By Mike CagleAlternatives to using hot asphalt for built-up roofing systems and hot asphalt or a torch to apply modified bitumen roofing systems have been available for many years, but it is only in the last several years that we have begun to see a trend toward increased use of cold adhesives. This trend, in part, has been driven by the sensitivity of some individuals to hot asphalt fumes and additional safety measures required for torching.It was not until the last few years that manufacturers developed adhesives that are effective with insulation, substrates, and membranes, qualifying cold applied systems for Factory Mutual approval. As a result, cold applied systems now represent a very viable alternative for multi-ply bituminous roofing systems.These cold applied systems are particularly effective on roofing projects that have difficult access, such as high-rise buildings in downtown areas or in areas where odor can be of concern such as schools, hospitals, or hotels. Another advantage of these systems is that with specialized equipment they can be applied year-round and are particularly effective in cold weather.The techniques used in the application of cold applied systems are significantly different than those using hot asphalt or a torch. As a result, additional training is required. Also, it is important for roofing contractors to be aware of the special precautions that must be taken in using industrial materials that contain solvents. To decrease cure time of the adhesives, either more volatile solvents must be used or the use of higher solids contents is incorporated into product formulations. The more volatile solvents may have adverse effects on the modified bitumen compound, whereas the higher solids formulations have a higher viscosity, which may make application more difficult. However, careful formulation of the higher solids adhesives can provide a reasonable compromise, producing adhesives with low solvent content that still give acceptable set-up times.The industry also is innovating in other ways. Reusable 350-gallon totes are now being used as a container for the adhesive. A line is run from the tote to the roof so that the adhesive can be applied by a spray or pump. Once the tote is empty, it can be returned and reused, minimizing the use of valuable landfill space and disposal of hazardous material.The performance of a cold applied roofing system can be equal to those mopped in hot asphalt or torch applied. While both built-up roofing and modified bitumen systems can be applied with cold adhesives, the real growth in this application method is expected to come in modified bitumen systems that are less labor-intensive.In the future, we believe that there will be an increased demand for cold applied bituminous roofing systems. By combining the advantages of cold adhesives with the advantages of multiple plies of roofing membrane, the industry can offer its customers a roofing system with proven long-term performance, without some of the disadvantages of mopped or torch applied systems.Mike Cagle is market manager at Johns Manville Roofing Systems Group (www.jm.com), Denver.