We get called constantly about a bedroom over the garage that will not cool, a finished basement that stays clammy, or an upstairs that runs ten degrees warmer than downstairs. The homeowner usually assumes the air conditioner is too small. Far more often, the duct system cannot deliver the air the equipment is already producing.
Leakage is the biggest culprit. Duct running through an attic or crawlspace can lose a substantial share of its conditioned air through unsealed joints before it ever reaches a register — and in an attic in August, it is also picking up heat along the way. Sealing and insulating those runs frequently produces a bigger comfort improvement than new equipment would.
Undersized returns are the second. Systems need a path back as much as a path out. Many houses were built with a single central return expected to serve rooms whose doors are usually closed. The blower cannot move air it cannot get back, so the system short-cycles and rooms stay uneven.
Then there is design. Long flexible runs with sharp bends, crushed duct behind drywall, and branches added during a remodel without recalculating the whole system all restrict airflow. Ventilation and exhaust terminations matter too — the roof vent above is part of a system that has to breathe correctly to work at all.
Balancing is the finish. After installation we measure airflow at the registers and adjust dampers until each room gets its designed share. Skipping this step is why plenty of brand-new systems still have one uncomfortable room.
Before you buy a bigger unit, have the duct evaluated. Gask Technical Services designs, installs, repairs, and balances ductwork throughout Northern Virginia, D.C., and Maryland. Call (703) 398-2453.