Draught Proofing Windows and Doors: The Complete DIY Guide
Draught proofing is the single highest-return home insulation investment you can make — and most people skip it entirely in favour of more expensive solutions.
Here's the reality: up to 25% of a home's heat loss escapes through gaps around windows, doors, floors, and chimneys. A day spent draught proofing your home costs $30–$80 in materials and can save $150–$300 per year in heating bills. Nothing else in home insulation comes close to that payback speed.
In this guide, you'll learn:
How to Find Draughts in Your Home
Before spending money on materials, spend 30 minutes finding exactly where the cold air is entering. There are three methods:
Candle or incense test: On a cold, windy day, hold a lit candle or incense stick near window frames, door frames, skirting boards, electrical outlets, and the floor-wall junction. A flickering flame or moving smoke reveals a draught. Mark the locations with masking tape.
Hand test: Wet your hand and run it slowly around window and door frames. Cold spots reveal air infiltration. Less precise than the candle method but quick and safe.
Thermal camera or IR thermometer: If you want to be systematic, a thermal imaging app (many smartphones now have IR capability) shows cold patches on walls and frames in real time. The most reliable method for identifying all problem areas at once.
The most common draught sources are: window frame-to-wall junction, sash window meeting rail, letter boxes, keyholes, door bottom gaps, and loft hatches. Start with these before looking elsewhere.
Draught Proofing Windows
Windows lose heat in two ways: through the glass itself (addressed by secondary glazing → or bubble wrap insulation →) and through gaps around the frame. Draught proofing addresses the gaps.
Self-adhesive foam strip (easiest)
Foam weatherstrip tape is the fastest and cheapest draught seal. Press it into the gap between the window sash and the frame. The foam compresses when the window closes and springs back when open, maintaining a seal.
Cost: $5–$15 per roll (covers multiple windows). Lifespan: 2–5 years before the foam compresses permanently and stops sealing. Good for casement windows; less effective for sash windows (the sash slides past the seal rather than compressing it).
V-strip (spring bronze or plastic)
V-strip — also called tension seal — is a folded strip of metal or plastic that springs open to fill gaps. It's cut to length and pressed into the gap between the sash and frame, where it forms a long-lasting seal that the sash slides over.
Cost: $8–$20 per roll. Lifespan: 10–20 years for metal V-strip. Excellent for sliding and sash windows. More durable than foam but slightly more fiddly to install — use a putty knife to press it firmly into the groove.
Wiper or brush seal
A brush seal is a strip of dense bristles mounted in a holder, pressed against the moving sash. Excellent for sash windows where the sash needs to slide smoothly past the seal. Available in various pile heights to match the gap size.
Cost: $10–$25 per metre. Lifespan: 10+ years. More effective than foam for draughty sash windows; also reduces noise.
Rope caulk (renter-friendly, removable)
A soft, putty-like compound pressed into gaps with your fingers. Seals perfectly, is completely removable in spring (peels off cleanly with no residue), and costs almost nothing. Ideal for renters or anyone who wants a seasonal solution.
Cost: $5–$10 per roll. Lifespan: one season — remove and replace each year.
Draught Proofing Doors
Exterior doors are typically the worst draught offenders in a home, with four potential gap locations: the bottom, the two sides, and the top.
Door bottom (the biggest gap)
The gap under an exterior door is usually the largest and most impactful. Three options:
- Door sweep: A brush or rubber strip screwed to the bottom of the door, dragging across the floor as the door opens and closes. Highly effective, easy to install. Best for smooth floors — can catch on thick carpets.
- Door threshold strip: A raised rubber or brush seal fitted to the floor at the threshold. The door closes onto it. More durable than a door sweep as it doesn't drag on the floor surface.
- Draught excluder snake: A fabric tube filled with sand or polystyrene beads, placed against the bottom of the door. No installation required. Works well, zero cost to make yourself, but must be moved every time the door opens.
Door sides and top (frame gaps)
Use the same foam strip or V-strip methods as for windows — pressed into the rebate (the groove the door sits in when closed). Self-adhesive foam is the fastest install; spring bronze V-strip lasts longest.
Letter boxes and keyholes
A letter box without a draught flap is a direct hole in your front door. Fit a brush letter box draught excluder — a double-brush insert that seals the opening even with letters partially inserted. Cost: $5–$15. Keyhole covers are similarly cheap and easy — a simple metal flap covers the hole when the key isn't inserted.
Draught Proofing Sash Windows
Sash windows — the traditional double-hung type with upper and lower sashes that slide vertically — are notoriously draughty. There are four gap locations to address:
- Meeting rail (where the two sashes meet in the middle): Use a brush pile seal or flip-over lock-and-seal system. This is the most significant draught point on most sash windows.
- Sash sides (the sash slides in channels): V-strip or brush pile seal pressed into the channels. The sash must slide smoothly past, so don't overfill — test each sash moves freely after sealing.
- Top of upper sash: Self-adhesive foam strip on the top rail, compressed by the closed window.
- Bottom of lower sash: Self-adhesive foam strip on the bottom rail, compressed by the sill.
Full sash window draught proofing is one afternoon's work and typically saves £50–£100 per window per year in heating costs — making it one of the fastest payback home improvements available.
Other Major Draught Sources
Windows and doors get the attention, but several other locations lose as much heat and are equally easy to seal:
- Loft hatch: If your loft is cold, the hatch is essentially a hole in your ceiling. Fit foam strip to the hatch frame and add insulation board to the top of the hatch door. Big impact, often overlooked.
- Chimney: An open or unused fireplace creates a powerful draught up and out. A chimney balloon (an inflatable plug that fills the flue) costs $25–$40 and eliminates the draught entirely when the fireplace isn't in use. Remove before lighting a fire.
- Floor-wall junction and skirting boards: Old houses with suspended timber floors often have gaps where the skirting board meets the floor. Silicone caulk or flexible filler pressed into these gaps is a significant heat saver.
- Electrical outlets on external walls: In cold climates, electrical boxes on external walls can have significant cold air infiltration. Foam outlet insulators (fit behind the faceplate) are cheap and effective.
Best Draught Proofing Materials: Comparison
| Material | Cost per window/door | Lifespan | Best for | Renter-friendly? |
|---|---|---|---|---|
| Self-adhesive foam strip | $2–$5 | 2–5 years | Casement windows, door frames | ✅ Yes |
| V-strip (spring bronze) | $3–$8 | 10–20 years | Sash windows, sliding doors | 🟡 Mostly |
| Brush pile seal | $5–$12 | 10+ years | Sash windows, sliding doors | 🟡 Mostly |
| Rope caulk | $1–$2 | 1 season | Any frame gap, renters | ✅ Yes |
| Door sweep | $8–$20 | 5–10 years | Exterior door bottoms | 🟡 Mostly |
| Chimney balloon | $25–$40 | 10+ years | Unused fireplaces | ✅ Yes |
Renter-Friendly Draught Proofing
Renters can draught proof effectively without leaving any marks or making permanent changes:
- Rope caulk: Press into gaps, peel off cleanly in spring. No damage, no residue.
- Self-adhesive foam strip: Sticks without screws and peels off cleanly from most surfaces if removed within a season.
- Draught excluder snakes: No installation needed — just place against door bottoms.
- Chimney balloons: Push up the flue, pull string to deflate and remove. No installation at all.
- Heavy curtains: Floor-length curtains over draughty windows or patio doors provide significant draught reduction with zero installation. Even more effective combined with rope caulk on the frame.
Combined with bubble wrap window insulation →, renter-friendly draught proofing can reduce heating bills by 20–30% over winter with under $50 in total spend.
Frequently Asked Questions
What is the best draught proofing for windows?
For casement windows: self-adhesive foam strip is the easiest and fastest option, lasting 2–5 years. For sash windows: brush pile seal at the meeting rail plus V-strip in the sash channels gives the best long-term result. For renters: rope caulk pressed into frame gaps is completely removable and very effective for one season.
How do you draught proof a sash window?
Seal four locations: brush pile seal at the meeting rail where the two sashes overlap; V-strip or brush pile in the side channels where the sashes slide; foam strip at the top of the upper sash; foam strip at the bottom of the lower sash. Test that each sash still slides freely after sealing. Full sash draught proofing typically takes 2–3 hours per window.
How much can draught proofing save on heating bills?
Draught proofing the whole house (windows, doors, loft hatch, chimney) typically saves £200–£300 per year in the UK according to the Energy Saving Trust, or $150–$350 in the US depending on climate and fuel type. At $30–$80 in materials, the payback period is often less than one heating season.
Is draught proofing worth it for renters?
Yes — rope caulk, foam strip, draught snakes, and chimney balloons all require no permanent installation and leave no damage. Combined, they can reduce heating bills by 15–25% at a cost of under $30 and are removed cleanly in spring. The investment pays back within weeks in a cold climate.
