Using duct tape is still today a very popular method for sealing air-ducts, especially in America. Installers and engineers start however realizing the drawbacks of using such a method:
Accessibility
Sealing a ductwork with a duct tape presupposes that you have enough access around the duct. This is most of the time a problem, as ventilation ducts are installed close to walls, other ducts or equipment to save place.
Labor
The time spent sealing ductwork with a tape is a substantial part of your installation costs which could be eliminated. Furthermore, the application must be carried out with care in order to obtain the expected results.
Purchasing Costs
The tape itself constitutes a cost which could be saved.
Air-tightness
Most importantly, testing has shown that many types of duct tapes in the market do not keep ductwork sealed for long. More information can be found in the article entitles "Duct Tapes flunk Berkley Lab Tests" (The NEWS, August 31, 1998).