Studies have shown that heating and cooling systems can lose up to 30% of their efficiency due to leaks in the ductwork. The solution is to seal the ductwork at the joints where ducts connect together. Use of duct sealant will save you money on energy costs when operating your forced-air heating and cooling equipment. In some states, such as California, it is required by law to inspect and seal the ductwork when replacing heating and cooling equipment connected to ductwork. See more details about sealing ductwork in this helpful article about duct leakage.