Ductwork design is a critical factor in keeping living spaces livable during hot summers and cold winters. Shelling out big bucks in energy costs to condition the attic and crawl space—or empty voids inside walls—while the rest of the house is hard to cool or heat is a classic symptom of leaking ductwork. Back in the days of cheap energy, residential ductwork often got little respect in the construction process. Cost cutting often took precedence instead. Today, the legacy of bad ductwork design and fabrication is manifest in many homes where air loss from deteriorating ducts can be as high as 30 percent of total airflow.
Professional duct testing takes the guesswork out of evaluating duct efficiency. Indeed, building codes in many states now require procedures like the duct blower test whenever new ducts are installed or the central A/C or furnace is upgraded.
Duct Blower Test
After closing and sealing all vents in the system, the technician connects a blower fan to the duct system at the air handler. Pressure and airflow sensors are installed inside the ductwork and linked to a computer programmed with data about the size of the duct layout. As the ducts are pressurized by the blower to a standardized level, sensors monitor internal pressure as well as the volume of airflow through the blower required to maintain consistent pressure. The computer software crunches those numbers into a precise calculation of the amount of duct leakage, expressed as a percentage of total airflow.
While the ducts are pressurized, the technician can inject artificial smoke into the system to pinpoint the exact location of leaks. Effective duct sealing generally requires several approaches:
- Joints between duct spans are sealed with mastic and/or metal foil tape, then permanently fastened with sheet metal screws.
- Collapsed or corroded spans beyond repair are cut out and replaced.
- Where a large number of pinhole leaks make individual repair impractical, the internal surfaces of the ductwork may be coated with a liquid sealant blown in with compressed air.
For more on ductwork design and testing, contact P.K. Wadsworth Heating & Cooling today!Follow @PKwadsworth
Paul Wadsworth is the President and Owner of P.K. Wadsworth Heating and Cooling. For 37 years, Paul has been providing heating and cooling services to the Greater Cleveland area. P.K. Wadsworth has been a trusted Cleveland HVAC service company for over 75 years. The company understand the area's construction and local heating and air conditioning needs. Paul has an MBA from the University of Michigan and a B.S., Industrial Engineering from Purdue University. Paul is the Chairman of COSE's Energy Advisory Council. He's been President of the Cleveland Air Conditioning Contractors of America and a founding member of the local chapter. Paul was born and raised in Cleveland and has been active in the local community. He resides in Cleveland, Ohio with his wife and two sons.
The opinions and statements contained in this article are for general informational purposes only and are not instructions. Only trained, licensed and experienced personnel should attempt installation/repair. The author assumes no liability for the opinions/statements made in this article. Any individual attempting a repair or installation based on this article does so at their own risk of loss.