Defining the Ultimate Wall Through Testing Laverne Dalgleish Air Barrier Association of America 1600 Boston Providence Highway, Walpole, MA 02081 866-956-5888 • ldalgleish@airbarrier.org IIBEC 2020 Virtual International Conve ntion & Trade Show | June 12-14, 2020 D algleis h | 167 Laverne Dalgleish has been involved in the construction industry for over 30 years and has focused on improving the quality of construction, both by improving materials and improving the processes for installation. He spends a great deal of time working on codes and standards and works with the building enclosure industry to produce standards that are useful to the industry and allow for choice of materials for a specific project. 168 | Dalgleis h IIBEC 2020 Virtual International Conve ntion & Trade Show | June 12-14, 2020 ABSTRACT SPEAKER The building industry is bombarded with new and improved materials, with everybody saying they are the best. How do you know? How do you choose? Do you need the best material available? This paper walks you through a new means of defining what the ultimate wall is for your project. Every building is unique, and the old “one-size-fits-all” mantra does not work anymore. This new approach allows you to customize the ultimate wall for your project using anybody’s materials. IIBEC 2020 Virtual International Conve ntion & Trade Show | June 12-14, 2020 D algleis h | 169 ABSTRACT If you don’t set goals, you are not likely to achieve them. This presentation provides a road map for building enclosure performance— specifically wall assembly performance— which includes materials, subassemblies, assemblies, and systems. The concept of an “ultimate wall” presented in this paper is a new approach being proposed by the author, where building assemblies are evaluated rather than individual materials. A proposed approach to evaluating building assemblies is outlined herein. TODAY’S BUILDINGS Today’s buildings are becoming more complex and using more innovative materials, while at the same time, the construction cycle has been reduced by using design-build and other approaches to the construction process. We cannot say this change is good or bad, but we can say that it changes the way we should look at construction materials used in our buildings. In addition to all these changes, we are moving toward low-energy-use buildings; call them net zero, net-zero ready, Passive House, or anything else you want. As you determine your approach on how to construct a low-energy-use building, the first thing that you should see is that the building enclosure needs to perform at a high level and be the best you can build. There are two reasons for this: first, you get one shot at doing it right the first time, or you face expensive repairs and upgrades; and second, the mechanical equipment needs to be sized correctly based on the performance of the building enclosure, in order to have any hope of operating efficiently. Some people say that it is more cost effective to put more efficient equipment into a poor- or average-performing building than investing in the building enclosure. Your building enclosure is expected to last hundreds of years. We don’t think in those terms, but we do expect our investment in a home or building to always be there. My home was built 40 years ago, and I expect to be able to sell it to someone who will have it for another 40 years. We need to do upkeep and repairs, but when was the last time that you needed to change the insulation in a building as it no longer performed due to the length of time it has been in the building? If we expect building materials to last 100-plus years, then the initial cost needs to be spread over the life of those materials. We do expect to replace our mechanical equipment every 15 to 20 years, but we don’t expect to change the insulation and other components in our building enclosure. Our building enclosure must be designed and built to last. MATERIAL PROPERTIES We need to change the way we currently look at materials. The most blatant example is the fixation we have on the “permeability” of materials. We get all concerned about the water vapor transmission rate of an air and water-resistive barrier (WRB) material. I hear salespeople touting that their material is better as it has a permeance rating that is one perm higher than their competition. The different between one perm and two perms or even one perm and ten perms is almost not worth measuring. We give these very small measurements too much validity. People spend hours researching materials to find one that has a high perm rating, only to then use that material in an assembly where the material needs an adhesive to install it, and that material is combined with other low-permeance materials. The result is that you have not achieved what you expected, as the assembly has a completely different permeance rating than that of the single material you selected. In the case of thermal insulation, the batt or board is clearly marked with the R-value so people may feel confident that by using the material, they will have a well-insulated building enclosure. People involved in the design or construction of buildings realize that when you place that R-21 batt between steel studs, you probably end up with an effective insulation value of R-7. Even that does not take into consideration all the other thermal bridging that may occur in the building assembly. Many building models use single-dimensional heat flow, but we know that heat flows in three dimensions. We are starting to understand that if we calculate heat flow in three dimensions, we get a different answer. We know that the air and WRB needs to be continuous for the material to perform properly. We take the utmost care in choosing the material, insisting that the installation is impeccable, and we inspect the installed material to make sure there are no defects. Then the cladding contractor installs their material, which results in potentially thousands of holes through the air barrier material. The effect that these thousands of penetrations have on the airtightness and watertightness of a material is currently unknown. Many design professionals meticulously Defining the Ultimate Wall Through Testing As you determine your approach on how to construct a low-energy-use building, the first thing that you should see is that the building enclosure needs to perform at a high level and be the best you can build. assemble all the technical data sheets for the different materials they specify. The information provided may be very detailed and precise, but keep in mind that the test procedures have been standardized for the purpose of comparing materials only; if you change the atmospheres in the test, you get different answers. Material specifications state that the material performance values are to be used for quality control and to compare materials but do not indicate end-use performance. Thermal insulation is tested at a standard mean temperature of 24°C (75°F) with a delta of 22°C (72°F), and if you change these conditions, you change the results. In real life, the amount of time that the insulation is exposed to these temperatures might be measured in seconds per year. Many materials—especially those that use air to provide the insulation—have an increased R-value when the temperature goes down and a decreased R-value when the temperature goes up. This applies to many materials but not necessarily all materials. With cellular plastic, if the temperature drops significantly, the blowing agent can condense, and the R-value goes down. The water vapor transmission rate needs to be determined at many atmospheres so that you are provided with an indication of how the material will perform when installed. ASTM E96, Standard Test Methods for Water Vapor Transmission of Materials, in a Note, advises that 23°C (73°F) and 27°C (80°F) have been used, but the document does not require a set temperature, and we know that relative humidity (RH) cannot be separated from a temperature. The test method does offer Procedure A, which is a gradient of 0% RH to 50% RH (essentially 25% RH)—also referred to as the dry cup method. The building code requires this atmosphere for many materials referenced in the building code. How often will the wall cavity be in that condition? Change the conditions and you change the water vapor transmission rate of the material. All materials will have different water vapor transmission rates when the temperature and RH change. The building code requires the desiccant method for some materials and the water method for other materials. You cannot compare one material with another if you are using two different methods. The same material will have two different water vapor transmission rates when tested at two different atmospheres (Table 1). As an example, consider typical fluid-applied air barrier and WRB materials tested by both the desiccant method and the water method. Keep in mind that this is the same material, but it shows the difference in material properties when subjected to different atmospheres (Appendix A). All of this shows that we can no longer simply choose materials independently and then put them together in an assembly and expect the materials to perform as tested in a laboratory and at the specifications published by the manufacturer. IMPORTANCE OF ASSEMBLY PERFORMANCE A wall assembly’s performance is the result of the performance of several materials working together. This is what counts. Each material has properties which either help or hinder the heat flow, liquid water ingress, water vapor transmission, and air leakage. The performance of a building assembly is also not just about the performance of each material used in the assembly combined, it is also dependent on how the wall was constructed. There are countless materials on any construction job site which meet the Air Barrier Association of America (ABAA) and the International Energy Conservation Code (IECC) requirements for an air barrier material of having an maximum air leakage rate equal to or less than 0.02 L/(s·m²) at a pressure difference of 75 Pa (0.004 CFM/ft² at a pressure difference of 1.57 pounds). If you only considered the air leakage rate of the material, a truckload of sheetrock delivered to the job site would meet the requirement for an air barrier material. How the materials are assembled and the installation practices used will have a huge impact on the performance of the assembly. After all, the best materials improperly installed will not provide the performance intended or required. Flashings are used to divert water to the exterior, but if they are installed with sections missing, are installed backwards, or are otherwise not complete, they will not provide the protection from water ingress into the building. The bottom line is that you need a properly constructed wall assembly—not simply a collection of materials haphazardly put together—for the building assembly to perform. The critical issue is the performance of the building assembly, not the performance of a single material. FUNCTIONS OF A WALL In the 1963 Canadian Building Digest, Neil Hutchinson defined the functions of a wall, and this list is still used today by design professionals. Neil identified the functions of a wall assembly as being the following: Principal Requirements of a Wall 1. Control heat flow 2. Control air flow 3. Control water vapor flow 4. Control rain penetration 5. Control light, solar, and other radiation 6. Control noise 7. Control fire 8. Provide strength and rigidity 9. Be durable 10. Be aesthetically pleasing 11. Be economical When you look at this list, you may identify functions that a single material may be able to do. However, no single material can provide a given function without being properly installed. Any material may perform better or worse, depending on how it has been used in conjunction with the other materials in the wall assembly. 170 | DalgleisEISh IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Fluid-Applied Material Desiccant Method Water Method Difference Minimum WVT Rate 0.751 629 738% Maximum WVT Rate 943.22 1,692.54 79% Mean WVT Rate 17.1 1,007 5,789% Minimum % Difference 4.96 5.15 4% Maximum % Difference 4.3 1,810 41,993% Mean % Difference 199.19 32.032 65% Table 1 – Sampling of water vapor transmission rates (from ABAA website for fluid-applied evaluated material). PROBLEM WITH TESTING EVERY BUILDING ASSEMBLY One way to approach this is to say that if you intend to use a specific assembly in a building, you need to conduct an assembly test for heat flow, air flow, water vapor flow, rain penetration, noise control, fire resistance, structural strength, and accelerated aging. You would obtain extremely good information on the performance of your building assembly if you tested every assembly for every building in every location, but the cost per project would be horrendous. A different approach would be to follow the example of NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components, where technically, you need to conduct large-scale fire tests every time you change any given material, including the fasteners. This would be an excessive burden on manufacturers. The industry instead generally conducts an NFPA 285 test on the “worst-case” assembly they want to market, and then has engineering judgements done on substitutions of individual materials. These engineering judgements may or may not be acceptable to the authority having jurisdiction. RISK MANAGEMENT APPROACH A different approach is needed in the construction industry. This approach combines many things that are already being done, but it incorporates a declaration approach such as what is used in European Union (EU) material standards. The EU standards are not allowed to discriminate in a material standard, so they are not material specifications, they are simply a list of test methods that need to be conducted on a material. The manufacturer conducts the tests and declares the performance of a material for each test. It is then up to the country to determine what level of performance of the material is required in buildings. In North America, we went through this phase years ago and now have true material specifications where the minimal performance levels of the material are set. A person buying a material that meets the material specification knows what they are buying, and it makes it easy to compare different materials if the units in the test methods are the same. THE ULTIMATE WALL The Ultimate Wall is a wall that meets the performance level required for a building based on location, the intended building use, the expected life of the building, and any other performance levels that the owner wants to set. This is different than a “perfect wall,” which is a wall assembly intended to work anywhere. The Ultimate Wall will have been tested to determine its performance in all the functions listed above. Assembly tests are relatively new and expensive, and take time to conduct. But the result is getting true information (to the extent possible) regarding how that building assembly will perform. CONTROL HEAT FLOW The ASTM test for heat flow, ASTM C1363, Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus (Figure 1) takes into consideration all the thermal bridging (Figure IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 D DalgleisEISh | 171 Figure 1 – Thermal bridging impacts the wall’s performance. Figure 2 – Guarded hot box test apparatus. 2) in the wall assembly, the influence of all the material on heat flow (not just the thermal insulation material), and how the different materials work together. You get a better understanding of the thermal performance of the wall assembly at steady-state conditions. We know that if thermal insulation is tested at different mean temperatures, you can get different results. As a designer, you need to know how the whole wall assembly works at different exterior temperatures. A set of standardized mean temperatures needs to be established so that different wall assemblies can be compared. CONTROL AIR FLOW We know that the air flow is only controlled when the air barrier is continuous over all six sides of the building. As mentioned earlier, sheetrock alone is sufficient to meet IECC requirements regarding air leakage rates. However, the air barrier system must be designed for the building, and then the air barrier materials, accessories, and components must be properly installed. When conducting a whole-building airtightness test (Figure 3) in accordance with ASTM E3158, Standard Test Method for Measuring the Air Leakage Rate of a Large or Multizone Building, the result is learning the air leakage rate of the whole building as built. This is the only information that can be used to show the air leakage rate of the whole building. Now the contractor needs a fighting 172 | DalgleisEISh IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Figure 3 – Whole-building airtightness test being conducted. Figure 4 – Constructing a wall for testing. chance to make the building enclosure airtight. A wall assembly (Figure 4) is tested to ASTM E2357, Standard Test Method for Determining Air Leakage Rate of Air Barrier Assemblies, using a standardized base wall to allow for comparison to other wall assemblies and to provide information on how that air barrier assembly was constructed. When the contractor replicates the test wall on a construction site, they will have a reasonable expectation that the site-built wall will perform as well as the wall that was tested in a laboratory. Depending on the location and the height of the building, the loads on the air barrier assembly may be different. Currently, ASTM E2357 has a single set of loads for the conditioning of the wall assembly. These conditions are for 80% of the buildings that have three stories or fewer. Additional conditioning loads need to be defined for buildings that are higher. The manufacturer can choose a certain set of loads in which a wall assembly will perform, and they will be automatically approved by the ABAA for all levels that are lower than the levels chosen. A set of conditioning loads needs to be established so that different wall assemblies can be compared at different loads imposed. CONTROL WATER VAPOR FLOW Many people are concerned about the water vapor transmission rate of a single material. We must get off that bandwagon. Wall assemblies need to dry, but the performance of a single material cannot determine the performance of a wall assembly. The wall will dry or not dry, based on all the materials in a wall assembly and how they are integrated. It is the wall assembly performance that is important, not a single material. ASTM E2321 – 03(2019), Standard Practice for Use of Test Methods for Determining the Water Vapor Transmission (WVT) of Exterior Insulation and Finish Systems (EIFS) is going in the right direction, but a new test method is required to test a full wall assembly. Many labs have environmental chambers where the atmospheres on each side of the assembly can be controlled. In using environmental chambers, different environments can exist on the exterior with the interior controlled at a set environment. A set of atmospheres needs to be established in order for different wall assemblies to be tested so that the results can then be compared against other systems or to compare how systems perform under various environmental conditions. CONTROL RAIN PENETRATION Stopping water ingress is the most critical function a wall assembly can provide. Water ingress can be in the form of liquid water penetrating the WRB or water vapor being transported by air leakage and then condensing. Do not mistake liquid water ingress with condensation that shows up in a wall assembly due to air leakage. Warm, moist air from inside or outside leaks through a wall assembly where it cools to the dew point and then appears as liquid water. Many assume that this liquid water came from the outside through a leak in the WRB. To see the potential for water ingress, you can obtain information from the ABAA and the Oak Ridge National Laboratories where a calculator has been developed to show how much water is transported by air leakage. Water penetration is controlled with the use of shingles, flashings, and WRBs. A complete wall assembly is needed to provide this function. I find it ironic that the WRB industry does not have a test method to determine the water resistance of a wall assembly. The best we have is AAMA 501, Laboratory and Field Test Specifications for Metal Curtain Walls, Including Performance Characteristics, Test Specimens, Methods, Recommended Practices, Test Apparatus and Testing Procedures, which says to look for water coming past the interior finish of a wall. That is too late. It is critical to know if water will get past the WRB and into the wall (Figure 5). If the water is already in the wall and now starting to flow out of the wall into the interior of the building, you are too late. Even if the water only goes into the wall and not out of the wall, this will cause a multitude of problems. The ABAA Research Committee is working on a standardized test method for water resistance of wall assemblies. The test method incorporates a specimen like the one used in ASTM E2357. The specimen is conditioned as required in ASTM E2357, and the air leakage rate is determined. The specimen is then subjected to transverse loading, racking, and restrained environmental conditioning. It is then tested for water resistance with a modified ASTM E331, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 D DalgleisEISh | 173 Figure 5 – Dynamic water resistance test on a wall assembly. (Figure 6). A key component to the test method is determining when and where the water gets past the WRB. A set of pressure differences, spray rates, and time need to be established so different wall assemblies can be compared. CONTROL LIGHT, SOLAR AND OTHER RADIATION The baseline wall used in ASTM E2357 only includes a blank window consisting of a window frame with a piece of plywood instead of glass. Light and solar control will not be dealt with in this wall assembly test, as separate testing of the fenestrations needs to be conducted. CONTROL NOISE Sound transmission is becoming a big issue with tenants. The baseline wall can be tested, and the sound transmission rate of the wall assembly can be determined in accordance with standard test methods like ASTM E336, Standard Test Method for Measurement of Airborne Sound Attenuation Between Rooms in Buildings. CONTROL FIRE The most common wall assembly fire testing is NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components. This test method has a very specific specimen that needs to be used. The fire control of different wall assemblies can be compared using this test method. PROVIDE STRENGTH AND RIGIDITY The strength and rigidity of a wall assembly is in the hands of the engineers involved to determine what is required and how the wall assembly needs to be constructed. As such, this is outside what is included in testing of the Ultimate Wall. BE DURABLE At this point, there are no durability test methods for wall assemblies. Discussion is being held on how this could be done and what could be involved for testing. As such, this cannot be included in the Ultimate Wall at this time. BE AESTHETICALLY PLEASING The architect for the project has complete control over what he or she believe is aesthetically pleasing. As such, this is outside what is included in the Ultimate Wall. BE ECONOMICAL This is a combination of what the owner wants to spend, what the architect wants to design, what the contractor can build, and then, everybody’s definition of what is economical. As such, this is outside what is included in the Ultimate Wall. HOW TO EXPRESS THE ULTIMATE WALL PERFORMANCE As the Ultimate Wall will be different for different projects, manufacturers need to express in a simple format their wall’s performance. Borrowing from the EU’s way of expressing performance of materials, the declaration could look some like Table 2. The numbers provided would be the result of the testing done on the wall assembly. The wall assembly construction would be detailed with both the material requirements and the installation requirements. The design professional will need to determine what performance level they require for a specific project in a specific location. Once they have the requirements, they would review the different wall assembly test results to determine what assembly meets their requirements. The durability of the assembly needs to be taken into consideration. How will that wall assembly perform once exposed to UV, heat, and moisture? This is an area where there is currently little data. This is a paradigm shift from a designer selecting different materials and putting them together themselves into a wall assembly. As I talk to designers, they tell me that they do not have the time, nor do they have the data to determine how different materials work together and therefore cannot determine the overall wall performance. They are asking for help in understanding how a complete wall assembly will perform in different climates. WHAT IS NEEDED TO FILL IN THE BLANKS There is a lot of work to be done to achieve the goal of developing the Ultimate Wall. Keep in mind that the Ultimate Wall needs to be flexible so that the owner and the designer can choose a wall that meets their requirements for their building in a specific location. The Ultimate Wall is one that performs as intended for the building. One person’s requirements will be different from another person’s requirements, so the Ultimate Wall needs to be chosen from a list of wall assemblies that are tested and available for construction. The work that needs to be done includes: 1. Determine the requirements for the wall; water, air, heat, and vapor are key, but what else needs to be included? 174 | DalgleisEISh IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Figure 6 – Static water resistance test for a wall assembly. Ultimate Wall Performance Water Ingress WI-XXX Air Leakage AL-XXX Thermal Transmission TT-XXX Water Vapor Transmission WVT-XXX Sound Rating SR-XXX Fire Rating FR-XXX Durability DR-XXX Table 2 – Ultimate Wall performance. 2. Develop assembly testing requirements and assembly test methods. 3. Develop different levels for every wall assembly requirement. 4. Develop a coding method to clearly identify wall performance. 5. Develop/update material specifications for all air and WRB materials. 6. Develop test methods that directly and specifically address air and WRBs. 7. Develop sub-assembly testing to allow for changes of material in an assembly without having to retest the complete wall assembly. 8. There will be other work identified as the work progresses. FUTURE OF BUILDING ASSEMBLIES We are building more and more complete buildings with more sophisticated materials and expecting them to perform at a higher level than ever before. The only way to get the building performance that is required is to become more holistic in our decision making. We can no longer determine wall assembly performance based on the testing of a single material; we must look at how different materials perform when they are combined in a specific wall assembly. When the expected performance of buildings was low, we could allow a lot of leeway in how we constructed buildings and how we used the materials. We can no longer construct buildings that way, as performance requirements are much higher today. We need to take a new approach to building construction, and defining the Ultimate Wall is a step in that direction. IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 D DalgleisEISh | 175 We can no longer determine wall assembly performance based on the testing of a single material; we must look at how different materials perform when they are combined in a specific wall assembly. 176 | DalgleisEISh IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 APPENDIX A Data from the ABAA Website Comparing Desiccant Method to Water Method for Fluid-Applied Materials (http://www.airbarrier.org/technical-information/evaluated-assemblies-2/) Dry Wet Difference Percentage 0.751 6.29 5.539 738% 1.28 6.48 5.2 406% 2.52 32.6 30.08 1194% 2.86 44 41.14 1438% 3.32 12.5 9.18 277% 3.4 39.6 36.2 1065% 4.3 1810 1805.7 41993% 4.92 57.3 52.38 1065% 4.96 5.15 0.19 4% 5.53 377 371.47 6717% 5.53 377 371.47 6717% 5.7 720 714.3 12532% 5.72 720 714.28 12487% 5.81 1004 998.19 17181% 5.81 1004 998.19 17181% 6.4 26 19.6 306% 6.699 857 850.301 12693% 6.86 202 195.14 2845% 9.411 48.745 39.334 418% 9.62 598 588.38 6116% 13 58 45 346% 17.1 1007 989.9 5789% 19 652 633 3332% 19.448 32.032 12.584 65% 25 145 120 480% 32 2066 2034 6356% 34.39 741.6 707.21 2056% 41.1 817 775.9 1888% 47.3 526 478.7 1012% 55.3 661 605.7 1095% 55.3 661 605.7 1095% 103.72 1677 1573.28 1517% 107 480 373 349% 108 351 243 225% 121.26 797.94 676.68 558% 133.8 1584 1450.2 1084% 154.44 1430 1275.56 826% 199.19 1186.88 987.69 496% 217.36 1229 1011.64 465% 311.74 1944 1632.26 524% 402.11 1387.7 985.59 245% 418 870 452 108% 453.02 581.15 128.13 28% 620.8 1002 381.2 61% 656 1384 728 111% 687.96 1269.84 581.88 85% 766.48 1332.76 566.28 74% 859 1015 156 18% 859 1015 156 18% 943.22 1692.54 749.32 79% Difference in Water Vapor Transmission Rate
