Ductwork and Airflow in Ellensburg

In Ellensburg the heating season is the long one, and it decides which duct problem gets noticed. A weak run here is a complaint that runs a whole season, not a bad two weeks in August.

A run that crosses an unheated attic or a vented crawl space carries the warmest air in the house through the coldest air on the property, and the gap is at its widest on the coldest night of the year — the night the far bedroom gets judged. Where the heat comes off a furnace, the supply air is around 120°F to 140°F and the space the run crosses is below freezing. A joint leaks the same amount in October as it does in January; what changes is how much heat leaves with it.

Where the runs sit inside a heated basement, a leaking joint gives most of its heat back to the house. The same joint in an unheated attic or a vented crawl space sends it outdoors instead, and it does that every hour of a season this long. Which of the two a house has decides whether a duct leak costs comfort or costs money, and where the runs go is worth saying on the phone.

The July dew point here sits below the temperature of the air inside a supply run, so a badly insulated attic run warms what it carries instead of sweating on it. What a leaking return does instead is carry dust. It draws attic or crawl space air into the system, and the filter only catches what came through it, which is why a house that is kept clean can still have a black filter and gray register faces. Dry air also makes the measurement cleaner: with almost nothing going into moisture, the temperature split across the coil reads as airflow and little else, and one reading separates a duct problem from an equipment problem.

On a heat pump, a duct problem reaches the electric bill before it reaches anyone's comfort: a run that cannot move enough air leaves the house behind the thermostat setting, and the thermostat answers by calling in the resistance strips. The strips warm the house and hide the duct problem in the same motion, which is why nothing looks broken.

A clean filter is the one thing on the shelf that changes airflow at all, and where it has not been changed since the last season it is worth doing before the phone comes out. What it cannot do is reach any further than itself: a filter gives back the air the system already had, and it does nothing for a run that is crushed, pulled off its collar or leaking into a crawl space, and nothing for a return that was always too small. The version that backfires is the upgrade: a dense one-inch filter sold for allergens takes more pressure than the slot was built for, and a system already short of air gets shorter. A room that stays wrong with a clean filter in was never a filter problem.

Duct tape is named after the job it fails at. The cloth-backed roll dries out on a warm duct and releases, usually within a couple of years, and the joint is open again with nothing to show for the afternoon. What holds is mastic brushed on, or foil tape carrying a UL 181 marking on the roll — and both need the joint clean and dry, which is what a crawl space makes difficult.

Shutting the registers in unused rooms feels like it should send the air somewhere useful. Air does not redistribute itself, it raises the pressure in the duct, and higher pressure pushes more of it out through every leak the system already has. Trimming one register that overshoots is a different matter, and it is what a damper is for — the difference is one adjustment against half the house closed off. A booster fan at a register does anything at all only where the run behind it is sound, and on a run that is leaking or pulled off its collar it changes nothing.