Can the ductwork be modified to carry more air?

When measured airflow falls short of what the selected equipment requires, the duct system can be modified. Field guides sort an existing system into three outcomes: acceptable as is, modify, or replace. The least invasive gains are usually on the return side: a larger return drop, an added return, a lower-resistance filter, sealed leaks, and replacement of crushed or kinked flex duct. Supply-side gains mean larger trunks or branches.

In many Steamboat structures the ducts run behind finished walls and floors and are limited by the framing they were built into. What can be changed is what can be reached: typically the air handler connections, the return, and any exposed runs. The measurement says how far short the system is; the structure says how much of that can be recovered.

Last reviewed 2026-09-06. Accurate to the best of our knowledge as of that date. Rules change — that's why the date is there.