If you've got old timber double-hung windows, you know the sounds. The rattle when a truck goes past. The low whistle on a windy night. The cold draught you can feel across the room even though the window is shut. And every winter, the same thought: should we just replace them?
Here's the good news. You almost certainly don't need to — and replacing them is usually the wrong move.
The glass isn't the problem
It's tempting to blame the thin old glass, and yes, single 3 mm glass isn't a great insulator. But that's rarely why your room feels cold and draughty. The real culprit is air and noise leaking around the sash, through the operating gaps — not through the glass itself.
A double-hung window is a clever bit of engineering, but it has a lot of moving edges:
- Two sashes that slide past the beads
- Two meeting rails that join in the middle
- A bottom rail that sits against the sill
Every one of those edges is a potential gap. In fact, these windows were originally built with a small "penny gap" so the sashes could move freely. Add a century of paint build-up, timber movement and loosened joints, and those small gaps turn into a direct pathway for draughts, dust, rattles and street noise.
Why the hardware-store fixes fail
Most people reach for foam tape first. It's cheap, and it fails fast. Foam compresses unevenly, falls off, and degrades — and if you use enough of it to actually block the gap, it stops the sash sliding or the window latching. Worse, it does nothing for the rattle, which is often the thing keeping you awake. You end up with a window that's harder to open and still noisy.
The reason is simple: those fixes work against how the window is built, instead of with it.
The fix the rest of the world already uses
Sealing the operating gaps of a sash window is standard practice across Europe and England — it's even covered in Historic England's guidance on draught-proofing heritage windows. The principle is straightforward: get the window working properly again, then fit discreet seals in the exact spots the air is bypassing.
For a double-hung, that means four key points:
- Where the sashes slide — a discreet brush-type seal so the sash still glides, but the air gap all but disappears.
- The parting-bead channel — the run the sashes travel in, and a big source of constant cold air movement when it leaks.
- The meeting rails — that join in the middle is one of the single biggest leak points for both air and noise.
- The internal staff beads — sealing the room-side perimeter and stopping the rattle.
Done properly, the seals become built into the working window. You'd never know they're there — you'll just notice the draught is gone, the rattle has stopped, and the room is quieter.
What you'll actually feel afterwards
- Rooms that feel less draughty and hold their temperature
- Windows that feel tight and firm, not loose and rattly
- Less dust getting in, and no more whistling on windy days
- Real noise reduction, especially where rattles and gaps were the main offenders
- Lower heating and cooling bills — and you keep your original windows
Do it yourself, or have it done
Sealasash has sealed 25,000+ timber windows this exact way. If you'd rather leave it to a carpenter, that's the service. But if you're handy and happy to pull the sashes apart, the Sellaseal Double-Hung Window Draught Sealing Kit puts the same professional-grade seals, beads and sash cord in your hands, with step-by-step instructions — delivered anywhere in Australia.
Your windows survived a hundred years. With the right seals, they'll be the warmest, quietest part of your home for the next hundred.