Where your ducts run changes everything
In most homes, a lot of the ductwork runs through conditioned space — inside interior walls and ceilings. Those ducts are surrounded by air that’s already comfortable, so they lose very little on the trip to your rooms. But when ducts run through an attic that hits 130°F in July or a crawlspace near freezing in January, it’s a completely different story — those duct walls are fighting an extreme temperature the entire way.
Sealing and insulating fix two different problems
Sealing closes the gaps so air doesn’t leak out of the ducts. Insulating stops energy from passing straight through the duct walls. Here’s the part most homeowners never hear: even a perfectly sealed duct with no insulation still bleeds energy by conduction. In a blistering attic, the cool air you paid for soaks up heat through the bare metal and arrives lukewarm — no leak required. Sealing can’t touch that. Only insulation can.
What an uninsulated attic duct really costs you
On one Salt Lake Valley home, we measured the air coming off the AC coil, then measured it again at the register at the end of a long, uninsulated attic run. It arrived 14°F warmer — the attic had heated the air right back up before it ever reached the room. That family was paying to cool air the attic was quietly undoing. No amount of inside-the-duct sealing fixes that; insulation does.
Signs your ducts need insulation
- An upstairs or far room that never keeps up in summer
- The room farthest from the unit is always the worst
- High summer or winter bills on a system that otherwise tests fine
- Ducts that sweat in summer, or feel hot or cold to the touch in the attic
- Bare metal, or thin, crushed, or missing duct wrap
How we insulate attic & crawlspace ducts
First we seal the duct joints from the outside by hand, right where the leaks are. Then we wrap the runs in proper R-value insulation, seal the boots where the ducts meet your ceilings, and make sure the space itself isn’t making things worse. It’s straightforward work that usually costs a fraction of an aerosol interior-sealing job — and in an unconditioned space, it does far more for your comfort.
Why interior duct sealing won’t fix this
This is exactly why we steer most homeowners away from pricey interior duct sealing like Aeroseal: it can close leaks, but it does nothing about energy soaking through bare duct walls in a 130° attic. If someone is quoting you thousands to spray-seal the inside of your ducts, read this first: Is Aeroseal worth it? → And if your real problem is a hot upstairs, start here: Why is my upstairs so hot? →
Find out if your ducts are costing you
We’ll measure your real airflow, check where your ducts run, and tell you straight what’s worth doing — no pressure, no sales pitch.