Air Barrier Applications Utilizing Insulated Metal

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 building envelope. 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 water vapor, 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, humidity 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, air conditioning, 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, thermal comfort 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 vapor barrier, 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 thermodynamics 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 economizer. A building proper building materials. The two main factors integrity. Water infiltration 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

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