Ductwork & airflow

When one bedroom is always cold, the problem usually lives in the ducts, not the furnace. We measure airflow at the registers, find the crushed, leaky, or undersized runs, and repair, seal, or rebalance them so the supply air ends up in the rooms instead of the joist bays.

It is worth a look if some vents blow hard while others barely whisper, if the upstairs runs hot all summer, or if dust piles up faster than it should. Sealed, balanced ductwork also takes real strain off the furnace and the A/C, so both tend to last longer.