Where do ducts leak in a typical Iowa house?
Leaks concentrate at joints and transitions, and they matter most where ducts run through unconditioned space — an attic, a vented crawlspace, or an unheated garage. Air lost there is lost entirely, and worse, return-side leaks actively pull dusty, humid, or cold air into the system.
The usual leak points
- Joints between duct sections that were never sealed, only taped
- The plenum connection where the duct meets the furnace cabinet
- Boot connections where the duct meets a floor or ceiling register
- Panned joist returns in older Des Moines homes, which leak into wall cavities
- Disconnected flex duct in an attic or crawlspace — surprisingly common
Why is one room always hotter or colder?
Uneven temperatures are usually a distribution problem rather than a capacity problem. The room at the end of the longest duct run receives the least air; a bonus room over a garage loses heat on five surfaces instead of three; a second floor fights the fact that hot air rises.
Before recommending equipment, we look at whether that room is actually getting the airflow its load requires. Adding a return, resizing a branch, correcting a crushed flex run, or balancing dampers frequently solves what a homeowner assumed needed a whole new system.
What does duct sealing involve?
Accessible ducts are sealed with mastic — a brushed-on compound that stays flexible — or with foil-backed tape rated for the job. Standard cloth duct tape is the one thing not to use; it dries out and falls off within a few years, which is why we find so much of it hanging loose in basements.
Sealing accessible runs in a basement or crawlspace is straightforward and delivers immediate, measurable improvement. Ducts buried in finished walls are harder to reach, and in those cases the honest answer is that we seal what we can access and address the rest with balancing.
Is my return air undersized?
Very often, especially in homes built before the 1990s. Supply ducts get the attention, but a system can only push out as much air as it can pull back. Undersized returns show up as whistling registers, doors that swing on their own, rooms that go stale with the door closed, and a blower straining against pressure it was never designed for.
A quick self-check: close an interior door with the system running. If it slams or you hear air rushing under it, that room has supply air with no path back. Undercutting the door, adding a transfer grille, or running a dedicated return fixes it.
Frequently asked questions
How much can duct sealing save?
Homes with significant leakage in unconditioned space often see meaningful reductions in heating and cooling costs, and just as importantly, rooms that never held temperature start to. The savings depend entirely on how leaky the system was and where the ducts run, so we would rather assess yours than quote a national average at you.
Should I close vents in unused rooms?
Generally no. Closing vents raises static pressure across the whole system, which strains the blower, can freeze an evaporator coil in cooling, and pushes more air out through existing leaks. It rarely saves what people expect. Zoning is the engineered way to condition parts of a house differently.
Do I need new ductwork with a new furnace?
Not usually, but the ducts should be evaluated as part of the job. A modern variable-speed system is more sensitive to duct restriction than an old single-stage unit, so the existing ductwork needs to be capable of the airflow the new equipment expects. We check that before install rather than discovering it after.
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