A step-by-step DIY guide to sealing drafty doors and windows in your Los Angeles home. Find leaks, pick the right weatherstripping or caulk, add a door sweep, and cut wasted heating and cooling.
To weatherproof doors and windows, find the drafts, then seal them: caulk the gaps that don't move, weatherstrip the parts that do, and add a door sweep at the bottom. That's the whole job. It's a low-cost afternoon project, and it pays you back every month.
The reason it matters is simple. Air sneaks in and out around old seals, and your AC or heater works harder to keep up. Sealing those leaks makes a real dent. The U.S. Department of Energy estimates the potential savings from reducing drafts in a home may range from 10% to 20% per year (Energy.gov, Detecting Air Leaks).
In Los Angeles, that cuts both ways. Sealed doors and windows keep summer heat outside so your AC isn't fighting a losing battle. Come winter, the same seals block cold drafts and wind-driven rain. This is one of the easiest wins on any seasonal home maintenance checklist.
Key Takeaways
- Reducing drafts around doors and windows may save 10% to 20% a year on energy, per the U.S. Department of Energy.
- Use caulk for stationary gaps (window frames, trim) and weatherstripping for moving parts (doors, operable windows).
- Find leaks first with a simple hand test or a smoke test from an incense stick before you buy any materials.
- A door sweep or threshold seal stops the draft under an exterior door, a common LA culprit.
- Air sealing plus insulation saves an average of 15% on heating and cooling costs, per ENERGY STAR.
Why Drafty Doors and Windows Cost You Money
Every gap around a door or window is a tiny hole your conditioned air escapes through. Multiply that by a dozen openings and the loss adds up fast. In summer, hot LA air leaks in and your AC never gets a break. In winter, warm air leaks out.
Sealing isn't just about drafts, either. It works alongside insulation. ENERGY STAR reports homeowners save an average of 15% on heating and cooling costs (about 11% on total energy) by air sealing their homes and adding insulation (ENERGY STAR). Air sealing is the cheap half of that equation, and it's the part you can do yourself.
What You'll Need
Gather your supplies before you start. Most of this comes from one hardware store trip.
- Weatherstripping (V-strip/tension seal, foam tape, or vinyl)
- Exterior-grade caulk and a caulk gun
- A door sweep and, if needed, a threshold seal
- Utility knife, scissors, and a tape measure
- A clean rag and rubbing alcohol to prep surfaces
- Optional: window insulation film kit for winter
Time: 2 to 4 hours. Difficulty: Beginner. Cost: Usually under $75 for a few doors and windows.
Step 1: Find the Drafts
By the end of this step, you'll know exactly where your air is escaping. Don't skip it. Sealing the wrong spots wastes time and materials.
Start with a visual check. Look for daylight around closed doors and gaps where trim meets the wall. Then use these DOE-recommended tests:
- Hand test: On a windy day, run a slightly damp hand around the edges of doors and windows. A draft feels cool.
- Smoke test: Light an incense stick and pass it slowly along the edges. Where the smoke wavers or gets pulled sideways, there's a leak.
- Dollar-bill test: Close a door or window on a dollar bill. If it slides out without dragging, the seal is too loose.
Mark each leak with painter's tape so you can find it again.
Step 2: Caulk the Gaps That Don't Move
By the end of this step, the stationary cracks around your frames will be sealed. Caulk is for parts that stay put, like the joint where a window frame meets the wall.
The Department of Energy draws the line clearly: use caulk for cracks and openings between stationary components, and weatherstripping for parts that move (Energy.gov, Weatherstripping).
- Clean the gap and let it dry. Caulk won't stick to dust or damp surfaces.
- Cut the tube tip at a 45-degree angle for a bead that matches the gap.
- Run a steady, continuous bead along the crack.
- Smooth it with a wet fingertip within a minute or two.
Use exterior-grade caulk on outside-facing gaps. Sealing where trim, siding, and frames meet is a core part of exterior home maintenance that keeps water out too.
Step 3: Weatherstrip the Parts That Move
By the end of this step, your doors and operable windows will close against a fresh seal. Weatherstripping handles the moving pieces caulk can't.
Pick a material for the job. DOE notes felt and foam tapes are cheap and easy but wear out faster, vinyl holds up well and resists moisture, and metal strips last for years (Energy.gov, Weatherstripping).
- Measure each side of the door or window opening.
- Cut the strip to length with scissors or a utility knife.
- Wipe the surface with alcohol so the adhesive grips.
- Press the strip firmly into the jamb where the door or sash contacts it.
- Open and close a few times to check for smooth contact with no gaps.
Choose a type that can take the friction of that spot. A door edge and a sliding window sash see very different wear.
Step 4: Add a Door Sweep or Threshold Seal
By the end of this step, the gap under your exterior door will be closed. That gap is often the biggest single leak in a house, and no amount of side weatherstripping fixes it.
A door sweep is the classic door draft stopper. It mounts to the bottom of the door and brushes the threshold.
- Measure the door width and cut the sweep to fit.
- Hold it against the door bottom so it just touches the threshold.
- Mark the screw holes, then screw it on.
- Test the swing. It should seal without dragging hard.
If the threshold itself is worn, a threshold seal or new weatherstrip insert restores the contact. On uneven or badly warped doors, this gets fiddly. If yours won't seal no matter what, it may be time to bring in a handyman rather than fight it.
Step 5: Seal Drafty Windows for the Rainy Season
By the end of this step, your leakiest windows will be sealed against LA's winter storms. Older single-pane windows lose the most, and weatherstripping alone may not be enough.
Clear window insulation film is a cheap fix. You tape it around the frame and shrink it tight with a hair dryer. It's nearly invisible and blocks the draft for the season, then peels off in spring.
Do this before the first big storm. Sealing drafty windows is one line item in a full rainy-season home maintenance routine that keeps water and cold out together. Check that weep holes stay clear so trapped water can still drain.
Common Mistakes to Avoid
A few errors undo the whole job. Watch for these.
Sealing over dirt or moisture. Caulk and adhesive strips need a clean, dry surface. Skipping prep is why seals peel off in a month. Wipe every surface first.
Using caulk where you should use weatherstripping. Caulk a moving door edge and it cracks the first time you open it. Match the material to whether the part moves.
Ignoring the door bottom. People weatherstrip the sides and forget the biggest gap is underneath. Always add a sweep.
Buying before testing. Guessing where leaks are wastes materials. Run the hand or smoke test first, then buy only what you need.
What Success Looks Like
If you did it right, closed doors and windows feel snug with no cool trickle when you run your hand along the edges. The dollar-bill test now drags. Rooms hold their temperature longer, so your AC and heater cycle less.
Over a year, that's where those DOE and ENERGY STAR savings show up on your bill. It's not a dramatic overnight change. It's a steady 10% to 20% you stop wasting on drafts, month after month.
Frequently Asked Questions
How do I find where a draft is coming from?
Run a slightly damp hand around door and window edges on a windy day; drafts feel cool. For a clearer read, pass a lit incense stick along the edges and watch where the smoke wavers. Both methods come straight from the Department of Energy.
What's the difference between caulk and weatherstripping?
Caulk seals stationary cracks, like the seam where a window frame meets the wall. Weatherstripping seals parts that move, like a door or an operable window. Use the wrong one on a moving part and it cracks or peels quickly.
How much can weatherproofing actually save me?
The Department of Energy estimates reducing drafts may save 10% to 20% a year. ENERGY STAR reports air sealing combined with insulation saves an average of 15% on heating and cooling costs. Your result depends on how leaky your home starts out.
Is weatherproofing worth it in mild LA weather?
Yes. LA summers push your AC hard, and sealed openings keep hot air out so it runs less. In winter, the same seals block drafts and wind-driven rain. The savings apply year-round, not just in cold climates.
Weatherproof Now, Save All Year
Sealing your doors and windows is a cheap, beginner-friendly project that trims your energy bill every month. Find the leaks, caulk what's fixed, weatherstrip what moves, and cap it with a door sweep.
If a warped door, tricky threshold, or hard-to-reach window won't seal, we can handle it. NC Services is an insured Los Angeles handyman serving LA, Santa Monica, Culver City, the South Bay, and the San Fernando Valley. Contact us or call (323) 989-4840 to book a weatherproofing visit.
