Why does an inspector observe supply registers in every room rather than sampling one?

Distribution problems are room-specific by nature, so sampling one register cannot find them. The condition being looked for is a room that receives no conditioned air at all, or noticeably less than it should — most often a room added later without extending the duct system, a finished basement or attic space, or a bonus room over a garage. These rooms are exactly the ones an occupant complains about after moving in, and they cannot be identified from the equipment or from a single register. Walking every room and noting where supply exists is also the way to spot the related issue: a room with supply but no return path, no transfer grille and a door that closes, which pressurises when the door shuts and starves the rest of the house. Both findings come from the same walk.

Distribution problems are room-specific, so only observing every room reveals which rooms receive no supply or inadequate supply — commonly additions and converted spaces the duct system never reached.

General inspections evaluate whether conditioned air is distributed to habitable rooms. Additions and converted spaces are commonly served inadequately. Rooms with supply but no return path pressurise when doors close.

Every Room, Every Time. The room that got missed by the duct system is the one nobody thought to check.

A room with supply, a closing door and no return or transfer path is a pressure imbalance finding worth reporting alongside missing supply.

• •Sampling registers instead of walking every room
• •Overlooking additions and converted spaces
• •Noting supply without checking the return path