The Mistake: Blaming the Thermostat First
Here's what usually happens. The electric bill comes in higher than expected, and the first move is to argue about the thermostat setting or blame the AC unit for running too much. That's the tempting answer because it feels fixable in thirty seconds — bump the temperature, change the filter, call it solved. Nobody wants to go stand in the garage and inspect a door.
But if your garage is attached to the house — which most homes in this area are — the garage door is basically a fourth exterior wall for your living space. If it's not sealing properly, you're paying to heat or cool the outdoors on the other side of a thin sheet of metal, and that air exchange works its way into the house whether anyone touches the thermostat or not.
Why an Attached Garage Behaves Like Part of the House
A detached garage doesn't matter much for your energy bill. An attached one does, for a simple reason: it usually shares at least one wall with conditioned living space, and often there's a room directly above it. When the garage swings from near-100°F in the afternoon sun to much cooler overnight, that temperature swing pushes through the shared wall and floor into the rooms next to it. Your AC or heater then works harder to compensate for a room that's fighting a losing battle against an uninsulated garage next door.
The entry door between the garage and the house gets blamed sometimes, and it's worth checking too, but the much bigger opening is the garage door itself — it's the largest moving panel in most homes, and it only needs small gaps to leak a lot of air.
Where the Gaps Actually Come From
This isn't about one dramatic hole. It's usually several small failures stacking up:
- Bottom seal (astragal): The rubber strip along the floor dries out, cracks, or gets compressed flat after years of use. Sun exposure and heat speed this up.
- Side and top weatherstripping: Same story — vinyl or rubber that's brittle, torn, or pulling away from the track.
- Panel warping: Metal doors that take direct afternoon sun for years can bow slightly, which throws off the seal along the whole edge, not just one spot.
- Loose or worn-out rollers and track misalignment: If the door isn't closing square in the frame, no amount of new weatherstripping fixes the gap.
Dry, hot stretches without rain accelerate all of this — the same dry season that kicks up dust and occasional wildfire smoke is hard on rubber and vinyl seals. Then winter rain shows up and finds every gap the summer sun created, which is often when people finally notice water or drafts and trace it back.
How to Check It Yourself Tonight
- Flashlight test: At night, have one person stand inside the garage with the door closed and the lights off. Have the other person shine a flashlight around the entire perimeter from outside. Any light visible from inside means air is getting through there too.
- Paper test: Close the door on a piece of paper at a few points along the bottom and sides. If it slides out easily, the seal isn't gripping.
- Hand check: On a hot or windy day, run your hand along the door's edges. Moving air you can feel is moving air you're paying for.
- Look at the rubber: Cracked, flattened, or shrunken seals are a visual giveaway — you don't need a tool to see when weatherstripping is done.
The Trade-Offs, Honestly
Replacing worn weatherstripping and a bottom seal is inexpensive and often the right first move — it solves the obvious air leaks without touching the door itself. But if the door is an older, uninsulated single-layer panel, new seals only go so far; an insulated door (ranges widely by size and material, typically a few hundred dollars more than a non-insulated equivalent) does more to buffer the temperature swing in the garage itself, which matters most if there's a bedroom or living space directly above it. Sealing is the cheap fix; insulating the door is the longer-term one.
When to Call Rialto Door & Opener
If the flashlight or paper test shows gaps, or the door looks warped and won't seal evenly no matter how new the weatherstripping is, that's worth a visit. Our Garage Door Maintenance service covers weatherstripping, bottom seal, and roller/track adjustments so the door actually closes square again. If the panels themselves are sun-warped or the door is old enough that sealing won't solve it, we'll walk you through Garage Door Installation options, including insulated doors suited to hot inland summers and the dry-to-rainy swing we get every year.
If you're going back and forth about where the energy is going, give Rialto Door & Opener a call — we serve Rialto, CA and nearby communities, and we can tell you in one visit whether it's the door or something else.