Signs the ductwork is the problem, not the equipment

Ductwork is the part of the system nobody looks at, because most of it is out of sight and none of it has a brand name. It is also where a large share of comfort complaints actually live. Leaky, undersized or badly routed duct will defeat any equipment connected to it.

What to look for

• Rooms that are consistently several degrees off from the rest of the house, in both seasons.
• Dust reappearing within days of cleaning, which suggests return leaks pulling from a basement, attic or crawl space.
• A basement or attic that is noticeably conditioned when nobody is trying to condition it.
• Noise: whistling at registers, or a boom from duct flexing when the blower starts.
• Visible disconnections, tape lifting at joints, or flexible duct sagging between supports.

The number that settles it

Total external static pressure, measured across the air handler. Most residential equipment is rated for about 0.5 inches of water column. Readings well above that mean the blower is working against the duct rather than moving air through it, and that shows up as poor comfort, high bills and shortened equipment life. It takes a few minutes to measure and it is the honest starting point of any conversation about replacement.

Sealing before resizing

Sealing accessible joints and correcting crushed or kinked runs is a far smaller job than rebuilding a duct system, and it often recovers most of the loss. Get the leaks and the obvious restrictions dealt with first, then measure again before anyone proposes tearing out ductwork.