Sash window draught-proofing

Draughts and rattles are the most common complaints about older sash windows, and they are also the easiest to fix. Modern draught-proofing systems are discreet, effective and sympathetic to period joinery — they cut the cold air and the noise without changing how the window looks. This guide explains how draught-proofing works, what it improves and how it fits alongside other sash work.

Why old sashes draught

A sliding sash needs a small gap to move freely, and over time that gap widens as timber shrinks and paint layers wear. The parting bead and staff bead that guide the sashes can loosen, and the meeting rail where the two sashes overlap rarely seals tightly on an untreated window. The result is cold air, whistling on windy days, and the familiar rattle. None of this means the window is failing — it simply lacks seals that were never originally fitted.

How draught-proofing works

The usual approach routes a fine brush pile into the frame runners, the parting bead and the staff bead so the sashes slide against a soft seal. A compression or brush seal is added at the meeting rail to close the gap where the sashes cross. Done well, the window still slides smoothly, the seals are barely visible, and draughts and rattles are dramatically reduced. Because the work is carried out on the existing window, the period appearance is preserved.

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What draught-proofing improves

The most noticeable change is comfort: fewer cold spots, less noise from the street, and no more rattling in the wind. Reducing uncontrolled air movement also helps a home retain heat, which can support lower energy use over a heating season, though the exact saving depends on your home and habits. It is a modest, sensible improvement rather than a dramatic one, and it is often the best-value first step for an older window.

Draught-proofing with restoration

Draught-proofing is most often done as part of a wider restoration, when the sashes are already out and the beads are being renewed. Combining the work is efficient and gives the best result. See our restoration guide for what a full project involves, and our guide to sash mechanisms if your sashes also need re-cording or rebalancing.

Getting it done well

Use an installer experienced with sash windows so the seals are matched to your beads and the sashes still run freely afterwards. Ask for a clear scope covering the runners, beads and meeting rail, and compare a couple of quotes to understand fair value. When frames also need repair, it usually makes sense to price the two together.

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