Richard Trethewey shows an innovative new way to seal ducts from the inside. (See below for steps.)
Steps for How to Seal Leaky Ductwork:
1. Remove the grilles from all of the supply and return registers.
2. Plug each duct register with foam rubber and wide strips of tape.
3. Pressurize the duct system with a blower fan.
4. Use a computer to analyze the data to determine the amount of air leaking from the ducts.
5. Use the blower fan to mist the inside of all the dust with liquid-rubber sealant.
6. The sealant will find and plug all air-leaking holes, cracks, and seams.
7. After applying the sealant, run another pressurized blower test to verify the improved results.