Stand next to your front door on a breezy day and hold the back of your hand an inch from the frame. If you feel even the faintest stir of air, you’ve found a gap that’s been costing you money since you moved in. No thermostat setting fixes it, because the air you pay to heat or cool is leaving the building before it ever does its job.

One gap is rarely alone. According to the U.S. Environmental Protection Agency’s ENERGY STAR program, adding up every leak, hole, and gap in a typical home’s envelope—the walls, windows, doors, and floors that separate inside from outside—is the equivalent of leaving a window wide open. This isn’t a symptom of a defective home or a bad landlord. It’s just what happens when a building goes years without anyone checking and repairing the seams.

Energy is the pathway to sustainability we’re talking about this week: the set of practices that help you use less energy overall and shift whatever you do use toward cleaner sources. Sealing your home’s envelope is an easy step that applies to just about everyone—it doesn’t matter whether you rent or own, or how you heat and cool your home. If you have windows, doors, and outlets on an exterior wall, you have this problem, and you can work on it this week.

Where the Gaps Actually Are

Windows and doors are the obvious suspects, but the U.S. Department of Energy’s guide to air sealing also lists electrical outlets and switch plates, and the spots where pipes, cables, and vents pass through exterior walls, as common leak points—smaller individually, numerous collectively. You can find them without any special equipment. Close a window on a piece of paper: if you can pull the paper out with no resistance, the window isn’t sealing properly. At night, with the lights off, have someone hold a flashlight around the outside edge of a closed exterior door while you watch from inside; any light you see is air finding the same path. Hold your hand near outlet and switch covers on outside walls on a cold or windy day—a draft there means the box behind it was never sealed to the wall.

Fixing leaks usually requires one of two materials. Caulk handles anything that doesn’t move: the seam where window trim meets the wall, gaps around pipe and cable penetrations, cracks in baseboards along an exterior wall. Weatherstripping handles anything that does move: felt, foam tape, or a V-shaped vinyl strip along a window sash or door frame, plus a door sweep for the gap under an exterior door. Foam gaskets made specifically for outlet and switch plates cost only a few dollars for a multipack and take seconds to install—no rewiring, just removing the cover plate, inserting the gasket, and putting the plate back.

ENERGY STAR estimates that sealing air leaks and adding insulation together can save an average of 10 percent on a home’s annual energy bill nationally, and up to 20 percent on heating and cooling specifically. Sealing is the half of that project almost anyone can do without an attic, an insulation contractor, or a landlord’s approval; insulation is the bigger job for whoever controls the building. Since electricity on the North American grid still mostly comes from burning fossil fuels, the less energy any of us wastes, the less air pollution gets generated to make up for it. That’s a fitting thought heading into tomorrow, September 7, the United Nations’ International Day of Clean Air for Blue Skies.

A Bonus Check, If Ducts Apply to You

About two-thirds of U.S. households use a central, ducted system as their main heating and cooling equipment, according to the U.S. Energy Information Administration. If your ducts run entirely within your living space, then leaks in them are fine. But if your ducts pass through a hot attic, a vented crawlspace, or an unheated garage, some of the air moving through that ductwork may escape through leaks and poorly sealed joints before it ever reaches a vent, reducing your system’s efficiency by as much as 20 percent. Look for dirty, darkened insulation around duct connections; that discoloration marks where air has been filtering through for years, and seal what you find with mastic sealant or metal foil tape. Don’t use plastic or fabric duct tape, which doesn’t withstand the heat and dust in a working duct system.

Your One Step This Week

Pick the exterior wall of your home with the most windows, the front door, or wherever you already suspect a draft and check for leaks using the paper, flashlight, and hand tests described above. Seal what you find: caulk for anything fixed, weatherstripping for anything that moves, a door sweep for the gap under the door, foam gaskets for the outlets. None of that requires a permit, a contractor, or owning the building.

The cost of a caulk gun and a few dollars of weatherstripping is an investment that keeps paying you back every season your heating and cooling runs. For a deeper dive into window-specific upgrades, a fuller attic and basement sealing project if you have access to one, or a complete weatherization checklist, explore Sustainable Practices: Your Handbook for Effective Action and the related articles below.

Note: How does Sustainable Practice use AI? We use AI for research so that our materials are more trustworthy, not less. In no case do we publish anything we have not personally reviewed, edited, and written to our standards and specifications. You can trust our human use of current resources, our 30+ years of lived experience in the sustainability field, and our judgment of the science we rely on.

Fred Horch and Peggy Siegle, Principals, Sustainable Practice

References and Resources

  • Why Seal and Insulate? — U.S. EPA ENERGY STAR (a typical home’s envelope leaks are equivalent to a window left open year-round; 9 of 10 U.S. homes are under-insulated; up to 10 percent annual energy bill savings from sealing and insulating together)

  • Sealing Behind Window & Door Trim Project — U.S. EPA ENERGY STAR (paper test and other simple ways to check a window or door for leaks)

  • Consumer Guide to Air Sealing the Home — U.S. Department of Energy (common DIY-accessible leak points including door frames and wall penetrations for pipes, vents, and wiring; caulk and weatherstripping materials)

  • Benefits of Duct Sealing — U.S. EPA ENERGY STAR (up to 20 percent efficiency loss from leaky ducts; the general link between home energy use and air pollution from power generation)

  • Duct Sealing — U.S. EPA ENERGY STAR (20 to 30 percent of duct-system air typically lost to leaks; recommends mastic sealant or metal tape over fabric duct tape)

  • International Day of Clean Air for Blue Skies — United Nations (designates September 7 as a global observance on air quality and air pollution)

Related One Step Articles

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Sustainable Practice empowers you to protect our planet in practical ways. Share this article with a renter who thinks there’s nothing they can do about their energy bill—a caulk gun and a few dollars of weatherstripping say otherwise.