When it comes to the efficiency of your heating, ventilation and air conditioning system (HVAC), one of the most overlooked factors is the condition of your ductwork. Failing to properly seal your ducts can lead to a host of problems from wasted energy to reduced comfort levels. Sealing those gaps is one of the cheapest and most effective ways to save your energy dollars.

Finding leaks

Start by locating where air leaks are occurring. It could be any place where two materials meet, such as the foundation walls and the flooring or where there’s an opening to the outdoors. Gaps can also occur around exterior doors and cracked caulking around window frames. Another area to check is in the attic — gaps around ceiling fans, recessed light fixtures and electrical outlets.

Fixing leaks

If you find any leaks, sealing them is a simple project you can do yourself with supplies available from your local retailer.

  1. Windows: Seal windows with exterior caulk. Your best bet is silicone or siliconized caulk.
  • Where the window meets the frame, scrape out any existing caulk and make sure the area is clean and dry.
  • Cut the tips of the caulk at a 45-degree angle and load it into the caulking gun.
  • Run the tips slowly and evenly along the base of the crack.
  • Finish by running a wet fingertip along the bead of the caulk to smooth it out.
  • Doors: Fix gaps around exterior doors with weatherstripping and a door sweep.
  • Measure the top and sides of the door and cut pieces of weatherstripping to fit each.
  • Peel back the covering from the adhesive and press the weatherstripping to the inside of the doorstop, ensuring a snug fit.
  • Cut the sweep (if needed) to match the width of the door and attach it with adhesive or screws.
  • Attic: Ceiling fans, recessed lighting fixtures and electrical outlets in the ceiling below your attic are potential sources of air leakage.
  • From the attic, pull back the insulation to find the cutouts and seal them with caulk or expandable foam.
  • Check for and seal gaps around plumbing vents, furnace flues and ductwork.
  • Seal the attic door or access with weatherstripping.

Learn more about minimizing energy losses in ducts at