How to Seal Windows and Doors

Feel that draft? That’s money blowing out of your house. The gaps around your windows and doors might look small, but add them up and you’ve got the equivalent of a window wide open all winter. Sealing those gaps is one of the highest-return home improvements you can make—better ROI than new windows, cheaper than a furnace upgrade, and you can do it yourself in an afternoon.

Why This Matters

Heated and cooled air escapes through every gap in your home’s envelope. The biggest culprits:

• Window frames – Gaps between frame and siding, between sash and frame, around trim
• Door frames – Gaps between door and jamb, threshold and floor, frame and wall
• Old or failed caulk – Cracked, shrunken, or missing sealant
• Worn weather stripping – Rubber, foam, or vinyl that’s lost its flexibility

The Department of Energy estimates that air leaks account for 25-40% of heating and cooling energy waste in the average home. That’s a quarter to nearly half your bill going out through cracks you could seal for $50 in materials.

Benefits of sealing:

• Lower energy bills (10-20% savings on heating/cooling)
• More consistent temperatures throughout house
• Less dust and pollen infiltration
• Reduced noise from outside
• Fewer bugs finding their way in

Assessment: Find the Leaks

Before you start sealing, find the problem areas:

Visual Inspection

Walk around your house and look for:

• Visible gaps between window/door frames and walls
• Cracked, peeling, or missing caulk
• Daylight visible around closed windows and doors
• Weather stripping that’s cracked, compressed, or missing

The Hand Test

On a windy or cold day:

• Hold your hand flat near window and door edges
• Move slowly around the perimeter
• Feel for air movement (cold spots indicate drafts)
• Pay attention to corners and where frames meet

The Candle Test

For hard-to-find leaks:

1. Close all windows and doors
2. Turn off any combustion appliances
3. Light a candle or incense stick
4. Hold it near potential leak points
5. Watch for the flame or smoke to waver

Mark problem areas with painter’s tape so you can find them later.

Materials You’ll Need

Caulk

For gaps less than 1/4 inch wide:

• Latex caulk – Easy to apply, paintable, cleans up with water. Good for interior. Lasts 5-10 years.
• Silicone caulk – More flexible, waterproof, not paintable. Good for exterior and wet areas. Lasts 20+ years.
• Siliconized latex – Hybrid, paintable, more flexible than plain latex. Good middle ground.

Weather Stripping

For gaps around moving parts (doors, operable windows):

• Self-adhesive foam tape – Cheap, easy, not durable. Good for low-traffic areas.
• V-strip (vinyl or metal) – More durable, creates tight seal on door edges
• Door sweeps – Attach to bottom of door, seal gap at threshold
• Tubular rubber/vinyl – Good for wide gaps, durable

For Large Gaps

• Backer rod – Foam rope that fills deep gaps before caulking
• Spray foam – Expanding foam for large gaps (be careful, hard to control)
• Rigid foam – For very large structural gaps

Step-by-Step Sealing

Windows

1. Prepare the surface

• Scrape out old, cracked caulk with putty knife
• Clean surfaces with rubbing alcohol or soapy water
• Let dry completely

2. Seal the exterior frame

• Apply caulk where window frame meets siding
• Use consistent pressure, smooth bead
• Tool (smooth) with wet finger or caulk tool

3. Seal the interior frame

• Apply caulk where window trim meets wall
• Don’t caulk the window sash (moving parts)
• Smooth bead before it skins over

4. Add weather stripping to operable windows

• Apply foam tape to the sash where it meets the frame
• Don’t prevent the window from operating
• Check that window still locks properly

Doors

1. Check the threshold

• Door should meet threshold evenly
• If there’s visible light underneath, adjust or replace threshold
• Add a door sweep if needed

2. Seal the frame

• Caulk where door frame meets interior and exterior walls
• Remove old caulk first

3. Replace weather stripping

• Remove old, compressed weather stripping
• Clean surface thoroughly
• Apply new weather stripping to door stop (the part the door closes against)
• Ensure door still closes and latches easily

4. Check door alignment

• If door rubs or doesn’t close properly, alignment may be off
• Adjust hinges before adding weather stripping
• A door that doesn’t close properly won’t seal properly

Tips for Better Results

• Don’t skimp on surface prep – Caulk won’t stick to dirt, dust, or old caulk
• Cut caulk tube tip at an angle – Gives you more control
• Practice on cardboard first – Get a feel for the caulk gun
• Work in temperatures above 40°F – Caulk won’t cure properly in cold
• Don’t overfill gaps – Excess caulk looks bad and is hard to clean up
• Smooth while wet – Once caulk skins over, you can’t smooth it
• Keep a wet rag handy – For cleaning up mistakes and smoothing

Warning Signs of Problems

• Drafts even after sealing (missed spots or bigger problems)
• Caulk cracking within a year (poor quality or wet surface)
• Weather stripping compressed flat (time to replace)
• Door difficult to close/latch (weather stripping too thick)
• Condensation between window panes (failed seal, not a draft issue)
• Visible gaps that reappear (settlement or structural movement)

If gaps keep reappearing in the same spots, you may have foundation or structural issues that need professional evaluation.

DIY vs. Call a Pro

DIY: Caulking, replacing weather stripping, installing door sweeps, basic draft sealing. This is very doable homeowner work.

Call a pro: Replacing windows or doors, fixing structural gaps, addressing foundation issues, whole-house air sealing with blower door testing, extensive rot repair around windows/doors. Find a handyman →

How Often to Reseal

• Inspect: Annually in fall before heating season
• Caulk: Every 5-10 years (exterior), 10+ years (interior)
• Weather stripping: Every 3-5 years, or when compressed/visible gaps appear
• Door sweeps: When worn, typically 5-7 years

The Bottom Line

You don’t need new windows to stop drafts—you need a caulk gun and a weekend afternoon. A $30 investment in caulk and weather stripping can save you 10-20% on your energy bills. Walk around your house, find the gaps, seal them up. Your house will be more comfortable, your bills will be lower, and you’ll stop paying to heat the great outdoors.