Hot, dry summers expose losses in ducts outside the living space
During a hot, dry Tye summer, the difference between cooled rooms and an attic, garage, crawlspace or other unconditioned space is large. A leak in a duct running through one of those areas lets cooled air escape before it reaches a register. Leaks on the return side pull hot, dusty unconditioned air into the system instead.
That lost air makes the equipment run longer to cool the house and can make a properly functioning air conditioner seem too small for the job. The problem is not always a visibly disconnected duct. Crushed flex duct, weak joints, missing insulation and return ducts that are too small all restrict the air moving through the house.
We evaluate the duct system with airflow and leakage in mind, including the return side. Sealing supply leaks keeps cooled air headed toward the rooms; sealing return leaks stops the system from drawing attic, garage or crawlspace air into the home. Pressure imbalances and poor return-air design also explain why some rooms stay harder to cool than others.