How do I stop drafts from old windows without replacing them?

Short answer

You can cut drafts dramatically without replacing the windows by sealing air leaks around the trim and sash, adding the right weatherstripping, installing interior shrink film or storm panels for winter, re-glazing any loose panes, and insulating gaps around the frame. Most fixes are DIY-friendly and cost about $10–$50 per window, with bigger upgrades (interior storms) from $40–$150 per opening.

How to find the leaks

Before you buy materials, pinpoint the trouble spots:
- Hold a lit incense stick or a smoke pencil around the sash edges, lock, meeting rail, and trim; watch for smoke movement.
- At night, have someone shine a flashlight from outside; look for light leaks.
- Check glass-putty lines and pulleys on old double-hungs; feel for cold air.

Mark the leak locations with painter’s tape so you can target them.

Quick fixes you can do today (10–30 minutes per window)

• Lock the sash and adjust latches: A properly engaged lock pulls the meeting rails tight. Slightly reposition the keeper if needed.
• Rope caulk (removable): Press into seasonal gaps around the sash or meeting rail. Great for renters. $6–$10 per window.
• Draft snakes/thermal curtains: Add at the sill and hang insulated drapes to cut convective drafts immediately.
• Shrink film window kit: Apply double-sided tape to the interior trim, stick the film, and heat it tight with a hair dryer. $12–$20; 20–30 minutes.

Weekend upgrades (1–2 hours per window)

1. Seal gaps at the interior trim and sill

   • Cut away cracked caulk and run a new bead where casing meets wall and stool. Use paintable acrylic-latex (with silicone for flexibility) indoors.
   • For larger gaps between frame and wall, gently pry off interior casing and inject low-expansion “window & door” foam, or pack foam backer rod plus caulk. Reinstall trim.

2. Weatherstrip the sashes (double-hung or slider)

   • Clean contact surfaces with mineral spirits or alcohol.
   • Install adhesive V-strip along the jamb channels where the sash slides, and at the meeting rail. Use metal spring bronze for a long-lasting pro solution (advanced DIY).
   • Apply EPDM or high-density foam tape to the bottom rail and parting stops as needed. Close and test for smooth operation; adjust thickness to avoid binding.

3. Re-glaze loose or rattling panes (wood windows)

   • If the putty is cracked, remove it carefully, set new glazing points, and bed the glass in fresh glazing compound. Allow proper cure before painting.

4. Add an interior storm panel (highest performance without replacement)

   • Options include magnetic acrylic panels, compression-fit frames, or DIY acrylic with magnetic tape. Expect $40–$150 per opening and major draft reduction.

5. Seal the exterior (on a dry day)

   • Scrape and replace failed caulk where the exterior casing meets the siding and where the sill meets trim. Use exterior-grade elastomeric or polyurethane sealant. Do not block weep paths.

Materials and tools

• Weatherstripping: self-adhesive V-strip, spring bronze, EPDM foam tape
• Sealants: acrylic-latex (paintable) for interior; polyurethane/silicone for exterior; rope caulk for seasonal use
• Backer rod (for gaps), low-expansion “window & door” spray foam
• Shrink film kit or interior storm panel kit
• Glazing compound, glazing points (for wood sash)
• Tools: caulk gun, utility knife, putty knife/painter’s tool, glass scraper with razor blades, pry bar, measuring tape, square, heat gun/hair dryer, miter shears or scissors, drill/driver, safety gear (gloves, safety glasses, mask)

You’ll find these by category in the ToolStash catalog: weatherstripping, window & door foam, glazing tools, and sealants.

Useful specs and rules of thumb

Gaps:
- < 1/4 in: caulk
- 1/4–1/2 in: backer rod + caulk
- > 1/2 in (non-moving): low-expansion window & door foam

Caulk bead: 3/16–1/4 in; tool within 5–10 minutes.
Application temps: 40–90°F (check label).
Weatherstrip compression: aim for ~25–50%.
Shrink film: apply with room temp 65–75°F.

Safety

• Lead paint: Homes built before 1978 may have lead. Avoid dry sanding; use a P100 respirator, plastic containment, and wet scraping. Consider an EPA RRP-certified pro for extensive work.
• Glazing and glass: Wear cut-resistant gloves and eye protection. Support panes to avoid breakage.
• Foam and sealants: Ventilate the area, wear gloves, and protect finished surfaces. Use only low-expansion foam to prevent frame distortion.
• Ladders: If sealing exterior upper-story windows, follow ladder safety.

Tips for best results

• Clean and dry surfaces before applying tape or caulk; wipe with isopropyl alcohol for better adhesion.
• Test-fit weatherstrip thickness. Too thick = sticky operation; too thin = leaks.
• Warm adhesive-backed products with a hair dryer in cold rooms to improve bond.
• Prioritize the worst orientations first (north and windward sides).
• After weatherstripping, lubricate wood sash tracks lightly with paste wax for smooth movement.

Common mistakes to avoid

• Using high-expansion foam around frames; it can bow jambs and jam the sash.
• Caulking everything shut: don’t seal weep holes or necessary drainage paths.
• Choosing non-paintable silicone where you plan to repaint.
• Skipping surface prep; caulk over dust will peel quickly.
• Overstuffing weatherstrip so the window won’t latch or loses egress function.

When to call a professional

• Widespread rot, spongy sills, or failed structural members.
• Multiple panes need re-glazing or glass replacement.
• Suspected lead paint and you’re not RRP-certified.
• You want custom-built interior or exterior storm windows for best year-round performance.

With a few targeted steps—diagnose, seal the frame, weatherstrip moving parts, address glazing, and add an interior storm—you can turn leaky old windows into solid performers for a fraction of replacement cost.