CONTINUING EDUCATION

AIR BARRIER APPLICATIONS UTILIZING Presented by: INSULATED METAL PANELS

LEARNING OBJECTIVES

Upon completion of this course the student will be able to: 1. Recognize when a dedicated air barrier is appropriate and when assembly approaches are the preferred solution. 2. Learn which wall and roof assemblies work best in different climates and which can be used universally. 3. Review the best approaches to mitigating thermal bridges when using assembly approaches. 4. Learn when vapor barriers can double as air barriers and when they cannot. 5. Recognize the conditions and applications where a radiant barrier is useful.

CONTINUING EDUCATION

AIA CREDIT: 1 LU/HSW AIA COURSE NUMBER: ARDEC2016.3

Use the learning objectives above to focus your study as you read this article. To earn credit and obtain a certificate of completion, visit visit http://go.hw.net/AR1216Course3 and complete the quiz for free as you read this article. If you are new to Hanley Wood University, create a free Image courtesy of MBCI learner account; returning users log in as usual.

By Matt Sisul, PE

COURSE OVERVIEW in building construction, and their component the relative advantages of insulated metal parts, with special focus on air barriers. The panels, particularly under certain circumstances, This course provides guidance for architects and practicing architect or builder often has end-to- and key specifics and guidelines for specifying builders on design and installation considerations end responsibility for a project from conception metal panels for code conformance. relating to the use of insulated metal panels to execution. There is generally a wide variety and their suitability as the air barrier assembly of building products available for construction, INTRODUCTION TO BUILDING of a . Topics covered include although the selection of the materials that ENVELOPE BARRIERS an introduction to air barriers and insulated comprise the exterior may be constrained metal panels, as well as an overview of code Advances in building materials over the last by the local environment and climate, the and regulatory requirements when designing for century have revolutionized architects' and building's function, the budget and the vision energy code compliance and common design builders’ relationship with buildings. At the of the architect, builder, or owner. and installation practices and techniques. turn of the 20th century, the architect/builder With the aid of this lesson, architects and had limited options for materials, and the This lesson should serve as a refresher builders will be armed with increased concept of using multiple materials to achieve for architects and builders on the subject knowledge regarding enclosures and their optimal construction had not yet come into of building enclosures, including their component parts, the various options available, being. Thus, a wood building was made of fundamental functions, how they are employed wood, and a stone building was made of CONTINUING EDUCATION

stone. The material selected thus served both promote the growth of mold, which can be this arrangement, for example glass curtain walls, as protection from the elements and support a health hazard to occupants and potentially the principles remain the same and the various for the weight of the building itself. This was affect the structure itself. Water and air can components of the enclosure are still represented. true whether or not the material selected was enter a building through the same openings, the best material for these specific and very and, in addition, water can enter through air in Figure 1 different tasks. The invention of new materials the form of , so it is important to led to innovations such as steel framing and protect against both. Temperature plays a role reinforced concrete, but with these innovations too, as temperature differentials from inside came product specialization and the ability to and outside air can promote condensation tailor choice of material to specific tasks, such inside the building enclosure. as structural support, protection from sun, Water, air and temperature controls directly air, rain and vapor, and insulation. Over time, affect the comfort of the building’s occupants. building enclosures have continued to improve Excessive heat or cold, or mold can as an increasing array of new materials have render a space unusable by the building’s been added to the available options. occupants. Adequate control layers defend In modern construction, the concept of the a building against comfort issues, although enclosure has been deconstructed into specific a building's comfort is typically controlled functions such that the architect/builder can primarily by the heating, , and Components of a building enclosure/wall assembly. Image courtesy of MBCI handpick different materials that will best fulfill ventilation system (HVAC). Buildings employ those functions. At this basic level, a building’s mechanical and electrical means for controlling The cladding is the outermost feature of the enclosure requires: occupant comfort, and adequately installed enclosure, as it protects against solar radiation, • Cladding to protect the building and control layers work with the HVAC. impact, wear and tear, and debris. enclosure from solar radiation, wear and There is much discussion within the building The water, air and vapor control layers are all tear, impact, etc. community about the general relationship located behind the cladding and outside of the • Moisture control that keeps out both liquid between control layers and HVAC. In many structure. These three control layers are inside of water and water vapor. office buildings, discontinuities or gaps in the thermal insulating control layer. The thermal the control layers lead to excessive use of control layer is outside other control layers in • Air control that prevents unwanted airflow HVAC energy. A building may have a tight order to properly function in all environments. into the building, which often affects seal preventing air and moisture, but limited The arrangement ensures that, in cold climates, or conveys moisture. insulation, leading to inefficient HVAC the vapor control layer is the same temperature • Structure to hold up the enclosure and give operation. Tall glass office buildings with as the interior space, preventing condensation. it shape. windows of limited insulation result in excessive This is true in hot climates as well, and there is • Thermal control to ensure buildings stay cool heat increases when the sun is shining. also the added benefit that any condensation that does occur will occur on the outside face of in hot climates and warm in cold climates. The HVAC is necessary even when the control the , where it can be drained, thus layers are properly designed and installed These requirements are referred to as cladding, protecting the structure. control layers, and structure. to create a seal against outside elements. A properly sealed building allows in very little Control Layer Requirements by Climate A CLOSER LOOK AT CONTROL LAYERS outside air. As a result, the HVAC systems Buildings should suit their local environment or of commercial buildings are designed to The rules of as they apply to climate. When designing or selecting control bring in outside air to prevent the interior air buildings are (very broadly) as follows: layers, care should be taken in considering how from becoming stale over time and possibly the materials selected will perform in the local • Heat tends toward cold; developing an unpleasant odor. The unit environment. For the convenience of designers, • Wet tends toward dry; and also conditions the air to match the interior all counties in the United States are organized environment prior to introducing it. This • Air tends from high pressure to low pressure. into a limited number of climate zones, which may seem counterintuitive, however modern determine code requirements. By limiting the The control of air, water and heat is important HVAC units are designed to do this in a very variety of climate zones, designers can quickly to the architect and builder for many reasons. energy-efficient manner using a special piece identify control layer requirements and select Foremost is protecting the buildings’ structural of equipment called an . A building proper building materials. The two main factors integrity. Water into a building with a leaky envelope short circuits this considered in determining climate zones are over time will lead to a number of structural operation and leads to poor interior conditions temperature and moisture. problems, depending on the materials used as well as energy inefficiency. in the building. Water will cause rust in steel Average temperatures vary, generally increasing The Proper Arrangement of Control Layers members and steel reinforcement. Rust in steel from north to south, but high and low reinforcement can cause concrete or masonry Control layers are typically placed between the temperatures also vary throughout the year, so to spall or break out. Water on wood can exterior cladding and the interior structure of a the main consideration is cooling degree days, cause rot, and water in general on surfaces can building’s enclosure. While there are exceptions to or number of days per year where the average CONTINUING EDUCATION

temperature exceeds a given temperature. Cooling degree days are directly related to the Figure 2 amount of energy required to keep a building cool, so, intuitively, it makes sense that regions with a higher number of cooling degree days would require additional insulation. However, areas with a lower number of cooling degree days are typically quite cold in the winter, so insulation requirements are high in those regions as well. It is actually regions in the middle, with mid-range cooling degree days and relatively mild winters that require the least amount of . Climate zones are also organized by moisture level. There are three major categories: moist, dry, and marine. Moist zones are common throughout the eastern half of the country and include areas with either high humidity or heavy rainfall. The moist zone is further divided into typical moist, which is north, and warm-humid moist, which is south. There are special considerations in warm-humid moist zones around vapor and condensation control that differs from northern International Energy Conservation Code Climate Zone Map. Image courtesy of IECC climates. Dry zones are found in the western wide variety of materials can serve as air barrier AIR BARRIERS mountainous regions and marine areas are on materials, including mechanically fastened • Continuous air barrier: air barrier without gaps the west coast. The International Energy Code building wraps, self-adhered membranes, or discontinuities, required in order to properly Council has produced a map of climate zones that fluid-applied materials, insulating boardstock, prevent passage of air can be used by designers when selecting control non-insulating boardstock, spray polyurethane • Air barrier material: primary element providing layer requirements. foam, poured concrete, metal and glass. Air continuous barrier to the passage of air barrier materials can be used anywhere in a • Air barrier accessory: an air barrier component that DIFFERENT TYPES OF BARRIERS/ building assembly where it is necessary to stop connects adjacent materials CONTROL LAYERS air movement into or out of a space. An air • Air barrier assembly: a collection of air barrier barrier accessory provides a seam between materials, accessories and auxiliary materials Water Barrier applied to walls, joints, and junctions to control adjacent air barrier materials. Air barrier air movement It is essential that water that has made it past assemblies are the collection of air barrier the exterior cladding of a building does not materials that, together, control air movement. further penetrate the assembly. Materials that In mixed climates, it is not always clear where perform this function are considered water Air can move through a material itself (air the vapor barrier should go. Unless a building resistive barriers. These may be mechanically permeance) or through holes or gaps in a is cooled to an extreme level, like a refrigerated fastened building wraps, fluid applied material (air leakage). The air permeance of a building, the wintertime approach of having membranes, cellular plastic, self-adhered, material determines whether it is appropriate to the vapor barrier inboard of the insulation building paper, or any other material designed use as an air barrier material. should be used in mixed climates. to resist water in its liquid form. They are used Vapor Barriers In general, air barriers are designed to resist air with flashing or other supporting materials movement across their surfaces when subjected to achieve a shingled effect that routes water Materials that reduce the movement of to relatively high pressure differences, such away from exterior sheathing. water vapor are vapor barriers. This is largely as those created by wind blowing against an dependent on the thickness of the material. A There are three methods of testing a material's exterior wall. However, air barriers are generally vapor barrier can be a mechanically fastened not airtight materials per se. They are typically water resistance. These include the boat sheet-material, some self-adhered membranes, method (ASTM D779), the "water ponding" fibrous materials treated with polymers. Using fluid-applied materials, insulating boardstock fibrous materials allows the building envelope method (CCMC 07102 section 6.4.5), and the or medium density spray polyurethane foam. hydrostatic head method (AATCC 127). to breathe under small pressure differentials to The location of a vapor barrier in an assembly is allow any moisture trapped behind the barrier Air Barriers dependent on climate. They are installed on the to dry. warm side of the insulation; in warm climates, A continuous air barrier, without gaps or this is the exterior, while in cold climates, it is Conversely, vapor barriers are designed to resist discontinuities, is required to properly the interior. Many, but not all, air barriers often migration of water vapor across their surface. prevent air passage. Materials that perform this function as vapor barriers. This migration is driven not by wind but by the function are referred to as air barrier materials. A CONTINUING EDUCATION

vapor pressure of water, which is very small QUIZ compared to air pressure differentials created by wind. Thus, vapor barriers are generally airtight materials such as polyethylene, which 1. The idealized arrangement of control layers in the building envelope is: is why they can double as air barriers when a. Cladding, Structure, Insulation, b. Structure, Cladding, Insulation, used with certain types of insulation. This is a Air/Water/Vapor Control Layers Air/Water/Vapor Control Layers common approach used with closed-cell rigid c. Cladding, Insulation, Air/Water/Vapor d. Cladding, Air/Water/Vapor Control Layers, Structure Control Layers, Insulation, Structure foam boards (provided the joints are sealed)

and IMPs, eliminating the need for a dedicated 2. According to the IECC climate zone map, Chicago, IL is located in which climate zone? air barrier. However, this is a poor approach a. Zone 2 b. Zone 3 when using fiberglass batt insulation because c. Zone 4 d. Zone 5 air driven into the insulation greatly reduces its effective R-value. 3. How might a vapor barrier differ from an air barrier? a. Air barriers do not allow air to pass through while b. They are the same thing Insulation vapor barriers are water proof Thermal insulation is a material with low c. Air barriers resist air movement across the surface d. Vapor barriers are both water tight and air tight but allow the building envelope to breathe and dry thermal conductivity that reduces energy e. c and d consumption by preventing heat gain and loss through the building envelope. Typical 4. Insulated Metal Panels are considered pre-manufactured assemblies because: materials are fiberglass, cellulose, polystyrene a. They are previously manufactured components b. They are manufactured of various materials or polyurethane. assembled on site and delivered to site as single units c. They are multiple layers assembled one Radiant Barriers at a time on site Radiant barriers are materials that reflect, 5. Common control layer issues avoided by proper installation of Insulated Metal Panels include: rather than absorb, infrared radiation. Radiant a. Dew point within the building envelope b. Air gaps in the building envelope barriers are not insulation; they have no c. Thermal bridging d. All of the above inherent R-value. However, they can be used in conjunction with insulation and air cavities 6. Why is the dew point a concern to designers? to reduce transmission of heat in the form of a. Dew collecting on the building surface may migrate b. Warm air on the interior of a building will condensate when infrared radiation. Thus, an assembly with an into the structure in the pre-dawn hours in contact with a cool surface, leading to moisture build up incorporated radiant barrier will transmit less c. Warm air on the exterior of the building may collect d. All of the above energy overall. However, they will conduct heat on the vapor barrier of an air conditioned building so they should be installed on the cold side 7. According to the IECC and ASHRAE 90.1, which test corresponds to the strictest limits in terms of cubic feet per minute per of an air cavity with as little physical contact square foot of wall area (cfm/ft² at 1.57 psf)? with other materials as possible. This makes a. Air Barrier Material Testing b. Air Barrier Assembly Testing them ideal for attics and cavity walls to reduce c. Air Barrier Whole Building Testing d. Air Barrier Component Testing cooling costs. 8. Insulated Metal Panels allow for faster construction because: TYPES OF ASSEMBLIES a. They do not require iterative application of materials b. They can be assembled by fewer tradesmen An assembly is a collection of materials c. a and b d. None of the above incorporated into a single product consisting 9. How is thermal bridging avoided between adjacent IMP roof panels? of cladding in addition to all control layers. a. Standing seam b. Exterior seal and interior seal Assemblies may be constructed one layer at c. Direct contact between thermal control layers a time on site, or they may be prefabricated

and sold as a single unit consisting of multiple 10. Which of the following is considered an “out-of-plane” discontinuity? layers. Each layer is made of a different a. Seam between panels b. Pipe penetrating through panel material; however, it is common for layers to c. Window opening d. Interface between wall and roof repeat within a single assembly. SPONSOR INFORMATION

This article continues on Ähttp://go.hw.net/AR1216Course3. Go online to read the rest of the article and Since 1976, MBCI has provided customers with quality metal roofing and wall products, superior service and complete the corresponding quiz for credit. competitive pricing. It remains the industry-leading manufacturer of metal roofing and metal wall panels and other products. With its large product selection and full engineering and design capabilities, MBCI supports both the design community and our customers from project conception through project completion. CONTINUING EDUCATION

Membrane (water control layer, air control Figure 3 Exterior face (water control layer, air control Figure 4 layer, vapor control layer) layer, vapor control layer)

Protection board Thermal control layer Thermal control layer

Vapor Vapor Profile Profile

Membrane (air control layer and Interior face (air control layer and vapor control layer) vapor control layer) Gypsum board Insulated metal panel Metal deck

Site-built assemblies can be used in all climate and environmental conditions. A pre-manufactured insulated metal panel roof assembly can also be used in all climate and Image courtesy of MBCI environmental conditions. Image courtesy of MBCI

Site Built Assemblies skylights and any number of other features. Thermal Bridging Moreover, although most control layers An example of a typical "site built" roof assembly Another common issue with "site built" wall are designed as a relatively impermeable is presented in Figure 3. Note that the roof and roof assemblies is thermal bridging. membrane, the membrane is a series of membrane functions as the water, air and vapor Thermal bridging frequently occurs when panels with edges and corners, connected control layers, which are exterior to the thermal insulation is interior to the wall assembly control by seams. The most challenging control layer control layer, or the insulation. There is a second layer in cavities between repeating structural to successfully install throughout a building membrane functioning as an interior air and elements. This is the case in wood framing and is a continuous air barrier, because small vapor control layer, to the interior of the thermal cold form steel framing. Framing members imperfections during construction are common, layer. On the interior, drying occurs from the are directly connected to the exterior cladding as are design flaws that result in air leakage in lower membrane, and, on the exterior, from the with screws or nails to ensure the structural the transition between walls and roof. upper membrane. This assembly can be used in all integrity of the wall or roof assembly. However, climate and environmental conditions. Dew Point Concerns the framing acts as a conduit, allowing heat to transfer from the exterior to the interior. The Pre-Manufactured Assemblies Condensation occurs when warm moist air comes insulation is therefore bypassed. (Insulated Metal Panels) into contact with cold surfaces. During the design of a building, the designer should determine An example of a pre-manufactured insulated ADVANTAGES OF PRE-MANUFACTURED dew point contours, which will inform when and ASSEMBLIES (INSULATED METAL PANELS) metal panel roof assembly is presented in Figure where condensation will occur. Calculating the 4. Like the "site built" roof assembly, there is Pre-manufactured assemblies are an innovative dew point is particularly important in northern an exterior membrane that functions as the way to avoid the issues described above. Pre- climates where warm humid air on the interior water, air and vapor control layer, and an interior manufactured assemblies, like insulated metal of the building is coming into contact with cold membrane that functions as an air and vapor panels, achieve a continuous air barrier due to air on the exterior of the building. The dew point control layer. Between the two is an insulated specialty joints and seams. Since the insulation is the temperature at which cooling water vapor metal panel, which functions as the thermal is sandwiched between layers of waterproof starts to condense. The dew point temperature control layer. This assembly can also be used in and air resistant single skin metal panels, will vary based on the relative temperature all climate and environmental conditions. condensation cannot occur within the control and humidity. Condensation will collect on the layer. Finally, concealed fasteners embedded in surfaces below the dew point, which are those COMMON ISSUES WITH CONTROL LAYERS the insulation and covered on both sides of the surfaces coming into contact with warm air. Sealing the Building Envelope joint prevent thermal bridging. When thermal insulation is interior to the It is relatively simple to avoid thermal bridging One of the biggest challenges in installing structure or control layers, the control layers are at and interior condensation in installation of pre- the wall and roof assemblies is ensuring the or close to the exterior temperature. The outside manufactured assemblies like insulated metal building envelope is properly and continuously surface of the insulation is in contact with the panels. However, there is more room for error sealed. Buildings are complex, and the control layers on one side and the interior finishes in achieving a continuous air barrier, which is a enclosure requires a number of penetrations on the other. Assuming a linear gradient between complex endeavor. The following section covers for proper functioning, including for windows, either side of the insulation, the dew point is in detail the testing and code requirements for doors, vents, plumbing, and architectural likely somewhere within the insulation. (Caution: air barriers. features such as reveals. In addition, buildings Radiant barriers will violate this assumption.) require multiple interfaces, including at building Condensation could then occur within the AIR BARRIERS, CODES & COMPLIANCE corners, between material types, between the insulation, but it is more likely to occur on the foundation and the wall, and between the wall surface of the insulation and at structural contact The energy code governing the design of a and the roof, roof drains, roof hatches and points throughout. building’s air barrier depends on the type of CONTINUING EDUCATION

building and the state or locality where it is being and components (sealants, tapes, etc.) that have Low-Rise Framed Building Walls built. The two main building energy codes are an average air leakage of not greater than 0.04 ◾ ASTM E 1680: Standard Test Method the American Society of Heating, Refrigerating, cfm/ft² at 1.57 psf when tested in accordance for Rate of Air Leakage through Exterior and Air-Conditioning Engineers (ASHRAE) code with ASTM E 2357, ASTM E 1677, ASTM E Metal Roof Panel System 90.1 (latest edition 2013) and the International 1680 or ASTM E 283, depending on material Energy Conservation Code IECC (latest edition application. As noted above, air leakage describes ◾ ASTM E 283: Standard Test Method 2015). The ASHRAE code is called the Energy air escaping through holes or gaps in a material, for Determining Rate of Air Leakage Standard for Buildings Except Low-Rise Residential while air permeance describes air passing through Through Exterior Windows, Curtain Buildings and applies to all buildings except low a material. As such, air barrier assemblies are Walls, and Doors Under Specified rise residential buildings. The IECC code covers tested for air leakage not air permeance. Pressure Differences Across the Specimen both commercial and residential buildings. • Whole Building Air Barrier Whole Building Testing (IECC Despite the overlap in code coverage, the general C402.5 or ASHRAE 90.1 5.4.3.2.f.3) ◾ ASTM E 779: Standard Test Method rule is IECC covers all residential and ASHRAE for Determining Air Leakage Rate by 90.1 covers non-residential. This corresponds to Another alternative is to test the entire building Pressurization. the manner in which states have approved the envelope in accordance with ASTM E 779. code. The version of the code (which corresponds The building envelope passes if the total air Insulated Metal Panels to publication year) varies, as different states and leakage is less than 0.4 cfm/ft² at 1.57 psf. This Insulated Metal Panels (IMPs) are assemblies localities update the codes at different rates. is referred to as the "" test and comprised of two single skin metal panels allows the architect or builder to make their Both codes contain prescriptive and on either side of an insulating control layer. own determinations regarding the installation performance based requirements to allow The interior insulation consists of a rigid foam of the continuous air barrier, testing the designers flexibility when specifying air core such as non-CFC polyisocyanurate. IMPs outcome after the building is built. barriers. Prescriptive measures prescribe represent an evolution in metal building actions, materials and specifications without The risk when relying on whole building testing construction and can be used in most metal substitution to meet code. For example, is that unforeseen errors in the selection of building applications. Metal buildings have “plywood with a thickness of not less than the material, joint detailing or installation may grown in popularity over the years due to their 3/8 inch (10 mm),” and joints must be sealed lead to a higher than expected air permeability. relative ease of construction and low cost. according to manufacturer’s instructions. It can be very costly for the contractor or Initially, metal buildings were used in industrial Performance based metrics set criteria for the building owner to try to remediate gaps in the and commercial applications like warehouses outcome, and allow the designer to decide continuous air barrier after the fact. For that and factories where aesthetics were not a how that outcome will be achieved. The code reason, it is recommended that the architect priority for the architect or builder. Innovations specifies the metric and testing requirements or builder select materials or assemblies that in product lines have led to greater diversity of for air barriers. The metric is cubic feet of have been shown to pass their respective tests colors, textures, and accessories, and architects air per minute per square foot area passing and follow manufacturer recommendations for and builders now choose to use metal buildings through an air barrier when the pressure joints and seams from the onset. for a variety of building types, including differential is 1.57 pounds per square foot. residential, office, retail, and institutional. Green Buildings: IgCC and LEED Design The testing requirements vary based on the Initially, metal buildings were comprised of type of material. Both ASHRAE 90.1 and IECC A designer seeking to comply with ASHRAE steel or cold formed steel structure with metal approach air barriers at three scales: material, 90.1 or IECC may specify compliant materials panel cladding. Insulation was draped between assemblies and whole building. or assemblies and detail manufacturer the panel cladding and structure, compressing recommendations for joints and seams in the Air Barrier Material Testing (IECC it and causing it to lose R-value. The metal drawings. In addition, green building codes like C402.5.1.2.1 or ASHRAE 90.1 5.4.3.1.3.a) panel itself was the air and water barrier, the International Green Construction Code (IgCC) and insulation was placed between structural From the perspective of the designer, air barrier or achieving LEED credits require the whole supports on the inside of the metal panel. compliance is achieved by selecting and verifying building be tested per ASTM E 779. IgCC requires This led to similar problems as experienced approved individual materials or membranes a maximum air leakage of 0.25 cfm/ft² at 1.57 psf. with other building methodologies, including such as plywood, foam plastic insulation board, In summary, testing requirements are as follows: thermal bridging, discontinuities in air barriers, spray foam, gypsum board, or bituminous roof and condensation. The IMP, an advance • Materials membrane. The codes provide prescriptive in metal building construction, eliminates requirements for common materials or allow ◾ ASTM E 2178: Standard Test Method for those issues. alternative materials that have an air permeability Air Permeance of Building Materials not greater than 0.004 cfm/ft² at 1.57 psf when Additional Benefits • Testing Assemblies tested in accordance with ASTM E 2178. IMPs provide a number of other benefits, as ◾ ASTM E 2357: Standard Test Method well. For one thing, they allow for faster dry-in, Air Barrier Assembly Testing (IECC for Determining Air Leakage of Air with fewer tradesmen, than constructing C402.5.1.2.2 or ASHRAE 90.1 5.4.3.1.3.b) Barrier Assemblies an assembly one layer at a time. They are Alternatively, air barrier compliance can be ◾ ASTM E 1677: Standard Specification for lightweight and available in a wide range achieved by selecting an assembly of materials Air Barrier (AB) Material or System for CONTINUING EDUCATION

of attractive finishes and colors. In addition, they are easier to maintain than other exterior Figure 5 Exterior systems, while still meeting the same high sheathing Cavity requirements for performance. insulation In fact, IMPs are manufactured to meet the requirements of the model building codes and insurance listing agencies, including ratings for fire, structural strength, thermal transmittance, foam core properties, water leakage, and air infiltration. Moreover, they minimize the risk of errors that will negatively impact performance, Interior resulting in better in-place quality, weather lining integrity, and appearance. Manufacturers provide testing documentation verifying that Thermal bridging in typical metal building assemblies. Image courtesy of MBCI factors affecting positive and negative wind to aesthetic demands for walls and greater thermal bridging. In "site built" assemblies, the loads and the load carrying capacity of the flexibility in joint direction (corrugations can cladding is attached to the structure directly, panels meet specified project requirements. run horizontally as well), more configurations through the control layer and around the Types of Panels are available. The specifications of wall panels cavity insulation, an arrangement that leads to are similar to those of roof panels: thermal bridging as shown in Figure 5. Roof Panels • Wall panels can be 24 to 42 inches wide. IMPs avoid thermal bridging by ensuring the Metal roof panels are the most commonly attachment is concealed within the insulation associated type of panel. They have been • Runs vary from 1 foot to 53 feet, as shown in Figure 6. The experimental employed for over 100 years as inexpensive, depending on geometric requirements. modeling reflected in the picture demonstrates mass produced, easily installable roofing material. • Panel thickness ranges from 2 to 6 inches. thermal performance across seams. Initially introduced as corrugated iron sheets with • Panels may have a flat appearance, an easily recognized wave pattern, a variety of be embossed with a pattern or contain Figure 6 shape profiles are now available with corrugations typical striations. of varying width and pattern. The specifications of insulated roof panels are as follows: Foam Core • Roof panels can be 36 to 42 inches wide. IMP core properties vary slightly depending on • Panels can be cut to the exact specification the type of foam used by the manufacturer. The required or multiple panels can be placed foam system must ensure structural integrity and side by side to achieve the desired length; adhesion of the foam to the metal faces. single panels, where applicable, reduce the Joints & Fasteners number of joints in a roof. The following are the available types of joints • Sides between panel runs can be locked Isotherms in 3" IMP Color Infrared and fasteners: Image courtesy of MBCI into place with standing seams or Figure X: Isotherms in 3” IMP Figure X: Color Infrared overlapping edges. • Double tongue-and-groove interlocking Applications rainscreen joints; • Fasteners are concealed within the insulation Insulated metal panels are used in a variety • Offset double tongue-and-groove with layer, eliminating thermal bridging. of applications because of their excellent extended metal shelf for positive face performance characteristics and competitive • The exterior skin is metal panel of 22 or fastening; and 24 gauge. in-place costs. Examples of building • Mechanically closed single lock standing seam applications using IMPs: • The interior skin can be 22, 24 or 26 gauge. at the exterior side joint with interior side joint • Aircraft hangars and service facilities • Each panel contains an insulating being a single tongue-and-groove interlock. foam core. • Banks, corporate offices and The manner in which the IMP is fastened to the municipal buildings • Panel thickness ranges from 2 to 6 inches. structure dictates the viability of a continuous • Churches • Panel facing is Galvalume©, Zincalume©, or insulation or continuous air barrier. Concealed pre-painted steel. fasteners are preferred to ensure overlap • Cold-storage and food-processing plants between panels. Wall Panels • Healthcare facilities Thermal Bridging • Manufacturing facilities Wall Panels are similar to roof panels in composition. In fact, they were initially just IMPs meet the definition of continuous • Retailers, including auto dealerships roof panels installed vertically. However, due insulation, and do not experience significant • Schools and universities CONTINUING EDUCATION

• Sports complexes, museums and is more challenging, as walls may have multiple Exterior seal providing Figure 7 convention centers continuity of the exterior in-plane perforations such as openings air control layer and Interior seal providing vapor control layer continuity of the interior for windows, doors, and mechanical and • Warehousing and distribution centers air control layer and Flashed and drained vapor control layer electrical systems. Out-of-plane discontinuities, joint Direct contact between including interfaces at wall corners and INSULATED METAL PANELS AS thermal control layers of AIR BARRIERS adjacent panels provides between the wall and the roof and foundation, continuity of the thermal control layer require special attention. IMPs are well suited to perform all control Like wall joints, the standing seam joint contains two seals to connect the interior and layer functions. They are designed to ensure exterior air and vapor control layers. In the case of standing seam, the exterior seal is Punched Openings continuous insulation and a continuous air located inside the standing seam. Image courtesy of MBCI Windows and doors that are installed in barrier can be easily achieved by the building of overlap. Flashing prevents water infiltration, openings in the building enclosure are often designer and builder provided the designer/ while interior and exterior seals connect the referred to as “punched openings.” builder pay special attention to problem areas air and vapor control layers of adjacent panels. The “joints” between window units and described below. When specifying an IMP Between the seals, there is direct contact doors are required to meet the same control product, consult the manufacturer and request between the thermal control layers, thus requirements as those for joints in the panels the applicable ASTM testing results for the ensuring thermal control continuity. themselves, which are the same control material and assemblies. In addition, seek requirements as those of the entire assembly. guidance regarding special details to ensure Standing seam roof panel joints are similar to This means that there should be continuity a continuous seal can be achieved between wall panel joints though slightly different in between the respective control layers of the panels, at all perforations (windows, doors, appearance. Like wall joints, the standing seam joint and those of any adjoining components. piping, etc.), corners, and interfaces. If the joint contains two seals to connect the interior building will be undergoing an ASTM E 779 and exterior air and vapor control layers. In blower test, consult the manufacturer for the case of standing seam, the exterior seal is Windows and doors that guidance regarding preparation for the test located inside the standing seam. and common issues. For example, it is advisable Wall Systems are installed in openings to perform the blower test prior to installing in the building enclosure interior finishes. If the finishes are complete, As noted above, ensuring continuity in joints and the building exceeds the leakage maximum, between panels is relatively easy, and the are often referred to as it can be expensive to remove finishes so as to manufacturers generally can assist with this. “punched openings.” identify leaks, and to then rebuild. Maintaining continuity for entire wall systems

CONTINUOUS AIR BARRIER & SEALING DETAILS Figure 8 Inside The lesson concludes with guidance for the corner Air seal air seal designer and builder on special details that Panel joint Panel end require additional attention when designing clip for continuous air barriers with IMPs. This Exterior panel joint section covers both in-plane and out-of-plane flashing discontinuities. In-plane discontinuities are those that occur between panels and around openings.

These are closed by using accessory products Head flashing around joints and sealing with a sealant. Out-of- Opening framing plane discontinuities, including those that occur at the interface of wall corners, between the Jamb flashing wall and the roof, and between the wall and the foundation, are more challenging for the designer Sill flashing and builder and require special attention.

Joint Design Outside corner For IMPs to function as continuous air or flashing insulation barriers, joints between panels must meet the same control layer requirements as the assemblies themselves. On any given panel, each control layer, including the water, air, Base flashing Insulated vapor control layers and thermal insulation, metal panel must be connected to the respective control layer on adjacent panels. IMPs utilize tongue- and-groove joints to allow for multiple points lllustration of various wall system discontinuities. Image courtesy of MBCI CONTINUING EDUCATION

The figures to the right illustrate control layer continuity at a window head above and sill Insulated metal panel Figure 9 Figure 10 below. Note that there is both an interior and Drainage cavity Sealant Sealant exterior sealant at the head, whereas there Closure trim Termination bar is only a single interior sealant at the sill. The single interior seal allows both drainage and air Brick veneer entry to occur at the bottom of the window. Membrane This air entry pressurizes the gap at the sill Drip closure and head utilizing the principle of pressure Brick veneer equalization to limit the effect of wind induced Head trim Drainage cavity air pressures. The membrane closure can be Membrane closure Sealant and Insulated metal panel either a fully adhered membrane strip or a fluid backer rod applied flashing. Continuity Control Layers— Window Head—Note the interior and exterior sealant at the head. Window Sill—Only a single interior sealant is provided at the sill. Roof to Wall Connection Image courtesy of MBCI Image courtesy of MBCI Roof to wall control layer continuity must be maintained for each control layer. The roof to Fully-adhered roof membrane Perimeter of roof insulation wrapped in air control wall connection will vary based on the building Figure 11 membrane to block airflow from roof to parapet Figure 12 Protection design. Two common roof to wall connections Two (2) layers insulation: joints are low and high parapet assemblies. Figure 11 staggered horizontally and vertically Insulated metal panel Sealant Thermal break shows an example of a low parapet assembly. Membrane closure Membrane strip strip air seal Membrane capillary break/air seal Note that ensuring the air barrier is continuous Gasket Sealant requires specific accessory materials. Concrete slab Base extrusion Metal deck Insulated metal Gypsum sheathing Continuity Control Layers— panel Polyethylene Air control vapor barrier Foundation to Wall Connection membrane Weep Open web steel joist Rigid insulation There must also be continuity been the Dampproofing Granular capillary respective control layers in the foundation to break wall connection. In foundation assemblies, thermal bridging can be prevented by installing a “structural” thermal break such as Low Parapet Assembly—Note that ensuring the air barrier Base Overhang—The structural panel connections have been rigid insulation under the steel framing as is is continuous requires specific accessory materials. omitted for clarity. Note the rigid insulation thermal break. graphically presented in Figure 12. ◾ Image courtesy of MBCI Image courtesy of MBCI

RESOURCES

1. https://www.airbarrier.org/resistive/difference_between_air_barriers_vapor_barriers_and_water_resistive_barriers.php 2. http://energy.gov/energysaver/radiant-barriersguidelines-and-standards/buildings-and-sites/about-the-ada-standards/guide-to-the-ada-standards/chapter-4-entrances,-doors,-and-gates