How to Seal Drafty Windows and Lower Energy Bills
Cold air slipping through a window can make a room uncomfortable, even when the heater is running. In summer, gaps around frames can also let hot air, dust and outdoor noise inside. Sealing these leaks is a practical home improvement that can reduce heating and cooling demand without replacing every window.
Australian homes experience a wide range of conditions, from humid Queensland summers to chilly Melbourne mornings and cold Tasmanian winters. The right draught-proofing method depends on the window style, the size of the gap and whether you rent or own the property.
Find Where Air Is Escaping
Start by checking the window on a windy day. Slowly move a lit incense stick, a strip of tissue or a smoke pencil around the sash, frame, locks and corners. If the smoke moves or the tissue flutters, air is passing through. Keep flames away from curtains and other combustible materials, and use a safer tissue test where appropriate.
Pay close attention to sliding windows, older timber frames and aluminium windows with worn seals. Gaps may also appear where the frame meets the wall, particularly in older brick homes or weatherboard houses. A window can look closed while still allowing a steady draught through a failed rubber gasket or loose latch.
Inspect the surrounding architraves as well. If you can see cracks in the plaster, peeling paint or a visible line between the frame and wall, the problem may require caulk rather than a replacement window seal. Bradley’s Home offers broader home upgrade ideas that can help you assess related comfort and maintenance projects around the house.
Choose Materials That Suit the Window
Self-adhesive foam tape is inexpensive and simple to fit, making it useful for small, even gaps around hinged windows. It compresses when the window closes and can reduce rattling. However, foam deteriorates faster in direct sun and may leave adhesive behind when removed.
Rubber, silicone or EPDM weather seals generally last longer and cope better with regular opening and closing. V-seal strips work well on narrow gaps, while brush seals are useful for sliding windows. Choose a product rated for the gap size rather than applying thick material that prevents the sash from locking properly.
For fixed cracks between a frame and wall, use a flexible exterior-grade gap sealant. Acrylic gap filler can be painted and suits sheltered indoor areas, but neutral-cure silicone is often better around moisture-prone locations. Clean and dry the surface before application, since dust and grease reduce adhesion.
Curtains and blinds can support your draught-proofing work. Blockout curtains with a close-fitting pelmet limit heat exchange around the glass, while cellular blinds add an insulating air layer. These treatments are particularly helpful in bedrooms and living areas with large single-glazed windows.
Compare Sealing Options
The most suitable solution depends on the location of the leak, the window’s movement and the level of durability you need. A low-cost strip may be sufficient for a spare room, while a frequently used living-room window benefits from a stronger seal.
| Sealing method | Best for | Typical durability | Installation difficulty |
|---|---|---|---|
| Foam weatherstrip | Small gaps on hinged windows | Low to medium | Easy |
| Rubber or silicone seal | Moving sashes and regular use | Medium to high | Easy to moderate |
| V-seal strip | Narrow gaps around timber or metal windows | Medium | Easy |
| Brush seal | Sliding windows and tracks | Medium | Moderate |
| Flexible caulk | Fixed cracks around the frame | High when correctly applied | Moderate |
| Secondary glazing film | Single glazing and temporary insulation | Seasonal | Easy |
A draught stopper placed along the bottom of a window can help when the gap is large or the frame is uneven. It is a temporary measure rather than a substitute for repairing the seal. Avoid blocking drainage holes in aluminium or uPVC frames, as these openings allow condensation and rainwater to escape.
If you are shopping at Bunnings or another Australian hardware retailer, take a photo of the frame and measure the gap before buying materials. Product packaging often lists the suitable gap range, adhesive requirements and whether the strip is intended for interior or exterior use.
Install Weatherstripping and Caulk
Remove old tape, loose paint and deteriorated sealant first. Wash the surface with mild detergent, allow it to dry completely and wipe it with a suitable solvent only if the manufacturer permits it. Do not apply adhesive weatherstrip to a damp, dusty or flaky surface.
Cut each strip to length without stretching it. Fit the seal to the stationary part of the frame where possible, then close the window gently to test the compression. If the sash becomes difficult to operate, the material is too thick or positioned incorrectly. Check that locks, handles and drainage channels remain usable.
When sealing a fixed joint, run a steady bead of flexible caulk along the crack and smooth it with a damp tool or gloved finger. Masking tape can create a cleaner edge. Allow the sealant to cure for the time stated on the cartridge before painting or exposing it to rain.
Do not seal over weep holes or cover the entire track of a sliding window with adhesive. These mistakes can trap water, cause mould or stop the window from opening as an emergency exit. In a rental property, removable foam strips and temporary window film are usually safer choices than permanent alterations, but check the tenancy agreement before making changes.
Handle Australian Weather Conditions
Sun exposure is a major concern for Australian window seals. A product that performs well inside a shaded room may crack or peel on a north- or west-facing window. Select UV-resistant weatherstripping for exposed areas, especially in Perth, Brisbane and inland regions where strong sunlight can shorten the life of adhesives.
Humidity also affects how well a sealant cures. In tropical and coastal areas, choose mould-resistant products for rooms such as laundries and bathrooms, and ventilate the space while the material dries. Condensation on cold glass can point to poor ventilation as well as air leakage, so use exhaust fans and open windows briefly when outdoor conditions are suitable.
In cooler parts of Victoria, New South Wales and Tasmania, sealing windows before winter can make a noticeable difference to comfort. Thermal curtains and rugs can then help retain warmth. In hot climates, external shade, awnings and closed blinds during the afternoon reduce solar heat gain, so the air conditioner does less work.
A ceiling fan can improve comfort while you fine-tune the building envelope. During warmer weather, a fan lets you set the air conditioner a little higher; during winter, reverse operation on suitable models can circulate warm air. Before choosing one, check this guide to the right fan size for your room.
Keep Savings Working
After sealing the windows, repeat the tissue test and inspect the room during both heating and cooling seasons. A successful repair should reduce noticeable air movement without making the window difficult to open. Check the seals every few months for compression, peeling or cracks, particularly after a hot summer.
Energy savings also depend on how the rest of the room performs. Close curtains at night in winter and during hot afternoons, keep doors shut between conditioned areas, and clean reverse-cycle air conditioner filters regularly. Efficient lighting will not stop a draught, but replacing older lamps with LEDs reduces heat and electricity use across the home; practical lighting upgrades can complement a wider energy-saving plan.
If a window frame is rotten, warped, badly corroded or permanently fogged between double-glazed panes, sealing tape may only hide the underlying fault. A glazier or qualified building professional can assess whether reglazing, hardware replacement or a new window is more economical. Seek specialist advice if the opening is a required escape route or if water is entering the wall cavity.
Make a short list of the windows with the strongest draughts, measure their gaps and repair the easiest leaks first. Pick UV-resistant materials where the sun is intense, preserve drainage paths and test every window after installation. A careful afternoon of draught-proofing can make rooms quieter and more comfortable while helping your heating and cooling system use less energy.