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Boost Thermal Performance in Metal Building Systems

These five steps will improve a metal building's thermal performance

Contrary to common misconceptions outside the industry, metal buildings can prove ideal solutions when peak thermal performance is required. The same building codes apply, regardless of whether a building is steel or concrete, and with a steel building, each component has the opportunity to enhance efficiency. Here are five steps to ensure the buildings you design and construct are achieving advanced thermal performance:

 

Accurately Measure

While R-values are the most common unit for assessing thermal performance, calculating the U-factor offers a more precise measurement. U-factors quantify the heat flow through an entire assembly, taking into account any thermal bridging and insulation compression. R-values focus on single components, and cannot simply be added together to identify assembly-wide performance.

 

Mitigate Thermal Bridging

Steel-to-steel connection points at the roof purlins and wall girts offer prime opportunities for heat to be transferred or lost. Proper mitigation is crucial. Thermal spacer blocks and mineral wool or fiberglass insulation are important tools in maintaining thermal performance. To get the most out of these measures, it's important to ensure there is no compression of the insulation, otherwise the U-factor will suffer.

 

Make an Educated Selection

The thermal performance of steel wall systems can vary greatly. Combining blanket insulation with thermal spacer blocks can increase wall system efficiency. Discrete thermal spacer blocks where wall panels attach to the girts can reduce thermal bridging that occurs through the fasteners. It also helps minimize insulation compression. Another highly efficient option is insulated metal panels. The benefits of this approach are numerous. Insulated metal panels can accommodate as much as 4 inches of foam insulation. They also save on labor costs by installing in one step and circumventing the need for additional finishing work along the perimeter walls inside of a facility, thanks to their attractive interior panel.

 

Accommodate Additional Insulation

The roof is a primary concern when determining a structure's thermal performance and, similar to wall systems, there are several options: Insulation systems with liner panels that sit atop the roof purlins can achieve U-factors down to 0.052 Btu/hr ft2 F and accommodate up to 13 inches of uncompressed blanket insulation. This approach also facilitates easy access to purlins to accommodate suspended light fixtures or duct work. And, in some cases, the liner panel eliminates the need for roof bracing because it acts as the diaphragm.

There are newer panel options without liners that allow for insulation to be placed above the purlins. This method uses structural brackets to raise the roof panel system up to 6 inches or more, creating enough space to lay fiberglass insulation with minimal compression. Newer options are much more thermally efficient than more conventional above-the-purlin solutions that significantly compress insulation.

 

Reduce Air Leakage

Focus on properly designing, detailing and installing air barriers to ensure they are effective. The roof and wall assemblies are crucial aspects, and many manufacturers test their assemblies for air leakage. Using results provided by the manufacturers can be more specific to your project than results from the Metal Building Manufacturers Association, which came from testing on generic assemblies. Insulated metal panels and the facings of blanket fiberglass insulation can serve as components of an air barrier system when the sidelaps are sealed.

For steel building systems to continue to be solid options amidst a climate with strict energy codes and customers who increasingly understand the economic value of efficiency, thermal performance must be competitive with other building approaches. A highly efficient steel building does not need to be complex to design or install. Today's innovative options offer opportunities to reduce man hours during construction and can make building maintenance and upkeep easier. The benefits of a steel building approach when looking to achieve thermal performance are many. Understanding the various approaches, and their performance and benefits, will help you counsel clients in making the best choices for their needs.

Kevin Hutchings is product training manager at Butler Manufacturing, Kansas City, Mo. To learn more, go to www.butlermfg.com.