Drafty windows are responsible for up to 30% of heat loss in a typical home. Fixing them is one of the most cost-effective home improvements you can make — most solutions cost under $30 and take less than an hour to complete. This guide covers every method from simple weatherstripping to secondary glazing, so you can choose the right fix for your situation.
How to Detect a Draft
Before spending money on materials, confirm exactly where cold air is entering. Two reliable detection methods:
Candle or tissue test. Hold a lit candle or a thin sheet of tissue paper close to the window frame on a windy day. Move it slowly around all four sides, the corners, and around the locking mechanism. Any flicker or movement indicates a draft.
Hand test. On a cold day, hold your palm about one inch from the frame and move it slowly around the perimeter. You will feel temperature differences where cold air is entering.
Mark problem spots with masking tape before you start repairs so you know exactly where to focus.
What Causes Drafty Windows
Understanding the cause helps you choose the right fix and avoid wasting money on the wrong solution.
Deteriorated Caulk
Caulk around the window frame cracks and shrinks over time, especially in climates with repeated freeze-thaw cycles. This is the most common cause of drafts in homes more than ten years old and one of the easiest to repair yourself.
Worn Weatherstripping
Weatherstripping seals the gap between the movable sash and the frame. It compresses and loses its seal over years of use. If your windows rattle when closed, or you can feel air around the edges even with the window shut, worn weatherstripping is the likely cause.
Failed Seals in Double-Pane Windows
Double-pane windows contain insulating gas between the panes. When the seal fails, that gas escapes and the window loses most of its insulating value. Fogging or condensation appearing between the panes — not on the surface — is the telltale sign of seal failure.
Warped or Settled Frames
Wood frames absorb moisture and can warp over time, creating irregular gaps that caulk alone cannot always bridge. If the frame has visibly shifted or the window no longer sits square, this may be the cause.
How to Fix Drafty Windows: 5 Methods
Fix 1: Replace Weatherstripping
Best for: Windows that rattle, don’t close flush, or where you feel air around the sash when the window is closed. Cost: $5–$15 Time: 30–45 minutes
Remove the old weatherstripping completely by pulling it away from the frame. Clean the channel with rubbing alcohol and allow it to dry fully. Cut new self-adhesive weatherstripping to length and press it firmly into position along all four sides of the window frame. Close the window and check that the seal is consistent with no gaps.
Fix 2: Recaulk the Frame
Best for: Gaps between the window frame and the wall, cracked caulk on exterior frames, and older homes where the original caulk has dried out. Cost: $5–$10 Time: 20–30 minutes
Use a utility knife or caulk remover tool to cut out all old caulk completely — never apply new caulk on top of old. Clean the surface and let it dry. Load a silicone caulk cartridge into a caulking gun and apply a continuous bead along the joint between the frame and the wall. Smooth with a wet finger. Allow 24 hours to cure before rain exposure.
Use paintable latex caulk for interior gaps and 100% silicone caulk for exterior gaps where water resistance matters.
Fix 3: Window Insulation Film
Best for: Single-pane windows, windows with failed seals, or any window where you want to reduce heat loss through the glass itself without replacing it. Cost: $10–$20 Time: 20 minutes
Apply double-sided tape from the kit around the entire window frame. Cut the window insulation film slightly larger than the window opening. Press it firmly onto the tape starting from the top edge. Use a hairdryer on medium heat to shrink the film until it is completely clear and taut, working from the center outward. When correctly installed, the film is nearly invisible and reduces heat loss through the glass by up to 55%.
Fix 4: Draft Excluder Tape
Best for: Windows with small, uneven gaps or windows that don’t close quite flush. Cost: $3–$8 Time: 15 minutes
Self-adhesive foam draft excluder tape is the fastest fix available. Peel the backing and press the tape onto the closing edge of the window frame — the surface that the sash presses against when the window shuts. It creates an immediate compression seal and stops rattling. This works well as an emergency fix or for windows you rarely open.
Fix 5: Secondary Glazing
Best for: Single-pane windows in older or historic homes where full replacement isn’t an option, or where maximum insulation and noise reduction is the goal. Cost: $50–$150 per window Time: 1–2 hours
Secondary glazing involves fitting a second panel — typically acrylic or thin glass — on the inside of the existing window. Magnetic versions attach to a thin metal strip that you fix around the frame using double-sided adhesive, and the panels snap on and off so you can remove them in warmer months. Secondary glazing reduces heat loss through the window by up to 60% and noticeably reduces outside noise, making it one of the most effective drafty window repair options available without full replacement.
Cost Comparison at a Glance
- Draft excluder tape — $3–$8, takes 15 minutes
- Recaulking — $5–$10, takes 20–30 minutes
- Weatherstripping — $5–$15, takes 30–45 minutes
- Window insulation film — $10–$20, takes 20 minutes
- Secondary glazing — $50–$150 per window, takes 1–2 hours
For most homes, combining recaulking on the exterior and new weatherstripping on the interior sash covers the majority of drafts for under $25 in materials.
When to Call a Professional
DIY methods work for the vast majority of drafty windows. Contact a window contractor if:
- Condensation or fogging appears between the panes of a double-pane window — this requires professional glass unit replacement, not a surface fix.
- The window frame is visibly warped, cracked, or rotted.
- The window will not close or lock correctly after replacing weatherstripping.
- You are working with a listed or historic property with restrictions on materials.
Replacing a sealed insulated glass unit typically costs $150–$400 per window for parts and labor. Full window replacement runs $300–$1,000 or more per window depending on size, material, and installation complexity.
Frequently Asked Questions
How do I know if my windows are drafty?
The most common signs are cold spots near windows on still days, higher-than-expected heating bills, condensation or frost on the glass, a faint whistling sound when wind picks up outside, and visible cracks or gaps in the caulk around the frame. Use the candle or hand test described above to confirm and pinpoint the location.
How much does it cost to fix drafty windows yourself?
Most DIY fixes cost between $5 and $30 per window in materials. Weatherstripping and recaulking together typically cost under $25 and cover the most common causes of drafts. Secondary glazing costs $50–$150 per window but delivers the highest performance improvement.
Can I fix drafty windows myself?
Yes. Weatherstripping, recaulking, window film, and draft excluder tape require only basic tools and no prior experience. Secondary glazing installation takes slightly more care but is achievable by most homeowners with a drill, a tape measure, and one to two hours.
Does window insulation film actually work?
Yes — when properly installed. The film creates a sealed air gap between itself and the glass that acts as an additional insulation layer, reducing heat loss through the glass by up to 55%. It is most effective on single-pane windows. When applied correctly with a hairdryer, it is nearly invisible.
Is it better to repair or replace drafty windows?
Repair first. Recaulking and replacing weatherstripping eliminates most drafts, costs under $25, and lasts several years. Replacement is only the right call when the sealed unit of a double-pane window has failed, the frame is structurally damaged or rotted, or the window has exceeded its useful lifespan.