highly publicized case of what has been called “sick building syndrome.” Although the cause of the problem was never verified, speculation has focused on the adhesives used to install the carpet and on a chemical by-product known as 4-PC (4-phenylcyclohexene), which is released from the carpet’s backing material.
Several years later, in 1992, Dr. Rosalind Anderson in Dedham, Massachusetts ran some tests exposing mice to air drawn from carpet samples that people suspected were making them sick. Much to everyone’s surprise, many of the samples caused severe neurotoxic reactions and even death. Moreover, it wasn't only new carpet she was testing. Some of the samples were up to twelve years old.
The Anderson Lab findings led to a flurry of activity and concern about health problems from carpets, but even now—two years after their first reports—little more is known about carpet toxicity, and some have cast serious doubts on the validity of the findings. Air quality expert Hal Levin explains that Anderson Labs is a commercial testing laboratory and not a research facility, and their methodology is not scientifically valid. The test Anderson uses, ASTM-E981, or the mouse bioassay test, was developed to determine respiratory irritation, not toxicity. The carpet samples from which the test air was drawn were heated to abnormal temperatures, and the mice were exposed to concentrations inappropriate even for the irritation test, according to Levin. Finally, the air samples to which the mice were exposed were never tested for concentrations of pollutants, even after the mice died.
EPA scientists, using their own equipment in Anderson’s laboratory, also found mice dying, according to Anthony Pollino, an aide to Congressman Bernard Sanders who witnessed the tests. Yet when the EPA researchers attempted to replicate the results in their own labs, making modifications to increase the scientific validity of the tests, their results were much less conclusive. Although there are no widely accepted explanations for Anderson’s results, much of the scientific community refuses to support her work. “ I regard her results with a high degree of skepticism,” says Dr. Alfred Hodgson of Lawrence Berkeley Laboratories (LBL). In a recent North Carolina court case concerning health effects of carpeting, the judge refused to admit Anderson’s affidavit testimony due to her lack of support from the scientific community.
After receiving several hundred complaints about possible carpet-related health effects, the U.S. Consumer Product Safety Commission (CPSC) commissioned a study by Hodgson and others at LBL of chemical emissions from carpets. Dozens of chemicals released from carpets were observed and 31 were positively identified. Emission levels of these chemicals were then compared to existing data about their health effects. As the measured emissions were considered peak values to which people would be exposed for only a few hours or days, they were compared only to known short-term health effects. No attempt was made to assess the possible effect of chronic or long-term exposure. As measured, none of the chemicals approached levels known to be hazardous upon short-term exposure.
Of the chemicals released, most notable are styrene and 4-PC, both of which come from the SB latex backing that is used on 95% of carpets. Styrene is a known toxin and suspected carcinogen. 4-PC has not been shown to be toxic, but it has a detectable odor even at levels below one part per billion and is the chemical most responsible for the distinctive smell associated with new carpets. It is also less volatile than many of the other chemicals measured, so it continues to be emitted at measurable levels for a longer time.
After the EPA headquarters incident, all the chemical companies supplying SB latex to the carpet industry joined forces to create the Styrene Butadiene Latex Manufacturers Council. The council coordinated response to public concerns about the material and sponsored several tests on the toxicity of 4-PC, none of which indicated toxic effects.
Vinyl-backed carpet tiles used in some commercial installations were also tested. They emitted a distinctly different set of chemicals, notably vinyl acetate and formaldehyde. These, too, were determined by the CPSC study to be at levels far below those likely to contribute to adverse health effects.
The CPSC study’s authors offer several explanations for the carpet-related complaints, given that they didn’t discover any notable health hazards in their tests. First, there may be interactive effects between two or more of the many chemicals involved that greatly exceed the impact of any one substance. Second, they only tested four random samples. It may be that periodic fluctuations in the manufacturing process may generate occasional batches of particularly volatile carpet with far higher emissions. IAQ expert Levin echoes this possibility as a likely scenario. Whatever the reason, health complaints associated with carpets, including severe neurological and respiratory problems, continue to surface.
One component of the problem appears to be that some people are simply much more sensitized to the effects of chemicals that have no noticeable effect on most. These individuals with Multiple Chemical Sensitivity (MCS) or Environmental Illness (EI) appear to be severely affected by conditions that most people consider normal. Advocates for this community point out that most of them can identify a specific event, when they were exposed to unusual levels of toxins, that “tipped them over the edge.” They warn that the syndrome may result from the cumulative effects of low-level chemical exposure and that everyone is potentially at risk.
In an agreement negotiated with the EPA, The Carpet and Rug Institute (CRI) began a testing and labeling program in 1992. The program was widely criticized by consumer advocates and the attorney generals of several states for failing to warn consumers about potential hazards and for inadequate testing. The program was strengthened in January 1994.
At present, each carpet line is tested four times a year for four categories of emissions: total volatile organic chemicals (VOCs), styrene, 4-PC, and formaldehyde. As no industry standards exist, somewhat arbitrary maximum emission levels, measured at 24 hours after manufacture, have been established. Products that pass the test can carry the new label (see illustration).
The Canadian Carpet Institute (CCI) recently joined with CRI in offering this labeling program. All testing for the program and most of the industry- sponsored research on carpets has been done by Air Quality Sciences, Inc., of Atlanta, Georgia.
Consumer advocates are pleased that the labeling program has been improved and that the label now includes a warning for chemically sensitive individuals. They point out, however, that the testing is still not nearly frequent enough to catch occasional bad batches of carpet and that the tests are checking for far too few substances. Improvement is occurring though. While about 20% of carpets tested failed when the testing began in 1992, “there has been a marked decrease in the emissions of the carpet now being tested,” according to CRI spokesperson Kathryn Wise, “and the percentages of those not meeting the criteria are way down.” Meanwhile, the State of Washington has proposed a program establishing maximum emissions for new carpet used in State projects that are stricter than the industry’s voluntary standards.
Adhesives & Sealants
It is not at all clear that the carpet itself is the biggest IAQ problem in new carpet installations. The carpet industry is quick to point out that carpet adhesives and seam sealants emit far more pollutants, especially in the first few weeks after installation. Carpet cushions, or pads, may be at fault as well.
In a typical commercial installation, carpet adhesive is spread over the entire surface, covering between 7 and 16 square yards per gallon, depending on the carpet type. There are many different types of adhesives, but the majority are based on SB latex, the same resin used in carpet backing. With such a large volume used, adhesives have generally been by far the largest short-term source of VOC emissions, but change is underway.
Although true solvent-based adhesives have not been used since 1970, most adhesives have continued, until recently, to use volatile solvents to emulsify, or liquefy, the bonding resin. Until 1990 VOC levels in these adhesives typically ranged from 200 to 600 grams per liter (g/l). Air quality regulations promulgated in 1990 in southern California limited VOCs in adhesives to 150 g/l. This became an accepted standard nationwide in 1991, according to Ken Knudtzon of DAP, chairman of the Floor Covering Adhesives Manufacturers Committee of the National Association of Floor Covering Distributors. The California regulations are based on VOC levels as calculated from the ingredients; actual levels measured in the adhesives tend to be slightly higher.
Since 1991 IAQ concerns have led adhesive manufacturers to find ways to reduce solvent levels even further, and some now claim a calculated VOC level of zero. They have accomplished this reduction by using heat or other processes, instead of solvents, to emulsify the resin. Several manufacturers, including the W. F. Taylor Company and the Henry Company, now sell only low-VOC products, and products with calculated levels below 50 g/l are now available from all manufacturers.
Early generations of low-VOC adhesives were harder to work with than traditional products, giving them a bad name with installers. “When the new adhesives first came out, their adhesion properties were not as good,” said Fred Williamson, president of the flooring firm CSI/CDC Corp. in New York City. Product performance is continually improving, however, as manufacturers get more experience with the new formulations. “We test some of our competitors’ products, and the ones they have now are better than the ones they had a year ago, which were better than the year before that,” Knudtzon reported. Although the low-VOC adhesives are at present more expensive to make, Knudtzon insists that the cost is no more than 5% higher to the installer.
Seam sealants have been another serious offender, releasing known toxins including 1,1,1-trichloroethane and toluene. The trichloroethane must be eliminated by 1996 to meet new government regulations, and some manufacturers have introduced new formulations with zero calculated VOCs.
Many IAQ experts suggest that the biggest problem with carpets may not be new carpet emissions at all. Once installed, a carpet acts like a filter for anything in the air, trapping particulates and pollutants. Anything carried onto a carpet on shoes or wheels can also become lodged in it. Hydrocarbons from a street or pesticides from a yard can enter the carpet matrix. Outdoors, ultraviolet sunlight eventually breaks down these chemicals, but in the carpet there is nothing to remove them. Frequent and effective vacuuming can reduce the accumulation of such contaminants, but not even hot-water extraction can eliminate them all.
VOCs can be adsorbed onto carpet fibers, stored there for an indefinite time, and eventually released back into the air. Thus, carpet that is exposed when an area is painted, for example, can become loaded with VOCs from the curing paint. These VOCs can then add to the overall pollutant level in the space for an extended period of time, long after the paint has cured and stabilized. Wool fibers appear to have an even greater capacity than synthetics for trapping VOCs, especially formaldehyde and nitrogen oxides. Some wool-industry-sponsored research suggests that such substances are chemically bonded to the wool and will not be released, but such claims haven’t been verified.
Carpets are also an ideal environment for dust mites, which consume flakes of dead human skin and leave highly allergenic excrement. Wet carpet is an ideal breeding ground for another allergen: mold and mildew. In fact, most experts recommend that any carpet that has been wet for over 24 hours be removed, because there is no effective way to eliminate the mildew growth. Some aggressive cleaning products can themselves leave toxic residues in carpet, especially if they are improperly used.
Broader Environmental Issues
The most common carpets today have nylon face fibers that are stitched into a polypropylene
The fibers are locked in place with a coating of styrene butadiene latex (SB latex, sometimes called SBR for styrene butadiene rubber) adhesive on the underside. A thick application of SB latex—as much as two pounds per square yard of carpet—is the secondary backing for most inexpensive carpets.
There are many variations: nylon face fiber may be either nylon 6, made from a single molecule type, or nylon 6,6, made from two alternating molecules. Or, the face fiber can be polypropylene, polyester (possibly including recycled PET from soda bottles) or wool. Except in the case of all-natural woven wool carpets, which are sometimes woven into a jute primary backing, polypropylene is almost always the primary backing material. Higher-end products sometimes have a fabric or polymer secondary backing, often attached to the carpet with a thin coat of SB latex. Occasionally a synthetic foam cushion is laminated directly to the back of a carpet, which can then be attached directly to a hard surface.
In residential applications, carpet is typically installed using tackless strips around the perimeter, over a cushion that is stapled to the subfloor. Commercial installations typically use adhesive, in two layers if a separate cushion is used, or one if a cushion is built into the carpet or if no cushion is needed.
Backing materials such as styrene butadiene latex are highly reactive compounds, made up of several toxic components. Because they are applied at the carpet mill in liquid form, they may not always see ideal curing conditions. “The fibers themselves are very clean,” LBL’s Hodgson said. “Almost all of the emissions are originating from the backing materials.”
4-PC is an unwanted by-product of SB latex production that occurs when manufacturing conditions and mixtures are imperfect. Even though tests have failed to turn up any evidence of serious toxicity, the industry has reduced average 4-PC levels from 250 ppm to less than 90 ppm since the public concern about 4-PC surfaced in the late 1980s.
Indoor Air Bulletin reports that some recent tests of SB latex have revealed non-detectable levels. Apparently public concern has led to better quality control.
In some carpet products small amounts of SB latex are used to attach secondary backings of polypropylene or polyurethane. Woven carpets, because they are inherently more stable than tufted carpets, also require far less adhesive backing.
PVC is controversial as a material, yet two companies with strong claims of environmental awareness are using it as backing.
Both Collins & Aikman (C&A) and Interface Flooring Systems make vinyl-backed modular carpet tiles, and C&A also makes a vinyl-backed broadloom product. Larry Moot of C&A defends the backing material as a moisture barrier, arguing that by keeping any water on the carpet surface it prevents unhealthy fungal growth. He acknowledges, however, that with modular tiles liquid can easily seep through the seems. Elizabeth Moore of Interface points out that PVC is uniquely compatible with their proprietary antimicrobial additive, Intersept®. She claims that Intersept is safer and more effective than the alternatives and, as a result, is often selected for health-care facilities.
C&A is not a member of CRI and does not participate in the carpet labelling program, but they do provide detailed emissions data on their products, which meet the stricter State of Washington standards. Moot points out that C&A’s tiles—with their built-in backing and adhesive—meet tighter standards than CRI testing requires for carpet alone. Another plus is that the tiles don’t require any seam sealants.
Milliken Carpets, another large carpet tile producer, has a proprietary backing material made of a combination of polypropylene and polyethylene.
Indoor Air Bulletin reports that Milliken’s backing emits only one-tenth the VOCs of more conventional PVC backings.
Five types of carpet cushion are commonly used today: bonded urethane, prime urethane, sponge rubber, synthetic fiber, and rubberized jute. Bonded urethane, the most common cushion for residential installations, is made by bonding together scraps of urethane cushion material from the automotive and furniture industries, and from old carpet cushion. Prime urethane is made by foaming large “loaves” of urethane and then slicing them into sheets. While the foaming used to be done with ozone depleting CFCs, hydrocarbons such as methyl butane are now commonly used.
Sponge rubber cushion is synthetic rubber material than has been vulcanized, or foamed. Off-spec or waste fibers from carpet manufacture are sometimes made into firm cushion for use where a spongy feel isn’t desirable. For all-natural carpet systems, jute fiber bonded with natural latex is available from specialty suppliers.
Carpet dyeing has traditionally been one of the most polluting stages in the carpet manufacturing process, as large amounts of contaminated water are dumped from used dye-baths. Among dyeing systems, piece dyeing of carpets is generally the most wasteful method.
Solution dyeing of nylon is the most environmentally responsible method. Pure pigments are added to the polymer solution as the fibers are extruded. Once a specialty item, solution-dyed nylon is becoming increasingly common, but it works best when making large runs of single-color carpet. Otherwise a lot of nylon can be wasted in trying to match colors on a production run, according to Jerry Dickerson of Monsanto’s research division. Some carpets are not dyed at all, but printed after assembly using textile printing techniques.
Carpets and carpet fibers are treated in many different ways to achieve desired qualities. Among these, stain-resistant fiber treatments, such as Scotchguard™, have become standard in recent years. While industry representatives insist that such treatments are safe, some consumers are convinced otherwise. Antistatic and antimicrobial treatments are also used.
Another process that has a history of environmental problems is the mothproofing of wool carpets. In Europe, where wool carpets are more common, contamination of waterways with insecticides has been a major issue. Most countries have strict regulations governing release of polluted water, so a lot of effort has gone into new approaches. Westex Carpets, in the U.K., is using one of the newest, called the Autofoam Mothproofing System.
Along with environmental concerns, mothproofing chemicals in the carpet are also a health concern for many. Kirsten Childs of the Croxton Collaborative specified wool carpet for the Audubon headquarters remodel in New York City, and considers the mothproofing a necessary evil. For homes, some prefer untreated wool carpet, but this is hard to find.
Reducing Waste in the Industry
Many mills are finding ways to improve their processes to save money and natural resources. After Ray Anderson, CEO of Interface, became committed to making his company a good environmental steward, many improvements became possible. At one plant in LaGrange, Georgia, for example, water use has been cut from 12 million gallons per month to less than 3 million. Technical Manager Lewis Engle reports that the savings were accomplished by finding ways to recycle water from one process to another before discarding it. Solid waste disposal is also a major issue. Tons of off-spec fiber and carpet scraps build up every year, leading to many waste reduction and material re-use initiatives. Carpet fiber is being tested as a reinforcement in concrete. Carpet manufacturer Shaw Industries, Inc., is building a new 120,000 ft2 research and development facility with used carpet fiber as reinforcement. Ten pounds of fiber per cubic yard of concrete was used for the floor slabs, driveways, and walls of the building. Another manufacturer, Collins & Aikman, is making plastic lumber profiles from whole used carpets.
One of the most wasteful practices in the carpet industry is the use of large binders for distributing carpet samples to designers and architects. They are bulky, non-recyclable, and quickly become obsolete as new carpet styles are introduced. Interface Flooring Systems has addressed this problem by introducing new display binders made of recycled and recyclable corrugated cardboard.
In another example of waste reduction, Hoechst Celanese recently changed the way they package bales of polyester fiber for shipment to carpet mills. Instead of wrapping the bales with polypropylene and metal straps, the entire package, including labels, is now polyester, like the fibers. It can all be returned to the company for recycling.
Carpet disposal is a major solid waste issue. Over 60% of the new carpet installed is replacing old carpet, amounting to about a billion square yards, or 3.5 billion pounds, of discarded carpet every year. With the tons of carpet piling up in landfills threatening to become another public relations problem for the industry, several carpet manufacturers and carpet fiber producers have been developing carpet recycling programs.
Nylon is a relatively expensive polymer, so many companies are working on ways to separate the nylon face fibers from the carpet backing and recycle the nylon. One strategy is to chemically break down, or depolymerize, the nylon. Nylon 6, because it is based on a single source molecule, caprolactam, lends itself more easily to depolymerization than nylon 6,6. BASF and AlliedSignal, the two main suppliers of nylon 6 to the carpet industry, are both focusing on this strategy for remanufacturing virgin-quality nylon 6.
BASF has recently announced a program for collecting any carpet made with its nylon 6 face fiber. The company will shave the face fibers off the carpet and, by depolymerization, recycle them back into carpet fiber. The carpet backing materials will likely go to incineration with energy recovery.
AlliedSignal is pursuing a different technology. Earlier this year the company signed a cooperative research agreement with the Department of Energy’s National Renewable Energy Lab (NREL) to commercialize a technology developed at NREL called selective pyrolysis. Selective pyrolysis calls for heating the carpet in a controlled manner in the absence of oxygen. Each resin breaks down into its monomer components within a specific temperature range, so by controlling the temperature and other factors, each resin can be recaptured separately. NREL claims that this process can generate caprolactam for less than half the cost of making virgin material and consumes only one-third the energy.
DuPont and Monsanto, suppliers of nylon 6,6, are moving in another direction (though DuPont claims that it has developed a technology for depolymerizing nylon 6,6, and will have a plant running by 1999 to do this).
They are focusing on methods for recycling the nylon resin for molding into car parts and other applications. As these uses don’t require as pure a nylon resin, they can be accomplished without depolymerization. In fact, Monsanto is planning to license the procedure for a new resin that includes 25% to 30% recycled plastics—a mixture of the nylon and polypropylene from carpets. The company is reportedly negotiating with recyclers for production of the resin and working with The Ford Motor Company on applications for it.
While Monsanto is not interested in collecting any used carpet until they have figured out how to make use of the material, DuPont began collecting used carpet in the northeastern states in 1990. DuPont’s Partnership for Carpet Reclamation works with major installers, taking any type of old carpet at a cost comparable to what the installer would pay for landfilling. CDC/CSI Carpets of New York City is one of DuPont’s participating installers. CDC/CSI president Fred Williamson finds the program very popular among their corporate clients: “They’re very pleased to hear that we can recycle their carpet. At no extra cost they can still know that they’re being environmentally sensitive.”
In reality, however, most of the carpet collected so far through DuPont’s Partnership for Carpet Reclamation has been burned for energy recovery. Only carpet with DuPont’s nylon 6,6 fiber and polypropylene backing is separated and recycled. DuPont is still researching ways to reuse or recycle the other types of carpet it collects.
In October 1994, the company announced a $1.2 million expansion of the program, to be operational nationwide by August 1995. Even then, however, the 500,000 pounds per month the company plans to collect will represent less than 0.2% of the used carpet discarded nationally.
Some of the same technologies for re-use of industrial waste fibers are being tested for used carpets. In addition, old carpet can sometimes be reused as geotextile—covering landfills or stabilizing soils under roadways.
Some in the carpet industry argue that, due to its high fuel value and clean-burning properties, incineration with energy recovery is an appropriate end-use for old carpet. A project at Argonne National Laboratories is even experimenting at making clean-burning synthetic “coal.” To do this, shredded carpet is carbonized by heating it to 550°F in the absence of oxygen. The end product reportedly provides more Btus per pound than natural coal and burns much more cleanly.
One company is hoping to centralize collection services and reduce duplication of efforts by handling carpet collection and processing for a range of carpet and fiber manufacturers. United Recycling, Inc., of Minneapolis, Minnesota, is using a mechanical system to separate nylon and polypropylene fibers from carpets with 90% to 95% efficiency, according to Robin Young, CEO of United’s parent company, Environmental Technologies USA, Inc. United Recycling plans to have carpet collection and processing centers operational in a number of major metropolitan areas within two years.
Finally, it should be noted that used carpet in good condition can be donated to nonprofit housing agencies and other charitable organizations. It’s safest to reuse carpet that has been well maintained, without hazardous cleaning agents. The Loading Dock in Baltimore sells or gives away 600 to 700 rolls of carpet each year, according to John Lambertson. While most of this is new carpet remnants donated by carpet distributors or retailers, 10% to 20% is used carpet and carpet tile. Hotels are a frequent source of commercial-grade carpet in good condition.
Recycled Content in Carpets
PET, or polyester, is the only carpet fiber made today with significant recycled content. Two hundred and seventy-three million pounds of polyester fibers are used in carpeting in the U.S., about half of which is recycled material.
The most visible company producing carpet from recycled PET is Image Industries, Inc. (formerly Image Carpets). Image collects and processes post-consumer PET containers for recycling. Their in-house carpet manufacturing plant affords them an outlet for the lower spec and colored recycled resin that isn’t marketable for higher-grade uses. This outlet allows Image to specialize in recycling containers other than soda bottles. Non-soda containers tend to be more contaminated and harder to separate from other resins, making them undesirable to less sophisticated recyclers. Image also sells recycled PET resin to other carpet manufacturers, including Talisman Mills.
Though not widely known in consumer circles, Wellman Inc. is an even larger recycler of PET resin, supplying several carpet mills. The recycled content of its material has been certified by Scientific Certification Systems, Inc., of Oakland, California.
Polyester is generally considered to be a less durable fiber than nylon, so polyester carpets are usually used only in residential applications, which receive less wear than commercial installations.
While carpet may be a good use for off-spec PET recyclate, high-quality recycled PET may be better reused in soda bottles or other fabrics where it can be recycled again. PET is not valuable enough to justify the cost of separating it from other fibers once it is in a carpet. PET recycler Wellman acknowledges that separating and recycling the PET from carpets is not currently economically feasible. Thus, PET carpets may be made of recycled material, but they are not yet recyclable.
Another fiber manufacturer may soon increase the recyclability of PET carpets. Hoechst Celanese, the largest supplier of virgin polyester to the carpet industry, is developing a carpet system made entirely of polyester. Shaw Industries, the largest carpet manufacturer, is reportedly working with Hoechst to produce the carpet, named Treviera One. Four or five mills will be introducing the all-polyester carpets in 1995, according to Hoechst. Ironically, although the stated goal of producing the all-polyester carpet is easy recyclability, the product is not expected to be made with any recycled resin.
As a fossil-fuel-based product, carpet is relatively energy intensive to produce. Most carpet is made using petrochemicals. Even if they are in a safe form in the final product, which some might question, these chemicals must be contained and handled very carefully during manufacturing to prevent environmental and health problems. But carpet’s biggest drawback from a lifecycle perspective is its short useful life compared to other floorcoverings.
The most commonly quoted useful life for both residential and commercial carpet is eight years. Allowing for replacement costs, any long-term lifecycle cost or environmental lifecycle assessment paints a harsh picture of carpet. A recent study by Canada Mortgage and Housing Corporation comparing the embodied energy and environmental impacts of several flooring materials pronounced carpet to be the worst.
Similarly, an environmental lifecycle assessment comparison of linoleum, vinyl, wool carpet, and nylon carpet from the University of Utrecht in The Netherlands put the nylon carpet at the bottom. Indoor air quality impacts of the materials were not considered in this Dutch study, which pronounced natural linoleum the clear winner, followed by wool carpet, sheet vinyl, and nylon carpet. The wool carpet compared in the study was tufted, with synthetic backing and adhesive, not natural backing. The energy required to ship the wool from New Zealand was estimated at 10% of the total embodied energy of the carpet and would likely have been an even higher fraction of the total for all-natural carpet.
Both of these lifecycle assessments looked only at standard residential carpet products. These products typically use lower-quality nylon and relatively large amounts of SB latex adhesive—about 28 ounces per square yard of carpet—to bind the fibers to the backing. Some higher-quality commercial-grade carpets are likely to be less toxic and may rate better from an overall environmental perspective. Woven carpets, for example, require far less adhesive than the far more common tufted products.
In spite of all the research and development that has gone into synthetic fibers for carpets, wool is still considered the most desirable fiber, according to CRI, and for good reasons. Wool has appearance characteristics that synthetics have not yet matched, it has natural flame resistance, and it remains more durable than most synthetics. In fact, after the World Trade Center bombing in New York last year, extensive repairs were done to the main lobby with the original wool carpet in place, on the assumption that it would have to be replaced. After the last machines drove out, however, the managers discovered, much to their surprise, that with a thorough cleaning the carpet remained as good as new.
A rash of alleged health problems with carpet have yet to be properly explained, suggesting that all carpets, and especially the less expensive synthetics, should be used with great caution. In addition, the relatively short life expectancy of most carpet and the heavy dependence on fossil fuels as a raw material make it incumbent on those specifying carpet to see that it will be maintained and protected for a long, safe service life. The recommendations that follow are far from exhaustive, but they are a step towards safer, better floorcoverings.