How To Locate And Repair Leaks In Your Air Conditioning Ductwork

Most homes lose over one-fourth of their cooling capacity to leaks within air conditioning ductwork, This needless waste of resources is costly and keeps your home from being as comfortable as it should be. Fortunately, an average homeowner can locate and repair most leaks within air conditioning ductwork. Below is what you will need to find and fix the leaks as well as information on how to go about it:

Tools and supplies needed

  • Aluminum foil metal tape – you can purchase foil tape at home improvement and hardware stores; do not use duct tape as it will not continue to hold fast over a lengthy period of time.
  • Infrared thermometer – these thermometers are often equipped with a laser pointer for accuracy.
  • Silicone caulk – any kind of silicone caulk is acceptable.
  • Fluorescent adhesive dots – these are sold in the office supply section of most retail stores.
  • Work gloves – leather gloves provide excellent cut resistance from sheet metal edges.
  • Caulk gun
  • Scissors
  • Respirator
  • Flashlight, lantern or work lights

Locating and repairing the leaks

1. Prepare for safety – air conditioning ductwork is routed through basements, attics, crawl spaces and between walls, so access can be difficult as well as dangerous. For example, walking around in a dark, cramped attic can present potential hazards such as electrical shocks, tripping and falling hazards, stinging insects and a myriad of other hidden snares. Here is how to stay safe:

  • Don't work when you are tired – your level of alertness drops when you become fatigued and hot, so call it a day if you feel tired and you have trouble concentrating.
  • Wear gloves when working with ductwork – sheet metal used to construct ductwork is razor sharp on its bare edges, and gloves will prevent serious cuts.
  • Adequately light your work area – if you are in an area with nonexistent or insufficient lighting, set-up electrical lanterns or work lights to fully illuminate the surrounding area.
  • Use a respirator in attics and other enclosed spaces – insulation, dust and other airborne particles can irritate your airways and even provoke allergic responses. Keep your nose and mouth covered when necessary.
  • Beware of heat-related illness – drink lots of water and take frequent breaks to cool down if you are working during warmer months.

2. Evaluate your ductwork for obvious leaks and problems – once you are prepared to work safely, begin by conducting an overview of your ductwork. Look for any obvious leaks such as rips, tears, separation between joints, and other problems. Be sure to take note of any ducts that are crushed or kinked. Mark any problems you find with fluorescent adhesive dots so you will remember where they are later.

3. Search for leaks with the thermometer – if your air conditioner isn't running, switch it on for the upcoming steps. Next, use your handheld infrared thermometer to search for invisible leaks. Slowly pass the infrared sensor over the ductwork in a systematic fashion. For example, move the thermometer in a circular, corkscrew pattern around the ductwork as you proceed. Take at least 5 readings for each linear meter of ductwork to ensure you don't miss pinhole leaks. Mark any areas with a dot that show significantly lower temperatures than those in the immediate surrounding area.

4. Repair leaks along flat seams with caulk – once you finish locating and marking leaks, it is time to repair them. Leaks for joints and junctions with flat edges are repaired with silicone caulk. First, clear dust and other debris away from the seams near the leak. Next, apply a 5 millimeter rope of silicone caulk along the edge so it seals the gap. Allow the silicone caulk to dry overnight, then recheck your repair with your infrared thermometer to be sure you covered the leak. Apply additional caulk to seal any remaining leaks.

5. Fix leaks within the round ductwork with tape – for leaks on round ducts, you will need to apply aluminum foil tape. Clean up any dust or debris at the site of the leak, and wrap tape all the way around the duct, if possible. Be careful when applying tape not to crush the duct or dislodge any joints between sections. Cut the tape cleanly with a pair of scissors. Perform another temperature reading to ensure you covered the leak. Should you still have problems, contact an HVAC specialist for more information.