Things You'll Need:
- Duct sealing mastic
- Wide metal or plastic duct straps
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Step 1
Determine if you have leaky ducts. If you have high summer and winter utility bills, fluctuating temperatures between rooms, ducts that run through your garage, crawlspace or attic or if you see kinked ducts you probably have ducts that are leaking.
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Step 2
Hire a professional to check your duct system if you are not sure you have leaky duct work and ducts are especially difficult to access. Professionals can run a test using forced air through ducts to determine if your ducts leak.
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Step 3
Look at duct work that is insulated to see if there are streaks of dirt around the seal. This is a sign you have a leak under the insulation at a duct joint.
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Step 4
Check for air leaks around joints where duct work meets heating or cooling units, around the plenum and areas where ducts split. You will see open spaces, and cracks in old tape or mastic and dust or lint collected around areas that are leaky.
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Step 5
Support flex duct work with metal hanging straps at five foot intervals. This should be a regular installation step but many times installers do not support every five feet. This causes duct work to sag, detach and leak.
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Step 6
Use duct sealing mastic to seal ducts and joints. Mastic is a thick paste sold in tubes.
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Step 7
Apply mastic around joints, collars and corners of the entire air or heating system including unit and plenum areas.
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Step 8
Squeeze a thick line around the inside of the bigger duct opening and slip the next section inside when sealing actual duct work.
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Step 9
Check and seal each of the following areas:
• Disconnected sections or connections
• Connections between air unit and plenum
• All seams including the major unit, plenum, and duct work
• Returns and boots
• Joints between duct branches
• Seams that run lengthwise down duct work
