This CE Center article is no longer eligible for receiving credits.
Flooring of one type or another is used in virtually every building project. Indeed, it may even be a renovation project unto itself. How many square feet of flooring is needed? Likely the same number of square feet as in your building, plus any outdoor deck or activity areas. With such a ubiquitous nature and far-reaching implications for design and construction, it has also been the focus of intense scrutiny in terms of its impact on both indoor and outdoor environments. The flooring industry has responded in recent times by changing the way it sources materials, updating its manufacturing processes, and seeking out and achieving independent, third-party certifications to meet green building standards. In that regard, many now conduct life-cycle assessments (LCAs) on their products to look at the specifics and impacts from the “cradle” or material-sourcing phase through the manufacturing process and then to the “gate” phase, where it is ready to be shipped to a jobsite. Others may look at it all the way to the “grave,” where it is used to the end of its useful service life and then either recycled or disposed of. Based on this process, some also have environmental product declarations (EPDs) available that report the objective findings of the LCAs.
Photo courtesy of Lonseal Flooring
Manufacturing advances now make commercial flooring more appealing, sustainable, and durable over the life of the building in which it is installed.
In this course, we will review some of the different types of indoor and outdoor flooring products and materials that are available for high-performing commercial floor assemblies. In the process, we will look at the ways they each address sustainability and green building principles that allow design and construction professionals to create better performing, better designed, and more sustainable projects.
Sustainable Self-Leveling Underlayments
Any flooring contractor will readily point out that all flooring requires a good subfloor to perform well. Sometimes that is straightforward to achieve in new construction, sometimes not. In renovation projects, the quality of the subfloor may be difficult to determine at best and problematic at worst. Hence, it is common to use an underlayment that can provide an appropriate surface for the flooring and cover over or correct many deficiencies in the subfloor in the process. A common choice for an underlayment over wood and concrete subfloors is a cementitious self-leveling underlayment (SLU) product. While cementitious products tend to carry a very high carbon footprint, some new SLU products have been developed that achieve much more favorable sustainability attributes.
Photos courtesy of USG
Installing a self-leveling underlayment (SLU) helps assure the long-term durability and performance of the finish flooring. Selecting an SLU that has sustainable qualities helps with overall quality of the building.
SLU Overview
SLU products are generally an aqueous mixture of hydraulic cements (i.e., cured with water), fillers, polymeric binders, and additives. The type and amount of cements, chemical additives, as well as the amount of water in the binder are used to control the key properties, such as flow, setting behavior, and compressive strength. The dry product is mixed with water and applied to a subfloor to achieve a smooth surface that is either suitable for use as is or as a substrate for other flooring materials. SLU products are used in both interior and exterior applications and are available both in un-sanded (i.e., sand is added as a filler at the jobsite) and sanded (i.e., no additional sand is required at the jobsite) formulations. There are a range of SLU products that come with a wide variety of performance attributes to suit different jobsite requirements, such as compressive strength, self-healing behavior, working time, setting time, crack resistance, the need for a wear surface, the presence of feathered edges, tolerance for high humidity and moisture, freeze-thaw and salt resistance, etc.
Achieving Sustainability
Traditional SLU products consist of a combination of portland cement and calcium aluminate cement (CAC) as binders, sand and limestone as fillers, and various additives. The sustainability issue with portland cement and calcium aluminate cement is that they are produced using energy-intensive processes. As such, they have a relatively high global warming potential (GWP) value, which is basically a function of two factors: formulation (i.e., inherently high GWP values for cement binders) and transportation (i.e., heavy weight). An understanding of the contributions of each of these factors allows for selecting a self-leveling underlayment that has a reduced GWP.
The following table illustrates the GWP impacts of these two cements compared to other options. Note that the values used in the graph represent approximate cradle-to-gate GWP impacts. They are for illustrative purposes only and will vary depending on the LCA process followed. Flue-gas desulfurization (FGD) stucco refers to FGD gypsum that has been calcined so that it has setting properties.
Image courtesy of USG
The GWP value for each of the materials shown above represents the amount of greenhouse gas (i.e., kilogram CO2-eq.) emitted during the cradle-to-gate production of 1 kilogram of that SLU ingredient. Using an FGD gypsum-based SLU instead of a traditional SLU that utilizes CAC saves the equivalent of approximately 52 gallons of gas per ton (907 kilograms) of SLU. A value of 10 kilogram CO2-eq. is roughly equivalent to using 1 gallon of gasoline or driving 25 miles by passenger car.4
The key to minimizing the GWP impact of any self-leveling underlayment product is to first inspect the EPD, which should be readily available from the manufacturers. When scrutinizing EPD documents for comparisons, be sure that the results are based on the same functional unit. Also recognize that one way of lessening impact on GWP is to use an un-sanded SLU product versus a pre-sanded one since this removes the impact of transporting sand across the country by truck and instead uses locally derived sand. This relatively simple difference can result in a potential GWP savings of approximately 20 percent with no change in the final properties of the installed product.1
A second means of lowering the GWP impact is to utilize products produced with FGD gypsum rather than with natural mined gypsum. FGD gypsum is derived from flue gas desulfurization during electricity generation from coal. Since it is a waste product, it is treated as having no GWP contribution other than that required to transport it from the power plant to the manufacturer and processing it for manufacturing. Using FGD gypsum as a raw material in the self-leveling underlayment product eliminates the need to mine an equivalent weight of gypsum from the ground.
Finally, at least one manufacturer uses an innovative, alternate cement formulation instead of traditional portland cement. This alternative is geopolymer cements, which are based on the reaction between fly ash, a waste product of burning coal for electricity generation, and chemical activators. As a waste product, fly ash does not contribute to the GWP of the flooring product. While this basic chemistry has been around since the 1970s, it is now being used in place of portland cement in self-leveling underlayment products. Using a geopolymer cement-based product compared to a portland cement-based product can reduce the overall GWP for a self-leveling underlayment by as much as 70 percent.2
The demand for SLUs with lower GWP and product-specific EPDs is being increasingly fueled by voluntary programs such as LEED v4.1 and others. Mandatory programs such as California’s law AB 262 known as the Buy Clean California Act requires state agencies to consider the embedded carbon emissions of industrial products.3 Preferential treatment is given to products that demonstrate reduced GWP values compared to a standard industry GWP value. Similar legislation is being pursued elsewhere and it is expected that this trend toward lower GWP products will continue, with additional building products added to the list of those targeted for a reduction in GWP.
More Sustainable Resilient Flooring
A very popular commercial flooring type is resilient floor coverings, which include sheet vinyl, vinyl tile, rubber, polymeric, and linoleum products. Architects and interior designers recognize resilient vinyl flooring in particular as a durable material for high-traffic areas or areas that need to be kept meticulously clean, such as health-care settings. Resilient vinyl flooring has become more favorable over the years in commercial spaces and is being specified in more settings due to updated design and material modifications for quality, high-performance, and more sustainable products. Some of the features that lead architects and interior designers to vinyl flooring are its ability to “bounce back” from the weight of objects compressing its surface; it is also better acoustically and more comfortable underfoot than some options. In addition, the durability, ease of maintenance, and moisture resistance contributes to its increased demand, particularly by building owners and managers.
Sustainability Standards
The Resilient Flooring Covering Institute (RFCI) is the not-for-profit trade association that has been at the forefront of helping manufacturers identify and advance the sustainability of resilient flooring products. In 2007, RFCI introduced a draft standard for trial use that addresses sustainable resilient flooring products in conjunction with NSF International, a not-for-profit, nongovernmental organization focused on public health and safety. The draft standard, known as American National Standard for Trial Use – NSF 332 – Sustainability Assessment Standard for Resilient Floor Coverings, is designed to help manufacturers of sustainable resilient flooring products demonstrate their commitment to the principles of sustainability.
RFCI, in conjunction with resilient flooring manufacturers, has also facilitated third-party-certified EPDs for resilient flooring. The EPDs report the industry average data for five product types based on LCAs following the flooring industry’s product category rules (PCR). Using all of this as a basis, RFCI has also developed its own FloorScore IAQ Certification program related to indoor air quality, particularly the emission level of specific volatile organic compounds (VOCs). For a resilient flooring product to receive FloorScore IAQ Certification, it must be independently certified by SCS, an internationally recognized third-party evaluation, testing, and certification organization. Certified products comply with the VOC emissions testing criteria of the California Specification 01350: California Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers, Version 1.2. Under this method, SCS 1) reviews all VOC emissions test reports for particular products generated by independent testing laboratories; 2) determines whether those test results meet the California Specification 01350 requirements for listed VOCs; and 3) conducts periodic manufacturing plant inspections to review product formulas, processing, and quality control to ensure the continuing integrity of the FloorScore seal.
Flooring of one type or another is used in virtually every building project. Indeed, it may even be a renovation project unto itself. How many square feet of flooring is needed? Likely the same number of square feet as in your building, plus any outdoor deck or activity areas. With such a ubiquitous nature and far-reaching implications for design and construction, it has also been the focus of intense scrutiny in terms of its impact on both indoor and outdoor environments. The flooring industry has responded in recent times by changing the way it sources materials, updating its manufacturing processes, and seeking out and achieving independent, third-party certifications to meet green building standards. In that regard, many now conduct life-cycle assessments (LCAs) on their products to look at the specifics and impacts from the “cradle” or material-sourcing phase through the manufacturing process and then to the “gate” phase, where it is ready to be shipped to a jobsite. Others may look at it all the way to the “grave,” where it is used to the end of its useful service life and then either recycled or disposed of. Based on this process, some also have environmental product declarations (EPDs) available that report the objective findings of the LCAs.
Photo courtesy of Lonseal Flooring
Manufacturing advances now make commercial flooring more appealing, sustainable, and durable over the life of the building in which it is installed.
In this course, we will review some of the different types of indoor and outdoor flooring products and materials that are available for high-performing commercial floor assemblies. In the process, we will look at the ways they each address sustainability and green building principles that allow design and construction professionals to create better performing, better designed, and more sustainable projects.
Sustainable Self-Leveling Underlayments
Any flooring contractor will readily point out that all flooring requires a good subfloor to perform well. Sometimes that is straightforward to achieve in new construction, sometimes not. In renovation projects, the quality of the subfloor may be difficult to determine at best and problematic at worst. Hence, it is common to use an underlayment that can provide an appropriate surface for the flooring and cover over or correct many deficiencies in the subfloor in the process. A common choice for an underlayment over wood and concrete subfloors is a cementitious self-leveling underlayment (SLU) product. While cementitious products tend to carry a very high carbon footprint, some new SLU products have been developed that achieve much more favorable sustainability attributes.
Photos courtesy of USG
Installing a self-leveling underlayment (SLU) helps assure the long-term durability and performance of the finish flooring. Selecting an SLU that has sustainable qualities helps with overall quality of the building.
SLU Overview
SLU products are generally an aqueous mixture of hydraulic cements (i.e., cured with water), fillers, polymeric binders, and additives. The type and amount of cements, chemical additives, as well as the amount of water in the binder are used to control the key properties, such as flow, setting behavior, and compressive strength. The dry product is mixed with water and applied to a subfloor to achieve a smooth surface that is either suitable for use as is or as a substrate for other flooring materials. SLU products are used in both interior and exterior applications and are available both in un-sanded (i.e., sand is added as a filler at the jobsite) and sanded (i.e., no additional sand is required at the jobsite) formulations. There are a range of SLU products that come with a wide variety of performance attributes to suit different jobsite requirements, such as compressive strength, self-healing behavior, working time, setting time, crack resistance, the need for a wear surface, the presence of feathered edges, tolerance for high humidity and moisture, freeze-thaw and salt resistance, etc.
Achieving Sustainability
Traditional SLU products consist of a combination of portland cement and calcium aluminate cement (CAC) as binders, sand and limestone as fillers, and various additives. The sustainability issue with portland cement and calcium aluminate cement is that they are produced using energy-intensive processes. As such, they have a relatively high global warming potential (GWP) value, which is basically a function of two factors: formulation (i.e., inherently high GWP values for cement binders) and transportation (i.e., heavy weight). An understanding of the contributions of each of these factors allows for selecting a self-leveling underlayment that has a reduced GWP.
The following table illustrates the GWP impacts of these two cements compared to other options. Note that the values used in the graph represent approximate cradle-to-gate GWP impacts. They are for illustrative purposes only and will vary depending on the LCA process followed. Flue-gas desulfurization (FGD) stucco refers to FGD gypsum that has been calcined so that it has setting properties.
Image courtesy of USG
The GWP value for each of the materials shown above represents the amount of greenhouse gas (i.e., kilogram CO2-eq.) emitted during the cradle-to-gate production of 1 kilogram of that SLU ingredient. Using an FGD gypsum-based SLU instead of a traditional SLU that utilizes CAC saves the equivalent of approximately 52 gallons of gas per ton (907 kilograms) of SLU. A value of 10 kilogram CO2-eq. is roughly equivalent to using 1 gallon of gasoline or driving 25 miles by passenger car.4
The key to minimizing the GWP impact of any self-leveling underlayment product is to first inspect the EPD, which should be readily available from the manufacturers. When scrutinizing EPD documents for comparisons, be sure that the results are based on the same functional unit. Also recognize that one way of lessening impact on GWP is to use an un-sanded SLU product versus a pre-sanded one since this removes the impact of transporting sand across the country by truck and instead uses locally derived sand. This relatively simple difference can result in a potential GWP savings of approximately 20 percent with no change in the final properties of the installed product.1
A second means of lowering the GWP impact is to utilize products produced with FGD gypsum rather than with natural mined gypsum. FGD gypsum is derived from flue gas desulfurization during electricity generation from coal. Since it is a waste product, it is treated as having no GWP contribution other than that required to transport it from the power plant to the manufacturer and processing it for manufacturing. Using FGD gypsum as a raw material in the self-leveling underlayment product eliminates the need to mine an equivalent weight of gypsum from the ground.
Finally, at least one manufacturer uses an innovative, alternate cement formulation instead of traditional portland cement. This alternative is geopolymer cements, which are based on the reaction between fly ash, a waste product of burning coal for electricity generation, and chemical activators. As a waste product, fly ash does not contribute to the GWP of the flooring product. While this basic chemistry has been around since the 1970s, it is now being used in place of portland cement in self-leveling underlayment products. Using a geopolymer cement-based product compared to a portland cement-based product can reduce the overall GWP for a self-leveling underlayment by as much as 70 percent.2
The demand for SLUs with lower GWP and product-specific EPDs is being increasingly fueled by voluntary programs such as LEED v4.1 and others. Mandatory programs such as California’s law AB 262 known as the Buy Clean California Act requires state agencies to consider the embedded carbon emissions of industrial products.3 Preferential treatment is given to products that demonstrate reduced GWP values compared to a standard industry GWP value. Similar legislation is being pursued elsewhere and it is expected that this trend toward lower GWP products will continue, with additional building products added to the list of those targeted for a reduction in GWP.
More Sustainable Resilient Flooring
A very popular commercial flooring type is resilient floor coverings, which include sheet vinyl, vinyl tile, rubber, polymeric, and linoleum products. Architects and interior designers recognize resilient vinyl flooring in particular as a durable material for high-traffic areas or areas that need to be kept meticulously clean, such as health-care settings. Resilient vinyl flooring has become more favorable over the years in commercial spaces and is being specified in more settings due to updated design and material modifications for quality, high-performance, and more sustainable products. Some of the features that lead architects and interior designers to vinyl flooring are its ability to “bounce back” from the weight of objects compressing its surface; it is also better acoustically and more comfortable underfoot than some options. In addition, the durability, ease of maintenance, and moisture resistance contributes to its increased demand, particularly by building owners and managers.
Sustainability Standards
The Resilient Flooring Covering Institute (RFCI) is the not-for-profit trade association that has been at the forefront of helping manufacturers identify and advance the sustainability of resilient flooring products. In 2007, RFCI introduced a draft standard for trial use that addresses sustainable resilient flooring products in conjunction with NSF International, a not-for-profit, nongovernmental organization focused on public health and safety. The draft standard, known as American National Standard for Trial Use – NSF 332 – Sustainability Assessment Standard for Resilient Floor Coverings, is designed to help manufacturers of sustainable resilient flooring products demonstrate their commitment to the principles of sustainability.
RFCI, in conjunction with resilient flooring manufacturers, has also facilitated third-party-certified EPDs for resilient flooring. The EPDs report the industry average data for five product types based on LCAs following the flooring industry’s product category rules (PCR). Using all of this as a basis, RFCI has also developed its own FloorScore IAQ Certification program related to indoor air quality, particularly the emission level of specific volatile organic compounds (VOCs). For a resilient flooring product to receive FloorScore IAQ Certification, it must be independently certified by SCS, an internationally recognized third-party evaluation, testing, and certification organization. Certified products comply with the VOC emissions testing criteria of the California Specification 01350: California Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers, Version 1.2. Under this method, SCS 1) reviews all VOC emissions test reports for particular products generated by independent testing laboratories; 2) determines whether those test results meet the California Specification 01350 requirements for listed VOCs; and 3) conducts periodic manufacturing plant inspections to review product formulas, processing, and quality control to ensure the continuing integrity of the FloorScore seal.
Selection Considerations
When selecting or specifying resilient floor coverings, there are a number of considerations and information to look for when comparing different products.
- First, look at the overall quality of the products being considered and make sure it addresses the needs of the building project. Recognize that all vinyl flooring is not made the same. There are economically priced products that consist of a basic and minimum formulation to be considered resilient but will typically wear out within five years, thus needing replacement. Conversely, high-quality vinyl products are formulated to last up to 10–20 years, thus providing a longer service life, more durability, and much less frequent need for replacement.
- Next, see if the potential flooring products can contribute to LEEDv4/4.1 and have an EPD for review. Some manufactures use the Environmental Product Declarations Option 1, which means they have a qualified industry-wide EPD that is appropriate. They may also use Sourcing of Raw Materials Option 2, which is a U.S. Green Building Council (USGBC) recognition of products ranging from 10–20 percent pre-consumer (post-industrial) recycled content. Products that are manufactured in a facility that has certifications from the International Organization for Standardization (ISO), including ISO 9001: Quality Management Systems and ISO 14001: Environmental Management Systems, indicate a greater commitment to sustainability on the part of the manufacturer and should be recognized in the EPD review process.
- Look for traits that demonstrate the product is low emitting for VOCs. Products that can demonstrate contribution toward LEEDv4/4.1 Low-Emitting Materials credits and are FloorScore certified are the best ways to determine this, and those products should be given preference.
- Determine if there are any other traits that set a product apart, such as features for increased infection control through antimicrobial formulations—particularly relevant in health-care and some educational settings. Similarly, look for adherence to specialty rating programs, such as the Collaborative for High-Performance Schools (CHPS) green building rating program especially designed for schools.
- Finally, safety is a feature that is relevant for all commercial flooring products and the products being considered should have slip resistance testing available for review.
Overall, performance and appearance need to go hand in hand when selecting resilient flooring. Jorge Marquez, president of Lonseal, Inc., emphasizes this point, saying, “We regularly hear the mistakes made when a floor is simply selected for its looks, which is most often based on cost and trendy style and overlooking the importance of durability and performance.” Too often, the results of a poor selection are that the original choice needs to be removed and a new flooring installed—a costly and not very sustainable outcome.
Photo courtesy of Lonseal Flooring
Resilient sheet vinyl flooring provides a smooth, continuous flooring surface without the seams associated with vinyl tiles.
Tile or Sheet Flooring?
Resilient vinyl flooring comes in two common forms: continuous sheet flooring on rolls and cut tiles of various sizes. A common issue with the tiles is the number of seams between them creating vulnerable edges where moisture can penetrate, cause the tile adhesive to loosen, or damage the subfloor. In that regard, sheet vinyl flooring is favorable for commercial spaces because it can usually be installed in just one or two solid, unbroken pieces. Unlike vinyl floor tile that comes with interlocking strips, sheet vinyl flooring uses welded seams, making it impermeable to water. This can be particularly important in health-care projects or other places where cleanliness, concerns about mold, or similar indoor environmental quality issues need to be addressed.
Vinyl sheet flooring is also available with a clear wear layer that acts as a stain-resistant surface barrier. A factory-applied urethane finish in particular has been shown to protect the flooring materials, reduce scuffing, and simplify routine maintenance. Such finishes are typically applied as a 30-micron wear layer that extends the life of the flooring. Finishes like this are one reason that maintenance cost differs between tile and sheet vinyl flooring. Tile may often be less costly than sheet initially, but vinyl tile most often requires an application of additional finish and periodic stripping. That introduces cleaners and chemicals into the indoor environment, whereas sheet vinyl flooring with a factory-applied finish can readily be cleaned with environmentally safe cleaners. Over time, the extensive maintenance required by vinyl tile can cause its lifetime cost to far exceed that of vinyl sheet flooring.
One of the other main reasons why architects choose sheet vinyl flooring is that it can be printed to look like a vast number of different materials, such as wood, stone, and cloth. Sheet vinyl can be printed with lines to mimic the look of wood planks and still benefit from a minimal seam application. Of course, there are many design and color options with both vinyl tile and vinyl sheet; however, sheet forms do not force a floor design that repeats smaller patterns. Unlike vinyl tiles, sheet flooring allows for the creation of very large designs or images, or a print with a grid pattern to resemble individual tiles if that is desired.
New products are being introduced in vinyl sheet flooring all the time as well. Of note are patterns and colors that are based on inspirations from nature, or biophilic designs. Biophilia is part of some green building programs because it acknowledges our human tendency to desire a connection with nature. Many visible building finish products, such as flooring, have used the findings of research scientists who have studied the connections between biophilia and human behavioral patterns. Done well, biophilic design can contribute to restorative responses, such as reducing stress, improving cognitive function/ creativity, improving well-being, and healing. The designs mimic things from nature, such as the bark of a tree, alluding to a harmonious relationship with the earth and offering a sense of healing and tranquility. It may also give a peaceful, harmonious effect when connecting with other architectural details, such as floor moldings. As such, biophilic flooring designs can be subtle enough to provide a smooth transition between rooms or interesting enough to help emphasize a focal point.
Photo courtesy of Lonseal Flooring
Biophilic flooring design takes cues from nature to help create an interior environment that can assist in human well-being and comfort.
Overall, top-of-the-line vinyl sheet flooring products are viewed as part of a durable, increasingly sustainable solution for all types and styles of commercial interior design. High-impact facilities, such as weight rooms and hot yoga studios, see the performance of this flooring in their demanding environments. Retail and hospitality spaces benefit from the products’ multipurpose use for flooring and even fixtures. Educational and childcare facilities are good candidates for these products when they demonstrate the certifications for safety and indoor environmental quality. Most other commercial flooring applications can consider this solution as well.
Thermally Modified Wood Decking
Projects that incorporate outdoor spaces or partly enclosed porches, terraces, etc. have some specific needs for the flooring of those spaces. Most notably, they need to be able to hold up against outdoor conditions, not just usage, as is the case with indoor flooring. In the interest of finding a sustainable option for this outdoor flooring, many architects turn to wood decking of some type. Since wood is a renewable material and has a favorable carbon footprint, it is a logical choice, as long as it is raised, harvested, and managed sustainably.
Wood has been used on building exteriors for centuries, but it typically requires ongoing maintenance to keep it from rotting, warping, or otherwise deteriorating. In recent years, architects have often turned to tropical wood because of its natural rot resistance and strength. One of the more popular such tropical woods is ipé from South America, specifically because it exhibits high-strength, long-term durability and rot resistance due to its high density. The problem with this choice is that it is being cited by international environmental organizations as becoming nonsustainable. This is due to over-harvesting and nonsustainable forest management practices.
A New Option
In the quest for finding other sources of truly sustainable, rot-resistant, durable wood, a new option has emerged known as thermally modified wood. This is a process where a common species of wood, such as white ash, scots pine, or spruce, is treated with heat and steam in a very precise, scientifically controlled manner. When done properly, thermal modification of wood results in boards that are more durable, more dimensionally stable and more rot resistant than virtually any other wood product available. Further, because the basic wood species used are readily available, they can be specified based on requiring responsible sourcing, sustainable harvesting, and minimizing carbon footprint throughout the milling and delivery processes. This can all be documented and verified by recognized sustainability organizations, such as the Forest Stewardship Council (FSC) or others. As such, thermally modified wood is coming to be seen as a sustainable alternative to ipé or other tropical woods since it delivers the same or better performance traits with demonstrated sustainability.
Photo courtesy of Thermory USA
Thermally modified wood is created from common, sustainable wood species that are treated with heat and steam in a very precise, scientifically controlled manner.
The process of thermally modifying wood is focused on enhancing virtually every fiber of the wood, from the surface all the way through to the core. Nonetheless, the wood still retains its natural beauty since the grain is preserved and the coloration enhanced. While the surface can be coated with a clear finish if desired, the thermal modification is intended to allow the wood to be exposed and weather naturally over time without degrading. As such, it is delivered in a natural light-brown color that is the result of the heat process, not a stain. Over time, that color lightens to a natural light grey—much the same way that exposed cedar and teak naturally age in color or metal develops a patina. All the while, the integrity and the natural beauty of the wood remains visible and intact.
Performance Test Results
From a performance standpoint, thermally modified wood that is used for decking and porch flooring has been tested to show some very attractive traits. (Note that it is also used as exterior cladding in some cases with similar results.) First, in terms of durability, thermally modified white ash has achieved a Class 1 durability rating (25+ years), while thermally modified scots pine is rated for 20+ years of rot resistance. More specifically, testing has been conducted with fungus spores introduced to thermally modified ash samples with the intention of promoting fungal growth over a period of time. These samples were contrasted with control samples to interpolate the class of rot resistance based on European standards. The result was that a Class 1 rot resistance was achieved in thermally modified ash, which means that, on average, when used for decking or cladding, it can be expected to last outdoors for at least 25 years or more with minimal maintenance or added oils.
Photo courtesy of Thermory USA and JJW Architects/Brahl Fotografi
Thermally modified wood has been tested and shown to be a durable, rot-resistant solution that maintains the beauty and natural appearance of the wood.
Strength testing is important for all wood products and is the basis for determining span lengths, impact resistance, etc. In that vein, thermally modified ash was evaluated by calculating moisture content, weight, and density, and then subjecting it to a bending device to determine the tested strength of samples. Based on this, the impact resistance was calculated to have no significant change in surface hardness or strength in comparison to standard kiln-dried ash. Hence, its strength and surface are extremely suitable for designs that call for a wood decking surface.
An equally significant trait of any wood used outdoors is its propensity to soak in moisture, causing internal stresses as it expands or contracts accordingly. Hence, testing has been done to determine the moisture content of thermally modified wood compared to standard kiln-dried woods in a set of specific conditions related to temperature and relative humidity. The resulting measured increase in the moisture content of thermally modified ash was shown to be significantly reduced compared to standard kiln-dried woods.
Additional testing has been done that shows that thermal modification reduces the formaldehyde content of the wood more so than standard kiln-dried woods. Additionally, the rate of fire spread and smoke production in thermally modified ash is such that it achieves a Class B rating compared to kiln-dried red oak, which results in a Class C rating. Finally, termite resistance has been shown to be better in thermally modified wood, particularly ash, compared to a control species of southern pine.
Overall, thermally modified wood is proving itself as a viable, sustainable decking and flooring solution for outdoor spaces. It has the capacity to contribute to LEED credits while remaining versatile, appealing, and very workable. Santosh A George, ASLA, MLA, and a senior landscape designer in Irving, Texas, sums it up this way: “We wanted to use a sustainable product that was long lasting with minimal maintenance through the year. Our research said modified wood was the way to go.” It appears that more design professionals are agreeing with him.
Flooring Protection
An overriding component to sustainability in buildings is to extend the useful service life of products and materials as long as possible. Those that need to be replaced often obviously have a larger carbon footprint than the same product that is able to last longer in place. Similarly, products like flooring that require regular cleaning and maintenance can either require a fair bit of energy and cleaning products to keep the floor clean or properties can be incorporated to reduce maintenance. Toward that end, many facilities owners are quite pleased when something can be done to increase longevity, reduce slip and fall risk, and improve cleanliness and appearance, all while reducing maintenance efforts and costs.
Clear Protective Coatings
Architects and interior designers can assist in this process by specifying a clear, protective sealer or coating over flooring to preserve, prolong, and protect the floor. This is particularly true for designs that use hard-surface flooring, such as tile, terrazzo, slate, decorative stone, concrete, or even brick pavers. Such finish coatings are based on clear siloxane formulations that covalently bond with the floor surface to produce a strong, thin, high-traction, wearing finish. They commonly deliver excellent long-term protection of the original flooring and wear resistance against foot traffic, both inside or outside. That means the flooring is protected from corrosion, abrasive wear, stains, ultraviolet exposure, and even graffiti or chemicals. In some cases, such coatings may also mitigate micrbial growth, reducing the growth of mold and mildew, and eliminating odors—all of which makes for a healthier indoor environment.
Clear hard-surface finishes contribute to sustainable designs in other ways beyond extending the life of the flooring. A clear, hard-coat surface finish also means reduced maintenance and cleaning costs, particularly if grout is present. Grout between tiles can be problematic since it can absorb dirt and grime, leading to a condition that can be very difficult to clean. The coating can cover and seal the grout, preventing it from harboring dirt or grime. It can also make it easier to clean since the need for waxing and buffing the floor can be eliminated. This not only generates a very real reduction in the cost of cleaning but also means that the building is consuming less cleaning products, thus reducing its environmental footprint during building operations. When cleaners are used, they can readily be selected from very effective green cleaning products instead of relying on harsher chemical cleaners that may be detrimental to the interior and exterior environment.
The University of Florida has used clear floor treatments since 2001 on more than 250,000 square feet of bathroom and common-area tile floors and more than 60,000 square feet of concrete flooring in the student union area. According to Jim Crocker, assistant director of housing, these treatments have provided:
- A 30 percent or more reduction in cleaning cost measured in time, labor, and chemicals.
- Significant odor reduction in the bathrooms due to the sealed grout.
- A marked improvement in the aesthetic surface appearance.
- A quicker cleaning turnover of rooms during semester changes.
- An easier means of removing chewing gum and stains from concrete.
- No mold growth on exterior concrete, which is significant in humid Florida.
Photo courtesy of Adsil
When specifying clear coating finishes for flooring, a matte finish can be selected, as shown here, or a high-gloss finish can be chosen.
Specifying Performance
When specifying clear hard-surface coatings that seal and create a sustainable finish, following are some traits to include.
- Both a gloss and matte finish are available and should be selected as appropriate to the project needs.
- The finishing product should meet the requirements of ASTM D4060-14: Standard Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser. This test method has been useful in evaluating the abrasion resistance of coatings. It covers the determination of the resistance of coatings to abrasion produced by the Taber Abraser on coatings applied to a plane, rigid surface. This standard is similar in content (but not technically equivalent) to ISO 7784–2.
- The finished surface should carry certification by the National Floor Safety Institute (NFSI certified) for use as a high-traction surface, wet or dry. The NFSI is recognized for researching various test methods by which materials can be evaluated for their degree of slip resistance and offers the most comprehensive evaluation process to date.
- For locations where cleanliness is a concern, the coating should also meet ASTM G21-15: Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi. This practice covers determination of the effect of fungi on the properties of synthetic polymeric materials.
- Where extreme temperature tolerance is needed, the coating needs to meet ASTM D2485-18: Standard Test Methods for Evaluating Coatings for High Temperature Service. These test methods cover the evaluation of the heat-resistant properties of coatings designed to protect surfaces exposed to elevated temperatures during their service life.
Properly specified, these products can be expected to perform quite well. Michael A. Kulp of Prestige Restoration & Maintenance in Long Island City, New York, has experienced the day-to-day aspects of using a quality clear coating on hard-surface flooring and notes, “To date, we have not had to correct a single condition where our coating did not deliver as promised, and many of our commercial installations have lasted over three years before needing a recoat. Residential installations can last a lifetime.” That is testament to their performance and durability, but in addition, he observes, “We have received countless compliments regarding the ‘wow factor’ of newly restored flooring, noticeable reduction of odors in restrooms, and ease of cleaning and labor reduction after installation.” The full experience of the space is improved, thus creating a better, more sustainable indoor environment for owners, occupants, visitors, and employees.
Conclusion
Flooring and sustainability have become synonymous in recent years due to concerted efforts by manufacturers of flooring products. Self-leveling underlayments are formulated that reduce environmental impacts. Resilient sheet flooring can be specified that is more sustainable than other alternatives. Wood decking can be used that relies on domestically harvested sustainable wood that is thermally modified for durability. Clear coatings over hard surfaces can extend the life of flooring, reduce the need for harsh environmental cleaners, and create a safer walking surface. Overall, designers have more and better options to choose sustainable flooring in building projects of all types.
End Notes
1Based on environmental product declarations for USG Performance Flooring products (in progress).
2Based on environmental product declarations for USG Durock™ brand EcoCap HT™ and USG Durock™ brand EXG™ Concrete Repair Patch products (in progress).
3Buy Clean California. USGBC Los Angeles. Web. 7 May 2019.
Peter J. Arsenault, FAIA, NCARB, LEED AP, is a nationally known architect, consultant, continuing education presenter, and prolific author advancing building performance through better design. www.pjaarch.com, www.linkedin.com/in/pjaarch
