Supply Duct

How supply ducts distribute conditioned air

After air passes through the furnace or air handler, it enters the supply plenum and fans out through a network of trunks and branches — sheet-metal rectangles, round pipe, duct board, or flexible duct — ending at the supply registers in each room. Good design balances three things: enough cross-sectional area to move the required airflow without excessive static pressure, sealed joints so air arrives at rooms instead of leaking into walls and chases, and insulation wherever ducts pass through attics, garages, or crawlspaces so the air arrives at the temperature it left the equipment.

Industry studies have long found that typical homes lose a meaningful share of their conditioned air through duct leakage — air you paid to heat or cool that never reaches a room. Crushed flex duct, disconnected boots, and closed or blocked registers add to the losses.

Diagnosing supply-side problems in your home

Classic symptoms of supply duct trouble in Southeastern PA homes: a far bedroom that never warms up in winter, a second floor that lags the thermostat by several degrees, whistling registers, and dust buildup around vents. Some fixes are simple — opening dampers, unblocking registers, replacing crushed flex runs. Others call for sealing accessible joints with mastic, adding a return, or rebalancing airflow room by room. Duct cleaning addresses the separate problem of debris accumulated inside the runs, which is common in older homes and after renovations. PJ MAC HVAC offers air duct cleaning along with heating and cooling service, so airflow complaints can be traced to their real cause.