Why Your Energy Bills Are High (And the Furnace Probably Isn’t 
the Problem)
The call usually goes the same way. The homeowner is convinced the furnace is failing, or the AC is shot, or somehow the utility company is skimming. We show up, check the equipment, and it’s fine. Then someone opens the attic hatch and the real story starts.
Leaky air ducts. Half the joints barely connected. Cloth tape dried out and is curling at the edges. Air is blasting into the attic like the house is trying to heat the outdoors.
It’s one of the most common things we find, and one of the most quietly expensive.
What Leaky Air Ducts Actually Do to a Home
Your HVAC system is built around a closed loop. Conditioned air moves through ducts, reaches the rooms, and the temperature evens out. That’s the whole idea.
When ducts leak, the loop breaks. Air escapes into attics, crawlspaces, and wall cavities, places that do nothing for your comfort. The system keeps running, trying to compensate, and the air that was supposed to cool your bedroom ends up heating the insulation instead.
I worked on a house where nearly 30 percent of the airflow was dumping straight into the attic. The homeowner couldn’t figure out why the AC ran all day in July. It ran all day because the house was only receiving about two-thirds of the cooling that the system was actually producing.
That’s not an equipment problem. That’s a delivery problem.
Why Newark Homes Have This More Than You’d Expect
Older housing stock is the short answer. Many homes in Newark were built when duct sealing wasn’t given much thought. Installers used cloth tape, which works fine at first, then dries out, cracks, and stops adhering after 15 or 20 years.
Renovations make it worse. Somebody finishes a basement, reroutes a duct run, reconnects it quickly, and moves on. I’ve seen duct connections that looked like they were held together by friction and optimism. Not careless work, necessarily. Just rushed.
The result, either way, is leaky air ducts running through unconditioned spaces, bleeding off airflow before it ever reaches a vent.
The Bill Creeps Up Before Anyone Notices
This is the part that catches people off guard. Leaky air ducts don’t announce themselves. The system still runs. Rooms still get some air. Everything seems functional until you look at twelve months of utility bills laid out side by side.
Because what’s actually happening is longer run cycles. The system can’t hit the target temperature as quickly, so the blower runs more, the compressor works harder, the gas burns longer. Every month, a little more than it should. Then one winter, the bill feels genuinely wrong and someone finally calls.
Homes with significant duct leakage can lose 20 to 35 percent of conditioned airflow before it reaches the living space. That’s not a rounding error. That’s a substantial portion of every dollar spent heating or cooling the house.
Comfort Complaints Usually Come First
Most people don’t pull out their energy bills until they’re already frustrated about something else usually a room that’s always too hot or too cold.
One bedroom freezes. Another stays warm regardless of the thermostat. The hallway’s fine. The pattern seems random, but it usually isn’t. If a branch duct is leaking before it reaches a specific room, that room gets weak airflow. Simple as that. The homeowner adjusts the thermostat, the system runs longer trying to compensate, and nobody connects it to leaky air ducts until someone actually looks.
Pressure Imbalances: The Unexpected Side Effect
Here’s something most people don’t realize until it’s explained to them.
When supply ducts leak air into unconditioned spaces, the house develops negative pressure. Air has to come from somewhere to replace what’s being lost so it gets pulled in through gaps around windows, door frames, and any other crack it can find.
In winter, that means cold drafts from places you’d never expect. In summer, humid outdoor air is pulled in, and the AC works harder to handle the extra moisture load. We once found a return duct leak that was actively pulling attic air dust, insulation particles, all of it directly into the system before it reached the living space. Bad for air quality, bad for equipment, and invisible unless you actually test for it.
What the Fix Usually Looks Like
Most duct repairs are not dramatic. We seal joints with mastic or proper foil HVAC tape, reconnect any separated sections, and insulate runs that pass through unconditioned spaces. If something is crushed or torn badly enough, we replace that section. Then we can apply an aerosol duct sealant to ensure your ducts are 100% sealed.
A couple of years ago we had a call from a Newark homeowner who assumed they needed a new AC unit. Bills had climbed every summer for three years. The equipment was in perfectly good shape.
The supply trunk in the attic had separated at a joint, and every time the system ran, conditioned air was blasting straight into the attic. Two hours of work, joints sealed and secured. Their next summer bill dropped noticeably.
FAQ
How much can leaky air ducts actually affect an energy bill?
In homes with significant leakage, 20 to 35 percent of conditioned air can escape before reaching the living space. That lost air forces longer run cycles, which compounds into noticeably higher bills over a full heating or cooling season.
What are the early warning signs?
Rising bills without a clear cause, rooms that don’t match the thermostat, weak airflow at specific vents, and dust that builds up faster than it should. None of these confirm leaky air ducts on their own, but together they’re a reliable signal.
Does duct leakage affect indoor air quality?
It can. Return duct leaks are the bigger concern if the system is pulling air from an attic or crawlspace, it’s also pulling in whatever’s up there. Dust, insulation fibers, and mold spores if moisture is present.
Is duct sealing worth it compared to replacing equipment?
Almost always. New equipment pushing air through leaky ducts still loses a significant portion of its output. Sealing first means any equipment new or old actually performs the way it’s supposed to.
How do technicians find the leaks?
Sometimes it’s obvious. Open the attic and you can feel air escaping at a joint. For less obvious cases, duct pressure testing pinpoints where and how much air is being lost before anyone starts guessing.
If the equipment checks out but the bills don’t make sense, look at where the air is going before it reaches the room. Leaky air ducts are easy to overlook because the system keeps running it just runs inefficiently and expensively, for years before anyone figures out why.
Fix the delivery system first. Then the equipment finally has a fair shot at doing its job.
