When discussing walk doors for a metal building, there are some general guidelines that most building manufacturers and builders can follow to ensure some consistency from building to building. The Steel Door Institute (SDI) commercial door specifications are a good starting point and provide reasonably good direction, but they may not be complete for comparisons of commercial door applications.
Consider many diverse variables when determining a good door fit
In other words, there can be a door that meets the general requirements of an SDI spec but may not be a best fit for the application—without looking deeper into other door characteristics.
Testing and Performance
Doors operate in a wide variety of ways and even with common components, based on other factors they may show varying levels of performance achievements. Many door manufacturers rely on the Florida Building Code registration requirements to drive the testing parameters and end results. The testing focus on meeting structural and air/water infiltration performance levels, with missile testing an additional test for those wanting to meet the coastline requirements. The unique consideration is that two similarly made doors may have different structural results, just because the manufacturer may choose to test to different levels. In essence, doors aren’t tested to failure, they are tested to the level a company wants to achieve. Ensure the doors are third-party tested and meet minimum foundational levels that makes sense for the end use application.
The old days of measuring the door “core” R value only is not a good representation of the opening itself. The better method is the total opening NFRC 100 test that provides a U value for the total opening, which includes the door, frame, threshold and weather seal and how they integrate with one another. The overlap with the air/water infiltration tests to the assembly U value will provide a good reference point to the door performance. A door may be structurally sound but with gaps along the door/frame edge or poor assembly quality, U values can be greatly impacted, and your energy efficiency will suffer. Having a thermal break in the door as well as the frame and threshold—defined as full thermal break system—is the best bet for getting the U values many want or need to achieve.
Finally, the issue of the actual material used in the door and frame is often overlooked. Steel doors and steel frames are obviously the most common material for many commercial/industrial door applications. However, many times the end use may call for or require something a bit different. Aluminum storefront doors provide a quality entrance for many office and retail buildings. Aluminum is a highly corrosive resistant material that allows doors to remain attractive over time without the wear and tear that steel doors may show over time. Buildings used for various agricultural purposes have often required the use of aluminum or fiberglass for animal confinement or other highly corrosive environments. Those materials are becoming more integrated into commercial building structures just for that reason, whereby the benefits of the corrosion-resistant material outweigh the steel material benefits.
Review the end-use requirements of a building before doing the cookie-cutter approach of using the same door every time. Testing and performance level minimums are a good starting point to ensure basic structural requirements are met. Then the energy efficiencies gained through highly engineered products—especially those with a thermal break door and frame—that provide strong U values are becoming more and more necessary. And finally, the use of materials can and should vary between diverse applications. Corrosive-resistant materials in particular are gaining more traction in many commercial, industrial and agricultural building applications.