The Call That Starts With "Our AC Bill Doubled and We Don't Know Why"
On a typical visit for this, a technician walks into the garage and sees daylight around the bottom seal before even touching the door. Maybe there's a gap at one corner where the weatherstripping has curled up and hardened in the heat, or the panels have swollen slightly from humidity and no longer sit flush against the frame. The homeowner usually says the same thing: the AC runs constantly, the room above or next to the garage feels warmer than the rest of the house, and nobody can agree on why.
Why a Garage Door Affects Your Whole House
If your garage is attached, it's not a separate building — it shares at least one wall, and often a ceiling, with living space. Air from the garage moves into the house through that shared wall, through vents, through gaps around the door into the mudroom or laundry room, even through electrical outlets. In Polk County's climate, that garage air is usually hot and loaded with moisture, especially during our long cooling season and the afternoon downpours that roll through in summer and fall.
When the garage door seals poorly, here's what happens: outside heat and humidity pour into the garage, the garage heats up well beyond the temperature inside your house, and that heat pushes into the adjacent rooms. Your AC then has to work harder to pull that extra heat load back out — not just once, but continuously, all day, every day the gap exists.
What Actually Lets the Heat In
- Worn bottom seal (astragal) — the rubber strip along the bottom of the door hardens and cracks from UV exposure and heat, leaving visible gaps.
- Perimeter weatherstripping — the strips along the sides and top wear out or pull loose, especially on older doors.
- Warped or swollen panels — humidity swings common in this area can cause wood or composite panels to swell, which throws off how the door sits against the frame.
- Gaps from an off-track or misaligned door — if the door isn't running true on its tracks, it may not close evenly, leaving a sliver of a gap along one side.
- Uninsulated door panels — even with no gaps at all, a single-layer steel or wood door with no insulation acts like a radiator, passing heat straight through to the garage air.
How to Tell If This Is Actually Your Problem
Before you settle the argument one way or the other, check a few things yourself:
- Close the door at night and shine a flashlight around the interior edges — any light leaking through from outside means there's a gap.
- Feel along the bottom seal and sides for stiff, cracked, or compressed rubber.
- Put your hand on the wall shared between the garage and the house on a hot afternoon — if it's noticeably warm, heat is transferring through.
- Check if the room next to or above the garage runs warmer than the rest of the house on the thermostat's zone sensor, if you have one.
What Fixes It
Replacing the bottom seal and perimeter weatherstripping is usually the first and cheapest step, often in the range of what a basic tune-up visit costs. If the door itself is older, uninsulated, or warped from years of humidity exposure, replacing it with an insulated door is a bigger investment but solves the problem at the source and also helps with sound and wind resistance during storm season. If the door isn't sealing because it's off track or the springs are worn and the door isn't closing fully square, that's a mechanical issue, not just a weatherstripping issue, and needs to be corrected first — new seals won't help a door that isn't hanging straight.
When to Call Kathleen Garage Door Experts
If you've checked for light gaps, felt the warm wall, and you're still not sure whether it's the seals, the panels, or the door's alignment, that's exactly the kind of call we take every week. We'll inspect the weatherstripping, check whether the door is tracking true, and let you know honestly whether a seal replacement will fix it or whether it's time to talk about Garage Door Installation & Replacement with an insulated model. We also handle Off Track Door Repair when misalignment is part of the problem.
If your garage door is quietly costing you money every time the AC kicks on, give Kathleen Garage Door Experts a call — we serve Kathleen, Lakeland, Mulberry, Plant City, Bartow, Winter Haven, Auburndale, and Polk City, and we can usually get someone out fast.