Green Bonds

The role of adhesives in environmentally conscious construction.

Although the idea of environmentally conscious building is as old as architecture itself, people tend to associate the concept with a lifestyle radically different from the mainstream. Green building is, however, a growing trend and does not have to mean living in a cave or building with hay bales. Even large-scale developers of residential homes are leaning toward more environmentally sound habitats with Energy Star-qualified homes that are at least 30% more energy efficient than homes built to the 1993 national Model Energy Code. The idea is that anyone can contribute to conserving natural resources and promoting healthier living spaces because even a series of small efforts will add up to significant improvement.

Going Green

In looking at the effects of environmentally conscious building on adhesive selection, it makes sense to turn to California. California has, from the beginning, been the leader in air-quality improvement efforts by passing the nation's first comprehensive clean air act in the 1950s, followed by the first volatile organic compound (VOC) regulations in 1986. Since California first began implementing VOC guidelines, the federal government has followed with nationwide VOC regulations, as well as more stringent regulations in other states and regions. California is also the source of the U.S. Green Building Council, which founded the Leadership in Energy & Environmental Design (LEED) Program. Today, over 19,000 architects and designers in the United States and Canada are LEED certified, with many more informally following all or part of the LEED principles. The LEED code specifically addresses adhesive selection in Chapter 4 by recommending that construction adhesives contain no more than 50-250 g/l of VOCs, depending on the application. The LEED code also suggests urea-formaldehyde be avoided.

Beyond LEED recommendations and VOC regulations, there are, according to California's leading "green" architects and designers, three basic factors to consider when making adhesive selections: building materials, third-party evaluations, and innovative raw materials/uses.

Building Materials

Ultimately, the materials and methods used to construct a building will determine the type of adhesive needed. Historically in the United States, wood has been the most prevalent building material for residential structures, and continues to maintain predominant levels of popularity. However, several forms of concrete have been gaining ground over the past several years, namely pre-cast concrete and concrete blocks. This particular method of construction can use cartridge and canned adhesives, but they will not be needed to the extent normally seen in wood frame houses. There will also be a significantly higher need for epoxies and chemical anchors in cement construction as opposed to wood.

An increased interest in chemical anchors will cause issues such as application to become more important. The industry is currently debating whether glass capsules or double-barrel cartridges are better. Some manufacturers have suggested the scarification of the substrate obtained when the capsule is broken will improve adhesion. Although this is not a completely unfounded claim, it has not actually been tested, and any difference is likely to be minimal. Small contractors prefer glass capsules because they do not require investment in nozzles, guns or mixing equipment. Still other contractors prefer the double-barrel cartridges because they offer flexibility in application amount. There is also a third method of application: the single-barrel cartridge. Although there are only a limited number of manufacturers who offer two-part chemical anchoring systems in single-barrel cartridges, the benefits are immediately noticeable. Single-barrel cartridges combine the freedom from additional investments with the flexibility of application. Most contractors already have a gun for use with single-cartridge systems because several other varieties of construction chemicals are packaged in the same way.

Although an increase in concrete-based homes due to environmental concerns is a niche market, it is expected to have a significant impact on the type and quantity of adhesive a contractor chooses to purchase.

Two alternatives to the traditional stick-built home are structural insulated panels (SIPs) and insulating concrete forms (ICFs). Both options offer increased energy efficiency and noise control due to their enhanced insulation qualities.

SIPs are made by laminating a layer of expanded polystyrene (EPS) between two layers of plywood or oriented strand board. The high-pressure lamination creates a strong building material that does not need a traditional wooden frame. SIPs generally use adhesive sealants to fill gaps and offer minor support to the mechanical fasteners such as nails and screws holding the panels in place. Adhesives may also be used to finish out the SIPs with drywall, although they can be ordered with the drywall already attached. The most important aspect of adhesives used in SIPs is that they be compatible with foam materials (EPS). Some adhesives may have a poor reaction with EPS and dissolve the foam. An increase in the use of SIPs as a building material is expected to translate into an increase in foam board adhesive sales.

Insulating concrete forms (ICFs) also use EPS. Walls are constructed using hollow EPS blocks. Builders then add steel supports and pour concrete between the gaps created by the blocks. ICFs have also been found to promote energy efficiency and expand the life of the structure. Green building principles are based on conserving natural resources and re-using items when possible. These are the primary reasons driving the usage of this building material. While the concrete itself does not necessarily require adhesives, the forms do. Spray-foam adhesives offer the best solutions for bonding these forms.

ICFs are also sensitive to certain types of adhesives. Several ICF manufacturers recommend spray-foam adhesives for creating the polystyrene block structure. ICF blocks are glued together before the reinforcing steel is added or the concrete is poured.

The special adhesives needs of ICFs and SIPs require contractors to select solvent-free adhesives. Two such adhesives recommended by ICF and SIP manufacturers are Dow's Enerbond SF spray-foam adhesive and Henkel's PL 300 Foamboard adhesive.

Third-Party Evaluations

Third-Party Evaluations are important because they allow people with specific environmental concerns to test adhesives for particular traits and chemicals. Third-party evaluations also allow builders to obtain more objective endorsements and recommendations on adhesives without the biases of parties with financial interests in adhesive sales or reputation. Some companies that perform third-party testing and evaluations are Green Guard, Scientific Certification Systems, and Building Green.

Green Guard tests and certifies products for air quality emissions. The only adhesive products tested and certified by Green Guard are ITW TACC C217 and C357. These products have been certified for "Indoor Air Quality," but are more for cabinetry and woodworking rather than general-purpose construction. Scientific Certification Systems also has certified few construction adhesives. SCS-certified adhesives are mostly for flooring, such as tile or carpet adhesives. Building Green lists Franklin's Titebond Solvent Free Construction Adhesive in its green materials database. It also lists Speed Grip, an adhesive used for installing residential siding.

Out of the three major third-party evaluating groups, only one addresses construction adhesives. Even so, it does not offer a large variety of approved construction adhesives. Part of the issue can be attributed to lack of unified testing standards, and lack of regulations requiring testing be done. The lack of construction adhesives certified by outside parties could be fortuitous for those who choose to have their materials tested. If a builder is looking for an adhesive that has a verified green status, and only finds one, it may have a significant impact on the brand of adhesive chosen.

New Materials/Uses

Currently, the construction industry is witnessing a move toward innovative materials. Researchers are looking for ways to use adhesives traditionally used in one industry in other industries. One merely has to look to the automotive, marine or electronics industries to find new adhesives. Industry crossovers are important because they offer a wider range of choices to adhesive users. According to basic number probability, the more choices available, the more power builders and architects have to choose greener options. Two things that make the crossing of industries possible are technological advances and industry changes.

Technological advances may allow adhesives from other industries because it has become easier to analyze and reformulate adhesives. Because the time taken to evaluate the properties of an adhesive has shortened, it is a more economically feasible solution to portfolio expansion. Adhesive crossovers due to industry changes, on the other hand, occur when new materials or methods are used in construction that make it more similar to another industry, thus opening the door to the possibility of crossovers. Industry-crossing adhesives are not necessarily a new idea, but become increasingly prevalent as industry evolves. Architects have begun to use 3M's automotive VHB tape, for example, in high-rise claddings. This is just one example of how the evolution of architecture to include metal buildings allowed automotive adhesives to be used in construction settings.

When looking at new materials for adhesive use, it is also important to recognize that adhesive raw materials are sometimes more suited for one application or industry over another. Two alternate materials industry participants have been speculating about recently are soy and mussel.

Soy is already being used as plywood adhesive. It has been found to be a greener and more cost-effective solution to manufacturing plywood than conventional options. From a beginning based in plywood, soy could also be formulated for other construction purposes and applications.

After scientists at Purdue University found the protein that causes mussels to attach to underwater surfaces in January 2004, much talk has been made about replicating the protein for uses in medical adhesives. The ability of mussels to withstand tidal and predatorial pressures suggests that their adhesive properties may be useful in high-rise buildings that also need to withstand pressure from multiple sources. At the moment, this is merely speculation and may not be structurally or economically worthwhile. But literally any advance made in adhesives brings with it the potential to also affect construction adhesives specifically. These findings and ideas, coming from other industries, should be giving researchers studying and developing construction adhesives an excellent advantage over starting from scratch.

Construction Adhesives and Green Building - A Tenuous Relationship?

Beyond VOC regulations, adhesives are often overlooked when it comes to green building practices. It is an area with many opportunities to gain end-user interest and prestige. Green building practices will continue to filter into mainstream building practices until there is no difference between the two. Adhesive manufacturers who recognize this and actively look at all angles of green building implications will be more sustainable in the construction adhesive industry.

Frost & Sullivan, a global growth consulting company, has been partnering with clients to support the development of innovative strategies for more than 40 years. The company's industry expertise integrates growth consulting, growth partnership services, and corporate management training to identify and develop opportunities. Frost & Sullivan serves an extensive clientele that includes Global 1,000 companies, emerging companies, and the investment community by providing comprehensive industry coverage that reflects a unique global perspective and combines ongoing analysis of markets, technologies, econometrics, and demographics. For more information, visit www.frost.com or e-mail Trisha Bradley at trisha.bradley@frost.com.