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Draught-Proofing Calculator — Materials & Savings Estimate
Calculate draught-proofing strip, chimney balloons and letterbox covers needed for your home. Estimate annual energy savings.
Doors & Windows
Front, back, side doors
Sliding sash windows
Hinged opening windows
Other Draught Sources
Chimneys not in use
Strip Roll Size & Pricing (optional)
Enter your supplier price for a cost estimate
Enter your supplier price for a cost estimate
Enter your supplier price for a cost estimate
Strip length per external door (default 6.0m)
Strip length per sash window (default 6.5m)
Strip length per casement window (default 4.0m)
Strip length per loft hatch (default 3.6m)
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How We Calculate This
This calculator estimates the draught-proofing materials you need by calculating the total perimeter of doors, windows and other openings that need sealing, then working out how many rolls of draught strip to buy.
Perimeter estimates used
- External door: ~6.0m perimeter (including threshold)
- Sash window: ~6.5m (two sashes, each with sealing perimeter)
- Casement window: ~4.0m perimeter (typical opening casement)
- Loft hatch: ~3.6m perimeter
Additional products
- Chimney balloon/sheep: One per unused chimney to prevent heat escaping
- Letterbox cover: A brush-type internal cover to reduce draughts through the letterbox
Energy savings
Savings are indicative figures from the Energy Saving Trust: around £85 a year (Great Britain) for draught-proofing doors, windows and floors, plus a separate ~£60 a year for each unused chimney you seal. These are national averages — your real saving depends on how draughty your home is and your energy tariff. Draught-proofing costs relatively little but can make a noticeable difference to comfort and heating bills, and is often recommended as a first step in improving home energy efficiency.
Frequently Asked Questions
According to the Energy Saving Trust, draught-proofing doors, windows and floors could save around £85 a year on energy bills in Great Britain (about £80 in Northern Ireland). Separately, draught-proofing an unused chimney could save around £60 a year on top of that. These are indicative national-average figures — your actual saving depends on your home, how draughty it is and your energy tariff. Draught-proofing is still one of the cheapest and most effective energy-saving measures. See our Heat Loss Calculator to model the impact of improved ventilation rates on heating demand.
Self-adhesive foam strip is cheapest and easy to apply but wears out after 1-2 years. Rubber or silicone strip lasts much longer (5-10 years) and provides a better seal. For sash windows, brush strip or specialist sash window draught strip gives the best results. V-strip (metal or plastic) is very durable for door frames.
If you have an unused fireplace, a chimney balloon or chimney sheep can prevent significant heat loss — an open chimney is essentially a permanent hole letting warm air escape. The Energy Saving Trust estimates draught-proofing an unused chimney saves around £60 a year. Always remove the balloon before lighting a fire. If the fireplace is permanently unused, consider having the chimney capped by a builder (while keeping a small vent to avoid trapping damp).
Yes, draught-proofing is a straightforward DIY job. Self-adhesive strip simply sticks to clean door or window frames. For sash windows, brush strip may require routing a channel into the frame, which is more involved. Letterbox covers and chimney balloons are very simple to fit. Most jobs can be completed in a few hours.
Yes — adequate ventilation is essential for indoor air quality and preventing condensation and damp. Do not block trickle vents in windows, airbricks, or extractor fans. Draught-proofing targets uncontrolled air leaks, not the controlled ventilation your home needs. Building Regulations Part F sets minimum ventilation requirements.
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.