Our Heating Bill Doubled and Every Window Tested Fine

The Smoke Test

We needed to see the air move.

I picked up a $12 pack of incense sticks at Target—the kind that come in a bundle of forty or fifty, usually sold in the candle aisle or near the essential oils. You could also use a smoke pen from Home Depot (around $30 in the electrical section, meant for HVAC diagnostics), but incense works just as well for this and you probably already know where to find it. Some people use a smoldering piece of paper or a cigarette lighter blown out mid-flame, but incense gives you a longer, steadier smoke trail without needing to relight every thirty seconds.

The method is dead simple. Light the incense, let it smolder for a few seconds until you’ve got a visible ribbon of smoke rising, then walk slowly through the room while holding it at arm’s length. You’re watching to see if the smoke drifts in a particular direction instead of rising straight up.

We started in the upstairs hallway, about six feet from the attic hatch. I stood still, holding the incense stick level with my shoulder.

Within thirty seconds, the thin trail of smoke began drifting toward the ceiling. Not randomly—toward the hatch. Not in a wild swirl like you’d get near a return air vent, but in a slow, deliberate lean. As I stepped closer, the smoke didn’t just drift. It bent at a sharper angle, then streamed upward in a steady current, like someone had opened an exhaust vent directly overhead. When I held the incense six inches below the edge of the hatch frame, the smoke column shot straight up and disappeared into the crack.

That column of smoke was our heating bill, visualized. Two months of expensive natural gas, turned into warm air, rising through our house and pouring into a freezing attic at a rate we couldn’t even feel with our hands.

I ran the same test at every other ceiling penetration—the light fixture boxes in the bedrooms, the bathroom exhaust fan housing—and found minor leaks around a couple of the recessed can lights, but nothing like the hatch. That was the main event.

But seeing the leak wasn’t the same as fixing it. And a small gap around a hatch—a quarter-inch of space on four sides—could that really make a hundred-dollar-a-month difference? We were about to find out.