In The Dark: A Practical Approach To Keeping Low-Slope Wood Deck Roof Systems Dry Jennifer Keegan, AAIA and James Willits GAF 1 Campus Drive, Parsippany, NJ 07054 Phone: 973-628-4117 • E-mail: Jennifer.keegan@gaf.com; james.willits@gaf.com RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 1 4 – 1 9 , 2 0 1 9 K e e g a n a n d Wi l l i t s • 1 4 3 Abstract The roofing industry has been focused on the energy-efficiency benefits of cool roofs. Most nonreflective membrane roofs are and have been reroofed with reflective membrane roofs. When this happens, the benefit of the previous dark roof to “self-dry” can be lost. Moving from a dark-colored membrane to a reflective membrane can reduce the drying potential of the roof system due to a reduction of heat gain, thus increasing the potential for damage from condensation in older assemblies. However, it has been very well documented that properly designed cool roof assemblies with appropriate air barriers do not have moisture issues. Additionally, it has been shown that nonreflective, self-drying roofs have concealed design flaws and improper venting due to their significant heat gain. This study includes extensive modeling of the effects of using dark-colored roof membranes versus reflective roof membranes on existing wood roof deck assemblies. A large-scale case study evaluates the effects of retrofitting a reflective membrane with a dark coating to determine its ability to mitigate condensation within the cool roof assembly that lacks a proper air barrier, and the potential to dry out the wood roof deck over time. Speakers Jennifer Keegan, AAIA – GAF – Parsippany, NJ JENNIFER KEEGAN is the director of building & roofing science for GAF. This position is focused on the relationships between individual roofing materials and the overall roof system and building envelope performance. Keegan has over 20 years of experience as a building enclosure consultant specializing in assessment, design, and remediation of building enclosure systems. Her experience ranges from design assist efforts, to forensic investigations, litigation support, and repair design. She provides technical leadership within the industry as the chair of the ASTM D08.22 Roofing and Waterproofing Subcommittee, and as an advocate for women within the industry as the educational chair for National Women in Roofing. James Willits – GAF – Parsippany, NJ JAMES WILLITS has nearly a decade of experience in the roofing industry as an installer, a project manager, a salesperson, and a training manager. As the building & roofing science specialist for the western region of GAF, Willits translates his practical knowledge and experience to building envelope performance, with a strong focus on the roofing materials and the complete roof system. He is well versed in presenting seminars that cover roofing theories and practice to a range of audiences. 144 • Keegan and Willits RCI International Convention and Trade Show • MarcRCh 14-19, 2019 West Coast wood-framed roofs are often constructed with the membrane installed directly to the wood deck and air-permeable insulation below the deck, between the rafters with unvented cavities. While this type of construction has been performing effectively over the past several decades, certain reroofing applications have uncovered the building science that has been working behind the scenes, unbeknownst to building owners, tenants, and the contractors that installed the roofs. For years, these roof systems have existed through continual wet–dry cycles, as explained by Desjarlais.1 In the cold months, the warm, humid interior air rises and condenses on the underside of the wood roof deck. When exposed to the sun, the roof heats up and dries out the system. While there were certainly condensation-related failures of conventional roof systems, as shown in Figures 1 and 2, this cycle typically continued behind the scenes, that is, until existing dark-colored built-up roof or black EPDM membrane was replaced with a cool or reflective roof to improve energy performance. Cases of wood deck deterioration—associated with changes in roof membrane from absorptive to reflective in low-rise multifamily residential housing—are by no means routine. However, examples initially became evident in the Pacific Northwest around 2010, and were later found along the West Coast, from Seattle to San Diego. Initial thoughts pointed towards cool roofs as the cause for these failures. However, research and extensive field data have shown otherwise.2 UNDERSTANDING THE FUNDAMENTALS OF BUILDING SCIENCE The West Coast wood-framed roof design has been widely used and accepted, but perhaps not fully understood. While condensation has been reported after the installation of a cool roof, the cool roof is not necessarily to blame. As Dregger stated, the installation of a cool roof can inadvertently disrupt a delicate balance between condensation and self-drying.2 First, let’s review the science behind these observations. • Heat and moisture flow from hot to cold. • Moisture goes from more to less. • Air goes from a higher pressure to a lower pressure. • Systems are always seeking equilibrium. The science is straightforward, but the factors are complex. According to the Department of Energy, approximately 40% of all energy consumed in the United States is attributed to commercial buildings, and air leakage is responsible for approximately 15% of the primary energy consumption. The typical West Coast wood-framed roof system is neither designed nor constructed to be airtight. But what does air leakage have to do with condensation? Water vapor, the moisture held in air, can diffuse through solid materials and can move through joints and openings with air movement. ASHRAE Handbook Fundamentals tells us that the amount of water deposited in a roof as a result of air leakage as compared to diffusion can be 100:1 or greater.3 Warm, moist air seeking In The Dark: A Practical Approach To Keeping Low-Slope Wood Deck Roof Systems Dry RCI International Convention and Trade Show • MarcRCh 14-19, 2019 Keegan and Willits • 145 Figures 1 and 2 – Deterioration of a wood deck in a modified–bitumen roof system. Courtesy of Phil Dregger. equilibrium condenses when it reaches a cold surface. The more water vapor in the air, the more condensation forms at the cold surface. This means that the air leakage into the roof system can allow for large amounts of moisture accumulation. The National Research Council (NRC) recently studied the impacts of air intrusion in roof systems and reports that air intrusion transports seven times more moisture into the roof system as compared to vapor diffusion during the heating season.4 Oak Ridge National Laboratory’s (ORNL’s) Air Leakage Energy Calculator demonstrates the significant impact of air leakage on moisture transfer. Figure 3 shows the substantial increase in moisture transfer within the building envelope as the air leakage is increased. An average midrise apartment building in Chicago can transfer over 250 ounces/sf/year compared to approximately 75 ounces/sf/year in a midrise apartment built to the International Energy Conservation Code (IECC) maximum air leakage requirements. This is why air leakage has become such an important factor in the recent addition of air barrier requirements to most energy codes in the United States. Given these fundamentals, it’s clear how buildings that have relatively modest amounts of humidity inside and are located in relatively mild climates can accumulate large amounts of moisture. This potentially explains the failures occurring in the West Coast wood-framed roof decks. During the evening hours and winter months, the wood roof deck temperature is similar to or below exterior ambient temperatures due to radiative cooling, as there is no exterior insulation to maintain the deck at interior temperatures. This means that in the winter, the roof deck is cold and its temperature regularly drops below the dew point temperature of the interior air. Seeking equilibrium, the warm, moist interior air flows into the cavity spaces between and through the glass fiber insulation batts, and condenses on the underside of the cold roof deck. When wood gets above 20% moisture content and exceeds the safe moisture-storage capacity, it starts the process of decay. The self-drying roof concept has been recognized for a long time.1,5 Condensation in these roof assemblies is not a new phenomenon and predates cool roof membranes.6,7 However, installing a cool roof, which is designed to decrease the thermal load from solar radiation, alters the balance between wetting and drying. Condensation was largely self-managed through the heating of a conventional framed roof assembly in the sun and summer heat, which facilitated downward drying, transferring the condensed moisture that had accumulated in the roof due to cold weather condensation back into the building where it originated. With the installation of a cool roof, the wood deck continues to accumulate moisture because it cannot dry as quickly or thoroughly as the conventional framed roof assembly. Another factor to consider is the membrane attachment method. Built-up roofing and modified-bitumen membranes are typically fully adhered to nailed base sheets on wood decks. However, many single-ply membranes are installed with mechanical attachment in the seams. This can lead to membrane billowing in high winds, which can pump air up from the building interior to the underside of the membrane (see Figure 4). This only exacerbates the issue, bringing more moisture up into the system. Highlighting the fundamental difference in drying potential between conventional and cool roofs, NRC research noted that the solar absorptance of the roof membrane influences the rate of drying of the roof system in the cooling season, which results in more drying time required in cool roofs as compared to conventional roofs.3 This leads to a potential disparity in the wetting-to-drying performance of the roof system. The science of self-drying roofs and the difference between conventional and cool roof performance is literally black and white. MODELING AND CONTRIBUTORS TO MOISTURE ACCUMULATION Our in-progress research leverages the opportunities to use building science to our advantage to mitigate the risk from the disrupted balance of the wetting and drying cycle. The 2014 study published by A.O. Desjarlais, H.H. Pierce, W. Woodring, and S. Figure 3 – Volume of air-transported moisture relative to air leakage. The baseline value in the table was calculated using the average leakage rate for midrise apartment buildings, which is 6.7 L/s.m2 (1.33 CFM/ft2) at 75 Pa.16 Figure 4 – Air intrusion into the roof assembly. 146 • Keegan and Willits RCI International Convention and Trade Show • MarcRCh 14-19, 2019 Pallin8 effectively demonstrated that highly reflective roof membranes are not the single-source cause of West Coast wood-framed roof deck deterioration.9 The study clearly identified that the climate conditions and level of indoor moisture play a significant role in the amount of moisture that can accumulate in the deck. This is graphically seen when the results are summarized for the highest moisture level defined in ASHRAE 160, “Criteria for Moisture-Control Design Analysis in Buildings” as shown in Figure 5. The propensity for water to accumulate on the wood deck is a consequence of vapor drive from the building interior. The warm, moist interior air rises through the below-deck, vapor-permeable insulation and into the cold wood roof deck when the exterior temperature falls (at nighttime and during colder months). When the exterior temperature rises, the vapor drive is reversed, driving some of the moisture back into the interior of the building. The 2014 study demonstrated that the potential for moisture accumulation can be reduced by variables that raise the temperature at the wood roof deck, such as radiative properties of roof membranes and/or above-deck insulation. Reducing the interior relative humidity (RH) also reduces the amount of moisture available to accumulate and cause problems with the wood roof deck.9 The in-progress research study is in collaboration with Dregger, and is modeled after the same six cities, the same four levels of moisture load, and the same assembly construction utilized in the 2014 study, with the exception of airtightness. The 2014 study was based on the “perfect building” concept with no air intrusion. This research focuses on determining the potential for wood deck deterioration with the introduction of air intrusion, and comparing the findings of the simulation to an active case study. This research study keeps many of the parameters consistent. The hygrothermal models calculated using WUFI9 took the following parameters into consideration: • Six West Coast cities, including San Diego, Los Angeles, San Francisco, and Sacramento in California; Portland, Oregon; and Seattle, Washington. These locations represent a broad array of geographic locations representing the different climates along the West Coast where wood deck construction is prevalent (Figure 6). • Four levels of interior moisture loads, including low, medium, high, and the high RH levels provided by ASHRAE 160 • A ½-in. gypsum board with a 10-perm latex paint was applied on the interior side of the roof. The air cavities created in these constructions are assumed to be unventilated. • Three different levels of below-deck fiberglass insulation thickness (R-11, R-19, and R-30). These levels represent reroofing situations where lower insulation values may be present, to situations in compliance with RCI International Convention and Trade Show • MarcRCh 14-19, 2019 Keegan and Willits • 147 Figure 5 – Summary of the 2014 evaluation of all the roof assemblies simulated with an excess of indoor moisture according to standard (ASHRAE 160, 2011).9 Figure 6 – The six cities in various climate zones along the West Coast included in the study. Figure 7 – The design of the modeled roof assembly.17 current energy codes that include higher insulation values. • Two different wood deck types: ½-in. plywood and oriented strand board (OSB) with two different rafter depths (8 and 10 in.), all common construction on the West Coast (Figure 7) • Two different roof membranes, both mechanically attached (one white and one black, with solar reflectances of 0.65 and 0.10, respectively) to simulate going from a nonreflective to a reflective California Energy Commission Title 24-compliant membrane. The workmanship was modeled to be satisfactory with no resulting water leakage. EVALUATION CRITERIA Following the evaluation criteria set in the 2014 study, failure is defined by the moisture content of the wood deck. The ASHRAE Handbook – Fundamentals states that decay in wood decks typically requires over 30% moisture saturation. Therefore, failure is defined as any set of parameters that result in over 30% moisture in the wood deck in the second or third years of the simulation. Parameters resulting in 20-30% moisture in the wood deck are defined as risky, as this level of moisture can reduce its structural strength, initiate mold growth on its surface, and cause dimensional changes that can cause visual degradation of the roof (Figure 8). ANALYSIS Air intrusion is incorporated into the simulations using the Fraunhofer Institute for Building Physics (IBP) air infiltration model, and assumes an airtightness commensurate with field observations.10 The program was used to simulate existing conditions to investigate the accumulation of condensation as well as evaluate retrofit strategies with respect to the hygrothermal response. Hygrothermal models were simulated for a three-year duration, eliminating the first-year data to rule out influence by initial moisture contents of the roof components. Data from the second and third years were compared to determine whether the moisture contents of the roof system exceeded the set threshold values or was increasing at a rate that will eventually lead to failure. Following the evaluation criteria from the 2014 study, the mechanically attached single-ply roof system over interior insulation in the Sacramento, California area (zone 3) resulted in an 18% moisture accumulation in the plywood deck within years two and three of the simulation (Figure 9), which, according to the evaluation criteria, is a system that passes without concerns of moisture accumulation. However, once we Maximum Water Content Evaluation Results in Years 2 and 3 of Simulation Value ≤ 20% Pass 20% < Value ≤ 30% Risk Value > 30% Fail Figure 8 – Evaluation criteria for simulation results. Figure 9 – Hygrothermal simulation for a highly reflective roof membrane, assuming no air intrusion.18 Figure 10 – Hygrothermal simulation for a highly reflective roof membrane, including air intrusion.13 148 • Keegan and Willits RCI International Convention and Trade Show • MarcRCh 14-19, 2019 change the model to include air infiltration, the moisture accumulation in the plywood increases significantly to 40%, which would result in failure (Figure 10). This result should be a cautionary tale to design professionals on the impact air intrusion can have on system performance. Our continued work will formalize our findings on the impact of air intrusion in climate zone 3 simulations for San Diego, Los Angeles, and San Francisco. The impact of air intrusion in climate zones 4 and 5 will be evaluated with simulations in Portland and Seattle. PARAMETERS OF THE RESEARCH CASE STUDY In order to assess the drying potential for these roof assemblies and confirm the performance predicted by the hygrothermal models, we have partnered with Dregger to evaluate the in-situ performance of five roofs in Northern California within climate zone 3, similar to the modeled Sacramento climate. The project is examining the drying potential of retrofit dark coated single-ply roof systems mechanically attached to wood decks with below-deck insulation by tracking temperature, RH, and dew point measurements in the rafter space, crawl space, unit interior, and ambient exterior spaces, as well as physical examinations through test cuts to observe actual conditions. The existing roof systems are composed of a 60-mil PVC membrane and two fire-rated slip sheets, mechanically attached to plywood deck sheathing with R-19 below-deck fiberglass batt insulation that was installed in 2009. These roofs have no intentional ventilation. The RH within the units measured to date varied between 40% and 50%, putting the interior conditions of these buildings in the medium moisture classification as defined by ASHRAE standards, although this does not yet include RH levels from January, so our wintertime RH levels are somewhat limited. According to the 2014 study, there should not be any issues with these highly reflective roofs in this location with medium moisture levels (Figure 11). The study began with the roof on Building #2, which was reroofed in 2009 with a white PVC roof membrane. The roof needed to be completely replaced due to advanced decay in just seven years of service. Since the decay was initially believed to be a result of water leaks, this roof was reroofed with a new mechanically attached 60-mil PVC roof membrane and all new plywood sheathing in October 2016. An air space was added below the roof deck to facilitate ventilation air movement. By April 2017 (just six months after replacement), nearly all of the new roof sheathing on Building #2 was found saturated (>30% water content), and Phil Dregger was hired to assess the situation. No source or cause of water intrusion was observed. However, the investigation revealed the effects of condensation and moisture accumulation. The plywood was getting wet, and nails were corroding. The other four study roofs were also examined in April 2017. Moisture readings found 10% to 40% of the total area of the wood decks to be saturated. The same evaluation of the roof on Building #2 was performed again in October 2017. Although at the low ebb of seasonal wetting and drying, saturated moisture readings of the plywood sheathing were still found over about 50% of the roof area. Improperly terminated exhaust vents and post-installation lighting were observed, thought to be contributing to some of the localized soft spots, and were remediated in Building #2, yet still exist in the remaining buildings. In January 2018, sensors were installed in the rafter space, crawl space, and unit interior and exteriors of all five units to RCI International Convention and Trade Show • MarcRCh 14-19, 2019 Keegan and Willits • 149 Figure 11 – Summary of the 2014 evaluation of the roof assemblies in the Sacramento area, indicating no risk with medium moisture levels.9 Figure 12 – Hygrothermal simulation for a highly reflective roof membrane, including air intrusion and a remediative dark coating.13 monitor temperature, RH, and dew point temperature measurements. In February 2018, a physical evaluation of all five roofs was conducted. The inspectors felt soft spots while walking the roofs in areas with increased moisture content. Moisture readings indicated saturated plywood sheathing on all five roofs, covering from 10% to 100% of the total roof area. Upon reviewing conditions around and throughout the buildings, it was documented that the crawl space, particularly in Building #2, was noticeably wet. It is likely the moist air from the crawl space is carried up into the roof assembly through convective currents following the plumbing lines. It was also noted that the combustion air for the furnace and hot water heater is drawn from the crawl space and, while the mechanical venting for these units is properly flashed through the roof assembly, the utility closet housing this equipment has openings directly into the crawl space and rafter space, presumably to connect with the attic ventilation. It is evident that the cross ventilation is drawing air from inside the building into the rafter spaces, instead of drawing in outside air. Sensors have been installed in the crawl space to monitor the RH levels to determine if this could be negatively impacting the roof performance. IN-PROGRESS RESEARCH CASE STUDY Revisiting the hygrothermal models, simulations were run to determine the impact of a dark coating on the roof. According to the simulation, the dark coating reduced the moisture accumulation in the plywood sheathing to less than 20%, which falls into the safe realm (Figure 12). It should be noted that the hygrothermal models do not account for real-life conditions observed in the roofs utilized for this research case study. Improperly terminated exhaust vents and air ducts, and the elevated RH levels documented in the crawl space are not considered in the simulations. It is unknown how these real-life factors will contribute to the overall performance of the roof assembly and its capacity to dry out over time. However, any source of warm, moist air adds to the humidity in an enclosed space. In May 2018, a dark, water-based acrylic coating was applied to the roof membrane of Building #2, and additional sensors were installed in the rafter space to evaluate the ability of the dark coating to dry out the wood roof deck over time. The dark coating was subsequently applied on the roofs of Buildings #1, #3, #4, and #5 on July 12, 2018. Initial findings with the installation of the dark coating look promising. The temperatures in the rafter spaces have increased approximately 45˚ Fahrenheit (Figure 13), as the dark coating allows for an increase in the thermal load from solar radiation and facilitates downward drying. Supporting this theory, the maximum dew point temperatures immediately increased, and then slowly started to reduce, potentially indicating that the plywood is drying out over time, and there is less water vapor in the rafter space (Figure 14). While the 2009 International Residential Code11 introduced the requirement for above-deck insulation on roofs with below-deck air-permeable insulation, these roofs, along with many others, were constructed before this requirement and are examples of the principles of building and roofing science. Modifying the hygrothermal model, the impact of above-deck insulation was evaluated to see if the insulation could increase the dew point temperature and reduce the risk of condensation. Figure 13 – Temperature fluctuation in the rafter space after the dark coating was applied. Figure 14 – Dew point temperature fluctuation in the rafter space after the dark coating was applied. 150 • Keegan and Willits RCI International Convention and Trade Show • MarcRCh 14-19, 2019 The amount of R-value in above-deck insulation necessary to warm the wood deck enough to reduce the moisture content to a level below 20% was evaluated using average weather conditions and, in this case, determined to require a minimum of R-5.6. According to the simulation, the added above-deck insulation reduced the moisture accumulation in the plywood sheathing to less than 20%, which falls into the safe realm (Figure 15). The owners are currently considering this option. UPCOMING EXAMINATION OF CRITICAL ASSUMPTIONS Monitoring of temperature, RH, and dew point continued throughout the year to determine the impact of the dark coating on the roof system. Moisture surveys were conducted in October 2018 and February 2019 to physically evaluate the moisture content and condition of the plywood roof decks. [Publication schedule of these proceedings did not allow for the results to be included herein, but they will be presented onsite at the convention.] This physical assessment will support or refute current findings in hygrothermal models when designing reroofing systems using highly reflective single-ply roof systems over wood decks. The research will evaluate remediation alternatives for consideration, including the addition of a dark coating on the cool roof to facilitate drying through heat absorption, and the installation of above-deck insulation to increase the dew point temperature and reduce the risk of condensation. While these efforts do not address the issue of moisture-laden air intrusion, they may lead to a modification of the assembly to allow building and roofing science to prevail—meaning the system will allow for sufficient drying such that moisture accumulation will no longer degrade the wood roof deck. RECOMMENDATIONS Using the validated base simulations, this research aims to provide remediation alternatives to better control condensation potential and reduce risk in retrofit and roof replacement situations where redesign and roof replacement are not a viable option for the owner and/or tenants. Coordination with the authority having jurisdiction to verify local code requirements is an important step in the repair design process. Remediation alternatives to be evaluated include the addition of a dark coating on the cool roof to increase the temperatures of the roof system and increase the drying potential, as well as increasing the amount of R-value in above-deck insulation necessary to warm the wood deck enough to reduce the moisture content to a level below 20 percent and mitigate the condensation risk in West Coast wood-framed roofs. The most effective approach is to insulate above the roof deck. It keeps the roof deck to temperatures closer to that of the interior spaces than that of the exterior environment. Even if the roof suffered from significant air intrusion, the moisture in the air would not condense if the deck remained above the dew point and, therefore, would not likely impact the integrity of the roof deck. Above-deck insulation falls in line with Lstiburek’s “perfect wall” concept in which the thermal control layer is on the outside of the structure.12 “The perfect roof” would encompass air, moisture, and thermal continuity all above the roof deck. The study by Desjarlais et al.8 showed that in many cases, 1.5-in. polyiso would be sufficient, but the degree of air leakage can significantly change the insulation requirements.13 Adding above-deck insulation to an existing roof can be quite costly. In these cases, the addition of a dark coating on the cool roof may be a viable option to increase the temperatures of the roof system and increase the drying potential. It should be noted that this option might not be compliant with Title 24, which may be a limiting factor, depending on the scope of work and the authority having jurisdiction. Some may consider installation of an air barrier below the insulation to prevent any moist air from rising into the roof system. However, there are many variables to consider in this decision, including local climate and building occupancy. Installing batt insulation below decks can be complicated by many factors, including existing pipes, ducts, and recessed lighting, and creating roof-to-wall interface continuity. If an air barrier is utilized, it is recommended that it be vapor permeable.14 Providing cross ventilation at each individually enclosed space is another option. However, this is rarely successful, and caution should be taken when utilizing ventilation to overcome air leakage. According to Peter Yost, “Condensation caused by air leakage in a roof assembly cannot be overcome by drying by diffusion or—in many cases—even by roof ventilation…you can’t vent your way out of an air-leakage problem.”15 CONCLUSIONS Highly reflective roof membranes installed over wood roof decks located in the West Coast with air infiltration challenges can lead to moisture build-up within RCI International Convention and Trade Show • MarcRCh 14-19, 2019 Keegan and Willits • 151 Figure 15 – Hygrothermal simulation for a highly reflective roof membrane, including air intrusion and above-deck insulation.13 the roof assembly, which can lead to a reduction in the structural capacity of the wood roof deck. Highly reflective roof membranes have inadvertently reduced the ability of leaky roof assemblies to be self-drying. Hygrothermal models support remediation efforts, including the application of a dark coating on the reflective membrane, as well as the installation of above-deck insulation. The next step in our research includes the evaluation of actual modified roofs (which is in progress) to support or refute current findings in hygrothermal models when designing reroofing systems using highly reflective single-ply roof systems over wood decks. While these remediation efforts do not address the issue of moisture-laden air intrusion, they may modify the assembly to allow building and roofing science to prevail, meaning the system will allow for sufficient drying such that moisture accumulation will no longer degrade the wood roof deck. ACKNOWLEDGEMENTS The authors would like to thank Phil Dregger for his engagement and attention to detail, and for including us in his continued research initiatives. REFERENCES 1. A.O. Desjarlais. “Self Drying Roofs: What! No Dripping!” Proceedings of the Thermal Performance of the Exterior Envelopes of Buildings. 6th Conference, Clearwater, FL. 1995, pp. 763-773. 2. P.D. Dregger. ”Cool Roofs Cause Condensation – Fact or Fiction?” RCI Interface. March 2013, pp. 19-26. 3. ASHRAE (1989). Handbook Fundamentals. Chapter 21, “Thermal Insulation and Vapor Retarders – Applications.” Atlanta, GA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 4. S. Molleti, B. Baskaran, and P. Beaulieu. “Air Intrusion Impacts in Seam-Fastened, Mechanically Attached Roofing Systems.” RCI Interface. March 2018. 5. Frank J. Powell and Henry E. Robinson. “The Effect of Moisture on the Heat Transfer Performance of Insulated Flat-Roof Constructions,” U.S. National Bureau of Standards, 1971. 6. R.B. Walters. “Condensation Modeling of EPDM Single-Membrane Roof Systems.” Second International Symposium on Roofing Technology. NRCA. 1985. pp. 391-395. 7. R.M. DuPuis. “Field Survey of Moisture Gain Behavior Within Single-Ply Roof Systems.” Second International Symposium on Roofing Technology. NRCA. 1985. pp. 261-264. 8. A.O. Desjarlais, H.H. Pierce, W. Woodring, and S. Pallin. “Practical Application of Hygrothermal Modeling of West Coast Wood Deck Systems.” RCI Interface¸ March 2014. 9. H.M. Künzel. “Simultaneous Heat and Moisture Transport in Building Components.” IRB Verlag, University of Stuttgart. 1995. 10. Fraunhofer. WUFI® Tutorial. “Handling of Typical Constructions in WUFI.” 2014. 11. 2009 International Residential Code, Table R806.4 and 2012 IRC, Table R806.5. 12. J.W. Lstiburek. “The Perfect Wall.” ASHRAE Journal. May 2007, pp. 74-78. 13. P.D. Dregger. “Good but Potentially Misleading Guidelines.” RCI Interface, May/June 2014, p. 8. 14. W. Tobiasson. “Vapor Retarders for Membrane Roofing Systems.” Proceedings of the 9th Conference on Roofing Technology. NRCA, Washington DC, 1988, pp. 31-37. 15. P. Yost. “Avoiding Wet Roofs. A building-science guide to insulating attics and roofs.” JLC Online. June 2018. 16. Oak Ridge National Laboratory. “The Addition of Moisture Transport to the Air Leakage Energy Calculator.” Presentation at ABAA. May 2018. 17. S. Pallin, M. Kehrer, and A.O. Desjarlais. “ORNL/TM-2013/551, Hygrothermal Performance of West Coast Wood Deck Roofing.” November 2013. 18. P.D. Dregger and J. Willits. “A Practical Approach to Low Slope West Coast Wood Deck Roof Systems—An Update.” Western States Roofing Contractors Association, June 2018. 152 • Keegan and Willits RCI International Convention and Trade Show • MarcRCh 14-19, 2019
