Using Metal Building Systems to Meet and Exceed the Energy Code

High-performance results include insulation options and improved air-infiltration sealing
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Sponsored by Metal Building Manufacturers Association (MBMA)
By Peter J. Arsenault, FAIA, NCARB, LEED AP

Responsibilities and Roles

Sometimes there is misunderstanding or confusion about who is in control of the parts of a metal building system. In fact, they should be treated no differently than any other building. The architect is still responsible for the design, including defining the code requirements, size, and shape of the building and the related attributes of the form of the building (length, width, height, roof slope, etc.) as part of normal practice. The structural system can be laid out (column spacing, beams, etc.) in concert with input from a structural engineer (provided by either the architect or the metal building manufacturer). The specifics of the exterior also remain under the purview of the architect, including the particulars of the building envelope, such as the insulation, cladding, and any openings (doors, windows).

Using the information contained in the construction documents based on the specifications developed by the design professionals, the building manufacturer can then develop the detailed engineered shop drawings for the building, similar to any other structural shop drawings. The communication path between the architect and the manufacturer is typically through the general contractor, just as with most building projects. Therefore, it is important that all parties are communicating well so that the details of construction are understood and pricing is properly done. It is also important to be clear on which materials and services are being provided by the metal building manufacturer and which are provided under the responsibility of other suppliers or subcontractors, especially for a hybrid building. The architect still needs to specify all of these items, while the general contractor coordinates the different trades and suppliers accordingly.

Understanding the roles of everyone in a project plays directly into meeting the requirements of energy codes. In metal buildings, just like any other building, the architects still need to specify and detail the types and performance criteria of the insulation as well as key requirements for air-infiltration control. Details of minimizing thermal bridging can be coordinated with structural engineers and the manufacturer. The energy efficiency of mechanical and electrical systems will still rest with the design professional designing and specifying these systems. The contractor will still be responsible for the proper field installation of all materials and systems related to energy usage and subject to the normal energy-code inspections.

When using metal building systems for a project, the details of coordinating the metal building components with other materials is still needed. In some cases, the details and processes are the same or similar to traditional building methods. In other cases, there are some specific methods and approaches that have become standardized and streamlined in metal buildings with which designers need to become familiar. These include the way that purlins and girts are typically used in metal buildings, and how this plays into the insulation of walls and roofing. It also includes the recognition that some insulating methods have become common with metal buildings that are not necessarily available or used in traditional building construction. Most metal building manufacturers have detail packages available for download from their website for the architect to reference.

With a basic understanding of the ways that metal building systems are fabricated and delivered, along with a recognition of the options and choices of detailing, we now turn our attention to applying the energy code to this process.

Relevant Energy-Code Provisions

In the United States, there are two common energy codes that are used. The first is prepared and published by the International Code Council and known as the International Energy Conservation Code (IECC). The second is prepared and published by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) and known as ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Construction. In most U.S. jurisdictions, the IECC has been adopted, but this code also recognizes ASHRAE 90.1 as an “equivalent” document that can be used as an approved alternate to show energy-code compliance. Note that equivalent does not mean identical—there are some specific differences between the two documents. Nonetheless, it has become generally accepted that the resulting energy performance of a building will be essentially the same by following either one. Therefore, the design and construction team needs to decide at the outset which code is being used to show compliance for all aspects of the building (no co-mingling of requirements is allowed—it is one or the other). Some jurisdictions, such as New York City and elsewhere, have made the decision already for all commercial buildings, stating that ASHRAE 90.1 must be used to show compliance. Other jurisdictions have other requirements, including the state of California, which has developed its own Title 24 Energy Code that contains more stringent requirements than either the IECC or ASHRAE 90.1. The design and construction team needs to be clear on what code applies at the location of its building project. Furthermore, since these codes are updated regularly, the team needs to be clear on what version or publication year of the code is required and in use. Providing this information to the metal building manufacturer early in the process is very important.

Despite these different codes, there are some basic provisions and principles that are common to all of them. These principles are based on the fundamentals of physics and engineering related to heat gain and loss, material attributes, and efficiencies of mechanical and electrical equipment. As such, these principles can be applied to any design. The codes then state the minimum threshold of performance in all these areas that must demonstrate code compliance. The same principles can be used to increase a building’s energy performance beyond the code-required minimum to higher levels called for in LEED or other voluntary programs.

Based on the above, following are the first aspects that need to be considered to meet the targeted level of energy performance.

Hybrid metal buildings can take many forms, with coordination, roles, and responsibilities of all involved being the same or similar to other projects.

Scope and Intent

Energy codes do not regulate energy consumption (i.e., fines are not issued if a monthly energy bill is too high), but rather they regulate “design and construction” just like other codes do. The focus here is “effective energy use and conservation” in buildings. The effective energy use part refers to mechanical and electrical equipment that needs to be energy efficient (i.e., controlling the amount of input energy needed to get a desired output, such as light or heat). The energy conservation part (i.e., reduce the need for energy in the building in the first place) is all about the building enclosure, including things like thermal insulation levels, windows, doors, and control of air infiltration (drafts). The energy codes require that these measures need to be effective long-term “over the useful life of the building” just like any other code provisions.

The intent of the energy codes is to focus on conditioned space, meaning building areas that consume energy for heating and cooling. It is important to note that the IECC does not recognize semi-heated buildings (i.e., buildings that are minimally heated but not cooled), a condition that is common in metal building applications such as warehouses and some industrial applications. This is one instance where using the approved alternate, ASHRAE 90.1, is necessary and more appropriate because it does address the semi-heated condition.

 

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Originally published in Architectural Record
Originally published in December 2020

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