ABSTRACT Green building assessment tools provide a means of measuring the “greenness” of buildings to help building designers make effective decisions regarding long-term sustainability. Because these tools typically are employed during the early phases of the building process, they may tend to place more emphasis on initial building design rather than long-term operating life. As a result, current assessment tools may fail to properly consider durability and the potential consequences of premature deteriora¬ tion on long-term building sustainability. Starting with a review of current green building rating systems from the perspective of building durability, this paper will discuss the importance of designing for durability and how durability should be defined, measured, and incorporated into the building process. The objective of the paper will be the development of a practical approach to building envelope durability that can be used to help designers, owners, and managers achieve truly sustainable building design and operation. SPEAKER Jim Hoff is an experienced researcher in the building materials industry, currently serving as research director for the Center for Environmental Innovation in Roofing in Washington, DC. Jim also serves as president of TEGNOS Research, Inc., a research and consulting organization dedicated to expanding understanding of the building envelope. Dr. Hoff holds undergraduate degrees in psychology and architec¬ tural design as well as a master’s and doctorate in management. He has published numerous research articles on building system performance, quality management, and life-cycle analysis. CONTACT INFO: jhoff@roofingcenter.org or 317-679-1542 Hoff – 98 Proceedings of the RCI 24th International Convention Sustainable Buildings: Addressing Long Term Building Envelope Dur bility INTRODUCTION By providing a means of mea¬ suring the “greenness” of build¬ ings and key building systems, rating programs such as the LEED Green Building Rating System™ may help building pro¬ fessionals make effective deci¬ sions in the design of sustainable buildings. Because they are usu¬ ally employed during the early phases of the building process, however, such assessment tools may tend to place more emphasis on the initial design of a building rather than its long-term opera¬ tional life. As a result, current rat¬ ing systems may fail to adequate¬ ly consider durability and the potential consequences of prema¬ ture deterioration on building sustainability. Because the materials that make up the building envelope are constantly exposed to harsh weather conditions and expected to perform without failure for many decades, some researchers have expressed concern that the current green rating systems may place too little emphasis on prod¬ uct durability. This concern was clearly articulated in a paper pre¬ sented at the 11th Canadian Conference on Building Science and Technology by Jamie McKay, a LEED Accredited Professional (LEED AP): The majority of green building assessment systems focus on the design of the construct¬ ed building, with little focus on the effect of the building system’s life during operation. This tendency has resulted in a failure of many rating systems to properly consider dura¬ bility, life cycle cost, and the effects of pre¬ mature building enve¬ lope failures. (McKay, 2007, p.l.) The concern articulated by McKay and other researchers appears to be shared by the majority of construction profes¬ sionals who design, specify, and manage today’s buildings. Accor¬ ding to a Building Design & Con¬ struction survey of over 70,000 building designers and owners, the strongest opinion regarding sustainable construction was that building materials should be eval¬ uated on the basis of life cycle cost, long-term durability, and maintenance, and not just envi¬ ronmental impact and energy sav¬ ings (“White Paper on Sustain¬ ability,” 2003, p. 17). In response to these concerns, this paper will examine the con¬ cept of durability and its relation¬ ship to effective green building assessment. Using examples from the commercial roofing industry, the paper will also explore possi¬ ble strategies to effectively incor¬ porate consideration of durability into the assessment of buildings and building envelope systems. WHAT IS DURABILITY? According to most dictionar¬ ies, the broad definition of dura¬ bility is the ability to exist for a long time without significant dete¬ rioration. When applied to build¬ ings and building components, durability is typically defined in a similar manner but with several important distinctions. The Cana¬ dian Standards Association’s “Guideline on Durability in Buildings” (CSA S478-95, Rev. 2001) provides one of the most recognized definitions of building durability in North America. According to this standard, dura¬ bility is defined as the ability of a building or any of its components to • perform its required func¬ tions • in its service environment • over a period of time • without unforeseen cost for maintenance or repair. In contrast to the simpler dic¬ tionary definition, durability as applied to buildings must offer more than mere survival: it must also be capable of performing required functions. In addition, these functions must be per¬ formed not only for a long time, but for a specified period of time. And finally, although normal deterioration will obviously occur, there should be no unforeseen cost associated with this normal deterioration. Given the impor¬ tance of these distinctions, each of these concepts should be care¬ fully examined in order to fully integrate durability into the over¬ all building envelope design process. Perform Required Functions Although some building com¬ ponents and systems may have a single required function, the mod¬ ern building envelope must fulfill many roles. First and foremost, the building envelope must serve as a moisture barrier to resist the intrusion of moisture in many forms, including rain, snow, hail, Proceedings of the RCI 24th International Convention Hoff – 99 ice, and vapor. In addition to resisting moisture, the building envelope plays an important role in the redirection of moisture, both stormwater drainage and condensation. As one of the most significant contributors to a building’s thermal efficiency, modern building envelopes also must resist the movement of heat and cold, and at ever -increasing levels as energy costs continue to rise. Building envelope compo¬ nents also must resist wind, snow, and service and seismic loads, effectively transferring these loads to the building’s structural system. The building envelope also must provide a sat¬ isfactory level of fire resistance to facilitate evacuation of the build¬ ing and to reduce the spread of fire to adjacent buildings. Finally, the building envelope may serve as an important work platform for the building, housing critical mechanical equipment that must be serviced periodically. And with the development of “green” (vege¬ tated) and photovoltaic wall and roof systems, the concept of the building envelope as a service platform continues to expand. Each of these important functions must be addressed within any truly sustainable design. And if any of these required functions are omitted or ignored, the long¬ term sustainability of the entire building may be adversely com¬ promised. In Its Service Environment The phrase “service environ¬ ment” suggests a twofold ap¬ proach to the external factors affecting a roof system. First, the building envelope is surrounded by a unique climatic “environ¬ ment” consisting of a constantly changing mix of sun, wind, tem¬ perature, and moisture in many forms. Depending on the specific location, some of these climatic forces may be much more severe compared to other climates and locations. As a result, special measures frequently must be taken to ensure that the long¬ term durability of the building is not jeopardized by unique and extreme weather factors. Examples of such extreme envi¬ ronments include severe hail¬ storm zones, coastal areas subject to hurricanes and wind-blown debris, cold climate regions sub¬ ject to rapid temperature drops, and desert areas subject to extreme ultraviolet degradation. A roof also performs its “ser¬ vices” within this environment; and to the extent that these ser¬ vices involve human support, the roof system may also be impacted by a variety of human behaviors. And just like unique and severe climatic conditions, human impacts on some buildings may be much more severe than other situations. Examples of critical human impacts may include fre¬ quency/ density of use, motivation and attitudes of occupants, and frequency of equipment and maintenance service. Over a Period of Time The period of time in CSA S478-95 is commonly referred to as the service life of the building component or system. Obviously, any failure of any element of the building envelope to achieve its intended service life will seriously compromise the effectiveness of green assessment tools in direct¬ ing design choices and materials selection. Without Unforeseen Costs The use of the word “unfore¬ seen” suggests several key consid¬ erations for the full integration of durability into sustainable build¬ ing envelope design. First, the possibility of unforeseen costs suggests that planning is required to ensure that no costs are unforeseen. In addition, there is an equally strong suggestion that some level of cost should be expected (foreseen) for a building component or system to achieve meaningful durability. As a conse¬ quence, the lack of a detailed plan regarding ongoing monitoring and maintenance or the lack of a real¬ istic budget for these activities may compromise the ultimate sustainability of any building. GREEN BUILDING DESIGN AND DURABILITY Green Design and Service Function Expectations Although green building rat¬ ing systems may be useful in identifying the environmental impact of a construction product or system, these tools may not be as effective in determining which product will best perform the required service functions. As a result, effective green building design still requires value judg¬ ments regarding the suitability of the products analyzed and the validity of the green rating values. An example of such critical value judgments may be illustrated by the low-slope roofing industry’s best-practice recommendation for the use of a cover board over all foam roof insulation materials (NRCA, 2007, p.46). Resistance to thermal transmission and accom¬ modation of traffic loads are two of the key required functions of a roofing assembly. By reducing the potential for crushing of foam insulation under traffic loads, a cover board may help to extend the thermal efficiency and useful service of the underlying insula¬ tion and even facilitate its recy¬ cling or reuse. However, if a “green” assessment of roof assem¬ blies with and without a cover board is conducted without any differentiation in the useful ser¬ vice life of the two assemblies, the assessment may erroneously con¬ clude that foam insulation with¬ out a cover board offers a lower environmental impact. This apparent contradiction may occur because the inclusion of a cover board (and all of the related man- Hoff – 100 Proceedings of the RCI 24th International Convention Table 1 – Service Life Estimates for Low-Slope Roofing Systems (Years) Data Source: Opinion Historical Approval Manufacturer Survey Study Agency Warranty System Type: (Cash”) (Schneider”) Reports” Offerings” Asphalt BUR 16.6 13.6 20 20 SBS Modified 16.6 17.3 20 20 PVC n/ae n/ae 35 15 EPDM 14.1 16.8-18.4 20 30 TPO no data no data 20 30 Notes: a. Mean service life from Cash (1997), based on an opinion survey of industry participants. b. Mean service life from Schneider & Keenan (1997), based on end-of-service field reports . c. Estimated service life from British Board of Agrement Technical Approvals (BBA, 2008): 1) Asphalt BUR: BBA Certificate 94/3062 Chesterfield Roof Waterproofing Systems 2) SBS Modified: BBA Certificate 91/2618 Icopal HT Roof Waterproofing Systems 3) PVC: BBA Certificate 08/4532 Sarnafil PVC Roof Covering System 4) EPDM: BBA Certificate 92/2791 Carlisle Syntec Systems 5) TPO: BBA Certificate 87/1849 Anderson SureWeld Systems d. Published warranty offerings from NRCA Low Slope Roofing Materials Guide, 2006-07, Vol. 2, Section 5, Roof Membrane Warranties. 1) Asphalt BUR: GAF Materials Corp. “Diamond Pledge™ Roof Guarantee.” 2) SBS Modified: GAF Materials Corp. “Diamond Pledge™ Roof Guarantee.” 3) PVC: Johns Manville International, Inc. “UltraGard Roofing System Guarantee.” 4) EPDM: Firestone Building Products Co. “Platinum Roofing System Limited Warranty.” 5) TPO: Firestone Building Products Co. “Platinum Roofing System Limited Warranty.” e. Data from the Cash & Schneider studies involved discontinued formulations of PVC that do not allow the data to be meaningful. ufacturing, installation, and dis¬ posal inputs) merely adds to the total environmental impact of the roofing assembly without con¬ tributing any acknowledged bene¬ fit for the potential increase in service life of the insulation. Similar examples of materials and practices that may add to durabil¬ ity and service life but may be overlooked based on initial envi¬ ronmental impact include the use of stone protection mats with bal¬ lasted roofing systems, the incor¬ poration of secondary membranes or other redundancy in hurri¬ cane-prone regions, and the use of thicker or redundant mem¬ branes in high hailstorm regions. Green Design and Service Life Expectations The accuracy of any green building rating system may be highly dependent on the validity of the service life assigned to the products and systems being eval¬ uated. To the greatest extent pos¬ sible, the assignment of a service life period should be based on reliable and reproducible data developed from rigorous scientific or empirical research. Unfortu¬ nately, little such service life data are available for modern building envelope systems, and what data are available appear to contain many limitations and contradic¬ tions. An example of these limita¬ tions and contradictions can be illustrated by a review of various service life estimates available for low-slope roofing systems. As illustrated in Table 1, estimates for the service life of almost all major low-slope roofing systems vary from slightly more than a decade up to 30 years, depending on data source and methodology. Given this sizable variation, how can the building designer establish an appropriate service life to conduct a meaningful “green” assessment? The best answer to this question may lie in several important distinctions among these estimates. One of the most apparent dif¬ ferences among these estimates is their temporal perspective. The relatively low service life estimates from the opinion survey and his¬ torical study may be considered backward looking because the estimates are based on the perfor¬ mance of previously installed roofs that may or may not meet today’s design and installation standards. In contrast, the rela¬ tively higher estimates based on product certifications and pub¬ lished warranty offerings may be considered more forward looking because the estimates may be Proceedings of the RCI 24th International Convention Hoff – 101 based on the expected future per¬ formance of roofing systems uti¬ lizing the most recent improve¬ ments in materials and installa¬ tion methods. These estimates of service life may also be differentiated based on the quality level they assume. As an example, the roof popula¬ tions from survey and historical studies may include a mix of roofs that were poorly designed, con¬ structed, and maintained, as well as those that included superior design, installation, and mainte¬ nance. In this regard, the roof populations covered by these mo¬ dels are more likely to represent average quality rather than the best that the industry should strive for. In contrast, the quality level expected by the agency certi¬ fications and published warranty offerings may be much higher because these estimates likely assume the best in both materials and practice. In this regard, agen¬ cy certifications and manufactur¬ er warranties are more likely to represent ideal results that may neglect to consider chronic prob¬ lems or unusual difficulties that must be overcome by truly sus¬ tainable roofing systems. In regard to service life esti¬ mates based on warranty term, it should be noted that warranty length may not be a representa¬ tive indicator of durability, since warranties represent both a con¬ tractual promise and a model specification. However, it is also worth noting that previous stud¬ ies of roofing warranties suggest that warranty length may be relat¬ ed to the redundancy or durabili¬ ty of the components used (Hoff, 2005), and research from other industries suggests that war¬ ranties may be a reasonably accu¬ rate directional signal of product longevity (Weiner, 1985; Kelly, 1988). DURABILITY TOOLS FOR A SUSTAINABLE FUTURE The contrast between forward¬ looking versus backward-looking service life estimates and average versus high quality levels may help identify a critical decision point for the building envelope industry. Should the industry move forward with the assump¬ tion that the roofs and other ele¬ ments of the building envelope installed on the green, sustain¬ able buildings of the future will be average in performance, or should the expectation be set higher? And if the industry decides to move forward with higher expec¬ tations, how does it develop and implement processes and controls to ensure this higher level of per¬ formance is attained? Although current understanding of long¬ term durability and service life may be limited, there are several tools that may be used and pro¬ moted by the building envelope industry to improve the durability of building systems and effective¬ ly integrate building envelope durability into sustainable build¬ ing practice. Failure Analysis/ Best Practice Guidelines One area of research that appears to have yielded useful results involves the evaluation of important failure mechanisms within modern building envelope systems. And although the rela¬ tionship between these failure mechanisms and overall service life is not fully quantified, under¬ standing of these failure mecha¬ nisms has fostered the develop¬ ment of effective countermea¬ sures to prevent, mitigate, or quickly repair these failure loca¬ tions. One of the most compre¬ hensive examinations of building envelope failure mechanisms was conducted by Bailey and Bradford in 2005. This study of over 24 mil¬ lion square feet of asphalt and single-ply roof systems managed by the U.S. Army identified criti¬ cal defects ranging from initial material selection to long-term maintenance activities that accounted for approximately 75% of all observed roof performance problems. In turn, the identifica¬ tion of these key defects was used by the authors to develop best¬ practice recommendations for all stages of roof system asset man¬ agement. Although little research is available to correlate failure analysis to eventual service life, it is likely that the defects observed by Bailey and Bradford contribute to the unusually wide variation in roof service life estimates previ¬ ously discussed in this paper. And if the defects observed in this study were effectively addressed using the countermeasures iden¬ tified in these studies, it is also likely that service life would quickly start to climb toward the higher end of current estimates. It is also important to note that almost all the recommendations from the Bailey and Bradford study are available in many cur¬ rent roofing industry best-prac¬ tice guidelines for roof system design, installation, maintenance and repair. An emerging example of the best-practice approach to durabil¬ ity can be found in the recent activities of the Performance Council for Constructed Roofing Systems (PCCRS). The objective of PCCRS is “to provide building owners and the roofing industry with conservative and dependable criteria for constructed roof sys¬ tems that achieve cost-effective, long-term performance relative to the roof system type. ’’(Bailey, 2004.) In order to achieve this goal, PCCRS has developed a con¬ sensus process that will allow the accumulated experience of the roofing industry to be identified, validated, and incorporated in best-practice guidelines for all major low-slope roofing system types. Hoff – 102 Proceedings of the RCI 24th International Convention This process begins with a cri¬ teria council composed of recog¬ nized and experienced roofing professionals representing all major industry stakeholders, including roof consultants, roof¬ ing contractors, building re¬ searchers, materials manufactur¬ ers, and building managers. The council appoints and oversees cri¬ teria development groups (CDGs) responsible for developing perfor¬ mance criteria for specific roof system types, addressing roof sys¬ tem design, materials, installa¬ tion, and maintenance issues. After the development of draft per¬ formance criteria for each roof system type, the criteria are sub¬ ject to extensive public review and comment before they are formally published. At the time of the drafting of this paper (August 2008), the first two performance criteria, (for built-up membrane roof systems and for spray polyurethane foam roof systems) are approaching the end of public review and should be formally published early in 2009. These two published docu¬ ments will be followed by the development of performance crite¬ ria for PVC and EPDM roof sys¬ tems, which hopefully will be pub¬ lished in 2010. Although the PCCRS criteria documents may provide the optimum way to con¬ solidate the “best of the best” in industry practice, the criteria do not specifically address the issue of service life in a quantifiable manner. However, these docu¬ ments may provide a productive platform to deal with service life expectations through the use of a second potential tool: durability planning. Durability Planning Roofing industry research in failure analysis combined with proven best-practice guidelines may set the stage for the effective use of planning to maximize roof service life and minimize environ¬ mental impacts. In addition to providing a useful definition of building durability as discussed previously, CSA S478-95 also pro¬ vides a comprehensive methodol¬ ogy and framework to make deci¬ sions on durability. The guideline addresses important elements of durability planning, including quality assurance, methods to predict service life, design and construction considerations, and operating and maintenance pro¬ grams. The guideline also pro¬ vides helpful overall procedures and sample project formats that can be utilized to develop and implement an effective durability plan for any building or building system. Generalizing from the durabil¬ ity planning recommendations in CSA S478-95, the following processes appear to be the most important steps in developing an effective durability plan for a roof¬ ing system: 1. Identify the critical durabil¬ ity determinants. Failure analysis from studies such as Bailey and Bradford (2005) will help building designers identify which design, mater¬ ial, installation, and service factors hold the most value in optimizing the service life of the roof system. 2. Identify the critical durabil¬ ity interventions. Using the recommendations derived from failure analysis research and industry best-practice guidelines, the building designer can identify specific interventions or countermea¬ sures to prevent or mitigate degradation of roof service life due to critical durability determinants. These counter¬ measures may take a number of forms, including initial design enhancements, ongo¬ ing inspection and mainte¬ nance procedures, and major renewal or repair initiatives of key roof system components and details. 3. Develop an action plan and timetable. Using the recom¬ mendations and the suggest¬ ed formats of the CSA dura¬ bility guideline, the building designer can develop a long¬ term actionable plan that can be incorporated into ongoing building maintenance activi¬ ties. These key steps for effective durability planning may appear obvious. But the wide variation in service life data of roofing systems previously discussed suggests that what may be obvious has never been seriously implemented on a large scale by building designers and owners. And if green building rating systems are to fulfill their long-term potential to reduce environmental impact, durability planning must become a vital and integrated part of these rating systems. In addition, because these steps may provide an effective way to evaluate different combi¬ nations of material, design, and service options to determine what combination will provide the low¬ est overall environmental impact, durability planning may con¬ tribute both to the identification of viable sustainable roofing options, and to the efficient evalu¬ ation and selection of the most suitable options for a particular building application. The use of key durability determinants and durability interventions may also facilitate rigorous evaluation of the trade-offs between increasing roof system durability (and per¬ haps increased roof system cost and environmental impact) in the initial design and installation of the roof system as compared to periodic increments of durability (at perhaps a lower overall cost and impact) provided by system maintenance and repair interven¬ tions. Proceedings of the RCI 24th International Convention Hoff – 103 An emerging example of dura¬ bility planning applied to the building envelope is currently under development by one of the newest CDGs formed by the PCCRS Council. Ed Kane, the chair of the EPDM Roofing System CDG, has developed a preliminary criteria development and durabili¬ ty planning matrix that incorpo¬ rates the key elements of PCCRS (design, materials, application, maintenance) along with the key elements of durability planning (required function, service envi¬ ronment, planned mainte¬ nance/ repair, service life period). In addition to the previously dis¬ cussed performance and durabili¬ ty dimensions, Kane has added the dimension of commissioning to verify and validate initial roof¬ ing installation and performance. A preliminary version of this matrix is provided in Appendix A of this paper. Using this type of matrix, the building professional may address each key dimension of roof system performance in a methodical fa¬ shion. Starting with a delineation of the service environment and the required system functions, the matrix allows the professional to consider the best criteria to address design, materials, appli¬ cation, and commissioning for each critical component of the building system. After identifying the critical performance criteria, the matrix then directs the build¬ ing professional to consider the long-term aspects of the roofing system for different service life periods, such as 20 years, 30 years, or longer. Critical issues addressed by the service life por¬ tion of the matrix include antici¬ pated inspection, maintenance, and repair activities, as well as possible trade-offs between these activities and eventual service life. Finally, the matrix directs the building professional to consider end-of-service issues, such as removal, disposal, replacement, and potential recycling opportuni¬ ties. Because the new CDGs have just been established at the writ¬ ing of this paper (August 2008), it is hoped that more information about this matrix approach to durability planning will be avail¬ able before the formal presenta¬ tion of this paper in March 2009. Combining Best-Practice and Durability Planning: The “Tenets of Sustainable Roofing.” With its emphasis on both the best practices and the planning processes necessary to achieve environmentally responsible roofs, the “Tenets of Sustainable Roofing” as developed by the CIB / RILEM Environmental Task Group (Hutchinson, 2001) may serve as a useful tool. The Tenets model uses a similar category¬ based approach as LEED, but only three basic categories are required: 1. Minimize the burden on the environment 2. Conserve energy 3. Extend roof lifespan Unlike the current LEED model, the Tenets model places a significant emphasis on the dura¬ bility of materials. While none of the five basic categories of the current LEED model address durability, the Tenets model dedi¬ cates one-third of its focus on durability and life cycle perfor¬ mance. And, with the exception of some elements of indoor environ¬ mental quality, the remaining two categories of the Tenets model fully cover all current LEED cate¬ gories. The Tenets model also con¬ tains 20 subcategories, many of which are strikingly similar to the subcategories in LEED. (See Appendix B for a full listing of the Tenets subcategories.) RECOMMENDATIONS GOING FORWARD Continued Development of Durability Planning Because the lack of meaning¬ ful consideration for durability within many green building assessment tools may fatally com¬ promise their results, the building envelope industry should insist that every green-building-envelope system assessment or rating be accompanied by a detailed durability plan that identifies and addresses key failure mecha¬ nisms, through enhanced robust¬ ness or redundancy, planned maintenance and repair, or a combination of both. Given the head start CSA Standard S478-95 offers in establishing a meaning¬ ful approach to consistent dura¬ bility planning, the industry should thoroughly familiarize itself with this standard and be prepared to promote it and advance it as a best-practice model. In addition, the prelimi¬ nary durability planning matrix developed by Kane (2008) appears to offer a productive format to accomplish this task. New Research Initiatives to Support Industry Best Practice As mentioned previously, there are a number of important industry best practice standards that may require value judgments when a green building assess¬ ment is conducted. As an exam¬ ple, the use of cover boards appears to offer long-term sus¬ tainable value, but little scientific research has been conducted to quantify this value or relate this value to the opportunity for reduced environmental impact. In a similar manner, industry best¬ practice guidelines for the use of multiple layers of roof insulation, the staggering of insulation joints, and the elimination of throughfastening thermal bridges also appear to provide long-term value in regard to energy efficiency, but Hoff – 104 Proceedings of the RCI 24th International Convention this value also lacks definitive research evidence to quantify its contribution to reducing environ¬ mental impact. Additional indus¬ try research in these and similar areas may be very helpful in ensuring that green building rat¬ ing systems incorporate the very best environmental benefits of modern low-slope roofing sys¬ tems. Use the “Tenets of Sustainable Roofing” as a Template As previously mentioned, the Tenets model offers almost every key construct contained within LEED, with the added benefit of including durability as primary category. The Tenets model also contains 20 subcategories (See Appendix B), many of which are strikingly similar to the subcate¬ gories in LEED. Given the suc¬ cinct but comprehensive struc¬ ture of the Tenets model, a credit¬ based rating system for roofing might be developed using the 20 Tenets subcategories as easily as (or perhaps more easily than) the current LEED model. If the roofing industry decides to develop and advance an inde¬ pendent rating program for roof¬ ing, the “Tenets of Sustainable Roofing” could provide the same broad-based but simple approach that has made LEED so popular. Or if the roofing industry decides to work within LEED to develop a “Roofing LEED” program, the Tenets may serve as a simple and effective reminder about the importance of durability. REFERENCES: Bailey, A. P., “Creating Perfor¬ mance Criteria: An Initiative to Develop Performance Cr¬ iteria for Roof Systems Begins with BUR and SPF, Pro¬ fessional Roofing, September 2004. Bailey, D. M., & Bradford, D., “Membrane and Flashing De¬ fects in Low- Slope Roofing: Causes and Effects.” Journal of Performance of Constructed Facilities, August 2005, 234- 243. BBA, British Board of Agrement Technical Approvals for Construction. Available www.bbacerts.co.uk. 2008. CSA, Standard Guideline on Dur¬ ability in Buildings S478-95 (R2001). Mississauga, ON: Canadian Standards Associa¬ tion, 2001. Cash, C.G., “The Relative Dur¬ ability of Low-Slope Roofing,” Proceedings of the Fourth International Symposium on Roofing Technology, 119-124. Rosemont, IL: National Roof¬ ing Contractors Association, 1997. Hutchinson, T. W., “Designing Environmentally Responsive Low-Slope Roof Systems,” In¬ terface, RCI, Inc., November 2001. (See Appendix B.) Hoff, J. L., “Equivalent Uniform Annual Cost: A New Ap¬ proach to Roof Life Cycle Analysis.” Interface, RCI, Inc., January 2007. Kane, E., Preliminary Durability Planning Matrix. Unpub¬ lished, 2008. (See Appendix A.) Kelley, C. A., “An Investigation of Consumer Product Warran¬ ties as Market Signals of Product Quality, Journal of the Academy of Marketing Science, 16, 2, 72-78, 1988. McKay, J., “Green Assessment Tools: The Integration of Building Envelope Dura¬ bility,” Proceedings of the 11th Canadian Conference on Building Science and Tech¬ nology. Banff, Alberta: Na¬ tional Building Envelope Council, 2007. NRCA Low-Slope Roofing Mater¬ ials Guide, 2006-07, Vol. 2. Rosemont, IL: National Roof¬ ing Contractors Association, 2006. NRCA Roofing Manual: Mem¬ brane Roof Systems – 2007. Rosemont, IL: National Roof¬ ing Contractors Association, 2007. Schneider, K. G. and Keenan, A. S., “A Documented Historical Performance of Roofing As¬ semblies in the United States, 1975-1996,” Proceedings of the Fourth International Sym¬ posium on Roofing Tech¬ nology, 132-137. Rosemont, IL: National Roofing Con¬ tractors Association, 1997. Wiener, J. L., “Are Warranties Accurate Signals of Product Reliability?” Journal of Con¬ sumer Research, 12, 2, 245- 250, 1985. White Paper on Sustainability, supplement to Building De¬ sign & Construction, Novem¬ ber 2003. Proceedings of the RCI 24th International Convention Hoff – 105 APPENDIX A PRELIMINARY DURABILITY PLANNING MATRIX: BALLASTED EPDM ROOFING SYSTEM Hoff – 106 Proceedings of the RCI 24th International Convention APPENDIX A PRELIMINARY DURABILITY PLANNING MATRIX: BALLASTED EPDM ROOFING SYSTEM (continued) At 60 Years • • ^^^moval/Recycling C© o z • • Peel up walk pads; recycle (similar to tires) • Cut seams out of membrane (6” per 30-50 ft width); recycle as energy source or into application to be developed • Vacuum ballast; stockpile for re-use • Route to processor for grinding and incorporation into walk pads or other application to be developed 0C O z • • No fasteners; inspect boards for re¬ use or route to existing recycling applications ♦ No fasteners; inspect boards for re¬ use or route to existing recycling applications c© o z • c© o z • • Do not remove unless necessary c a E 0 At 40 Years • • At 40 Years at*? 1 o Q • vl • • • • • • • • • Manag At 20 Years • • At 20 Years • • • • • • • • • • Beginning with Commissioning • Control roof access; maintain access log; • Inspect roof every spring/fall, after threatening activities on, above or near the roof, after new equipment or penetrations are installed, and after any activity that may have jeopardized the roof • Log leak reports along with related conditions • Confirm clean drains and good roof drainage • Any new rooftop installation shall be ‘ reviewed with the roofing contractor for its impact on the roof system Beginning with Commissioning • Review roof traffic patterns and add walkway pads where needed • After a high wind event inspect roof ballast for points of scour and evenly redistribute ballast to original sef^ag^ v a* Service Environment Required Function Roof System Element 11. Field Applied Coating 10. Membrane System Upgrade 09. Membrane Seifning 08. Membrane Securement 07. Membrane 06. Overlayment (incl fastening) 05. Insulation (incl fastening) [ 04. Insulation I (incl | fastening) I 03. j Underlay i merit 1 02. Vapor | control 01. Deck Proceedings of the RCI 24th International Convention Hoff – 107 APPENDIX B THE TENETS OF SUSTAINABLE ROOFING (CIB / RILEM Joint Committee on Roofing Materials and Systems – Environmental Task Group, October 2000) MINIMIZE THE BURDEN ON THE ENVIRONMENT 1. Use products made from raw materials whose extraction is least damaging to the environment. 2. Adopt systems and working practices that minimize waste. 3. Avoid products that result in hazardous waste. 4. Recognize regional climatic and geographical factors. 5. Where logical, use products that can be reused or recycled. 6. Promote the use of “green roofs” supporting vegetation, especially on city center roofs. 7. Consider roof designs that ease the sorting and salvage of materials at the end of the life of the roof. CONSERVE ENERGY 8. Optimize the real thermal performance, recognizing that thermal insulation can greatly reduce heating or cooling costs over the lifetime of a building. 9. Keep insulation dry to maintain thermal performance and durability of the roof. 10. Use local labor, materials, and services wherever practical to reduce transportation. 11. Recognize that embodied energy values are a useful measure for comparing alternative constructions. 12. Consider the roof surface color and texture with regard to climate and the effect on energy and roof sys¬ tem performance. EXTEND ROOF LIFESPAN 13. Employ designers, suppliers, contractors, tradespeople, and facility managers who are adequately trained and have appropriate skills. 14. Adopt a responsible approach to design, recognizing the value of the robust and durable roof. 15. Recognize the importance of a properly supported structure. 16. Provide effective drainage to avoid ponding. 17. Minimize the number of penetrations through the roof. 18. Ensure that high-maintenance items are accessible for repair or replacement. 19. Monitor roofing works in progress and take corrective action as necessary. 20. Adopt preventive maintenance, with periodic inspections and timely repairs. Hoff – 108 Proceedings of the RCI 24th International Convention
