Why does an inspector check that supply registers are present in each conditioned room?

A forced-air system conditions a room by delivering air to it, so a room with no supply register is not served — it will drift toward the temperature of whatever surrounds it and be noticeably uncomfortable in both seasons. Rooms end up unserved for identifiable reasons that are worth reporting: a space converted from a garage, porch or attic without extending the ductwork; a duct run that was capped during a renovation; or a register removed and drywalled over. The check is simple and mechanical — walk each conditioned room and confirm a supply exists — and it pairs naturally with confirming a return path, since a room needs both to actually exchange air. Register sizing, appearance and count are not the question; presence is.

Without a supply register a room receives no conditioned air and will not be heated or cooled by the system. The inspector confirms each conditioned room is actually served.

Forced-air systems require a supply register in each conditioned space and a return path from it. Rooms created by converting unconditioned space are frequently left unserved or served by an undersized extension.

Every Room Needs a Supply and a Way Out. No register means the room is not on the system at all.

Converted spaces are the usual finding: a bonus room over a garage, an enclosed porch or a finished attic often has no duct extended to it.

• •Checking that equipment runs without confirming each room is served
• •Expecting registers to be uniformly sized
• •Confirming supply while overlooking the return path