Energy Usage

Meeting energy codes or voluntary standards for green and sustainable buildings (i.e., IgCC, LEED, Green Globes, etc.) is another area where the perceptions of some people does not match the reality of built projects. The building envelope and all of the building mechanical and electrical systems can be completely customized just like any other building to achieve any level of energy performance or green building construction that is sought.

Metal buildings achieve energy and sustainability goals first by utilizing any of a multitude of high-performance insulation options—from mineral fiber batts to rigid boards or even spray-on insulation—all of which can meet or exceed energy conservation requirements. The International Energy Conservation Code (IECC) and the recognized equivalent standard ASHRAE 90.1 both have prescriptive insulation requirements specifically identified for metal buildings. This is not because the codes find MBSs to be inferior from an energy standpoint but because they recognize that there are alternative approaches to design and construction using MBSs. (The rest of the prescriptive requirements of the energy codes are based on very conservatively defined traditional framed construction.) Of course, the codes also offer performance methods of showing compliance utilizing software tools, such as COMcheck or energy modeling. This approach allows designers to select a balance of high-performance roof and wall insulation, windows, doors, and foundation insulation that works best collectively to save the most energy and money when considering all of the project requirements. In terms of the mandatory code requirements for air-sealing, the interlocking and gasketed edges of metal building panels provide excellent weather and airtightness if designed and installed properly. In addition, insulation manufacturers have products and systems specifically designed for metal buildings that integrate vapor retarders and liners that provide airtightness. The MBMA Energy Design Guide for Metal Building Systems is available at www.mbmamanual.com to help with energy analysis of MBSs.

Among the many traits of metal buildings, good stewardship of the environmental resources and sustainability have been demonstrated in the many LEED-certified metal buildings that have been constructed.

Sustainability

Can an MBS be documented as a green or sustainable building? Yes, in fact, many MBSs have achieved LEED certification at all levels (Certified, Silver, Gold, and Platinum). In addition to energy-conserving building enclosures, metal buildings are routinely displayed as good for the environment because they are made from recycled steel, are 100 percent recyclable, and thus produce a low carbon footprint. Similarly, cool metal roof coatings repel heat, reduce the urban heat island effect, increase solar reflectivity (decreasing energy consumption), and are designed to simply clip on optional solar panels. From a construction perspective, off-site fabrication reduces construction equipment emissions while faster cleanup is achieved because metal buildings generate more than 50 percent less job-site waste than other construction approaches. For a complete look at the lifetime impacts of an MBS, it is readily possible to conduct whole building LCA calculations during the design phase of a project. More information is available at www.mbma.com/Environmental_Performance.html.

Solar Installations

Directly related to sustainability, metal roofing provides a preferable substrate for crystalline/silicon solar photovoltaic (PV) arrays. Solar panels are easily installed on a standing-seam metal roof with fasteners that lock directly onto the standing seams and are hidden from view. The clips are especially beneficial because they do not require any penetration of the roof itself, thus avoiding possible water seepage. They also provide an installation advantage since on most other roofing types, a separate racking system is needed that is anchored to the roof by drilling into its surface. Mounting to a standing-seam metal roof is a better option since it eliminates the need for the racking and associated penetrations. Life expectancy is another reason metal roofs are best suited for solar arrays. The expected service life of a metal roof—recently shown to be 60 years or more—is a better match for the service life of solar panels. The current warranted life of solar panels is 20–25 years, and many of them prove to remain functional well after that. Few commercial roofs, other than metal, will last as long as the solar panels. Hence, if metal roofing is not used, all solar panels will need to be removed and reinstalled each time a roof is replaced, adding time and cost plus potentially causing damage to the system.

Complete Design Flexibility

Architects sometimes think there are too many design limitations involved in using a metal building. However, as noted already, every metal building is treated as a unique package and custom fabricated to meet the needs of each project. That means that there is more inherent design flexibility than many architects may realize. This flexibility is achieved in a variety of ways. The structure of an MBS can be designed to allow for custom dimensions and shapes with maximum flexibility to create a variety of plan configurations including ells, U-shapes, squares, rectangles, etc. Column-free interior space is achieved with long-span framing that allows complete freedom in the design (and potential future reconfiguration) of interior layouts. Since metal buildings are highly fire resistant, they allow more options in building size and layout when calculating fire areas under the building code. Further, ease of expansion can be built right into the original design by engineering end walls to become future interior structural frames.

From an exterior design standpoint, the opportunities when using MBSs are virtually endless. Visible or hidden metal roofs, coordinated or contrasting siding, detailing, and fenestration are all exterior design elements that can be selected and controlled. Among the other design features that have been successfully used are the following:

• Intriguing options for defining mass, space, proportion and symmetry
• High slopes in building designs creating dramatic roof lines that become signature building elements
• Exteriors clad with steel siding, wood, glass, aluminum, masonry, or concrete
• Clearstory roofs and daylighting elements to create rich, open environments
• Variable building panel and roof colors and textures to allow unique architectural statements
• Metal walls and insulated panels with vertical, horizontal, deep, or shallow lines that may be embossed, smooth, or flat to accommodate architectural aesthetics
• Decorative columns and varied arch forms that are coordinated with the overall design

In essence, the style, materials, and detailing of an MBS are all variable and limited only by the imagination and skills of the designer.