Standfirst: Drafty windows and doors waste heat all winter, and the cost shows up on every heating bill. The U.S. Department of Energy says windows are responsible for 25–30% of residential heating and cooling energy use — and sealing the leaks around them is one of the cheapest ways to cut that waste.
Why windows and doors leak heat
The big number: The U.S. Department of Energy says windows are responsible for 25–30% of residential heating and cooling energy use, because air leaks through gaps and heat travels easily through old, inefficient windows.
How much energy is wasted: Air leakage and poorly installed insulation can waste 20% or more of the energy used to heat or cool a home. That means a fifth or more of the heat you pay for can simply leave the house, through gaps around windows and doors and through places where insulation was poorly installed.
What sealing can save: ENERGY STAR says sealing air leaks and adding insulation can save up to 10% on annual energy bills. The EPA estimates homeowners can save an average of 15% on heating and cooling costs by air sealing their homes and adding insulation to attics, floors above crawl spaces and accessible basement rim joists. Those are averages, not promises for any one home.
Where to start: Before you buy anything, find where the air is getting in. The fixes below are cheap, and most can be done in a weekend. For a wider winter checklist, see our guide on how to prepare your home for freezing weather.
Find the drafts first
The hand test: On a windy day, hold your hand near window and door edges, and feel for cold air coming in. Move your hand slowly along the edge, and pay attention to the corners, where gaps are most common. A cold spot that you can feel with your hand is a draft worth sealing.
The tissue test: Watch a thin tissue flutter near window and door edges on a windy day. Hold the tissue close to the edge, and if it moves, air is getting through. It shows small leaks that your hand might miss.
What to look for: Check for worn caulk, cracked weatherstripping, and doors that do not close tightly. Worn caulk looks cracked, dried out, or pulled away from the frame. Cracked weatherstripping looks flat, torn, or hard. A door that does not close tightly will let light, air, or sound through, and it will feel loose when you push on it.
Check every window and door: Do the hand test and the tissue test on every window and every exterior door, not just the ones that feel cold. Make a short list as you go: which windows have worn caulk, which doors have cracked weatherstripping, and which doors do not close tightly. That list is your plan for the weekend.
Caulk vs weatherstripping: which goes where
The DOE rule of thumb: Caulk is for cracks between parts that do not move, and weatherstripping is for parts that move. That one rule tells you which material to buy for each gap.
Caulk: Use caulk for cracks between parts that do not move, such as window and door frames, and where pipes and wires pass through walls. The frame does not move, so a fixed seal works. Caulk fills the crack and stays in place, and it stops air from passing through the gap between the frame and the wall.
Weatherstripping: Use weatherstripping for parts that move, such as doors and operable windows. A door opens and closes, and an operable window opens and closes, so the seal has to flex. Weatherstripping is made to press against the moving part when it closes, and to spring back when it opens. If you used caulk on a moving part, it would crack the first time the door or window opened.
How to choose: Start with your list from the draft test. For each gap, ask one question: does this part move? If the answer is no, use caulk. If the answer is yes, and the part is a door or an operable window, use weatherstripping. Replace worn caulk where it is cracked or pulled away, and replace cracked weatherstripping where it is flat or torn.
Cheap fixes that work this weekend
Add a door sweep: Add a door sweep to the bottom of exterior doors. The bottom of a door is one of the most common places for a draft, because the gap under the door is easy to miss and hard to seal with weatherstripping alone. A door sweep closes that gap, and it moves with the door.
Add storm windows and storm doors: Add storm windows and/or storm doors. A storm window adds a second layer over an old window, and a storm door adds a second layer over an exterior door. The extra layer slows heat loss, and it also cuts drafts. Storm windows and storm doors are a bigger job than caulk, but they are still far cheaper than replacing a window or a door.
Install insulating shades: Install tight-fitting insulating window shades. The key word is tight-fitting: a shade that fits tightly against the window frame traps air and slows heat loss. A loose shade does far less, because warm air can move around the edges.
Use the sun: Open curtains on sunny south-facing windows during the day to let in warmth. The sun is free heat, and south-facing windows get the most of it during the day. Open the curtains in the morning, and let the sun warm the room. Close them at night, when the window would lose heat instead.
Add window film: Add window film. Window film is a thin layer that sticks to the glass, and it helps slow heat loss through old, inefficient windows. It is a cheap fix, and it works best on windows that are old and inefficient, where heat travels easily through the glass.
Start with the seals: Start with caulk and weatherstripping, because those are the cheapest fixes and they seal the gaps directly. Then add a door sweep, then window film or insulating shades. While you are working outside, it is also a good time to clean your gutters before winter.
Bigger upgrades worth planning
Storm windows and doors, done well: Storm windows and storm doors are also a bigger upgrade worth planning if you have many old windows. Plan them one window at a time, starting with the rooms that feel coldest.
Insulation where it counts: The EPA estimates homeowners can save an average of 15% on heating and cooling costs by air sealing their homes and adding insulation to attics, floors above crawl spaces and accessible basement rim joists. Air sealing stops the leaks, and insulation slows the heat that travels through walls, floors and ceilings.
The attic first: Attics are among the top places a home loses heat, so sealing attic leaks plus adding insulation helps the whole house. If you plan one bigger upgrade, start with the attic.
Old, inefficient windows: Heat travels easily through old, inefficient windows, and that is why windows are responsible for 25–30% of residential heating and cooling energy use. Replacing a window is a bigger job and a bigger cost, so plan it, and start with the worst windows first.
Heat safely: If you use an extra heater in a cold room, read our guide on how to use a space heater safely in winter first.
When to call a professional
Doors that will not close tightly: If a door does not close tightly even after new weatherstripping and a door sweep, the frame may be out of shape. A professional can tell whether the door needs to be adjusted, or whether the frame needs repair.
Gaps you cannot reach: Some gaps are in places you cannot reach safely, such as high windows, or where pipes and wires pass through walls in a tight space. A professional can seal those gaps safely, and can check for leaks you might miss.
Insulation work: Adding insulation to attics, floors above crawl spaces and accessible basement rim joists is often best done by a professional, who can check how much insulation is already there.
A home that still feels cold: If you have sealed the drafts and used the fixes above, and the home still feels cold, call a professional. There may be leaks in the attic or in other places you have not checked.
Help if money is tight
The Weatherization Assistance Program: The U.S. Department of Energy’s Weatherization Assistance Program helps income-qualified households make energy-efficiency upgrades at no cost. If you qualify, the program can help with the upgrades that cut heating bills, including air sealing and insulation.
What it covers: The program helps income-qualified households make energy-efficiency upgrades at no cost. That means the work is done without a bill to the household, for households that qualify.
How to start: Check whether your household qualifies, and apply through the program. The first step is to find out if you meet the income rules.
Why it matters: First freezes are arriving across much of the US, and home heating is a top winter search topic. Sealing windows and doors is cheap, and it cuts waste. For households that cannot pay for it, the Weatherization Assistance Program is the help that makes it possible. General information only; no product endorsement and no brand recommendations.
Sources: U.S. Dept. of Energy weatherization guidance, ENERGY STAR Seal and Insulate, NYSERDA/MyEnergy air sealing and insulation. By the Daily Trend USA Newsroom.
