aBstraCt thermal modeling software can be used to account for issues with elevated condensa- Many building owners and developers predict the location of a dew point within a tion levels by pressurizing the building and are concerned with the implications of building enclosure assembly, and thereby, removing moisture through increased wall upgrades in the energy code, and spe- assist designers in determining the appro- section drying potential or by increasing cifically, the requirement for continuous priate placement and permeance of air and the temperature, which in turn allows for exterior insulation around the building vapor retarders when continuous exterior increased vapor storage in the air. This is enclosure. There is concern over the initial insulation is used, as well as what changes impractical for a variety of reasons, not the cost, the lack of information that they cur- may occur to the traditional position of the least of which is exposing building occupants rently have regarding the payback period, dew point. When permeance and psychrom- to greater discomfort. and the question, “Will this really make a etry are not considered in tandem with the A more appropriate method of vapor con- difference?” The more pertinent question, upgraded energy code requirements, how do trol is to design and construct the building however, may be, “How will this make a we stop ourselves from hurting ourselves? enclosure with hygrothermal control. This difference?” The answer is not necessarily creates the design necessity to manage vapor as direct as initially expected. The coupled introdUction transmission and condensation formation, use of hygrothermic modeling during design Consider a glass of iced tea on a hot utilizing various approaches, including air and performance testing of building enclo- summer day. Intuitively, we know that barriers, vapor retarders, and insulation in sures with continuous exterior insulation this glass is going to “sweat.” This same exterior walls. Building components need to during the construction of a facility provide phenomenon can occur in building wall be designed and constructed in the appropri- much-needed information on how these systems. As migrates through ate locations to manage where condensation upgraded energy requirements affect the the building enclosure and moves toward occurs within the wall assembly. The design hygrothermal performance of the exterior the colder components with surface tem- intent is not to prevent condensation, but walls of a building. As one may expect with peratures below the dew point temperature, to manage where it will occur in order to simulating the hygrothermal performance of condensation occurs on those surfaces. minimize the effect on the building or its the building enclosure with continuous exte- Condensation is the change in physical occupants. rior insulation, the thermal transmission state from vapor into liquid (water) when in The appropriate design and construc- through the exterior wall is substantially contact with a solid surface. Condensation tion of exterior wall systems has become decreased. Inherently, with this decrease in in building construction can be an undesir- something of a moving target as we attempt thermal transmission, there is a decrease in able condition, as it may cause discomfort to build lighter, more sustainable buildings. moisture transport as well. When moisture through humid interior conditions, biolog- The industry is consistently learning more content is reduced, there is, intrinsically, a ical growth, corrosion, and deterioration, about how wall configuration changes will decrease in thermal transmission; and from as well as decreased energy efficiency of affect performance and the proper roles that there, the cycle continues. mechanical and building enclosure systems. air barriers, vapor retarders, and insulation The author will demonstrate how hygro- HVAC systems can be adjusted to should play in the ongoing transition from

2 2 • I n t e r f a c e a p r I l 2 0 1 7 the mass-wall mindset to rainscreens and of the world, and whether or not those sys- with the transfer of that heat and mass. For drainage walls. In addition to the consider- tems would perform as well as wood stud example, temperature conditions in a build- ation for advanced HVAC systems, we now walls. Research completed during this study ing influence moisture transport. Inversely have the factors of permeance and diffusion accounts for in-depth information on system and simultaneously, high moisture levels to consider, which will be further discussed thermal performance of various insulation result in increased heat losses. The analysis in this study. configurations of stud walls by use of the of heat and moisture coupling is known as As one may expect with continuous insu- ASTM C236 method, which has now been “hygrothermics.” lation (CI), thermal transmission through replaced by ASTM C1363, Standard Test Warme und Feuchte instationär (WUFI) the exterior wall is substantially decreased Method for Thermal Performance of Building Pro 5.2[11] is the computer software used in when compared to walls where the insula- Materials and Envelope Assemblies by this study to anticipate the outcomes of the tion is not continuous (e.g., stud walls with Means of a Hot Box Apparatus. Information various wall systems under review by hygro- insulation between studs). Inherently, with from the testing of the assemblies contained thermal modeling. WUFI provides realistic, this decrease in thermal transmission, there in the aforementioned study has shown that dynamic simulations regarding transient, is also a decrease in moisture transport. continuous exterior insulation has realized coupled one-dimensional heat and moisture When moisture content is reduced, there is benefits regarding thermal transmission of transmission in multilayered wall systems also a decrease in thermal transmission. In wall systems. when they are exposed to various climat- other words, generally, when you improve A second study completed by ic conditions. Factors considered in the one, you improve the other. Mukhopadhyaya, Ping, Kumaran, and van simulation include, but are not limited to, As one of the updated provisions in Reenen[3] investigated the role of Class interstitial condensation, the influence of the 2015 International Energy Conservation I, II, and III vapor retarders in exterior driving rain, airflow in the assembly, and Code (IECC),[1,2] building enclosure testing wood-framed stucco walls utilizing a 2-D the effects of proposed designs on building has been incorporated as a key tool in the simulation tool, hygIRC-2D.[10] The above- enclosure systems. verification of performance of the building referenced paper highlights the importance As with all software, there are many via air leakage testing of the thermal enve- of placing a vapor retarder with the appro- input requirements for beginning the model, lope, which is now mandatory. In alignment priate permeance correctly in the wall sys- and the accuracy of the model is highly with this provision, another key to avoiding tem and that the permeance of the total wall dependent on the quality of the data input. performance issues and potentially costly impacts moisture collection in the building With WUFI, the major considerations are: failures in building design and construction components. 1) components of the wall assembly, 2) ori- has become more than just planning—it is This paper is a collateral extension of entation, 3) surface transfer coefficients, 4) establishing and validating that the exterior the previously mentioned studies and uti- initial conditions, 5) time horizon, 6) hygro- of the facility meets the owner’s objectives. lizes the technology of a hygrothermal mod- thermal special options, and 7) climate This can be done through the verifica- eling tool that simulates heat, vapor, and information. These configurations are fur- tion process of building enclosure commis- moisture in one dimension. This simulator ther expanded in subsequent paragraphs. sioning (BECx). It is through the holistic will be used to model various insulation and lens of building wall comparison throughout vapor retarder configurations in multiple Components of the Wall Assembly the commissioning process—encompassing climate types in North America. The intend- The basic wall assembly that was mod- design, construction, and testing—that this ed outcome is a study that addresses the eled in different configurations is as shown study will view performance and consider- impacts of the updated IECC prescriptive in Figure 1. ations for multiple methods of insulating insulation requirements and recommended The material properties used for each exterior walls based upon the IECC pre- configurations, and provides guidance on of the building enclosure components are scriptive requirements. The focus of this optimizing building enclosure performance. as outlined in the materials database in paper will be on exterior stud walls with the WUFI software. The properties are combinations of both CI and insulation Wufi® and simulation inPut as derived through detailed comparisons within the stud cavity. This study is based reQuirements between known conditions and measure- on computer-based hygrothermal simulation Hygrothermal modeling aids in the ments taken through Germany’s Institute and modeling. These modeled wall systems understanding of moisture will rely upon data from previously conduct- conditions and the effects ed field testing for validation, as conducting of on building field tests for each configuration and climate enclosure systems, in type has proven to be inefficient. addition to accounting for the thermal response of researCh BaCkground those building systems A thermal study was conducted by and their components Kosny, Christian, and Desjarlais[30] on effec- from thermal loading by tive systems for in metal the outdoor environment. stud wall systems. The apparent goal of this Physically, the thermal study was to determine if metal stud walls and moisture conditions were an effective system for low-cost and of buildings and their Figure 1 – Base wall assembly w/CI, vapor retarder, energy-efficient buildings in various regions components are coupled sheathing, insulation, and wallboard from exterior to interior.

a p r I l 2 0 1 7 I n t e r f a c e • 2 3 of Building Physics’ outdoor testing and 7. , temperature-depen- studied Cities and Climate Zones laboratory simulations. dent Tucson, Arizona Zone 2 Each component included in the WUFI materials database is comprised of basic Orientation Seattle, Washington Zone Marine 4 values, such as: Studies show that during a rain Chicago, Illinois Zone 5 1. Bulk density (lb/ft3) event, approximately 30% of bulk New York, New York Zone 4 2. Porosity (ft3/ft3) moisture is shed from the wall, and 3. Specific heat capacity (Btu/lb°F) approximately 70% remains on the Charlotte, North Carolina Zone 3 [19-21, 29] 4. Thermal conductivity, dry, 10°C surface of the exterior cladding. Burlington, Vermont Zone 6 (Btu/h ft°F) ASHRAE 160, Criteria for Moisture- 5. Permeability (perm in) Control Design Analysis in Buildings,[29] Miami, Florida Zone 1 prescribes that through vapor diffusion Table 1 – Modeled cities. There are also hygrothermal functions and conductivity, approximately 1% of inherent to each component included in the the water retained on the surface penetrates radiation, and rain absorption. For the inte- materials database, such as: through the cladding. Solar radiation that rior components, the modeler can include 1. Moisture storage function is incident on the wall surface plays a sig- interior paints and other spe- 2. Liquid transport coefficient, suction nificant role in this process. Therefore, the cifics. In each model, the surface transfer 3. Liquid transport coefficient, redistri- orientation of the model is an important coefficient has been used to model interior bution aspect of simulation. For the purposes of latex paint on the interior wallboard. 4. Permeability, moisture-dependent this study, the wall systems will be oriented 5. Thermal conductivity, moisture- in the worst-case scenario for the climate Initial Conditions dependent type for ease of data interpretation and to Much like the information regarding the 6. Thermal conductivity, tempera- provide a more conservative model. material properties of the wall assembly ture-dependent components, the materials database con- Surface Transfer tained within the software also generates Coefficients initial moisture conditions for each com- H These coeffi- ponent in the wall assembly. These initial cients prescribe moisture conditions are considered to be H the extent to normalized. They are also derived from lab- H which the environ- oratory and field-testing data. H ment affects the most interior and Time Horizon exterior compo- The time horizon for this study will be H nents in the build- three years, dated from the time of simu- H ing enclosure sys- lation. tem. For the exte- rior components, Hygrothermal Special Conditions H the modeler can These data are the inputs for options implement provi- such as excluding capillary conduction or Figure 2 – Modeled city locations and corresponding climate types. sions for coatings, of evaporation, etc. For the pur- poses of this study, no special hygrothermal conditions were modeled.

Climate Information There are several important functions of the climate information section of the data input. The first is selection of the city and/ or climate type in which the simulation will take place for the exterior condition weather data. The cities that were modeled during this study were as shown in Table 1.[1,2] Secondly, there is the climate analysis factor in which the modeler has the ability to simulate the impacts of driving rain and sun radiation. This information is key in the selection of the aforementioned worst-case scenario orientation. Finally, the interior climate is chosen to Figure 3 – Example of indoor climate model. model the indoor conditions over the time

2 4 • In t e r f a c e a p r I l 2 0 1 7 thermal enVeloPe insulation ComPonent minimum reQuirements Climate 1 2 3 4 Except 5 and 6 Zone Marine Marine 4 All Other All Other All Other All Other All Other All Other Wood-Framed R-13 + R-13 + R-13 + R-13 + R-13 + R-13 + and Other R-3.8 CI or R-3.8 CI or R-3.8 CI or R-3.8 CI or R-3.8 CI or R-7.5 CI or R-20 R-20 R-20 R-20 R-20 R-20 + 3.8 CI Table 2 – Thermal envelope insulation component minimum requirements. horizon. There are various options for the climate zones is shown in Figure 2. veneer has been added to the base wall indoor conditions model, with those options In each city case, there will be varying model in order to simulate the most realis- being derived from the outdoor conditions wall system configurations, with the insu- tic conditions for in-place construction. For based upon standard algorithms. This study lation type and cladding type remaining the sheathing and interior wallboard, ½-in. utilizes the European Standard EN13788 constant. The variables will be the thickness gypsum board is used. The types of mem- for deriving indoor air humidity from the and placement of the insulation and the branes used are a spun-bonded polyolefin outdoor humidity using a variable moisture type of material used for the vapor retarder material, a 1-PERM sheet product (Class load, which is a function of outdoor tempera- pursuant with the IECC requirements. II), and a polyethylene vapor retarder (Class ture; and the interior conditions were mod- The interior conditions remained fixed I). The insulations used are fiberglass batt eled as a typical commercial facility. at a of 74°F (23°C), insulation in the stud cavity and extruded regardless of the time of year or location of polystyrene in the models where contin- study Parameters the modeled city. The humidity model used uous exterior insulation is used in vary- Varying configurations of insulation is Humidity Class 1 of European Standard ing thicknesses. The thicknesses of these wall components as prescribed in the 2015 EN13788. See Figure 3. two insulation types are based upon code IECC[2] will be examined in the study. The Unique climate-specific cases are used requirements in most models and in typical variations will be simulated in seven different to simulate the impacts of differing insu- standard board sizes for models beyond or cities with unique climate types as stated lation and vapor retarder configurations outside of the building code.[1] above. A map of these cities and their unique and products for each city modeled. A brick In addition to the various products used

a p r I l 2 0 1 7 I n t e r f a c e • 2 5 for simulation, the configurations of the wall models are also a variable in the overall simulation. The four wall systems modeled are in accordance with Table 2 from the 2015 IECC. The climatic-specific systems are R-13 + R-3.8ci, R-20ci, R-13 + R-7.5ci, R-20, R-20 + 3.8ci, and R-25ci. The systems outside of the building code are the CI systems of R-20 and R-25. These two systems were modeled in each of the selected cities in addition to the prescriptive requirements outlined in the building code.

simulation analysis There are several categories of output collected during this study. The categories Figure 4 – RH graph with warm temperatures and isolated 80% RH days. Extended periods reviewed and analyzed are as follows: of 80% plus would promote mold growth. 1. Total water content 2. Water content in layer 3. Temperature/relative humidity (RH) 4. Temperature/dew point 5. Dynamic temperature/RH/moisture content

Each of these outputs is cross-refer- enced to compile the full analysis required in this study. When reviewing these out- puts, several thresholds have been estab- lished to accompany known physical prop- erties, as well as to follow traditionally accepted industry standards. In addition, there are other indicators of low-performing wall systems, such as extended periods of elevated heat and RH that do not necessar- ily surpass a predetermined threshold. This specific scenario is typically considered to be the most conducive for premature deteri- Figure 5 – RH in sheathing in Burlington, VT: R-20 + 3.8 CI. oration of wall systems. The other previously mentioned thresh- olds are as follows: 1. RH at 100% 2. Intersection of temperature and dew point graphs 3. Water content in excess of allowable levels 4. Increased total water content over simulation 5. RH at or above 80% for 30 days (Figure 4), creating potential for mold growth[29]

results and disCussion The vapor permeance of the various vapor retarders modeled, coupled with the thermal resistance of the insulation in var- ious configurations and thicknesses, has a tremendous impact on the overall perfor- Figure 6 – RH in sheathing in Burlington, VT: vapor retarder, R-13 + 7.5 CI. mance of the wall systems modeled. Seven

2 6 • I n t e r f a c e a p r I l 2 0 1 7 cities were modeled with their specific cli- mate types, with a minimum of four simula- tions for each city. When complete, the total number of models totaled over 35, and the ultimate number of simulations exceeded 50, as some models were simulated multiple times with slight variations. The coupling effect of heat and mass transfer was clearly illustrated in each of the climate zones, although the extent of this impact was less severe in dry climate zones. The impacts of this were most extreme in marine and the warmer, more-humid climate zones, as one would presume. During the study, it was found that the lower the vapor permeance of the mem- brane, the more uniform the hygrothermal control of the wall system was found to be. Figure 7 – RH in sheathing in Burlington, VT: fully CI with 1-perm vapor retarder. It was also noted that the more insulation located outboard of the sheathing, such as with CI, the better the wall system per- formed from a hygrothermal control stand- point. This is outlined in representative example graphs (Figures 5-8) in order of worst to best performance. The focus of these representative graphs will be on the exterior gypsum sheathing in Burlington, Vermont, as this is the most severe case and best visually represents these findings. It should be noted that the previously outlined thresholds for concern are exceed- ed for only a brief period of time for either of these models, and that is during the early winter. See Figure 5. There wasn’t an increased possibility of reaching dew point in the sheathing during the simulation. However, it should be understood that these simulations focus on thermal impacts Figure 8 – RH in sheathing in Burlington, VT: fully CI with polyethylene membrane. and dew point analysis and assume perfect construction without significant flashing breaches, discontinuities, etc., which would allow bulkwater intrusion. Minor inconsis- tencies in the wall system could increase the potential for condensation to form on the sheathing in the lower-performing wall systems as shown in Figure 9. Higher-performing wall systems with more insulation outboard of the sheathing and a lower permeance membrane would perform as shown in Figure 10. The amount of moisture content in the wall components followed a similar pattern, confirming the findings of these simulations regarding vapor transmission and conden- sation. This is known to be true, as the software models the performance of the wall system regarding bulk moisture using the ASHRAE 160[29] model for shedding Figure 9 – Dew point in sheathing in Burlington, VT: R-20 + 3.8 CI. Less than 5°F gradient rainwater, as previously stated. Therefore, during summer.

a p r I l 2 0 1 7 I n t e r f a c e • 2 7 if the cladding remains a constant across each system, then an increase in moisture content would not be due to driving rain and bulk moisture. It would be due to absorption of vapor due to less hygrother- mal control of the total system. Further, the increases represented in moisture content are fractions of percentages, which implies that the absorption is that of vapor and not bulk moisture. Figures 11 and 12 represent this finding. In order to balance these representative graphs, note that this severity is not present in all cities and climate types. To illustrate this, Figures 13 and 14 represent the hygro- thermal impacts found in Tucson, Arizona, by outlining the moisture content in the Figure 10 – Dew point in sheathing in Burlington, VT. Fully CI with polyethylene membrane exterior sheathing. at nearly 20°F minimum gradient after equilibrium. As can be seen in Figures 13 and 14, there is not the same drastic effect on mois- ture content increase in Tucson as there is in Burlington. This begs the question: Why does the building code require nearly the same thermal insulation configuration in climate Zones 1 through 7? And why is there ambiguity in the vapor retarder prod- uct selection and placement if there are such overwhelming impacts?

ConClusions and reCommendations The true focus of this paper is the exterior sheathing in framed design and construction. There are several reasons for this, including indoor environmental quality impacts and structural support of exterior cladding systems. When mold growth and moisture content are considered, most will Figure 11 – Moisture content in sheathing in Burlington, VT: R-20 + 3.8 CI. look to the interior wallboard, as this is what is visible. However, the exterior sheathing is more closely the center of the wall system and acts as the base of protection from the exterior environment. Depending upon the climate type, the exterior sheathing may act as the surface for attaching the vapor retarder and continuous exterior insulation and/or serve as an initial air barrier in the wall system. Many may not consider this to be of such importance, but Figure 15 demonstrates otherwise. The mold growth on this building compo- nent has as much impact on indoor air qual- ity as mold growth on the interior wallboard would. Condensation only requires a tem- perature differential and a condensing sur- face. That condensing surface is very often the backside of the sheathing. Therefore, it Figure 12 – Moisture content in sheathing in Burlington, VT: fully CI with polyethylene becomes important for designers and con- membrane. struction professionals to consider the exte-

2 8 • I n t e r f a c e a p r I l 2 0 1 7 rior sheathing as a layer of great importance, and that is why the primary focus of this study became the exterior sheathing. As seen throughout the course of this study, the requirements outlined by the 2015 IBC and IECC have a considerable impact on the exterior sheathing. These requirements are often considered adequate because they do not regularly cause prob- lems that building occupants are readily aware of and report until they are directly impacted by mold. In terms of overall ener- gy conservation, which the IECC certainly covers, it would also be of value to take a long-term view of building sustainability and optimize wall systems for higher per- formance alongside the code’s mindset on durability. With this in mind, the list below Figure 13 – Moisture content in sheathing in Tucson, AZ: R-20. outlines some observations produced from this study. It should be noted, however, that these observations and recommendations should only be taken in the light of the input conditions outlined herein. 1. There is a compounding negative effect on wall performance when the air transport, vapor permeance, and thermal insulation placement of a wall system are not optimized. For example, if the insulation placement is not optimized, the vapor perme- ance is not appropriate, and air transport is not controlled, that wall system will not perform nearly as well as one in which the insulation placement is not optimized but the vapor permeance and allowed air transport are adequate. Figure 14 – Moisture content in sheathing in Tucson, AZ: fully CI. 2. As much thermal insulation as is economically feasible and construct- 4. A thorough understanding of the Kumaran, and D. van Reenen. ible should be moved outboard of the impacts of local climatic conditions “Role of in Wood- sheathing in the wall system to opti- and exterior wall best practices is Frame Stucco Wall in Various North mize performance, and it should be essential to proper design. Knowledge American Climates: Observations continuous to the maximum extent of the building code-defined climate from Hygrothermal Simulation.” practical. zones and prescribed thermal protec- Heat-Air-Moisture Transport, ASTM, 3. In several climate zones, splitting tion is also a necessity. STP 1519, ASTM International, West the insulation between the cavity 5. Clarity on the placement and perme- Conshohocken, PA, 2008. and continuous exterior insulation ance requirements of vapor retarders 4. J. F. Straube. “The Influence of Low- performs well and provides a qual- in wall systems for specific climate Permeance Vapor Barriers on Roof ity, economical, and constructible zones is critical to designing high- and Wall Performance.” Thermal system. This, however, is not true performing exterior wall systems. Performance of the Exterior Envelopes for all climate zones as currently of Buildings VIII, Proceedings of prescribed by the IECC. Further references ASHRAE THERM VIII, Clearwater, evaluation should be conducted in 1. International Code Council, Inc., FL, 2001, pp. 1–12. the climate zones with more extreme 2014. “International Building Code 5. A.N. Karagiozis, J. Lstiburek, and temperature gradients, such as (IBC),” USA, Illinois. A. Desjarlais. “Scientific Analysis of Zones 6, 7, and 8. Designing split 2. International Code Council, Inc., Vapor Retarder Recommendations insulation wall systems that perform 2014. “International Energy Conser- for Wall Systems Constructed in well and are durable in those climate vation Code (IECC),” USA, Illinois. North America.” Thermal Performance zones is the underlying challenge. 3. P. Mukhopadhyaya, F. Ping, K. of the Exterior Envelopes of Buildings

a p r I l 2 0 1 7 I n t e r f a c e • 2 9 Vapor Barrier on Response of Wood Frame Walls Using Hygr ot her m al IRC’s Advanced Hygrothermal Model Response of hygIRC.” Second Annual Conference Stucco Walls,” on Durability and Disaster Mitigation Intern ationa l in Wood-Frame Housing. 2001, pp. Conference on 221–226. 15. P. Mukhopadhyaya, M.K. Kumaran, and Technology F. Tariku, and D. van Reenen. (I CBEST) , “Application of Hygrothermal Ottawa, Canada, Modeling Tool to Assess Moisture 2001, p. 6. Response of Exterior Walls.” 8. P. Mukhopad- Journal of Architectural Engineering, hyaya, M.K. Ku- December 2006, 178. maran, and D. 16 P. Mukhopadhyaya, P. Goudreau, van Reenen. M.K. Kumaran, and D. van Reenen. Figure 15 – Mold growth on the interior side of exterior sheathing. “Role of Vapor “Influence of Material Properties on Barrier and the Hygrothermal Response of an X, Proceedings of ASHRAE THERM X, Interior Weather on Overall Ideal Stucco Wall – Results from Clearwater, FL, 2007, pp. 1–11. Moisture Performance of Exterior Hygrothermal Simulations.” Sixth 6. M. Kumaran, G. Mitalas, and M. Wall Assembly – Results from Nordic Building Physics Symposium. Bomberg. “Fundamentals of Trans- Hygrothermal Simulations.” CIB Trondheim, Norway, 2002. pp. 611– port and Storage of Moisture in World Building Congress 2004, 618. Building Materials and Components,” Toronto, Canada, 2004, pp. 1–10, 17. K. Kumaran, J. Lackey, N. Norman- ASTM Manual Series: MNL 18, http://irc.nrc-cnrc.gc.ca/pubs/full- din, D. van Reenen, and F. Tariku. Philadelphia, PA, February, 1994. text/ nrcc46864/nrcc46864.pdf. “Summary Report from Task 3 of 7. P. Mukhopadhyaya, M.K. Kumaran, 9. H. Hens. “Heat, Air and Moisture MEWS Project.” Report No. NRCC­ D. van Reenen, and F. Tariku. “Influ- Transport,” Final Report, Vol. 1, Task 45369, Institute for Research in ence of Sheathing Membrane and 1: Modeling, International Energy Construction, National Research Agency Annex 24. Laboratorium Council, Ottawa, Canada, 2002, pp. Bouwfysica, K.U. Leuven, Belgium, 1–68. 1996. 18. K. Kumaran, J. Lackey, N. Norman- 10. W. Maref, M.K. Kumaran, M.A. din, F. Tariku, and D. van Reenen. Lacasse, M.C. Swinton, and C. van “A Thermal and Moisture Transport Reenen. “Advanced Hygrothermal Property Database for Common Model – hygIRC: Laboratory Building and Insulating Materials.” Measurements and Benchmarking.” Final report from ASHRAE Research 12th International Heat Transfer Project 1018-RP, 2004, pp. 1–229. Conference. Grenoble, France. 2002, 19. J.F. Straube, E. Burnett, R. pp. 1–6. 1–11. VanStraaten, C. Schumacher. 11. H. Künzel. (2002). WUFI® PC-Program (2004). “Review of Literature and for calculating the coupled heat Theory – Report #1.” ASHRAE 1091 – and moisture transfer in buildings. Development of Design Strategies for Fraunhofer Institute for Building Rainscreen and Sheathing Membrane Physics. Holzkirchen, Germany. Performance in Wood Frame Walls. 12. J.F. Straube. Moisture Control and University of Waterloo, Building Enclosure Wall Systems. Ph.D. the- Engineering Group Report for sis, Civil Engineering Department, ASHRAE. University of Waterloo, Waterloo, 20. American Heating, Refrigerating and Ontario, Canada, April 1998. Air-Conditioning Engineers, Inc., 13. R. Djebbar, M.K. Kumaran, D. van “Commercial and Public Buildings,” Reenen, and F. Tariku. “Hygrothermal ASHRAE Applications Handbook. Modeling of Retrofit American Society of Heating, Measures in Multi-Unit Residential Refrigerating, and Air-Conditioning and Commercial Office Buildings.” Engineers, Atlanta, GA, 1999, Chap. 3. Client Final Report B-1110.3. IRC/ 21. X. Shi, C. Schumacher, and E. NRC, National Research Council, Burnett. (2004). “Ventilation Drying Ottawa, Canada, 2002, p. 187. Under Simulated Climate Conditions 14. P. Mukhopadhyaya and M.K. – Report #7.” ASHRAE 1091 – Kumaran. “Prediction of Moisture Development of Design Strategies for

3 0 • I n t e r f a c e a p r I l 2 0 1 7 Rainscreen and Sheathing Membrane Wall Systems.” Ninth Conference on – Thermal Disaster, or Modern Performance in Wood Frame Walls. Building Science and Technology. Wall Systems With Highly Efficient The Pennsylvania Housing Research/ Vancouver, Canada, 2003, p.16. Thermal Insulation.” Insulation Resource Center. Pennsylvania State 26. K. Ueno and J. Lstiburek. (2014). Materials: Testing and Applications: University Report for ASHRAE. “Guidance on Modeling Enclosure Third Volume. ASTM STP 1320, R.S. 22. R. Djebbar, D. van Reenen, and Design in Above Grade Walls: Expert Graves and R.R. Zarr, Eds., ASTM, M.K. Kumaran. “Environmental Meeting Report.” NREL, DOE. 1997. Boundary Conditions for Long-term 27. P. Mukhopadhyaya, M.K. Kumaran, Hygrothermal Calculations.” Eighth M. Rousseau, F. Tariku, D. van Kristophor C. International Conference on Building Reenen, and W.A. Dalgliesh. “Appli- Linster, RRO, Envelopes. Clearwater Beach, cation of Hygrothermal Analyses PE, LEED APBD+C, Florida, 2001, p. 13. to Optimize Exterior Wall Design.” CDT, is the 23. R. Jones. “Indoor Humidity Calcu- Second International Conference on National BECx lation Procedures,” Building Ser­ Research in Building Physics. Leuven, Practice Leader vices Engineering Research and Belgium, 2003, pp.417–426. for Terracon. He Technology. Volume 16, 1995, p. 28. J. Lstiburek. (2015). “WUFI – Barking has been involved 119. Up the Wrong Tree?” Building Science in more than 20 24. M. Nofal and P.I. Morris. “Criteria Insights. BSI-089. Building Science building enclo­ for Unacceptable Damage on Wood Corporation, Massachusetts. sure commission­ Systems.” Japan-Canada Conference 29. American Heating, Refrigerating and Kristopher Linster ing projects with on Building Envelope. Vancouver, Air-Conditioning Engineers, Inc. Terracon in the Canada, 2003, pp. 1–14. “Criteria for Moisture-Control Design last five years. His experience in the inves­ 25. M.K. Kumaran, P. Mukhopadhyaya, Analysis in Buildings.” ASHRAE 160- tigation, design, and observation of building S. M. Cornick, M.A. Lacasse, W. Maref, 2009, American Society of Heating, enclosure systems led to providing building M. Rousseau, M. Nofal, J.D. Quirt, Refrigerating, and Air-Conditioning enclosure commissioning services to nation­ and W.A. Dalgliesh. “An Integrated Engineers, Atlanta, GA. al commissioning firms, owners, and end Methodology to Develop Moisture 30. J. Kośny, J.E. Christian, A.O. users. These projects include renovations, Management Strategies for Exterior Desjarlais. “Metal Stud Wall Systems additions, and new construction.

a p r I l 2 0 1 7 I n t e r f a c e • 3 1