Each batch of sheet metal is made to differing levels of strength, size, and thickness depending on the exact performance tests it has to pass. For universal adoption of appropriate standards to be possible, it was necessary to create a governing body to regulate and approve particular use of components based upon their qualification. The Sheet Metal and Air Conditioning Contractors‘ National Association (SMACNA) is an international trade association that establishes the industry standards for acceptable construction material criteria used in HVAC. These codes declare the minimum allowable thickness for ventilation ductwork sheet metal across various sizes, shapes, and raw materials used for individual applications. Sheet metal has specific guidelines determined by use, which the product must be within after being manufactured or fabricated for:
To save on the money and resources in an initial investment, it is common to choose the least allowable thickness that fits into the design plans while still possessing the right qualifying tolerances. The thinnest acceptable sheet metal for ductwork used in a single dwelling is 28 gage or 0.013 and 0.018 inches for galvanized and aluminum, respectively. This measurement is for around duct smaller than 12 inches in diameter and a rectangular section no bigger than 8 inches. These figures are for construction according to the most recent edition of the updated codebook published in 2018. Additionally, there are also specs for the correct galvanizing coating that is supposed to be used as well, and knowing how to get all the details right is why it is important to have a professional handle all installations.
The sheet metal that is used to create ductwork that supplies ventilation to living and working spaces has to be able to withstand the pressure created by the system in order to follow the building code. The standard thickness increases for larger dimensions of piping made from sheet metal so it can withstand the stresses of greater length and diameter without buckling under its own weight. The two most common metals used for ductwork are aluminum and galvanized steel, and the requirements for both are listed in the International Mechanical Code book. Further guidelines are also found in the SMACNA HVAC Duct Construction – Metal and Flexible book, which further clarifies best practices for a host of possible scenarios. When you’re ready to find out what we can do for you, give us a call at 408-295-2182.