As conditioned air flows from heating and cooling equipment to the spaces where people live, excessive leaks compromise comfort, health, and durability while increasing energy costs. This is because conditioned air escapes ducts supplying heating and cooling, and potentially contaminated air is pulled into the ducts, returning air to the heating and cooling equipment. Professionally sealed comfort delivery systems are significantly air-tight at all seams and connections. Sealing helps conditioned air get where it is needed, at the correct temperature, without pulling in contaminants from crawlspaces and attics.