What Is Linoleum?
Natural linoleum is widely promoted and specified in the green building community. As an all-natural alternative to resilient flooring made from polyvinyl chloride (PVC)—including sheet vinyl and VCT (vinyl composition tile)—linoleum has a lot going for it.
Imports of linoleum are on the increase, with the product being used on projects ranging from the recently built Federal Reserve Bank in Minneapolis to the bathroom of our newly renovated EBN offices. But linoleum has some negatives as well, including higher cost than most sheet vinyl and relatively high rates of volatile organic compound (VOC) offgassing. This article will take a look at linoleum as a flooring material, examining the life-cycle issues relating to its production, use, and disposal, and describing available products.
What is Linoleum?
Linoleum manufacturing in Europe is highly sophisticated today—a far cry from the first linoleum plants in the late 1800s.
Source: Forbo Industries
First of all, linoleum is not vinyl, though the old term “linoleum” is still used by many to refer to vinyl flooring. Linoleum is a natural material made primarily from linseed oil, pine rosin, sawdust, cork dust, limestone, and jute. Invented and patented in Britain in 1845, linoleum was first manufactured in the 1860s in Scotland.
The first U.S. plant was built on Staten Island in 1872; in 1909 Armstrong built a linoleum plant in Lancaster, Pennsylvania. After World War II, with the burgeoning petrochemical industry, linoleum was increasingly replaced by vinyl flooring. In 1975, Armstrong closed its Lancaster plant, the last U.S. facility producing linoleum. Only recently, with renewed interest in natural building materials, alternatives to PVC, and design options offered by linoleum, has the product begun to reclaim some of its lost market share. Today, the U.S. is importing some $20 million to $25 million worth of linoleum annually from four factories in Europe. This is just 1% of the $2.6 billion resilient flooring market in the United States, but Armstrong’s recent purchase of the world’s No. 2 linoleum manufacturer, DLW Aktiengesellschaft in Germany (see Armstrong Reenters Linoleum Market), may hasten the return of this product to the U.S. market.
The primary raw materials in linoleum are renewable. Linseed oil is squeezed from seeds of the flax plant, which is widely grown in Canada, the U.S., and Argentina. Fertilization rates for flax are relatively low, compared with most other crops: nitrogen 31 lbs./acre (35 kg/ha); phosphorus, P2O5 15 lbs./acre (17 kg/ha); and potassium, K2O 13 lbs./acre (14 kg/ha). According to an agronomist EBN spoke with, flax is grown in the U.S. (primarily in North Dakota) in 3- to 6-year rotation with other crops, and requires no added nitrogen. Rosin is harvested from pine trees, primarily in Portugal—V-shaped cuts are made in the bark, and sap that drips out is harvested and distilled into rosin and turpentine. Sawdust is a by-product of lumber milling. Cork is the bark of a type of oak tree that grows in the Mediterranean region, particularly Portugal (see EBN Vol. 5, No. 1); the powdered cork used in linoleum is a by-product of manufacturing bottle corks, gaskets, and cork flooring. The fiber backing on most linoleum is a burlap or hessian made from jute, a plant that is grown in northeastern India and Bangladesh. Powdered limestone is used as a filler, and titanium dioxide is the primary pigment. Very small amounts of zinc-based drying agents are used in the processing (zinc having replaced lead in the mid-’70s), and a surface topcoat of acrylic is typically applied.
Bark harvested from the cork oak, Quercus suber, is one of the raw materials used in linoleum. The bark is renewable, being harvested every nine or ten years.
Source: Forbo Industries
Resources Used to Produce 1 Square Meter of Linoleum
Source: “Life-Cycle Assessment of Flooring Materials: A Comparison of Linoleum, Vinyl Flooring, and Solid Pine Flooring” by Åsa Jönsson, Anne-Marie Tillman, and Torbjörn Swensson. Swedish Council for Building Research, Stockholm, 1995.
Interestingly, there has been some discussion of a blight among cork oak trees threatening the supply of cork (see EBN Vol. 5, No. 4), but EBN was told by Arthur Dodge, Jr., who has been in the cork industry more than 50 years, that these rumors of a cork oak blight pop up every 10 or 15 years, and he’s never seen evidence of it.
He says the rumors are spread by cork producers in an effort to boost the price of cork.
The manufacturing process for linoleum is fairly straightforward. In a large tank, the linseed oil, rosin, and drying agent are mixed together. Oxygen is pumped through this mixture for about 24 hours, oxidizing and polymerizing the linseed oil to produce a jelly-like intermediary material called cement. In this process, cross-bonds form between the glycerides in linseed oil (linolenic acid, linoleic acid, and oleic acid), causing the hardening. The cement is left to mature for several weeks, then is mixed with the powdered wood, cork, limestone, and pigments.
This granular material is calendared (rolled into sheet form), during which time patterns are created, then the sheets are pressed onto the jute backing with heat. These long sheets are hung up in drying rooms maintained at 150°-180°F (66°-82°C) to cure for another two to three weeks —a modern linoleum plant can hold as much as 9 linear miles (15,000 m) of linoleum. The oxidation process that occurs during this curing provides much of the heat needed to maintain the high temperatures. The final stage is to apply an acrylic topcoating and package the linoleum for shipping.
The total manufacturing process takes about six weeks. VOCs are generated at several stages of this process: those produced during the initial oxidation in the large tanks are typically captured and burned to very high efficiency (99.9% pollutant removal); the VOCs released in the large drying rooms, however, are typically released to the outdoors. These emissions amount to 4.6 grams per square meter of linoleum produced, according to a 1995 report by Åsa Jönsson, Anne-Marie Tillman, and Torbjörn Swensson, “Life-Cycle Assessment of Flooring Materials,” published by the Swedish Council for Building Research in Stockholm. Solvents, chiefly toluene, butanol, and ethyl acetate are also released during manufacture, according to the report, although where they come from is not clear. They may come primarily from the acrylic topcoating. Most of the dust generated during linoleum manufacture is captured with filters.
The total embodied energy of linoleum, according to research by J. Potting and colleagues at Utrecht University in the Netherlands, is about 7,500 Btu/lb (17 MJ/kg), which translates to 5,000 Btu/ft2 (57 MJ/m2) for typical 2.3mm-thick material. A significant fraction of this figure is in the calorific (heat) value of the materials used to make linoleum, some of which could be reclaimed upon incineration of the used flooring. While this figure does include energy for shipping raw materials from the Americas and Asia to Europe, it does not include the additional energy required for shipping the finished product back to North America. At the other end of its life cycle—disposal—linoleum does very well from an environmental standpoint. The material is biodegradable and readily broken down, primarily into carbon dioxide and water vapor. If it is incinerated in a waste-to-energy plant, combustion should be very complete, with the linseed oil contributing significant energy.
Comparisons with Vinyl
Polyvinyl chloride (PVC), known commonly as vinyl, has the vast majority of the resilient flooring market worldwide and, especially, in the United States. Sheet vinyl and vinyl tile are typically 30% to 50% PVC by weight, while vinyl composition tile (VCT)—note that VCT is different from vinyl tile—is rarely more than 15% PVC (the rest primarily being inert fillers, such as calcium carbonate, and pigments). Both vinyl and linoleum require adhesives for installation, both require periodic maintenance to keep the floor looking good and to ensure a long lifetime, and both offgas VOCs (though the VOCs from linoleum are more noticeable). From an environmental standpoint, where the products differ most is in the upstream and downstream impacts of manufacture and disposal.
PVC contains chlorine, and many of our most troublesome environmental toxins are organic compounds that contain chlorine. These organochlorines, such as dioxins, PCBs, and the pesticide DDT, can survive for decades in the environment where they bioaccumulate—the concentrations increase in animals further up the food chain. There is concern that PVC and other chlorine-based compounds can be transformed into dioxins or other organochlorines and then be released during manufacture or when disposed of by incineration (see “Should We Phase out PVC?,” EBN Vol. 3, No. 1). Release of organochlorines is not known to occur during use of vinyl flooring.
In addition—and perhaps even more significant—the most commonly used plasticizers in vinyl flooring may be endocrine disruptors. (Plasticizers are added to various plastics to increase flexibility.) Endocrine disruptors are chemicals that your body can mistake for natural hormones; they can interfere with embryo development and reproduction (see review of Our Stolen Future in EBN Vol. 5, No. 6). The plasticizers of greatest concern in vinyl flooring are phthalates, such as the widely used di(2-ethylhexyl) phthalate (DEHP). In vinyl sheet flooring, plasticizers typically comprise about 27% of the product by weight. Vinyl tiles usually contain less plasticizer than vinyl sheet because they don’t have to be as flexible. VCT contains very little, if any, plasticizer.
Linoleum, by contrast, contains no chlorine and no plasticizers. All of the ingredients, with exception of the acrylic topcoat and the very small amount of zinc drying agent, are readily biodegradable.
Products and Applications
In North America, linoleum is sold primarily to the contract market for use in commercial buildings. It is generally available in three different thicknesses (2.0 mm, 2.5 mm, and 3.2 mm) for different applications and wear characteristics. Some products are available in greater thicknesses (4.0 mm and 4.5 mm). Thicker linoleum is recommended in heavy-use commercial and industrial buildings, though the very thick grades are rarely required. While linoleum has very good point-load characteristics and actually increases in strength over time, special grades are available for very high compressive loads. Linoleum is also naturally antistatic, which makes it an attractive product in office spaces with computer equipment; special conductive grades are available for applications where certain resistance properties are required, such as computer rooms. Linoleum is resistant to oil, grease, disinfectants, and many solvents. It has low flammability (Class B1), meets most slip-resistance standards, resists scorching, and works well with underfloor heating.
The two largest manufacturers of linoleum, Forbo Industries and DLW Aktiengesellschaft (now owned by Armstrong), offer a wide range of colors and styles of linoleum sheet and tile flooring products. The most common products have a marbleized look, but solid colors and innovative new styles, such as Forbo’s Artoleum® series, are also available. Imaginative designers and skilled installers can create beautiful and highly unique floors using linoleum. Most sheet linoleum is sold in rolls 61⁄2 feet wide (2.0 m) and about 100 feet long (31 m). Tiles are also available, either in custom sizes (cut from sheet product) or in standard sizes, typically 20” (510 mm) and 13” (330 mm) square.
Linoleum is often specified for healthcare facilities where hygiene is important because of unique bactericidal properties of the product. Linoleum continues to oxidize over its life, and this oxidation process apparently kills bacteria or prevents them from multiplying, thus reducing the need for disinfecting treatments. Tests conducted for Forbo Industries showed inhibition of the following bacteria: Bacillus cereus, Bacillus cereus (spores), Pseudomonas aeruginosa, Salmonella ryphimurium, Staphylococcus aureus, and Appergillus nigerrevisiae. No effects were seen with Saccharomyces cerevisiae.
Although the thinnest grades of linoleum serve the residential market in Europe, the product has not been widely marketed for this purpose in North America. If Armstrong, our largest flooring manufacturer, begins marketing linoleum again following their purchase of DLW, we can expect residential use to increase on this side of the Atlantic.
Finally, linoleum is also used as a countertop material. Forbo’s Desk Top product line, available in a wide range of colors, is designed specifically as an alternative to high-pressure laminate in office furniture, cabinetry, tabletops, counters, and display surfaces. The slightly spongy texture makes it an excellent writing surface. Architect Sandra Mendler of HOK’s Washington, D.C. office told EBN that they have specified both Forbo’s Desk Top product and flooring products for countertop applications; this afforded them additional design options and a variety of surface characteristics. Another Forbo line, Bulletin Board, is designed as a tackable surface for schools and offices; it is available in a dozen solid colors and has self-healing properties.
The range of colors and textures available today make linoleum, such as this DLW product, an ideal material for custom-designed floors.
Source: Gerbert Limited
As with other resilient flooring, linoleum is typically glued to a slab or subfloor. Linoleum manufacturers recommend a low-VOC, water-based SBR (styrene butadiene rubber) adhesive. The recommended adhesives for linoleum are different from those recommended for vinyl—vinyl flooring adhesives do not bond well to linoleum.
As with sheet vinyl, the slab or subfloor must be properly prepared. John Kamencik of Don-Vac, Inc. in Williston, Vermont, a commercial flooring company that installs $1 million to $1.5 million in VCT, sheet vinyl, and linoleum flooring per year, says that moisture testing of slabs is absolutely critical. The flooring industry, he said, “loses millions and millions of dollars in failed flooring jobs each year because architects didn’t specify moisture testing.” His company tests every job to make sure vapor emissions are within tolerable limits—no more than 5 pounds of water emissions per 1,000 square feet of floor (2.4 l/100 m2) over a 24-hour period. He said that 95% of their flooring installations are on concrete slabs and that if too much moisture is coming out of the slab, it can re-emulsify the adhesive—with any type of resilient flooring—and cause failure. “We’ve learned the hard way,” he told EBN. In situations where moisture content is too high, they use a product called SealFlex (at a cost of about $2.50 per square foot ($27/m2) as an underlayment on the slab; with this the floor can be warranted at up to 10.4 lbs. water/1,000 ft2day (5.1 l/100 m2day).
If resilient flooring is installed on a subfloor, make sure the surface is smooth and free from voids. If necessary, a (low-toxic) leveling compound should be used. Avoid using Luan plywood panels for the subfloor, because this tropical hardwood is not available from a certified source.
Linoleum flooring is “heat-weldable” using a specialized weld gun and weld rod available from linoleum manufacturers.
The unfinished joint is first grooved, then the weld gun heats the edges to a temperature of 750°-840°F (400°-450°C) and melts the weld rod into the groove. This produces a nearly invisible, impervious seam. Weld guns used for vinyl flooring may be adaptable to use with linoleum by replacing the nozzle.
Because of the importance of proper installation, Kamencik recommends including in the architectural specifications a requirement that linoleum be installed by a flooring contractor who has been certified by a linoleum manufacturer. Forbo offers a week-long “Master Mechanic” installer certification program, which is very involved. It is a pass-fail program, he said, that covers the entire range of installation issues.
Offgassing and Indoor Air Quality Concerns
If linoleum has an Achilles heel, it is the offgassing of VOCs that occurs as the linseed oil oxidizes over time. The VOCs given off by linoleum are mostly fatty acids, which have very strong odors even at low concentrations, and aldehydes, which are given off from the oxidation of fatty acids. James White, an IAQ expert with the U.S. Environmental Protection Agency, reported in a posting to the Green Building e-mail discussion group that EPA modeled the indoor air quality impacts from both linoleum and vinyl flooring for the recently constructed EPA research facility in Research Triangle Park, North Carolina. Using RISK, a computer IAQ modeling tool, they found that “both the vinyl and the linoleum generated very similar concentrations of vapor-phase organic compounds, approximately 35-40 ug/m3 VOC over the modeled scenario.” He said the linoleum products were primarily aldehydes but did not specify what chemicals were emitted from the vinyl. “We concluded that with respect to indoor air quality concerns there was insufficient difference between the two floor coverings to drive a decision,” he said in the posting.
Research published in the Danish journal Indoor Air in 1995 (in the March issue by B. Jensen and others, and in the September issue by P. Wolkoff and others) identified over 20 specific chemicals as contributing to the noticeable odor associated with linoleum. The most significant as sources of odors were hexanal, heptanal, hexanoic acid, 2-heptanal, heptanoic acid. The odors are described variously as “fatty-green,” “grassy,” “oily-fatty,” “rancid,” “acrid,” and “sweat-like.” Hexanal and hexanoic acid are oxidation products of linoleic acid, one of the primary glyceride acids in linseed oil. Some other chemicals were emitted in larger quantities, but they aren’t as significant in terms of odor.
Emissions of most of these compounds were found from new linoleum, with emission levels dropping dramatically over time. The researchers also studied a sample of “complaint” linoleum—older material that was causing an odor problem. Although they didn’t resolve the issue conclusively, their tests suggest that a rancid odor was created because the linoleum was installed over a concrete subfloor that remained damp.
After reviewing this research and other data, architect Anthony Bernheim of SMWM in San Francisco is concerned enough about VOC emissions and odors from linoleum that he has stopped specifying it for the time being. Dr. Virginia Salares, of the Canada Mortgage and Housing Corporation, is also concerned about linoleum. She told EBN that “the presence of odors in any building material is a concern,” especially for people with asthma, allergies, or chemical sensitivities. She said that one of her co-workers, who is chemically sensitive, specified linoleum when remodeling a CMHC office, then couldn’t go into the office for months because of odors emanating from the material.
Sandra Mendler of HOK has specified linoleum on various projects but isn’t particularly concerned about the odor or VOC issue. “Smell hasn’t been an issue that I’m aware of,” she reports. “I think of that as a fairly minor issue.” Mendler concurs with the research mentioned above that use of linoleum should be avoided in wet environments: “We think of it more like a wood-type product, as it’s made with a large proportion of wood flour. It doesn’t like to get wet, and it’s best if used with a dry maintenance system.”
Durability and Maintenance
One of the key things going for linoleum is its excellent durability. Over time, as the linseed oil continues to oxidize, linoleum gets stronger. The point-loading strength of standard linoleum increases from about 150 psi (1,030 kPa) just after installation (about the same as standard VCT) to as much as 700 psi (4,800 kPa). A linoleum floor has been in continuous use at the Radio City Music Hall, where the high-heeled Rockettes perform, for more than 25 years. As the material strengthens, however, it also becomes less flexible. In a floor with significant flexing or movement, it is conceivable that cracking could occur. Manufacturers claim that the expected life of linoleum is 30 to 40 years. This is somewhat longer than the expected life of most vinyl flooring products.
Surface treatment of linoleum is recommended following installation, then regular company-recommended maintenance should suffice. Forbo recommends dry maintenance as the preferred option. This involves spray cleaning and burnishing. Wet maintenance, similar to that required for VCT, can also be used but is not required. “Linoleum doesn’t require as much protection [as VCT],” explained flooring contractor Kamencik. With VCT, regular waxing is absolutely necessary, because the wax layer serves as the wear layer. “If you’re not walking on the wax, the VCT will get destroyed,” he said. Depending on the traffic, waxing as frequently as every other month may be required with VCT, according to Kamencik.
Nicks and damage to linoleum can be fixed by filling with a paste made from ground-up linoleum of the same color and polyvinyl acetate (Elmers®-type) glue. Stains can be removed by lightly sanding, then resealing the surface. Because linoleum is uniform top to bottom, there is not a concern of abrading through the wear layer—as is the case with sheet vinyl.
Linoleum is fairly expensive compared with VCT but competitive with high-quality sheet vinyl products. Typical installed costs are $3.50 to $3.75 per square foot ($38-$40/m2), according to Kamencik. Installations that include complex inset designs may be as high as $4 to $4.25 per square foot ($43-$46/m2) said Kamencik. By comparison, VCT averages about $1.50 per square foot ($16/m2) for a medium grade, and as much as $2 per square foot ($22/m2) for a premium grade. In large buildings with more than 15,000 square feet (1,400 m2) of VCT going in, such as supermarkets, costs can drop as low as $1 per square foot ($11/m2). Sheet vinyl ranges anywhere from $2 to $4.50 per square foot ($22-$48/m2), according to Kamencik, and as much as $5 per square foot ($54/m2) for premium slip-resistance product with heat welding of seams and flash coving.
Be aware, however, that first cost is only part of the total (life-cycle) cost of a product. Different types of flooring have very different requirements for maintenance and upkeep. VCT requires regular stripping and waxing—often as many as six treatments per year, depending on traffic. Linoleum also requires periodic maintenance but significantly less than is required for VCT. Forbo claims an annual maintenance cost of $1.45 per square foot ($16/m2) for VCT and $0.50 per square foot ($5/m2) for linoleum. Vinyl sheet flooring does not require regular maintenance, but in heavy-traffic areas its expected life may be significantly shorter than that of linoleum.
Recent Developments with Linoleum
The most important development with linoleum in the past ten years is the just-announced acquisition of DLW Aktiengesellschaft by Armstrong (see page 2). This could help to legitimize linoleum in North America. At the very least, Armstrong is likely to cease its negative publicity about linoleum now that the company is back in the linoleum business. If demand for linoleum grows to the point that the European factories cannot keep up, Armstrong will have access to state-of-the-art technology that could be used in the rebuilding of its mothballed linoleum factory in Lancaster, Pennsylvania.
Forbo Industries also has some exciting new developments. The company is introducing a new linoleum tile this December that will be thinner (2.0 mm) and priced to compete more directly with VCT. This 13” by 13” (330 mm x 330 mm) tile is being targeted specifically toward K-12 schools. In the residential arena, Forbo has begun test marketing a linoleum “plank” flooring product called Marmafloor. Planks 91⁄2” (24 cm) wide by 471⁄4” (120 cm) long have a layer of linoleum laminated onto a subfloor—much like laminate flooring but without tongue-and-groove edges. The product costs about the same as sheet linoleum but can be installed by do-it-yourselfers or builders. Forbo has not yet decided exactly how Marmafloor will be positioned in the market.
So What’s the Bottom Line?
Environmentally, linoleum has a great deal going for it. The product is made primarily from minimally processed natural ingredients. It contains almost no petroleum-based chemicals and no chlorinated chemicals. The resources used are renewable or plentiful. It is fully biodegradable. Compared with the primary competitor in commercial buildings, VCT, linoleum is more durable and requires less maintenance. From a life-cycle cost standpoint, the lower maintenance requirements will result in significant savings over time, compared with VCT.
The biggest concern about linoleum is the offgassing of oxidation products from the linseed oil. According to some, this offgassing is significant enough that we should avoid using linoleum. Others argue that while the chemicals have a strong smell, they aren’t very harmful, and that the environmental and performance advantages of linoleum over PVC outweigh these negatives. Continuing research on linoleum, particularly in Europe, may shed further light on the offgassing issue, but given what we currently know, we feel good enough about linoleum to recommend it widely. Indeed, we recently installed it in our own office. The key to success with linoleum, however, is proper installation. Follow manufacturers’ recommendations, use installers who have been properly trained, and test to make sure that the slab or subfloor is not too wet.