A well-designed building is defined by certain attributes that include, among other things, the ability of the building to achieve a desired level of sustainability. At a minimum, this means achieving energy performance that complies with energy-conservation code requirements. It can also include other green and sustainable attributes related to human health, material life-cycle assessments (LCAs), site impacts, and indoor environmental quality. These categories are more specifically defined and addressed in various codes and voluntary standards across the United States and elsewhere. Achieving building designs that incorporate any or all of these attributes at targeted levels can be realized using many different construction methods and building systems. This course will look at one particular construction type that has been successfully used for green and sustainable design, namely metal building systems. While some professionals have erroneously thought that such systems would mean a compromise on energy efficiency and sustainability, independent research and a review of their attributes clearly indicate otherwise. In reality, working with a metal building manufacturer to design a complete steel structural system with a coordinated set of building enclosure components can meet or exceed high standards for sustainability in a very cost effective manner.

All images courtesy of MBMA

Today’s metal buildings come in all shapes, sizes, and architectural styles, providing a sustainable solution for buildings of all types.

Metal Building Overview

When talking about metal buildings, different people may envision different things. Historically, metal buildings date back over a century ago to 1917 with The Austin Company in Cleveland. They had 10 standard designs, which is where the term “preengineered” originated since the designs were created in advance and were sold as an unmodifiable package. Then, during the 1920s and 1930s, the oil boom in the west created the need for quick and simple-to-construct buildings to provide for storage and basic shelters. The young but burgeoning metal building industry was quick to respond.

The use of metal buildings increased during World War II when large metal buildings were used for aircraft hangars; but most people identify early metal buildings with the venerable Quonset hut. Between 150,000 and 170,000 of them were constructed and in use by the end of the war. They were highly effective because they could be constructed quickly by military personnel and serve multiple purposes. Once World War II ended, metal building manufacturers began producing low-cost, quickly installed factory buildings that satisfied a post-world-war economic boom by providing relatively inexpensive utilitarian buildings. These structures served an important purpose: to house the economic and industrial engine that fueled America’s rise to prominence as a world superpower. This utilitarian role may still be foremost in the minds of some designers today, but metal building technology has progressed to allow for much more.

Metal building design and manufacturing has evolved to be a significant source for architecturally inviting and fully customizable structures. The industry has become a provider for site specific, fully engineered buildings such that no two metal buildings are exactly the same. As such, the industry has evolved from being based on standardized designs, to a source of custom design for every single building produced. In the 21^st century, metal building systems employ advanced, computer-based engineering, and building information modeling (BIM) technology to create building solutions that align with the specific needs of each project. While the interiors and exteriors can look completely different, based on the design requirements, the basic component types of a metal building system remain constant: rigid steel frames, wall girts, roof purlins, metal roofing, wall cladding, and bracing. A metal building manufacturer can also provide additional building envelope components, including insulated panels, fenestration, roll-up doors, and other features. These common components provide for economy without hampering design flexibility and creativity in the end product.

The basic elements of a metal building system include primary and secondary structural members, metal roofing systems, and metal wall-cladding panels.

Based on all of these advances, it should be no surprise to learn that metal buildings currently comprise approximately 40–50 percent of the low-rise nonresidential building square footage designed and constructed each year in the United States. As such, they have become the building system of choice for a full range of commercial, institutional, and industrial buildings in a broad range of sizes and architectural styles. One important attribute behind such widespread adoption is their design flexibility. Metal buildings allow for long clearspans (in excess of 400 feet) and variable eave heights, so they are very functional for small, medium, and large-sized buildings. Wide-open interior spaces created by these attributes are increasingly popular and equally valuable for manufacturing facilities, warehouses, showrooms, large retail buildings, recreation facilities, and athletic practice facilities.

Speed of delivery and construction is another key advantage that has helped with the growth of metal buildings. Once the building is designed, it can be manufactured in as little as two weeks. The engineered parts and pieces of the complete metal building package are delivered as a single-source package to the job site and received by a qualified erector. Once the project is staged on the ground, the metal building shell typically goes up much faster than conventional construction.

The growth of metal buildings is also attributed to the strength of a trade association founded in 1956 as the Metal Building Manufacturers Association (MBMA). The MBMA has represented and directly helped the industry grow over the past 60 plus years. Its activities include education, research, advocacy, and other programs on behalf of the entire metal building industry. As one of its key programs, the MBMA partnered with the International Accreditation Service (IAS) to implement a comprehensive, robust quality-assurance program. Known as IAS AC472: Inspection Programs for Manufacturers of Metal Building Systems, it is the most comprehensive quality-assurance accreditation program of its kind and is designed specifically for manufacturers of metal building systems. It is based on detailed quality-control requirements that must be independently audited twice a year to maintain accreditation. By setting this high standard of excellence, the industry has been able to demonstrate its competence while gaining the trust of design professionals and building owners.

With a basic understanding of where the metal building industry is today, let’s look now at the evolutionary state of green building design.

General Green Building Approaches

Green design and construction is no longer a specialty building type but rather has blossomed into a mainstream expectation of most building owners whether for reduced energy costs, improved marketing image, higher returns on investment, or as part of an organizational philosophy. All of this has led to the development and growth of a number of green building rating systems and standards that identify key sustainability categories and then indicate various means to quantify their relevance and impact as applied to a specific building. Perhaps the best known and most often cited program is the LEED green building rating system developed by the U.S. Green Building Council (USGBC), although there are others as well. In addition, the engineering community represented by the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) has long been involved in defining criteria for energy performance in buildings, such as the often cited and used ASHRAE 90.1: Energy Standard for Buildings except Low-Rise Residential Buildings. ASHRAE has also worked collaboratively with the USGBC and others to develop ASHRAE 189.1: Standard for the Design of High-Performance Green Buildings except Low-Rise Residential Buildings.

At the same time, the International Code Council (ICC) has developed a series of relevant model codes that have been widely adopted across the United States. The International Energy Conservation Code (IECC) regulates building design and construction with the intent of achieving energy conservation over the life of the building. In a collaborative move that recognizes there are multiple ways to achieve the same results, the IECC allows using the criteria in ASHRAE 90.1 as an equivalent means to demonstrate compliance with the IECC. Similarly, the International Green Construction Code (IgCC) was developed to go beyond just energy and address other categories of green and sustainable building design. In a welcome move and a reflection of the maturity of the industry, the most recent version of the IgCC is actually merged with ASHRAE 189.1 into a single standard, which can be adopted as a code by authorities having jurisdiction (AHJ).

Through this evolving development, all of these codes and standards address the same fundamental categories of green and sustainable design for buildings. These categories include the following, most of which are directly relevant to projects that use metal building systems:

Site-Related Impacts: Adding a building to an existing site will certainly impact things already there. The green and sustainable approach is to find ways that minimize harm to the site in terms of environmental aspects while maximizing benefit through methods that can actually improve environmental site conditions.

Water Conservation: Potable water is an increasingly valuable commodity in many locations due to population growth creating more demand or compromised sources of water that can reduce available supply. Buildings that reduce or eliminate the need for irrigation of plantings and reduce the volume of water needed for common activities related to drinking water, sanitation, and cleaning are clearly more sustainable than those that don’t address this fundamental aspect of design and construction.

Optimize Energy Performance: Addressing energy performance takes on several forms. The most significant and cost-effective first step is to address the building envelope by designing for conservation of energy through a reduction in energy demand in the first place. This is achieved through proper levels of insulation, elimination of thermal bridging, and controlling air leakage in opaque wall, floor, and roof areas of building enclosures. It also includes attention to details at fenestration, openings, and penetrations in these opaque areas to address the continuity of building enclosure barriers. The next step is to select HVAC and electrical systems that are efficient to operate, meaning that they use less energy to produce the desired end results of heating, cooling, lighting, etc. This is done through good engineering design and proper specification of equipment and systems that have been tested to demonstrate high levels of efficiency. Finally, the use of on-site renewable energy systems such as solar photovoltaic (PV) systems is recognized as a means to meet energy needs in buildings in a manner that is non-polluting and currently very cost-effective.

Green building rating systems and standards address interior and exterior aspects of buildings in multiple common categories.

Materials and Resources: This category is focused on the sustainable use of building materials and respect for the natural resources where they originate. That means addressing the inherent efficiencies of material use, use of recycled and low-impact materials, reduction or elimination of waste, and resiliency and durability of materials are all important. In order to identify and quantify these aspects of materials, international standards have been developed to create an LCA of materials and products used in construction. In order to carry out a LCA, product category rules (PCR) are often developed by trade and industry associations to determine the overall relevant parameters. Manufacturers can then use the established procedures and rules to create environmental product declarations (EPDs) for their particular materials and products.

Indoor Environmental Quality: Most green building standards recognize that many people spend more time indoors than they do outside, which can have direct impacts on all aspects of human health. Therefore, they promote or require the use of materials that do not use or emit substances that can be harmful either immediately or over time. For general psychological and emotional well-being, they also promote design options for natural daylight, views to the exterior, acoustical control, and similar conditions.

Innovation in Design: Green building standards and codes are not intended to limit creativity and innovation; in fact, they tend to encourage it. Therefore, customized designs and building systems can often be used to demonstrate project specific attributes that contribute to sustainability.

Based on all of the foregoing, let’s now discuss the ways these green building design approaches are applied to metal buildings. We’ll do so by looking at some of the main construction aspects of a building: structure, enclosure, materials, and mechanical/electrical systems.

Foundation and Structural Systems

The sustainability traits associated with the structural system of a building are directly related to the size, weight, and environmental impacts of the materials used for construction. In that regard, it is significant to note that metal building systems using optimized built-up steel frames and cold-formed structural members are structurally very efficient. That means they can use less steel for the same performance as building systems that use hot-rolled members (i.e., I-beams, columns, etc.). Since the metal building steel structure is custom designed to meet the needs for the project, the lighter-weight cold-formed steel members are simply engineered and shaped to put the strength where it is needed and eliminate any unnecessary dead-load weight. This applies to primary members such as columns and rafter beams as well as secondary members like purlins and girts that attach to the primary steel. Overall, that translates to an optimized, lighter-weight, custom-engineered steel structure. Further, since steel is commonly sold by weight, a lighter-weight structure also means project cost savings.

Metal buildings are structurally efficient. They can use 30 percent less steel and are lighter than conventional steel buildings.

A direct result of lighter steel structures is a corresponding impact on concrete foundations. Concrete is commonly regarded as one of the more energy intensive construction materials in use with a number of environmental impacts. Reducing the dead-load and steel-member sizes on concrete foundation systems can also mean reducing the size of the foundations—thus reducing the amount of concrete needed.

The steel used in metal buildings is sustainable overall. That’s because a typical metal building is produced from at least 70 percent recycled steel, thus substantially reducing the need for virgin materials excavated from the earth. In addition, the processing of recycled steel for producing goods for a metal building requires significantly less energy.

There are some other less obvious but still significant sustainability aspects of the primary and secondary structural members of a metal building. First is the fact that all of the components are custom designed and efficiently fabricated in an off-site controlled environment. They are then delivered according to a pre-determined construction schedule. Portions of the metal building package can be sequenced to arrive as needed so that the staging area on-site can be minimized—with reduced site impacts. And since there is usually little if any field cutting required, there is very little or no on-site waste.

Related to sustainability is the emerging focus on designing and constructing buildings that are resilient, meaning they can not only survive but also bounce back quickly after a natural disaster such as wind, seismic, and flood events. Metal building structural systems can be fully evaluated for such events with the members, connections, and bracing designed specifically for any of the potential hazards of the project location. Since they are custom designed, specifications can include requirements that go beyond the building code to satisfy an owner’s commitment to any performance or resiliency goal.