While the increase in energy costs is significant, protecting health and safety is the most important reason to seal ducts. Most connections are simply not sealed. There is also a problem with poor quality materials being used to seal ducts. Duct tapes do not provide a permanent seal. Their adhesive dries out.
Experts recommend duct sealing with mastic.
Insulation does not stop air leaks. Look for dirt streaks in duct insulation, they're a sign that air has been leaking from the ducts. A. Studies show that all types of ductwork can have problems with air leakage. Mastic works to seal metal, flexible, and fibrous ductwork. All seams in the air handling units, and plenums, takeoffs, boots, and other connections, especially site-built items.