When it comes to sealing leaking ducts, HVAC duct sealing tape is one of the most effective solutions. While duct tape may be a quicker and easier option, it is usually more expensive and not as long-lasting. For fibrous glass ducts, glass cloth and putty (GFM) have been found to adhere well to galvanized steel. It is important to note that the tightness of the ducts does not need to be absolute, unlike in a water pipe system. The name 'duct' can lead some people to believe that duct tape can be used to repair cracks in their home's ducts.
However, adhesive tape is not able to withstand temperature fluctuations and usually only lasts a few days at most. All the ducts were leaking water into the house, since the putty applied nine months ago had worn off on top of the ducts. I understand why some people would want to omit putty in ducts located within the conditioned space. However, this is not allowed, and other than turning the basement into a conditioned space, there is no way to convert the ducts into a conditioned space. To seal the boots to the attic floors and then seal the boots to the ceiling of my living room (before reattaching the grills), I used duct putty. Duct connections to the flanges of air distribution system equipment or sheet metal accessories must be mechanically fastened. Closure systems used with rigid fibrous glass ducts must comply with UL181A standards and bear marks 181A-P (for pressure sensitive tape), 181A-M (for putty), or 181A-H (for thermosensitive tape).
Closure systems used with flexible air ducts and flexible air connectors must comply with UL181B standards and bear marks 181B-FX (for pressure sensitive tape) or 181B-M (for putty).Sto manufactures two products - a mesh tape and a sticky material - designed for sealing air leaks at the seams of the coating. Sealing the ducts helps heating and cooling systems work more efficiently by maintaining air temperature. Although not specifically designed for ducts, high-quality curtain wall sealants have also been used for this purpose. These excerpts come from SMACNA's manual on metal and flexible standards for construction of air conditioning ducts.
