Energy Design Guide for Metal Building Systems

The Energy Design Guide for Metal Building Systems is a building manual published by the Metal Building Manufacturers Association (MBMA). MBMA is a non-profit trade association that promotes the design and construction of metal building systems in the low-rise, non-residential building marketplace. The Energy Design Guide was published in February, 2010, and was co-sponsored by the American Iron and Steel Institute (AISI).
Cover
Table of Contents
Energy Design Guide for Metal Buildings
Chapter 1: Introduction
Chapter 2: Metal Building Systems and Applications
Chapter 3: Energy Code Fundamentals
Chapter 4: Insulating Metal Building Systems
Chapter 5: Cool Roofs
Chapter 6: Daylighting
Chapter 7: Energy Codes and Standards
Chapter 8: Compliance Tools
Chapter 9: "Green" Rating and Certification Programs
Chapter 10: High Performance Buildings
Appendix A: Photovoltaic Roof Panels
Appendix B: Daylighting Design Guide
Metal Building Systems and Sustainable Building
Metal building systems are professionally engineered structures that provide cost-effective and efficient low-rise buildings for a wide variety of uses, such as religious facilities, retail stores, manufacturing facilities and warehouses, office buildings, shopping centers and community buildings . Each building structure is custom-engineered to the end user’s needs, and designed to be energy efficient . Additionally, steel, the heart of metal building systems, is the most recycled building material, according to the Steel Recycling Institute
Energy Design Guide Highlights
The Energy Design Guide for Metal Building systems provides detailed information on ways to increase the energy efficiency in metal building systems. It also has an overview of energy codes and standards, compliance tools and green rating programs, plus appendices on photovoltaic roof panels and daylighting design.
Some of the specific chapters for how to increase the energy efficiency of metal buildings focus on insulating metal building systems (chapter 4), cool roofs (chapter 5), and daylighting (chapter 6) There are also detailed guides on currently available compliance tools, energy codes and standards, and green building rating systems.
Green building rating systems are becoming increasingly popular for construction projects. These include well-known programs such as the USGBC’s Leadership in Energy and Environmental Design (LEED®), the Green Building Initiative's Green Globes™, and EPA's Energy StarProgram. These systems, and others, allow builders and owners to demonstrate that their practices and the building are energy efficient and represent sustainable practices.
Energy efficiency for metal building systems: Chapters on insulating metal buildings (chapter 4), cool roofs (chapter 5) and daylighting (chapter 6) convey information on specific ways to increase the energy efficiency of metal buildings.
Insulating: Metal building end-use has changed radically since the industry started in the late 1950’s. Insulation for metal buildings was mostly used as a condensation prevention blanket or to reduce noise from wind, rain, etc. In the 1980’s, insulation systems for metal buildings also began to address thermal concerns as their commercial applications expanded.
With the increased use of metal buildings for occupied commercial buildings such as retail, office space and community buildings, the conventional methods of insulating metal buildings would no longer suffice. Today there are numerous high-performance insulation systems for metal buildings that utilize a variety of materials. The requirement for building insulation performance is set by the local jurisdiction’s adopted building or energy conservation code, which is enforced by the building official. (reference, EDG, Chapter 4)
The methods of insulating a metal building include, but not limited to:
• Fiberglass insulation
• Filled cavity insulation systems
• Laminated fiberglass insulation
• Rigid insulation systems
• Composite insulated metal panels
• Hybrid systems
Cool Roofs: Cool roof performance is a function of two radiative properties: solar reflectance and infrared emittance. These two properties define how “cool” a roof product is. Both properties are part of the energy balance at the roof surface. The sun’s energy strikes a roof surface with ultraviolet, visible and infrared energy.
Solar reflectance is defined by the Cool Roof Rating Council (CRRC) as, “The ratio of the reflected flux to the incident flux.” In other words, the number reported for solar reflectance for a roof product is a decimal number less than one that represents the fraction of the total solar energy that is reflected off the roof. For example, “high” reflectance materials, such as white painted metal roofing, have values of around 0.70, or 70 percent. That is, only 30 percent of the energy from the sun is absorbed by the roof. (Reference: Cool Roof Rating Council, http://www.coolroofs.org)
Infrared emittance is defined by CRRC as, “The ratio of the radiant heat flux emitted by a sample to that emitted by a black body radiator at the same temperature.” In plain terms, emittance is a decimal number less than one that represents the fraction of heat energy that is re-radiated in the near infrared energy spectrum from a material to its surroundings. The greater emissivity value, the greater the ability of a surface to cool itself through radiative heat loss. For example, low emittance products such as unpainted Galvalume®, have values around 0.10, which is very low. Emittance is a critical measurement for municipalities that are concerned with the phenomenon known as the “urban heat island” effect.
Cool roof products come in a wide variety of types, including metal roofs, cold-applied coatings, light-colored EPDM membranes, rubber and asphalt shingles. The combination of performance differences between these products and climate conditions have made the issue of cool roofs a complex one for many specifiers, building owners and legislators. (ref: EDG, Chapter 5; CRRC, http://www.coolroofs.org )

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