Not all draught seals are created equal — and for a double-hung sash window, choosing the right type in the right place is the difference between a window that glides shut and seals tight, and one that jams, rattles, or leaks as badly as before.
After 25,000+ window installs, these are the products we trust for double-hungs, and exactly what each one does.
1. Twin-fin brush seals — the workhorse
Brush seals are the heart of a good double-hung seal. Unlike foam or rubber, a brush lets the sash keep sliding smoothly while its fine filaments fill the air gap. A twin-fin brush doubles up the barrier for better air and noise control.
Where it goes: into the beads where the sashes slide, and at the meeting rail. This is what quietly kills the draught without ever making the window hard to use.
Why not foam? Foam compresses unevenly, degrades, and either falls off or stops the sash moving. Brush seals work with a sliding window, not against it.
2. Parting bead — the channel between the sashes
The parting bead is the timber strip that separates the two sashes and gives them a channel to run in. On old windows it's often worn, painted-over, or missing chunks — and when that zone leaks, you feel it as a constant stream of cold air.
Replacing it with a clean, correctly-sized primed parting bead (ready to seat a brush seal) restores the channel and gives the seal something proper to bite against.
3. Staff bead — the room-side perimeter
The staff bead (or "inner bead") is the strip on the room side that holds the bottom sash in place. Seal here and you close off air movement at the internal perimeter — and, just as importantly, you stop the sash rattling in its frame.
A fresh primed staff bead with a brush seal fitted is what tightens everything up on the inside without changing the window's look.
4. Meeting-rail track and seal — the middle join
The two meeting rails join where the top and bottom sashes overlap in the middle. It's one of the biggest leak points on the whole window — for both air and noise — and it's the source of that classic sash-window whistle. A dedicated track and brush seal at the meeting rail tightens that join so the two sashes close together properly.
5. Quality sash cord — because a sealed window still has to move
Draught-proofing a window that doesn't run smoothly is a waste of time. If the cords are frayed or snapped (very common on old double-hungs), the sash won't sit or seal correctly. Good 6 mm sash cord — cotton exterior over a poly core — restores smooth, balanced operation so the seals can do their job. Replace the cords while you've got the window apart; it's the perfect time.
The rule that ties it all together
Every seal you fit has to respect the fact that a double-hung window moves. The goal is never "block the gap at any cost" — it's "close the gap while keeping the window working." That's why brush seals, properly-sized beads, a meeting-rail track and sound sash cord all work together as a system, rather than one miracle strip of tape.
Get the whole system in one kit
You don't have to source these products separately. The Sellaseal Double-Hung Window Draught Sealing Kit bundles all of it — staff bead, parting bead, twin-fin brush seals, meeting-rail track and premium sash cord — with step-by-step instructions, sized for windows up to 2 m × 1 m. It's the same professional-grade gear Sealasash uses on the job, now available to DIYers Australia-wide.
(A note: these products are matched to painted timber double-hungs on cords. If your windows are bare/stained timber or use a different balance system, get in touch before you buy.)