With the recent adoption of Minnesota’s new 2016 Energy Code, there has been some confusion and misinformation regarding the acceptability using tape to seal metal duct. The debate has been settled. Metal duct can be sealed with tape, provided it the tape is labeled UL181A/P
Originally, Don Sivigny, Minnesota’s State Energy Specialist, had the misunderstanding that there was no foil tape that met the UL standard for sealing metal duct, and conveyed this in many of the training sessions on the new energy code. In the e-mail string below, Don conveys he now understands that no UL standard exists that specifies testing criteria for either tape or mastic for metal duct. Therefore, if one concluded that tape was not acceptable for sealing duct, then mastic would not be acceptable either. As a result, Don now agrees that tape is a code approved sealing option per 603.9 of the Minnesota Mechanical Fuel and Gas Code(below). The MN Energy Code defers to 603.9 for duct sealing which explicitly approves the use of UL181 A/P tape for sealing metal duct.
2015 Minnesota Mechanical Fuel and Gas Code – (Referenced by the 2015 MN Energy Code)
Chapter 6 Duct Systems
All longitudinal and transverse joints, seams and connections in metallic and nonmetallic ducts shall be constructed as specified in SMACNA HVAC Duct Construction Standards—Metal and Flexible and NAIMA Fibrous Glass Duct Construction Standards. All joints, longitudinal and transverse seams and connections in ductwork shall be securely fastened and sealed with welds, gaskets, mastics (adhesives), mastic-plus-embedded-fabric systems, liquid sealants or tapes. Closure systems used to seal ductwork listed and labeled in accordance with UL 181A shall be marked “181A-P” for pressure-sensitive tape, “181A-M” for mastic or “181A-H” for heat- sensitive tape. Closure systems used to seal flexible air ducts and flexible air connectors shall comply with UL 181B and shall be marked “181B-FX” for pressure- sensitive tape or “118B-M” for mastic. Duct connections to flanges of air distribution system equipment shall be sealed and mechanically fastened. Mechanical fasteners for use with flexible nonmetallic air ducts shall comply with UL 181B and shall be marked “181B-C.” Closure systems used to seal metal ductwork shall be installed in accordance with the manufacturer’s installation instructions. Pressure-sensitive tape shall not be used as the primary sealant on ducts, unless it has been certified to comply with UL 181A or UL 181B by a nationally recognized testing laboratory and the tape is used in accordance with that certification. Unlisted duct tape is not permitted as a sealant on any duct.
Continuously welded and locking-type longitudinal joints and seams in ducts operating at static pressures less than 2 inches of water column (500 Pa) pressure classification shall not require additional closure systems.