THE TECHNOLOGY of AIR BARRIERS: a Durability + Design Collection the Technology of Air Barriers

THE TECHNOLOGY OF AIR BARRIERS: A Durability + Design Collection The Technology of Air Barriers

A Durability + Design Collection

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Contents

iv Introduction

Air Barriers 101: Basic Theory and Design 1 by John Edgar, Sto Corp.

Air Barriers: Simple Concept, Powerful Effect 8 by Gary Henry, PROSOCO Inc.

Optimizing Exterior Wall Design Through Performance Modeling 9 by Craig Boucher and Sonya Santos, Grace Construction Products Going Retrofit: Upgrade of Building Envelope Delivers Remedy for Ailing Housing Complex 13 by Douglas R. Sutherland, Bryan J. Boyle, and Kevin D. Knight, Retro-Specs Consultants Ltd.

Proof Positive: ASTM E 2357 Standard Provides Method to Measure 16 Air-Barrier Performance by Mark Kennedy and Craig Boucher, Grace Construction Products

NIST Investigation Takes Measure of Cost-Savings Potential of Air Barriers 20 by Craig Boucher, Grace Construction Products

Detail Oriented: Building Enclosure Expert Sees Integrated Design and 23 Coordinated Planning as Essential to Constructing Systems that Work by Joe Maty, D+D

New Barrier on the Block? Making the Case for Coatings on CMU 27 by Joe Maty, D+D

Introduction

This eBook consists of articles from Durability + Design (D+D), durabilityanddesign.com, and the Journal of Architectural Coatings (JAC) on technological advancements in architectural air barriers. More articles on this topic may be found online at durabilityanddesign.com.

Photo courtesy of Retro-Specs Consultants Ltd. Cover photo courtesy of Grace Construction Products 1

Air Barriers 101: By John Edgar, Sto Corp. Basic Theory and Design

Editor’s Note: This article apeared esearch conducted at Oak Ridge National Laboratories in Oak Ridge, TN, the National in JAC in February/March 2006. Research Council Canada, and many other institutions around the world has shown Rthat controlling airflow through the building envelope is more important and effective in reducing heat loss and moisture transport than controlling vapor diffusion. Rapidly growing This research has demonstrated that air leakage through the building envelope can transport exponentially more moisture through the building envelope than water vapor migration building-envelope through the envelope. Controlling airflow has reduced problems such as corrosion, deterioration of wall components, and the growth of mold. Other benefits are improved energy efficiency and technology offers indoor air quality. important benefits, Shut the door! Are you trying to heat the whole outdoors? How many times have you heard that saying? How many times have you said it? but attention to No one relishes the idea of allowing conditioned air, heated or cooled at great expense, to be wasted by drifting out the door. We are diligent with the obvious but miss the less obvious. Houses design and detailing and commercial buildings are full of holes that allow conditioned air to pass directly to the outside all through the heating and cooling seasons. A 1998 study showed that uncontrolled air leakage in are crucial to prevent houses accounted for up to 40% of the heating and cooling costs. It’s not hard to figure out. Add up all the gaps you have in a house, around window frames, door adverse effects frames, plumbing and electrical penetrations, and the attic-access hatch. In an average home you may end up with a square foot or more of wall area open to the exterior. Given the amount of energy passing through air leaks in walls, it’s not surprising to find that

Rough openings are treated before applying coating to entire wall. (Inset above): A coating, applied to an exterior wall that will be clad in stucco, is designed to eliminate a bond-breaker, like felt paper. Photos courtesy of Sto Corp. 2

making a building airtight is becoming a code requirement. The National Building Code of Canada has had air-barrier requirements in place for more than a decade. The Massachusetts Building Code now includes requirements for air tightness that mirror the Canadian requirements. Wisconsin has also included specific requirements for air tightness in its code. Most state building codes refer to ASHRAE 90.1 as the standard for meeting minimum energy requirements. ASHRAE 90.1 includes a provision for air tightness around penetrations, so in one way or another, most of the state building codes contain an air-barrier requirement. More than expensively conditioned air passes through these openings. For example, these gaps freely transmit sound, increasing the amount of noise pollution in a building. We learn quickly as children that if you want to know what’s going on you listen at the crack in the door. Dust, dirt, pollen, and other allergens are also carried in through openings in the wall. The spray of dirt around a light switch on an outside wall demonstrates that dirt is coming in. If you open an insulated wall around an opening, you may find the nice pink insulation has turned black. That’s because it’s filtering pollutants as air passes into the interior of the wall. Along with the particulate Fig. 1: Vapor drive through an matter, the air carries noxious fumes and other gases. Everything from traffic diesel exhaust to uninsulated wall radon gas can enter a building through openings in the walls and foundation. Aren’t you glad you shut the door?

Vapor barriers versus air barriers: An identity crisis? With the rising cost of energy, conservation is becoming a priority. A second issue, also vitally important, is water in the building envelope. We have little control over the cost of energy but total control over water. Part of that control requires an understanding of the differences between vapor barriers and air barriers. Vapor barriers are designed to resist water-vapor pressure and to slow the diffusion of water vapor through the building envelope. Water-vapor pressure is usually far lower than the air pressure on a structure. Water vapor moves from higher to lower pressures and from warmer to cooler conditions. A typical vapor barrier for a cold climate is a polyethylene sheet placed over interior studs prior to the installation of drywall. In some cases as little as a facing on the insulation batt is adequate to meet requirements for vapor resistance. Neither of these materials provides a continuous barrier, nor would they meet the requirements for air leakage of an air barrier. Years ago, houses were built with little or no insulation. Walls were solid masonry or frame, and en- Fig. 2: Vapor drive through an insulated wall ergy was cheap. Heat passed through and the wall remained warm. Vapor also passed harmlessly through because a warm wall has no dew point (Fig. 1). Then, as energy costs rose, builders added insulation to the envelope. This reduced the energy loss but changed the temperature of the exterior wall. Interior warmth no longer reached the exterior. Water vapor diffusing through the wall condensed within the colder wall cladding (Fig. 2). Condensa- tion resulted in deterioration. Vapor barriers were added to resist the diffusion of water vapor, thereby lowering the humidity level within the building envelope (Fig. 3). Air barriers, by contrast, stop the movement of air under pressure, along with the water vapor it contains. Where a vapor barrier might consist of polyethylene film or faced batts, the requirements for air- barrier materials and systems are much more stringent. An air-barrier system must be able to resist the live loads placed on it without failing. Live loads include wind pressure from the outside (including hurricanes), mechanical loads from heating and cooling equipment, and the stack effect of conditioned air rising or settling within the building envelope. For example, the minimum air leakage requirement for an air-barrier material—typically 0.02 L/(sec•M2) at 75 Pa. pressure (0.004 cfm/ft2 @ 1.57 psf)—is equivalent to the air leakage through a sheet of drywall. Most air-barrier materials are much tighter than that. Fig. 3: Vapor drive through an insulated An air-barrier “system” must completely wrap the building envelope. The system consists of materials wall with a vapor barrier (individual components), assemblies (such as a window), and the connections between them. Compo- nents of the air-barrier system must be connected in a manner that is capable of resisting equal loads, and must remain durable. 3

The codes recognize that perfection is not possible, and a system is permitted to be leakier than its individual components. This being said, the testing for a system, with all the connections, is brutal. The system must stand up to significant dynamic pressure changes, thousands of times, and still resist airflow. Clearly, a polyethylene sheet sealed with duct tape is not up to this task. We can see that the functions of a vapor barrier and an air barrier are completely different. Of course, nothing is ever entirely simple. Some air barriers also perform as vapor barriers. There are advantages and disadvantages to using an air barrier to perform both functions. More information on these issues is available at the web site of the Air Barrier Association of America (www.airbarrier.org). Suffice it to say here that a vapor-transmission study can be conducted to determine the best materials for the specific design. Typically, the designer of the building envelope does this before he specifies a product. If any changes are made in the product or in the design conditions (e.g., building use is changing to a swimming pool), then another study should be done to see if the new material or conditions might affect the performance of the envelope. Most manufacturers can do this.

Condensation control Water in the building envelope is one of the biggest sources of building failure. It can cause structural elements to corrode and water-sensitive materials to deteriorate, compromising the building’s durability. The presence of water in the building envelope is also a key ingredient in the growth of mold, which may increase health risks to the building’s occupants. The story gets worse when you include the amount of moisture that air carries with it. As discussed above, diffusion of water vapor through a wall occurs slowly. Only a portion of the humidity in a room passes into and through the building envelope to the outside. If an air leak exists, however, all the humidity in the room passes through the opening into the wall. If that humidity reaches a point where it is cool enough to condense, i.e., the dew point, large amounts of water will condense within the wall envelope (Fig. 4). Is this condensation significantly different from diffusion? Yes! The amount of water condensing from an air leak can be 30 or 40 times greater. In a simple comparison, over the course of a winter, vapor diffusion through a wall might produce enough water through condensation to fill a small coffee cup, whereas air leakage through a small hole can produce buckets of water. This is a lot of water for a wall to deal with; usually it overwhelms the drainage capacity of both the wall and the cladding material. Evidence of excessive condensation Fig. 4: Air leak through an due to air leakage is found as efflorescence on bricks around windows or parapet caps and, in some opening in the wall extreme cases, as icicles hanging from the side of a building. The examples above relate to a cold climate, but warmer climates are not exempt. In the South, the hot, humid air is generally outside and the interior is cooled. Historically, the heat of a Southern summer was abated by opening the interior to the outside and controlling the temperature and humidity as much as possible with shade, natural ventilation, and fans. The interior surfaces remained warm and condensation was limited to the glass of cold lemonade. Those days are passing; most new homes built in the South (and indeed in much of North America) have air conditioning. Southerners now experience the inverse of the cold northern climate, as they travel from an air-conditioned house to air-conditioned car to air-conditioned office. Now, in warm weather, the vapor drive is to the inside. House construction in the South is similar to that in other parts of the country, with the usual gaps and cracks that allow air to penetrate. When building codes were established to deal with the southern climate, they did not take into account the effect of air conditioning on the building envelope. Crawl spaces were required to be ventilated to allow for the removal of moisture from the soil. This worked well until the floor became cooled by the air conditioning above. Once the floor was cooler, water condensed on the underside and trouble began. Problems arising from air conditioning are not restricted to the South. Even in southern Canada and the northern United States, condensation can occur on the polyethylene vapor barrier designed to deal with winter humidity but subjected to cooling in the summer. This phenomenon is made worse when openings in the wall allow quantities of water vapor to enter the interior, where all the surfaces are cool. 4

(Left): Applying mesh over joints of exterior wall. (Center): Fill is spray applied over mesh to seal joints on an exterior wall. (Right): Coating protects the sheathing and works in concert with fill and mesh to create air barrier

Consider the typical modern hotel. There is a sealed air-conditioning unit in the wall under the window. The window does not open. The only visible ventilation is the gap under the door to the hallway and the bathroom fan, which turns on with the bathroom light. It has been demonstrated that turning on the bathroom fan will draw outside air up through the air-conditioner drain, through the exterior wall to the dividing wall between rooms and, from there, into the bathroom. The water vapor in the air will condense on the cooler interior finish, often vinyl wallpaper, resulting in mold and deterioration of the gypsum wallboard. What is the solution to this problem? Installation of an air barrier will stop the air flow through the building envelope and thus bring the amount of condensation under control. Simply wrapping the rough opening with an air barrier before installing the window and air conditioning unit would help. Making a building airtight has, as one might imagine, other consequences. The design of a building with an air-barrier system must take into account the requirements of ventilation. Bathrooms and kitchens will still be equipped with exhaust fans. Furnaces and fireplaces will still vent gases of com- bustion out the flue. Outside air (usually referred to as “make-up air”) must be brought in to accommo- date this. By making a structure airtight, or at least tighter, we reduce the amount of energy required to heat or cool. (You will recall from above that up to 40% of heating and cooling energy is wasted due to air leaks.) We can therefore reduce the size of the mechanical equipment required to provide that energy. In addition, the make-up air can be brought in at one location where it is filtered and pre-conditioned, thus reducing interior pollution and increasing occupant comfort. Make-up air can be brought directly to heating equipment so it is outside air, not previously conditioned interior air, that is consumed and sent up the flue.

Dealing with rain Perhaps the most critical function of an air barrier is that it can stop rain penetration. Start with the basic idea that if air cannot pass into the wall, water can’t. Leaks are more than openings where water can enter. In its simplest form, a leak has three elements; water, a hole or path, and a force to move water through the hole. This is referred to as the leak triangle (Fig. 5). If you remove any one of the three elements, there won’t be a leak. If there is no water, obviously there won’t be a leak. We can try to eliminate all holes where water can enter, but that has proven to be difficult. The one thing we can do with certainty to control leaking is to control the force that moves water through a hole and into the wall.

Forces that move water Fig. 5: Leak triangle There are five forces that move water into a hole in the building envelope. • Gravity. We can’t stop gravity, but we can use flashings and roof overhangs to deflect water away from windows and other openings. 5

• Kinetic energy. Raindrops possess kinetic energy, which will carry them at an angle, sideways in extreme conditions, into an opening. That’s why we run to close the window when it starts raining. • Surface tension. This is manifested when water collects and moves on the underside of something. Try slowly pouring water from a coffee cup and watch how the liquid clings to the surface of the cup and runs in a totally unexpected direction. The drip edge on a pitcher prevents this uncontrolled movement of water; so does the drip edge of a flashing. • Capillary action. This is a form of surface tension. Water is drawn into materials with small openings and travels upwards against gravity. We use this force to our advantage with paper towels and curse it when our pant cuffs trail in the water. • Pressure. This, along with gravity, can be the biggest cause of water penetration. Pressure difference across a wall is mostly generated by wind, although mechanical equipment and stack effect can add to the load. Fig. 6: Pressure difference To demonstrate how pressure difference can move water, we need look no further than a glass of causes a leak water with a straw. Remember the leak triangle? If the glass contains water, the first requirement is met. The straw represents the hole or path. The water will remain in the glass until we apply a negative pressure on the straw and move the liquid from the glass (Fig. 6). How much pressure does it take to move water up the straw? Approximately 21 pounds per square foot will lift water 4 inches in the straw. That is equivalent to the pressure generated by a 100-mph wind. How does an air barrier control the effects of such high pressure? Take your straw and put a plug in the upper end. Now try moving water up the straw. You might create a pressure difference of 100 pounds per square foot, but the water will not move up the straw one millimeter (Fig. 7). The plug is an air barrier, and it has removed the force from the leak triangle equation.

Applied knowledge: The air-barrier system in practice Fig. 7: Air barrier (plug) The above analogy using a straw provides a simple example of the effectiveness of an air barrier. prevents a leak Incorporating that understanding into construction details is more complex, but not all that difficult. An air-barrier system should enclose the entire building envelope—roof, walls, and foundations, and the different air-barrier materials must be connected in a manner that is airtight. Most air-barrier materials will cover large areas. Typically, air-barrier materials are peel-and-stick, trowel-applied, or spray- or roller-applied membranes. These materials are bonded to the underlying structure and, in effect, become part of the structure. The critical aspect of a barrier “system” is the connection between one material and the next. For example, a roof membrane may be airtight up to the Fig. 8: Detail for fluid-applied air barrier at transitions point where it laps over a parapet, and a peel-and-stick membrane may be airtight up to the top edge of the parapet. If these roof and wall membranes are not connected in a permanent way, then there is no “system.” The components must connect in a way that is durable because once the cladding and flashing are installed, the air barrier can no longer be easily accessed. The same is true for a window. Windows are rated for airtightness; so are wall membranes. Whatever component connects the two elements, it must bond to both the wall membrane and window, must be compatible, and must be durable. All of these components make up the plug in the straw.

Detailing and air barriers In designing details with an air barrier, we must accept two concepts that, at first glance, seem backward. 6

Fig. 9: Detail for transition at structural joint Concept number one—the air barrier becomes the principal protection against the air pressure acting on the building. That is why it must be bonded to the structure—to transfer the fluctuating wind load. Concept number two—the cladding and outer seals are now the back-up protection, designed to keep water away from the air barrier. The outer face of a building is exposed to all the environmental conditions—rain, wind, snow, and sun—and protects the inner seal, the air barrier. The cladding screens the air barrier and, as such, is called a “rain-screen” system. Why is this inside-out thinking important? Because the back-up protection (the outer skin) can be easily maintained and does not have to be perfect. In fact, if the air-barrier system is properly installed, the outer skin can be full of holes and the wall will not leak because the air barrier has removed the Fig. 10: Preparation of a rough opening force that moves water into the building envelope. In detailing, we do not ignore the fact that other forces (e.g., gravity) for a nail fin window are still at work. Water may get past the outer rain screen into the wall cavity. If so, good flashing and venting details will allow the water to drain freely to the exterior or to dry. These details will vary depending on the cladding material; the critical principle to keep in mind is that the air barrier must remain continuous. The accompanying details (Figs. 8–10) show ways that an opening can be made airtight and incorporate flashing to drain water that penetrates the cladding to the exterior. It is assumed for the purposes of these details that the air barrier is also a water-shedding surface. Most air barriers are resistant to water penetration, but when this is not the case, an additional water-shedding material must be installed. Plywood, for example, is airtight. If you seal the joints between sheets of plywood you have an air- barrier assembly. An additional water-shedding barrier would then be required over the outer face of the plywood. Materials from different manufacturers of air barrier possess unique properties, and how to detail them should be understood before using them. One should always check, either on the Internet or with the supplier directly, for updated information.

Conclusion The use of air barriers is gaining recognition in building codes in the United States and many other countries. The driving force behind this recognition is the need for energy conservation. It has been shown that up to 40% of energy consumption in buildings is caused by air leakage. The government finds it strategically important to reduce dependence on diminishing energy resources such as oil and natural gas, so there are increasing code initiatives to make buildings airtight and energy efficient. Deterioration related to water damage can be a major source of building failure. Over the last several decades, the introduction and expanded use of air conditioning has changed the way traditional building materials and methods perform. We have come to understand the key role that air leakage plays in the process. The inclusion of an air barrier in a wall can dramatically reduce the amount of water condensing in the building envelope. An effective air barrier coupled with balanced mechanical controls also improves the performance of buildings. Finally, the use of an air barrier with proper flashing and drainage can eliminate bulk water in- trusion into the building envelope. Leaking into the building envelope is reportedly the biggest source of construction litigation. One can only imagine the results if this problem is resolved. 7

Web sites with more information: • www.irc.nrc-cnrc.gc.ca National Research Council Canada, Institute for Research in Construction • www.ornl.gov Oakridge National Laboratories • www.airbarrier.org Air Barrier Association of America • www.wbdg.org/design/airbarriers.php Whole Building Design Guide, National Institute of Building Sciences, Air Barrier Systems in Buildings, by Wagdy Anis, AIA, Shepley Bulfinch Richardson and Abbott. JAC 8

Air Barriers: Simple Concept, By Gary Henry, PROSOCO Inc. Powerful Effect

Editor’s note: This article appeared in 2005 study* by the National Institute of Standards and Technology showed that an D+D News in September 2010. effective air barrier can slice a building’s natural gas costs by more than 40%, and Aelectrical costs by more than 25%. Those are savings that can’t be ignored as the days of cheap energy retreat ever further into the past, and sustainability takes on ever-greater urgency in the construction industry.

How do air barriers cut a building’s energy costs? Air barriers cover all openings in the structural walls of buildings. They are, simply, barriers to air. In hot weather, warm, moist air tends to infiltrate building walls through weepholes, failed mortar joints, and other penetrations in the masonry veneer. The air movement is driven by differences in air pressure between the inside and outside of the building. But if the structural sheathing or CMU backup is covered, continuously and seamlessly with an air barrier, that air just can’t go any further. It can’t get in through covered seams, joints and connections Block goes up over a red-colored, fluid-applied of the structural wall to possibly condense in the cooler inner recesses of the wall assembly. air barrier, sprayed or rolled on the structural In cold weather, warm, moist air from living spaces will leak into the wall assembly via electrical or wall. To be effective, the air barrier must be continuous, seamless, durable, and breathable. plumbing penetrations, or any other openings it can find. If there is a pathway to the great outdoors, via those seams, joints and connections in the structural wall, you’ve got an air stream of energy dollars blowing out of the building—just the same as if you left a door or window open. Remember your dad yelling, “Shut that door! We can’t afford to heat (or cool) the whole neighborhood!?” He was wise. In both hot and cold weather, air leaks add to the load of an already hard-working HVAC system. We’ll examine air-barrier technology and systems in more detail in the near future. For now, we’ll Above: Warm, humid air leaking in through the reiterate that if the structural wall is covered with a seamless, durable, continuous air barrier, the escap- exterior wall is stopped at the structural wall ing air—carrying that load of hard-earned energy dollars—is stopped. No stream, no loss=big savings. by the air barrier. It won’t get in to raise temperatures in the walls and make the HVAC Dad would approve. system work harder. Below: In cold weather, expensively heated air *NISTIR 7238 Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC tries to escape to the outside, taking your hard-earned energy dollars with it. An effective Energy Use air barrier shuts off all pathways to the outside, so you’re not “heating the neighborhood.” Gary Henry is a business communication specialist with PROSOCO Inc., a manufacturer of products for cleaning, protecting, and maintaining concrete, brick, and stone. A writer throughout his professional life, Gary has focused on construction-related issues since joining PROSOCO in 1999. His articles have appeared in a number of publications, including the Journal of Architectural Coatings (now Durability + Design). He also worked from 1981-2006 as a Navy journalist, both active and reserve, where he taught journalism and wrote about military activities for Department of Defense and civilian publications.

Though tiny, the staple holes in this house wrap are easily big enough to leak air. Air from living spaces finds its way to these portals through electrical outlets and plumbing penetrations, and seams and gaps in the structural wall. Unless a seamless, continuous air barrier—which this is not—interrupts the path, however indirect, air will find a way to escape. It carries energy dollars with it. 9

Optimizing Exterior Wall Design By Craig Boucher and Sonya Santos, Grace Construction Products Through Performance Modeling

Editor’s note: This article appeared in mploying an effective air barrier to prevent air leakage, energy loss and potential D+D News in July 2010. moisture problems is a priority for any building design today. Designing exterior wall assemblies that incorporate an air barrier and avoid moisture accumulation Ein problematic locations can be challenging. Proper wall design is crucial, as moisture accumulation due to vapor diffusion can cause a wide range of problems for buildings and occupants alike—from mold, mildew and poor indoor air quality to degradation of the structure itself.

The answer: A sophisticated tool Given these risks, it makes sense to analyze the potential performance of a given wall assembly before it is built. This can be complex, however, as several factors influence wall performance, including local climatic conditions, the location of insulating materials in relation to the air barrier, and the absorptiveness of the wall cladding. How can designers reduce their risk by analyzing these factors in relation to their wall design? Increasingly, designers are finding the answer to this question through a sophisticated digital tool called a hygrothermal modeling analysis. Just as designers of jet engines and high-pressure valves use modeling software to see how their designs perform under specified loads, architects can perform a similar analysis of their wall assemblies. A hygrothermal analysis is the study of coupled moisture (“hygro”) and heat (“thermal”) transport. Moisture is present in air (defined as relative humidity), and differences in moisture and temperature affect moisture vapor diffusion and heat transfer, respectively, through a wall. An air barrier within an exterior wall assembly prevents or greatly reduces air movement through a wall. Preventing uncontrolled air If designed and built correctly, wall assemblies that incorporate air transport of moisture that could condense and collect in unwanted barriers can prevent air leakage, energy loss, and potential moisture areas of the wall is an important step in moisture control. problems. These photos show air-barrier installation in progress. The hygrothermal analysis models vapor diffusion and heat transfer through an exterior wall assembly. This enables engineers and designers to investigate expected performance of exterior walls that utilize an air barrier.

Dynamic analysis One such analysis tool, the Perm-A-View™ service from Grace Construction Products, provides a dynamic calculation of temperature, moisture content, and relative humidity of materials in a multi-layer exterior wall assembly over time. Using a sophisticated computer model and actual historical weather data for a number of U.S. cities, as well as major cities in Europe and Asia, the analysis calculates expected wall-performance metrics for three factors of concern to building designers and owners: organic (mold) growth risk; corrosion risk; and energy efficiency. This data provides valuable insights on expected wall performance, helping architects optimize their wall-assembly designs, with particular emphasis on the type and location of air barriers.* 10

Wall Assembly 1 Wall Assembly 2 Liquid-applied vapor-permeable air barrier applied to the exterior gypsum Liquid-applied vapor-impermeable air barrier applied to the exterior gypsum sheathing. sheathing.

The analysis begins by gathering detailed information on the proposed wall assembly, including wall components (materials, thicknesses, air gaps, interior coating, stud type, and air- barrier type and location), plus information on the interior and outdoor climates, wall orientation, exterior color, building height, and other building details. The tool enables engineers to analyze different wall variations to compare their performance—such as using a vapor-permeable versus vapor-impermeable air barrier or placing air and/or vapor barriers in different locations in the wall assembly. This can be extremely helpful in optimizing wall design.

Modeling at work To understand how a hygrothermal analysis can provide valuable insight, consider the following sample analysis for a wall assembly in Chicago, Ill. The wall is composed of a metal panel facade, an air space, gypsum sheathing, fiberglass insulation in a stud cavity, and interior gypsum board. In this sample analysis, three wall assemblies are analyzed: A hygrothermal analysis was performed, simulating a 12-month period with typical climate and moisture patterns for Chicago. The following graphs show moisture content over time for the main wall components in each of the wall assemblies. These graphs can be used to determine if the moisture content level of a component is within acceptable limits. They can also help indicate the time of year that the moisture content of a wall component increases or de- creases, to help predict vapor drive direction and moisture accumulation within the wall assembly. The visual nature of the moisture content over time analysis clarifies some significant differences among the wall configurations: The moisture content of the fiberglass peaks at 4% for Wall 1, 6% for Wall 2, and 4.5% for Wall 3 (note, too, that in Wall 2 the peak moisture content of the exterior gypsum sheathing exceeds that of the fiberglass insulation).

Furthermore, the moisture content of the fiberglass insulation peaks in the early spring for both Wall 1 and Wall 2, yet it peaks in the autumn for Wall 3.

Mold and corrosion risk The hygrothermal report also provides an analysis of mold risk, expressed as the number of consecutive days that a material (in this case, the fiberglass insulation) stays above 80% relative humidity (RH)—an indicator of mold-growth potential. Mold needs three things to grow: mold spores (which are generally present everywhere); an organic food source (such as the paper facing of gypsum board or organic matter that can collect in fiberglass insulation); and moisture. The hygrothermal-analysis tool measures the moisture present in each wall component to provide an indication of mold risk. This data can be 11

Wall Assembly 3 Moisture Content Over Time: Wall 1 Liquid-applied vapor-permeable air barrier applied to the exterior gypsum sheathing and a polyethylene vapor barrier installed between the interior gypsum wall and the fiberglass insulation.

used to evaluate wall performance in correlation with ANSI/ASHRAE Standard 160, Criteria for Moisture Design Analysis in Buildings, which provides some exterior wall performance metrics. The report also provides an analysis of corrosion risk, or time of wetness, expressed as the number of hours per year when the relative humidity (RH) is greater than 80% and the temperature is warmer than 32 F. ISO 9223 uses this value to evaluate the cate- gory of corrosivity of metals. The time of wetness is an indicator of the potential for corrosion of metals in the wall structure, such as the steel studs located between the fiberglass insulation batts in this example. As you can see, in both the Mold Risk and Corrosion Risk analyses, the metrics for Wall 3 are significantly lower (better) than the other two wall designs.

Energy efficiency Finally, the hygrothermal analysis report provides an analysis of annual energy flux, the energy required to both heat and cool the Moisture Content Over Time: Wall 2 interior of the wall to maintain an average temperature of 70 F. The energy metrics are very similar for all three walls, indicating that the combination of air and vapor barriers used in Wall 2 and 3 do not negatively impact energy usage compared to the Wall 1 design. Based on this sample analysis, Wall 3 clearly offers advantages over the other designs in terms of moisture accumulation, offering reduced mold risk and corrosion risk.

Professional support While the technology behind modern hygrothermal analyses is impressive, having the analysis conducted by an engineer with experience in wall design and air barriers is ideal. With the analysis tool described here, an engineer with the company that developed the tool works with the designer to ensure that all wall-assembly details and building parameters are accurately en- tered into the analysis, as well as help interpret the results.

This can be extremely valuable when assessing multiple options. If poor results are obtained from analyzing the wall design provided by the designer, then the engineer can leverage previ- ous experience to offer alternative wall designs in the final hygrothermal analysis report. The overarching goal is to provide designers with information that helps them make the best choice of air barrier product and its location in the wall assembly. 12

Moisture Content Over Time: Wall 3 Comparison of Mold Risk numbers for all three walls

Comparison of Time of Wetness numbers for all three walls Comparison of Energy Flux for all three walls

With building designers and owners acutely focused on the challenge of vapor diffusion and condensation, today’s sophisticated hygrothermal analyses such as those described here can be an invaluable tool in reducing building risk long before construction begins.

More information www.graceconstruction.com/perm-a-view.

* Note that hygrothermal analyses, including the Perm-A-View service, do have limitations. Hygrothermal analyses typically do not consider air and water leakage or drainage, and multi-dimensional effects, such as thermal shorting or non- homogenous materials or wall penetrations. The analysis is limited to assessment of moisture content of wall components and is not to be interpreted as actual whole wall performance. JAC

Sonya Santos is marketing manager waterproofing Craig Boucher is currently a technical service manager with W.R. Grace, products North America at W.R. Grace. She has and has worked in the construction products industry for more than 10 years. worked in various marketing roles in the company’s Boucher is a member of the technical committee and board of directors Specialty Building Materials Division over the past of the Air Barrier Association of America (ABAA), and participates in the six years, focusing most recently on the commercial ULC (Underwriters Laboratories of Canada) Committee on Air Barrier air-barrier and waterproofing segments. She has a Materials and Systems. He has conducted hygrothermal analyses for BS in chemical engineering from Ohio University more than 300 U.S. projects. He has a BS in civil engineering from and an MBA from Babson College. Worcester Polytechnic Institute and is a LEED Accredited Professional. 13

Going Retrofit: Upgrade of Building By Douglas R. Sutherland, Envelope Delivers Remedy for Bryan J. Boyle, and Kevin D. Knight, Retro-Specs Consultants Ltd. Ailing Housing Complex

Editor’s note: This article appeared in design team charged with the task of retrofitting the building-envelope system of a JAC in May 2009. four-story, multifamily, special-needs housing complex in Winnipeg, Manitoba, faced a formidable challenge: how to do the job—intended to dramatically improve the Aoverall functional performance of the building envelope—without removing and replacing the entire wall. Adding to the challenge was the imperative of minimal disruption to the building’s occupants, as there was no provision for alternate temporary housing. The building’s exterior-wall composition, from the interior outward, was comprised of painted in- 1 terior gypsum, polyethylene vapor barrier, steel-stud backup wall, fiberglass batt insulation, ⁄2-inch glass-fiber-reinforced polyisocyanurate, cavity space, masonry ties secured directly to the steel studs, and exterior masonry. In some locations, a stucco exterior finish was used, with building paper and gypsum sheathing installed over the steel studs in lieu of the polyisocyanurate and masonry. Occu- pants had reported numerous cases of water infiltration into the individual suites. An investigation into these conditions revealed stained fiberglass insulation, corroded fasteners, and isolated mold growth—symptoms attributable not only to insufficient drainage, but also to in- effective management of air movement across the building envelope. Of primary concern was evidence that neither a defined air barrier nor drainage plane existed in the building-envelope system. While many of the interior-wall components would, by default, act as an air barrier if isolated from the other components, no clearly defined air-barrier system was in place. In other words, even with components that possess air-permeance characteristics that would satisfy Canadian national building code requirements for an air barrier, discontinuities in the plane of airtightness compromised the effective functioning as a barrier system. These discontinuities existed not only at the interface between adjoining components, for example, but also at the window- to-wall interface, the roof-to-wall junction, and at poorly sealed joints between adjacent boards of the polyisocyanurate.

Scope of the project It was recommended, and eventually agreed, that the building envelope would be retrofitted to bring it into compliance with the prevailing National Building Code of Canada (NBCC) requirements; that is, the building envelope would encompass an effective air-barrier system, with vapor barrier, thermal protection, and water management. To meet these objectives, the air-barrier system would need to be continuous, structurally sound, and durable. The redesign would include removal of all of the exterior facades and insulation, keeping in mind the necessity to cause as little disruption as possible, with no displacement of the occupants. 14

The reconstruction of the exterior wall would include cement-board sheathing, the air barrier, polyisocyanurate insulation, and either stone facade or steel siding. All of the windows were to be replaced with combination fixed and operable horizontal slider fiberglass windows. To address structural concerns with the existing steel studs, cement board was installed over the studs to provide additional structural support, with heavier-gauge steel studs installed at key locations to support the board. Existing batt insulation was checked and replaced as required to fill in gaps and voids. The existing polyethylene vapor barrier, as it appeared to be functioning adequately, was to be left intact. The critical need was for a solution providing a functioning air/vapor-barrier system, given that the polyethylene vapor barrier was already in place.

The air-barrier system: Selection and installation After researching the various products available, and keeping in mind project budget constraints, the project participants settled on a vapor-permeable air barrier. The system selected was Henry Company’s Air-Bloc 33 UV Resistant Vapor Permeable Air and Weather Barrier Membrane, a one-component, liquid-applied, rubberized (elas- tomeric) membrane. As an air-barrier material, its air permeability of 0.008 L/s/m2 satisfied project-specification and NBCC requirements, while its vapor permeance of 11.6 perms (@3 mm wet film) was sufficiently high so as not to create a vapor trap between the new barrier and the existing polyethylene. Additionally, the product’s watertight qualities would allow it to act as a secondary drainage plane to manage any water in- (Above): ASTM E 783 airtightness test in progress on filtration through the exterior facade. window-wall mock-up; (below): Membrane application Once the cement board and windows had been installed, Henry Company’s Blue- thickness of liquid-applied air barrier being measured. Photos courtesy of Retro-Specs Consultants Ltd. skin Breather Self-Adhesive Vapor Permeable Air Barrier Membrane was installed as the transition material between the windows and cement board. The company’s 990- 06 Yellow Jacket Reinforcement Fabric was placed on all joints between the cement boards. Application thickness would be critical to the effectiveness of the liquid-applied vapor-permeable air barrier. Since shrinkage during cure is minimal, one-time application was sufficient without the need to re-check the thickness once the material had off-gassed. Prior to installing the liquid-applied air barrier over the cement board, several sample installations were completed by the installer to determine the application method—given the existing conditions—that would result in a consistent membrane 1 thickness of ⁄8 inch while allowing the installation to proceed at a reasonable rate. One method attempted was to apply the air-barrier material “free hand” without a thickness guide. The contractor assigned two applicators to spray the coating on two different sample areas, checking membrane thickness as installation progressed. This method proved to be quite applicator-dependent, both in speed of installation and in obtaining the required thickness per area of coverage. A second method involved installation of a coat of air-barrier material and then 1 embedding two wires, each ⁄8 inch thick, into the membrane. The installer then trowel-applied the membrane, using the wires as a thickness guide. With this process, the measured thickness of the material was very close to the manufacturer’s recommendations. This method, however, presented two challenges: only small areas could be completed at a time using the wires as a guide, and irregularities in the rebuilt wall resulted in uneven thicknesses. Still, it was determined that the “wire guide” method would be used, as it was less installer-dependent and quicker than the “free-hand” method. With the wire-guide 15

method, the installer re-troweled after the wires were removed and re-checked the joints for applied thickness. Over the dura- tion of the project, the speed of installation improved as tech- niques were refined. To determine whether the system, as installed, satisfied specified requirements for airtightness, a mockup of a window and adjoining opaque wall was constructed. Mock-up components included a combination fiberglass window, cement board, liquid-applied barrier, Blueskin Breather, Aquatac Primer, and ure- thane foam. The mockup was tested for airtightness in general accordance with ASTM E 783, “Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Win- dows and Doors.” To conduct the test, a rigid, airtight chamber was constructed over the exterior of the test sample and pressurized at a series of negative pressures to determine the air leakage rates of the fixed unit, operable unit, and opaque wall. The measured air flow rate for the opaque wall was 0.034 L/s/m2, well below the maximum allowable 0.100 L/s/m2 project requirement. The completed building-envelope retrofit provides the potential for increasing the building’s lifecycle by as much as 35 years Building-envelope commissioning As part of the building-envelope commissioning process, the commissioning agent Retro-Specs Consultants Ltd. conducted several site visits over the course of the installation. The site- visit procedure included visual observation of the installation area and taking wet and/or dry film thickness measurements at randomly selected locations. Typically, the measured thicknesses met the specified requirement. At locations where the thicknesses were low—usually isolated to “lines” left by the guide wires—the installer was notified of the locations and was able to immediately perform corrective action. As a part of the contractor’s quality-control program, the applicator would also take wet-film thickness measurements during the installation process. In order to ensure that the entire air-barrier system would function effectively, other components comprising the completed system were tested rigorously. Sheet air/vapor barrier membranes installed at stairwells, parapets, and in transition Installation of liquid-applied air barrier in progress; areas were tested for airtightness at seams, masonry ties, and penetrations in general accordance wires being used as application thickness guide can be seen in lower right corner of photo. with ASTM E 1186 method 4.2.7, using an Air-Sure Leak Detector, and for membrane-to-substrate tensile adhesion in general accordance with ASTM D 4541 using a Com-Ten digital pull tester. In addition quantitative airtightness testing and airtightness “smoke” testing were conducted on a sampling of windows, including window-to-wall interfaces, in general accordance with ASTM E 783 and E 1186 method 4.2.6, respectively.

A new lease on building life The completed building-envelope retrofit provides the potential for increasing the building’s lifecycle by as much as 35 years. The resulting system is functional and effective, with no negative impact on aesthetics. The use of a high-perm liquid air-barrier material allowed retention of the existing polyethylene vapor barrier. As a result, the majority of the interior wall components remained intact, causing very little disruption to the occupants or the building’s usable space. JAC 16

Proof Positive: ASTM E 2357 Standard Provides Method to By Mark Kennedy and Craig Boucher, Grace Construction Products Measure Air-barrier Performance

Editor’s note: This article appeared in oday, no energy-efficient commercial building design is complete without a continuous JAC in August/September 2008. air barrier. Preventing air leakage is a critical factor in creating energy-efficient and healthy structures. Indeed, preventing air leakage can generate energy savings of up to T 1 36%, according to a recent study by the National Institute of Standards and Technology. In addition, a robust, continuous air barrier helps control moisture in wall structures. Moisture can degrade energy efficiency, cause structural damage, and is a major cause of mold and other health hazards that can contribute to “sick building syndrome.” For architects and specifying engineers, this simple reality begs a complex question: How do you know that a particular air-barrier assembly will effectively prevent air leakage? While manufacturers of air-barrier materials and products claim a variety of advantages, how can you validate the performance of products in the context of a typical application, under real-world conditions?

A uniform test The answer lies in a standard recently adopted by the American Society for Testing and Materials (ASTM): ASTM E 2357 Standard Test Method for Determining Air Leakage of Air Barrier Assemblies. Developed in collaboration with leading architects and structural engineers, ASTM E 2357 provides a uniform methodology for testing and measuring the leakage rate of air-barrier assemblies as they are typically used in building enclosures, under realistic wind load cycles. Prior to the development of ASTM E 2357, one could only evaluate performance for individual air- barrier assembly components—the air barrier alone, the flashing alone, or the sealing materials alone.

PhotosPhoto courtesy courtesy ofof GraceNuernbergMesse© Construction and Products Thomas Geiger© 17

This “piece by piece” approach does not provide for a holistic evaluation of real-world performance, where the interaction among components—and the interaction of components and wall elements, such as windows and other penetrations—is key to the assembly’s ability to maintain a continuous barrier. ASTM E 2357 addresses these limitations by enabling a uniform method of evaluating and comparing entire air-barrier assemblies. ASTM E 2357, the first such objective, uniform method available, has been adopted by the Air Barrier Association of America (ABAA) as a key element of its acceptance criteria. “ASTM E 2357 is the only test method that gives the user any information on the performance of an installed air-barrier assembly,” says Laverne Dal- gleish, Executive Director of the ABAA. “Every building contains multiple air- barrier materials. It is only when a material is selected and combined into an assembly that it actually performs the function of an air barrier. “ASTM E 2357 determines the air-leakage rate after being conditioned under real-world loads, which provides the user with a precise air leakage rate and confidence that it will provide this performance when installed. Data from ASTM E 2357 is critical to every design professional.”

Realistic wall specimen ASTM E 2357 defines a specimen wall assembly and test protocols for evaluating air-barrier performance. The specimen is a realistic, 8-by-8-foot wall mockup, complete with typical wall penetrations—window, galvanized duct, PVC pipe, post-applied brick tie-ins, and hexagonal and rectangular electrical junction boxes, all of specified dimensions—as well as roof and concrete-foundation interfaces (Fig. 2). The air-barrier assembly to be tested is applied to the wall, complete with flashing and sealing materials applied around all penetrations and at air-barrier joints in specified locations on the wall. The wall specimen is then mounted in a well-sealed test chamber with an air supply that allows application and measurement of both positive and negative air- pressure differentials across the wall structure.

The test procedure Once the specimen is secured in the test apparatus, the wall specimen is subjected to a specified Fig. 1 (Top): Photo of an 8-by-8-foot mock-up wall with penetrations wind load schedule and a window opening to be tested per ASTM E 2357. Fig. 2: Diagram of specimen wall for testing air barrier assembly with both positive performance, as specified in ASTM E 2357. and negative loads during the following three distinct loading stages (Fig. 3): • Sustained load – 600 Pa2 (12.5 psf) for 1 hour • 2,000 cyclic loads (positive and negative)—800 Pa (16.7 psf) pulses for 3 seconds, after which pressure is released until it returns to 0 Pa; this is performed 2,000 times with positive loads, followed by 2,000 negative load cycles. • Wind gusts—1,200 Pa (25 psf–equivalent to 99 mph) for 3 seconds

Fig. 3: Chart of wind loading schedule specified by ASTM E 2357 illustrating positive and negative sustained, cyclic, and gust loads to which the air-barrier assembly is subjected during testing. 18

After each stage, the air-barrier assembly is inspected for signs of damage, loosening or other failure that could compromise performance. Following the wind loading, the air leakage rate, or air permeance, is measured at a reference pressure of 75 Pa (air permeance is also measured at 25, 50, 100, 150, 250, and 300 Pa). Upon completion of the air-permeance measurements, air-barrier de- flection is measured. The result of this calculation is a measurement of air permeance expressed in terms of cubic feet per minute, per square foot (cfm/ft2) or liters per second, per meter squared (L/s*m2). As a yardstick, the ABAA-specified requirement for an air-barrier assembly tested according to ASTM E 2357 is 0.04 cfm/ft2 (0.2 L/s*m2) or less.

Fig 4: Photographs of some of the six wall specimens tested by Intertek. Each wall Testing the standard specimen was constructed according to In April of 2007, Grace Construction Products contracted with the independent laboratory Intertek ASTM E 2357 specifications, with one of the to conduct testing on several barrier assemblies per ASTM E 2357. Testing was conducted at Intertek’s three air barrier materials tested. Madison, WI, facility. Six wall specimens were constructed according to the ASTM E 2357 specifications, with a different air-barrier material applied to each set of two walls: a fully-adhered sheet membrane; a synthetic, spray-applied membrane; and a spray-applied, vapor-permeable, “breathable” membrane. Flashing membranes were used to flash the window openings on all wall specimens, and a liquid membrane was used in appropriate areas, such as water-bucking laps of flashing membrane and annular space around the duct, pipe, and electrical-box penetrations. After being subjected to the ASTM E 2357 standard wind-load schedule, air permeance for all three of the wall specimens was measured to be less than <0.0008 cfm/ft2 (0.004 L/s*m2). This represents air- leakage rates below the detectable limit of the laboratory test equipment for all three air-barrier assemblies tested. Intertek then took testing a step further, going beyond the wind loads specified by ASTM E 2357 to test the air-barrier assemblies under extreme conditions. They were subjected to the equivalent of 168-mph wind gusts (for comparison, the highest wind gusts recorded during Hurricane Katrina were Fig. 5: The air-barrier systems tested by Intertek withstood wind gusts equivalent approximately 150 mph) at which point the wall structure itself buckled under crushing air pressures to 168 mph, remaining fully adhered and of up to 72 psf (3445 Pa). The air barriers remained intact and fully adhered to the wall even as the intact while the substructure was brought underlying wall structure failed. to failure. 19

A key contributor to the ASTM E 2357 standard, Lance E. Robson Jr., AIA, of Building Envelope Technologies Inc., reviewed the test results and was pleased to see that the standard delivered the insight intended. “Air-barrier products have abounded on the marketplace in recent years as the industry has embraced a new understanding in building construction, which itself is a rare occurrence,” Robson says. “By providing test results utilizing ASTM E 2357, a product manufacturer can demonstrate the sufficiency of their materials when combined into an assembly that will work with the whole building system. This enables all interested parties to make informed decisions with assurance for the building’s design and sustainability.”

Editor’s note: This article was initially published in the March 2008 edition of Interface, the technical journal of RCI Inc. (The Institute of Roofing, Water- ASTM E 2357 provides a uniform method of evaluating and proofing, and Building Envelope Professionals). Questions or comments related comparing the performance of entire air-barrier assemblies. to this article to can be sent to [email protected].

1 “Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC Energy Use” (NISTIR 7238), Steven J. Emmerich, Timothy P. McDowell, Wagdy Anis, June 2005 2 The Pascal (Pa) is the scientific unit of pressure 1 Pascal = 0.01 millibar of air pressure. JAC 20

NIST Investigation Takes Measure of Cost-Savings Potential of By Craig Boucher, Grace Construction Products Air Barriers

Editor’s Note: This article appeared he use of air barriers in the commercial building envelope has grown in popularity in JAC in February/March 2006. over the past few years and has been linked to energy savings and improved build- Ting science. The National Institute of Standards and Technology (NIST) recently conducted an investigation to evaluate the potential energy savings created by air-barrier use. The following summary is based on an interpretation of the NIST investigation. The full 48-page NIST report can be found by using the following link: http://fire.nist.gov/bfrlpubs/build05/ PDF/b05007.pdf.

NIST Investigation’s results at a glance The NIST investigation predicted that using a properly installed air-barrier system capable of a target air leakage of 1.2 L/s-m2 on typical commercial buildings in the United States can provide an annual heating and cooling energy cost savings of about 32% to 39%, based on blended national-average heating and cooling prices. According to the study, the largest savings opportunity exists in heating-dominated climates such as Bismarck, ND, St. Louis, MO, and Minneapolis, MN. The intent of the investigation was to provide input to the American Society of Heating, Refrig- eration, and Air-Conditioning Engineers’ (ASHRAE) 90.1 Envelope Subcommittee, which is con- sidering the addition of a requirement for a continuous air barrier in ASHRAE Standard 90.1.

Background The NIST investigation concludes that air infiltration into a building may cause negative consequences such as degraded air quality and moisture damage of building components, in addition to increased energy consumption and subsequent costs. A properly installed air-barrier system includes materials for joint sealing, fenestration, and door sealing, in addition to the materials for the air barrier. Currently, the industry is working to develop ASTM standards to evaluate air barriers and measure all the aspects of the system as described above, including seams in the air barrier. These ASTM standards will provide the air-barrier industry with a tool to develop a quantitative specification for limiting air leakage.

The Investigation The NIST investigation evaluated a two-story office building, a one-story retail building, and a four-story apartment building in each of the following five cities, representing different U.S. climate zones: St. Louis, MO; Minneapolis, MN; Bismarck, ND; Miami, FL; and Phoenix, AZ. The buildings were built with HVAC systems, windows, walls, roofs, and other materials that are typical to new construction and meet current ASHRAE Standard 90.1 requirements. The investigation took into account typical thermostat (temperature) settings, lighting, recep- tacle loads, and occupant density for a weekday and weekend day for each of the building types in the simulations. The investigation’s simulations of energy, airflow, and annual energy use were conducted on each of the buildings to evaluate the following three levels of air tightness: • Baseline (6.6 L/s-m2 to 11.8 L/s-m2)—no air barrier based on existing building tests of air leakage; 21

• Target (1.2 L/s-m2)—achievable through good construction practices in installing a typical commercial-grade liquid-applied or sheet air-barrier material meeting ABAA (Air Barrier Association of America) and Massachusetts state requirements; • Best (0.2 L/s-m2)—achievable through an aggressive program of quality control during installation of a commercial-grade liquid-applied or sheet air-barrier material meeting ABAA and Massa- chusetts state requirements, combined with testing of air tightness and efforts to identify and repair any leaks. Each of the buildings was built with typical frame and masonry construction. A total of 90 simulations were evaluated, 3 buildings x 5 climates x 3 levels of air tightness x 2 levels of construction type. The blended energy costs used in the investigation were calculated from 2005 Energy Informa- tion Agency data for prices of typical heating and cooling energies. The final blended heating cost was based on 75% natural gas, 14% fuel oil, and 11% electricity to obtain a heating cost of $1.01 per therm. The final blended cooling cost was based on electricity alone to obtain a cooling cost of $0.0827 per kilowatt hour.

Results The NIST investigation data indicates that using a properly installed air-barrier system capable of a target air leakage of 1.2 L/s-m2 on typical U.S. commercial buildings can provide an annual heating and cooling energy cost savings of as much as approximately 32% to 39%, based on blended national-average heating and cooling prices. The most savings were realized in the pre- dominantly cold climates of the northern United States.

Bismark, ND Frame Buildings

$15,000

$10,000

$5,000

Total Energy Cost Total $0 Baseline Target Best Baseline Target Best Baseline Target Best Office Retail Apartment Energy Cost $9,534 $6,504 $5,373 $8,888 $7,021 $6,844 $6,763 $4,763 $4,230 Percent Savings 32% 44% 21% 23% 30% 37% Air Barrier Tightness

Minneapolis, MN Frame Buildings

$15,000

$10,000

$5,000

Total Energy Cost Total $- Baseline Target Best Baseline Target Best Baseline Target Best Office Retail Apartment Energy Cost $9,918 $6,060 $5,413 $8,754 $6,472 $6,173 $6,666 $4,412 $4,056 Percent Savings 39% 45% 26% 29% 34% 39% Air Barrier Tightness

St. Louis, MO Frame Buildings

$10,000 $8,000 $6,000 $4,000 $2,000

Total Energy Cost Total $- Baseline Target Best Baseline Target Best Baseline Target Best Office Retail Apartment Energy Cost $8,100 $5,231 $4,716 $7,231 $5,474 $5,373 $5,143 $3,644 $3,515 Percent Savings 35% 42% 24% 26% 29% 32% Air Barrier Tightness Bismark, ND Frame Buildings

$15,000

$10,000

$5,000

Minneapolis, MN Frame Buildings

$15,000

$10,000

22 $5,000

Total Energy Cost Total $- Baseline Target Best Baseline Target Best Baseline Target Best The study showed thatOffice frame and masonry typesRetail of building constructionApartment yielded similar results.Energy CostTherefore, $9,918 the accompanying $6,060 $5,413 charts $8,754 provide $6,472 a summary$6,173 $6,666 of the $4,412 frame type$4,056 of building constructionPercent Savings only. The summary 39% 45% figures provide 26% information 29% for total 34% heating 39% and cooling energy cost savings. Air Barrier Tightness

St. Louis, MO Frame Buildings

$10,000 $8,000 $6,000 $4,000 $2,000

$6,000 Phoenix, AZ Frame Buildings $4,000 $8,000 $2,000 $6,000

Total Energy Cost Total $- $4,000 Baseline Target Best Baseline Target Best Baseline Target Best Office Retail Apartment $2,000 Energy Cost $6,706 $6,096 $6,087 $7,301 $6,159 $6,158 $4,575 $4,439 $4,443

Total Energy Cost Total $- Percent Savings Baseline Target9% 9%Best Baseline 16% Target 16% Best Baseline Target3% 3%Best Office Air BarrierRetail Tightness Apartment Energy Cost $6,706 $6,096 $6,087 $7,301 $6,159 $6,158 $4,575 $4,439 $4,443 Percent Savings 9% 9% 16% 16% 3% 3% Air Barrier Tightness

Miami, FL Frame Buildings

$10,000 $8,000 $6,000 Miami, FL Frame Buildings $10,000$4,000 $2,000$8,000

Total Energy Cost Total $6,000$- Baseline Target Best Baseline Target Best Baseline Target Best $4,000 Office Retail Apartment $2,000 Energy Cost $8,001 $7,274 $7,274 $8,490 $7,271 $7,271 $4,413 $4,139 $3,897

Total Energy Cost Total $- Percent Savings Baseline Target9% 9%Best Baseline 14%Target 14%Best Baseline Target 6% 12%Best Office Air BarrierRetail Tightness Apartment Energy Cost $8,001 $7,274 $7,274 $8,490 $7,271 $7,271 $4,413 $4,139 $3,897 Percent Savings 9% 9% 14% 14% 6% 12% JAC Air Barrier Tightness 23

Detail Oriented: Building Enclosure Expert Sees Integrated Design, Coordinated Planning By Joe Maty, Durability + Design as Essential to Constructing Systems that Work

Editor’s Note: This article appeared in he devil is in the details, the saying goes. D+D in September/October 2011. A well-worn cliché, to be sure. But in the context of building-envelope systems, Teminently fitting. That’s certainly the central message driven home by the building-enclosure experts at the national engineering firm Simpson Gumpertz & Heger Inc. (SGH), and notably by Vince Cammalleri, senior principal with the firm and an authority on evaluating and repairing moisture problems in high-humidity buildings such as natatoria, hospitals and museums. “In our experience, the primary problem, if you had to pick out one, is in the details,” Cammalleri said during a recent conversation with Durability + Design. “Problem areas occur where the enclosure barrier systems terminate, transition or interface with adjacent assemblies. Whether it is the air barrier, thermal barrier, weather-resistive barrier, or vapor retarder, the gaps, discontinuities and eventual failures are much more likely to occur at critical detailing conditions than they would be in the field of the wall. Window/wall, floor/wall and roof/wall intersections tend to be key problem areas, Cammalleri said. “They seldom get the kind of attention they need. These are highly complex parts of buildings that commonly get overlooked.” Cammalleri leads the Building Science Practice group at SGH, specializing in the investigation, analysis and reme- dial design of building-envelope problems caused by moisture/vapor migration. He has extensive experience investigating and designing repairs for walls, roofs, glass curtain walls, and windows. A registered architect in 15 states, Cammalleri is a fre- quent speaker on the subject of building-enclosure design at conferences, and has published numerous papers related to building technology in the United States and Canada. He is formerly a visiting lecturer for the Department of Architec- ture and Urban Planning at the Massachusetts Institute of Technology and a former adjunct professor for the School of Architecture at McGill University. Simpson Gumpertz & Heger Inc. (SGH) served as structural engineer of record and building-enclosure consultant for The New Museum of Contemporary Art, the first major art museum to be built from the ground up in Lower Manhattan. Photos courtesy of Simpson Gumpertz & Heger Inc. Owner: The New Museum of Contemporary Art Design Architect: SANAA Executive Architect: Gensler 24

Durability + Design asked Cammalleri to draw on his 25-plus years of experience in building science to discuss common problem areas in building-envelope systems, and other issues and developments in design, construction and materials specification related to these systems. Some highlights of the discussion follow. Durability + Design: Why do these problem areas persist with building-envelope and air- barrier systems? These technologies are not all brand new. Cammalleri: Fundamentally, the reason for this is that there is no clear, single designa- tion of trade responsibility for constructing these details in a reliable and durable way. These intersections are typically small but critical areas of the building enclosure where the work of various trades comes together. Vince Cammalleri The problems generally occur where the work of one trade finishes and that of the next trade starts. At the window/wall interface, for example, a well-performing window and a properly installed air and weather barrier on the wall does not necessarily result in a reliable enclosure—the proper integration between the two systems remains the most critical and complex challenge. Similarly, complex interior corners where dissimilar wall systems and flashings intersect, particularly at the base of the wall, tend to lack the coordination and detailing needed to integrate the various systems. D+D: What are some of your key recommendations to address these issues? Cammalleri: These recurring problems can be prevented if the difficult transitions are recognized and addressed early in the design process, and coordinated efforts are taken to ensure that the various design disciplines, contractors and manufacturers are aware of the conditions and their detailing needs. Clear, large-scale, three-dimensional details are essential in providing the proper guidance to the installing contractors, but these are sadly lacking in many construction docu- ments. Similarly, sequencing drawings, prepared by the general contractor and coordinated with the relevant trades and design professionals, can go a long way in helping the design and construction teams understand the challenges and resolving them before it is too late. Unfortunately, many of these intricate details are identified during construction, when the pressures of time and budget are high and the probability of them being resolved adequately is low. Finally, proper field supervision by design professionals can help mit- igate these problems, but the additional expense associated with field monitoring is often considered unnecessary, resulting in critical details being overlooked. D+D: Can you elaborate on these problem areas in building-envelope systems, and give specific examples of how project participants should address them? Cammalleri: First and foremost, design professionals need to recognize the detailing complexity of building enclosures and provide sufficient guidance in the drawings, particularly at the critical details and transitions, to enable contractors to understand what is required, coordinate the appropriate trades, and budget accordingly. The growing tendency to address these important details with gen- The New Museum of Contemporary Art building consists of a series of eral qualifiers in the specifications rather than with clear detailing in the rectangular boxes shifted slightly off axis, with a skylight located at every shift. The braced-frame structural system with story-deep drawings is insufficient, and often leads to confusion and unnecessary trusses provides a column-free interior and carries the gravity loads change orders. To the extent possible, designers should be adopting an at the offsets. 25

integrated design approach, whereby the design and construction teams work together early in the design process to identify, coordinate, and resolve the barrier systems’ detailing needs. Designers should also be familiar with the properties, benefits and limitations of the various products on the market for thermal barriers, air barriers and vapor retarders and, more importantly, understand the different functions these barriers perform. Some materials can perform multiple functions, while others are intended to perform single functions. An understanding of how and when to use vapor retarders, for example, is critical. The latter is especially important in walls that have insulation in the stud cavity and outboard of the sheathing, where the appropriate vapor permeance of the weather-resistive barrier (and the need for an interior vapor retarder) depends highly on climate and needs careful consideration. D+D: You like to speak of the “four barriers” as the basis of wall design and construction. Can you discuss As structural engineer of record, SGH coordinated steel beam sizes and connection details this concept, at least in a general way? with the architect. The firm worked with the architect and the contractor on a design-build approach to develop the cladding, windows, curtain walls, and skylight systems, and consulted Cammalleri: Today’s building enclosures typically with the museum director, the architect, and the mechanical engineer to specify building- consist of layers of lightweight materials. Several of envelope systems to satisfy the high-humidity requirements of the museum gallery spaces. these layers are designed as essential barriers to resist and control the flow of four elements: water, heat, air, and water vapor. The building enclosure’s performance depends on the proper sequencing, detailing and assembly of these barriers. The function that each barrier is intended to perform must be evaluated independently, even if a single product is designated to perform multiple functions. The resulting design will inevitably have areas that are subject to moisture accumulation should one of the barriers fail. An effective and durable design will enable the materials concealed within the wall assembly to dry out and recover from occasional moisture exposure without deteriorating or becoming contaminated with microbial organisms. D+D: What kinds of developments, or trends, are you seeing in wall and building-envelope designs, and what are some of the key implications for design and construction professionals as a result of these trends? Cammalleri: The largest trends appear to be related to energy-efficient design. We’ve no- ticed the tendency for higher insulation levels in walls, resulting in split insulation systems (stud and cavity). This improves efficiency, but, depending on the type of insulation used, complicates the hygrothermal performance of the wall systems by cooling the sheathing. There is also more scrutiny being given to the selection of glazing to provide optimal daylighting performance while reducing solar heat gain. Glazing manufacturers are ad- dressing these demands through improved coatings and the development of dynamic glazing systems, wherein the glazing’s optical and solar-heat gain properties can be modified to respond to ambient conditions. We’ve also seen increased use of liquid-applied membranes to perform the function of air barriers, vapor retarders and weather-resistive barriers. Individual manufacturers are providing a larger selection of membranes for use for different hygrothermal needs, and some are offering accessory products for detailing that integrate with the wall membrane systems. 26

D+D: What, primarily, is driving this growth in the use of liquid-applied barriers? Cammalleri: Liquid-applied materials offer advantages in terms of economics, efficiency in application and monolithic nature of the cured membrane. An experienced contractor can cover a lot more area in a day, but you have to proceed cautiously, as the performance of liquid-applied membranes (as is the case with any field-applied liquid product) can be very susceptible to workmanship quality and ambient conditions at the time of application. The key with successful application of liquid-applied membranes lies, in part, with field workmanship, construction sequencing and monitoring. The use of qualified, certified and experienced applicators is very important, as each product has its own stringent requirements for surface preparation, joint reinforcement, application temperature, mixing ratios, membrane thickness, and other proprietary factors that can significantly affect the prod- A fluid-applied, vapor-permeable air barrier system is applied during uct’s ability to properly cure, perform and last. construction at San Jose Airport in California. Increasing use of liquid- The product’s ability to bridge cracks and seams in the substrate needs applied air-barrier materials typically is attributed to the technology’s application efficiencies, economics and monolithic nature of the cured careful consideration, as movement in the substrate can create cracks that membrane. Photo courtesy of Grace Construction Products propagate through the coating. Detailing considerations at flashings and window surrounds can become more difficult and much more sensitive to application workmanship, since wall membranes cannot simply be “lapped over” the vertical leg of flashings and other water-management components as they would with pre-fabricated membranes. Liquid-applied flashings have the added drawback that they are extremely weather and temperature sensitive, making year-round work in northern climates a challenge. D+D: Have there been any important developments in industry standards that affect how these membranes are used? Cammalleri: One of the most significant developments in industry standards is the latest version of ASHRAE 90.1 (2010), which includes provisions for a continuous air barrier and improved energy efficiency. The air-barrier requirements also include performance values for assemblies rather than just materials, and detailing requirements. The standard would likely become part of the next LEED version and be adopted in the 2012 IBC. D+D: As structural engineer of record for the New Museum of Contemporary Art in New York City, your firm served as building-enclosure design consultant in a building that would require high-humidity conditions in gallery spaces—conditions that present specific design challenges. Can you draw from this project to illustrate the approaches you’ve discussed with us here? Cammalleri: Dimensional restrictions in the wall design of the New Museum precluded us from placing the insulation outboard of the wall sheathing. Given that the building contains a humidity-controlled environment in a heating climate, a vapor retarder was installed on the interior of the wall, creating the need to provide a reliable, vapor-permeable air-barrier system at the exterior that could also perform the function of a weather-resistive barrier (back-up waterproofing) behind the wall cladding. The membrane selection was further complicated by the need to address specific criteria that would allow the wall to retain its two-hour fire-resistance rating. We selected a liquid-applied membrane that met these criteria, and detailed the enclosure accordingly. Membrane flashings at the openings lap into the wall membrane at the sill, while the membrane laps over the flashings at the heads. In addition, joints are reinforced in accordance with the manufacturer’s recommendations. A quality-control protocol included regular field visits to test adhesion, verify film thickness, and monitor application temperatures and other critical conditions and details. D+D 27

New Barrier on the Block: Making By Joe Maty, Durability + Design the Case for Coatings on CMU

Editor’s note: This article appeared ould conventional paint and coatings products, applied at quite conventional film in D+D in January/February 2012. thicknesses, function effectively as air-barrier materials? C Affirmative, argue representatives of one industry organization in the building- materials business—an organization that, by the way, is not made up of paint and coatings product manufacturers. In effect, yes, agrees a major building-code authority. Quite possibly, but with qualifications, comes the opinion from another corner—building- envelope specialists whose job it is to design wall-assembly systems that work effectively— or get called to ride to the rescue when things go awry. The proposition regarding the potential functionality of conventional paint and coatings products as air-barrier materials is being put forth with considerable vigor by the National Concrete Masonry Association. Representatives of the organization are scheduled to make their case for this proposition at the upcoming SSPC 2012 convention, during a technical- conference program developed by the SSPC’s new Commercial Coating Committee and sponsored by Durability + Design. Pending building-code provision offers opening for expanded coatings role in CMU construction, but questions remain on performance, installation details 28

In a paper to be presented during the Durability + Design Commercial Coating and Flooring Symposium, organized by the SSPC Commercial Coating Committee, Nicholas Lang and Jason Thompson of the Concrete Masonry Association will review a study that examines testing of concrete-masonry assemblies treated with paint and coatings products as air-barrier materials. Significantly, Lang and Thompson will point out that the 2012 International Energy Con- servation Code (IECC) will for the first time include air-barrier performance requirements, which will set air-permeance standards for materials, assemblies and buildings. These standards, Lang and Thompson say, will establish that concrete masonry walls coated with one application of a block filler and two applications of a paint or sealer coating will meet the required air-permeance performance criteria, on a “deem to comply” basis. The use of these products to provide air-barrier properties in concrete masonry building assemblies could have significant implications for commercial buildings of this type, which account for a sizeable portion of the commercial-building inventory as a whole. But the use of conventional paint and coatings products in this manner is a largely unknown commodity in the field, and the long-term performance of such materials in building assemblies remains to be determined. The use of relatively thin-film paint and coatings materials in this way differs from the application or installation of standard thick-film liquid-applied air-barrier materials and sheet membrane materials.

Study examines coated concrete masonry assemblies In the paper to be presented at the SSPC annual conference, the Concrete Masonry Association’s Lang and Thompson say the following concrete masonry materials and assemblies are “deemed to comply” as air barriers under the pending 2012 IECC: • fully grouted concrete masonry (listed as a material, but more accurately considered an assembly), and • a portland cement/sand parge or gypsum plaster at a minimum thickness of 5/8 inch (15 mm).

“Weeps” at the bottom of a concrete masonry wall assembly are commonplace and are used to drain moisture from the interior of the wall assembly. But they may compromise the air- permeance capability of the air-barrier system. 29

Also “deemed to comply” with the IECC, as an assembly, are concrete masonry walls coated with one application of a block filler and two applications of a paint or sealer. In the paper, Lang and Thompson agree that a number of proprietary air-barrier technologies are available for multi-wythe concrete masonry assemblies, including liquid-applied coatings typically used on the cavity side of the back-up wall, and various types of rigid insulation with properly sealed joints. But they say these materials do not provide an economical option for single- wythe concrete masonry, where both sides of the assembly will be exposed. As a result, the Concrete Masonry Association conducted a study aimed at developing a method for testing of the air-barrier capabilities of concrete masonry assemblies using several types of conventional coatings to control air permeance. Lang and Thompson describe the development of a method for testing of the air- barrier capabilities of a concrete masonry assembly in which commercial coatings and block-filler materials were employed, along with sealing of test specimens using grout, self-adhesive rubberized asphalt flashing and silicone caulk. The air-permeance performance of test specimens was evaluated in accordance Gap in the system: A roof-wall junction showing coping with ASTM method E2178, which is used to measure air flow through an assembly (metal flashing), EPDM roofing and paint on the exterior of CMU block. Located between the EPDM roofing and the at six pressure differentials. The materials applied to the concrete masonry assem- painted CMU is a section of uncoated block that is not sealed blies included high-quality, conventional latex paint; latex block filler; an acrylic by a contiguous air-barrier assembly that connects the water repellent; and a silane-silloxane water repellent. coating on the wall to the roofing membrane. The single-wythe assemblies measured 56 inches wide and 64 inches high, with a nominal thickness of 8 inches. Without application of the latex paint or block filler, the air permeance of the assemblies was well above the levels required under the ASTM test method. But the air permeance fell well under the required levels using either the latex paint or the latex block filler, according to the figures in the Lang and Thompson paper. The paper, however, emphasizes that when testing concrete masonry assemblies in this way, the outermost masonry cells (units) should be solidly grouted, and the bottom of the test specimens should be sealed either though painting or with a rubberized asphalt flashing material. All “non-incidental” areas of the assemblies must be sealed. In the study project, two coats of block filler and two coats of epoxy paint were used for this purpose. Based on the study project, the authors concluded that: • the use of a single coat of a high-quality latex paint reduced the air permeance of the assembly by 94%, producing a permance level well below the IECC proposed requirements for an air-barrier assembly; • the use of a single coat of masonry block filler reduced the air permeance of the assembly by 86%, and also brought the permeance down to a level well below the proposed requirements for an air-barrier assembly; and • the use of an acrylic micro-emulsion water repellent or a silane/siloxane water-repellent coating also considerably reduced the air permeance of the concrete masonry assembly, but not to levels below the proposed air-barrier requirements.

Flip side: Test findings seen as just part of task facing industry The study project described by Lang and Thompson makes the case that conventional paint- type coatings can significantly reduce the air permeance of concrete masonry wall assemblies. 30

The study, however, leaves unanswered a number of questions that come into play with any air-barrier or building-envelope system or assembly, says Kevin Knight, a longtime expert on air-barrier and building-envelope systems, who heads Retro-Specs Ltd. Knight, whose resume includes more than 25 years of experience in the development of building-envelope testing and commissioning protocols, also is scheduled to speak at the SSPC Commercial Coatings and Flooring Symposium. His topic is “The Impact on the Painting Industry by New Building Codes and Standards for Air/Vapor Barriers.” The Concrete Masonry Association project study shows that concrete masonry treated with coatings can function as an air barrier. But an air barrier must also demonstrate a capacity to perform this task over an extended service life, to resist cracking, and to bridge cracks and gaps in the wall surface, Knight said. “CMU comes in many different forms, light, medium and heavy weight (or density); smooth, split and scored face; and installation methods of the coatings may differ from block to block,” Knight said. “Most air-barrier systems are multifunctional, and have other properties, by design or default, that must address vapor diffusion and water drainage,” he said. In addition, the potential vapor-barrier property of such an assembly must be taken into account, as a vapor barrier could cause entrapment of moisture in the wall if the location of the barrier (inside or outside of the wall) is not correct for the An air barrier must demonstrate a capacity to perform over given hygrothermic conditions. “Therefore, designers have to consider the build- an extended service life, to resist cracking, and to bridge ing’s conditioned space, climate, the properties of the material, and the air barrier’s cracks and gaps in the wall surface. location in the wall.” The IECC calls for integration of the coated concrete masonry air barrier with other components of the building assembly as a whole—windows, doors, mechanical openings, and the roof, Knight said. “The question of a robust design detail between the assemblies is, who draws it (architect or shop drawings from the trade) and which trade owns it? This is not a new problem, as the traditional air-barrier systems are still fighting over this issue.” Also a complicating factor is the presence of “weeps” in a concrete masonry wall assembly, which are commonplace and are used to drain moisture from the interior of the wall assembly. But the presence of these weeps may compromise the air-permeance capability of the assembly. Finally, Knight said, is the matter of ensuring that what the lab tests show is what happens in the field. “We have to prove that what was tested in the lab can be repeated in the field for compliance with the IECC. Standards and guidelines have to be adopted to address field test methods to ensure compliance. Training and education of the labor force is needed—not on how to paint, but how to make the paint a functional air barrier.” “Just by saying we have a material acting as air barrier, doesn’t mean we can simply move forward,” confident that the technology will function adequately as part of a system, Knight says. In addition to the long-term performance and aesthetic properties of the paint, the designer, specifier and owner must now add functionality an air barrier to the paint, as a requirement. Knight adds, however, that concerted efforts by the relevant players can succeed in address- ing these challenges, with an emphasis on the “concerted” mandate. “Collectively, we can meet all the challenges. Working as a team, SSPC, NCMA, manufacturers, designers, and testing agencies with the (SSPC) Commercial Coating Committee are well on the way to help the industry adopt the new IECC.” D+D