Furnace and central air ducts that leak air or are poorly insulated are big energy wasters. Seal duct seams and connections that run through your attic, crawl space, basement and garage with mastic duct sealant or metal-backed tape, then wrap in insulation to keep them warm in winter and cool in summer. Also check connections where vents meet floors, walls and ceilings, where leaks commonly are found.

Skill Level: Advanced to Professional
Homeowners can access many of their ducts and connections themselves, while a professional contractor can inspect and repair the whole duct system.
Cost Range: $2-$3 per roll of duct-sealing tape
Get the special duct-sealing tape, not regular silver "duct" tape.
Savings: 20% in energy
A duct system that is properly sealed and insulated makes a home more comfortable, energy efficient and safer.