Sash Window Draught Proofing: Fitted by Restoration Specialists

Professional sash window draught proofing

• End draughts and window rattle at the source, not just mask the symptoms
• Help your home’s energy efficiency and EPC rating
• Reduce noise and help keep dust out
• Stay completely invisible: the seals sit inside new timber beads, machined to match and primed
• Leave your sashes gliding better than before, not jammed like stick-on DIY strips
• Need no scaffolding in 95% of cases, because sashes come out from inside the room

Why are sash windows draughty?

Now, a sliding sash needs a few millimetres of clearance to move at all.

Multiply that small gap around the full perimeter of two sashes and it adds up to the equivalent of leaving the window open a crack all winter.

Historic England puts it plainly: about one-fifth of a home’s heating is lost through windows, and most of that escapes through air gaps rather than through the glass.

Then add a century of seasonal movement.

Timber shrinks, beads wear, putty perishes, and the gaps grow. The same oversized channels that let the cold in also let the sashes knock about in the wind, which is your rattle. Draughty sash windows and rattling sash windows are one problem wearing two hats.

There are four ways people deal with it:

• Stick-on foam strips from a DIY kit: cheap, but short-lived
• Silicone or sealant around the fixed edges: helps a little, but does nothing for the sliding gaps
• Replacement windows: expensive, and your home’s character goes in the skip
• Professional draught proofing, fitted within a proper restoration: that’s where we can help

How our sash window draught proofing works

We don’t stick seals onto tired old beads.

Draught-proofing over unsound timber is wallpapering over a leak, so we take your sashes out from inside the room, put right whatever the survey found first (frayed cords, seized pulleys, rotten timber), and then fit new staff bead and parting bead with pre-installed brush pile, primed and fitted.

Brush pile is the usual choice.

Where a window calls for it, we set an acoustic foam seal into the same groove in the bead instead: the sash slides just as freely, the gap closes more tightly, and more of the street noise stays outside. It’s a hard-wearing compression seal built into the timber, nothing like the stick-on foam strip from a DIY kit.

Seals sit at every point where air sneaks through.

Because the seals are carried in new, replaceable beads rather than channels routed into your Victorian sashes, the system copes with boxes that have gone slightly out of true, which, after a century, most have. The pile itself is a renewable part, so when it eventually wears, it’s replaced without disturbing the joinery.

Everything goes back primed, not painted. Exterior painting can be added as an optional extra, but it isn’t in the standard estimate or quote, and the new beads take paint like any other timber.

Does it actually work? Historic England says air infiltration through a sash window in good condition can be cut by as much as 86% with draught-proofing.

Whole houses, whole elevations

We take on projects of five windows or more. It’s how we can send a proper restoration team to your home, and it’s why the results last.

Because everything is done on-site, we work on houses with garden or yard space for our workbenches. Flats, sadly, don’t give us the room we need. How bays, French doors and coupled sashes count towards the five is on our minimum order page.

Draught-proofing is the silent hero of the restored window world: you never look at it, and it earns its keep every cold night for decades.

How much does sash window draught proofing cost?

Draught-proofing costs £260–£360 per window, and that buys you new staff bead and parting bead with pre-installed brush pile, primed and fitted while your sashes are out for restoration, not seals stuck to the old ones.

For context, a national cost guide puts the average at £318 per window. That £260–£360 is the draught-proofing element of a full overhaul of every window, priced on top of the restoration itself rather than folded into it.

Across a typical five-window project, budget £1,300–£1,800 for the draught-proofing element. If you’re reglazing your original sashes with vacuum glass, draught-proofing is already included in that package.

Our full sash window repair prices are published, so you can see where every pound goes before you ring us.

One more thing on price: draught stripping is zero-rated for VAT, 0% until 31 March 2027 and 5% after that, while cord, pulley, rot and decoration work is charged at 20%. There’s a fuller explanation on our 0% VAT on draught proofing page.

Is it worth it? Historic England’s draught-proofing guidance spells it out: draughts make people feel colder, so they often turn the heating up and run it for longer.

A draught-free room feels warmer at a lower thermostat setting.

The same guidance is careful to add that how much heat your windows lose depends on how many you have, how big they are and what state they’re in, which is exactly what the survey tells you.

And if a heat pump is on your list, an MCS-certified installer sizes it from a heat loss calculation that records your windows as the surveyor finds them, which is why, as we see it, the windows come before the heat pump.

Can you draught proof sash windows yourself?

In some cases, yes. If you’re renting, or nursing one cold room through a winter, a DIY draught proofing kit and a careful hour are a sensible stop-gap.

The trouble is what happens next. The Energy Saving Trust is blunt about it: foam strips “do not work well” on sliding sash windows, and its advice is to fit brush strips or consult a professional. And no kit fixes the reasons your windows leak in the first place: worn beads, dropped sashes, perished putty. Proper draught proofing for sash windows starts with the window, not the seal.

Here’s the thing about a stick-on strip on your sash. The sash slides, so anything stuck to a moving face is dragged and peeled every time you open the window.

And the strip only seals the face it’s stuck to, while your draught is coming through the whole perimeter of two sashes and the full height of both bead channels, on beads that have worn hollow. So the strip fails at the bead, and the draught carries on.

Do sash windows need ventilation after draught proofing?

They do, and they keep it. A draught is simply ventilation you didn’t ask for: the difference between opening a window because you want to, and the window deciding for you.

Your sashes still open, and more smoothly than before, so you can air a room whenever you choose, and the Energy Saving Trust notes that controlled ventilation like this helps reduce condensation and damp.

Draught proofing never touches trickle vents or airbricks.

Tell us at the survey if any room has an open fire, a gas fire or another appliance that burns fuel. Historic England says those rooms need care, with specialist advice before anything is sealed, and the Energy Saving Trust says the fixed ventilation openings a flueless or open-flue gas heater needs must not be blocked.

Draught-proofed is not hermetically sealed; it’s a door you can open rather than a hole in the wall.

Casement windows, bay windows, all timber windows welcome

Now, don’t let the name on the van fool you.

We draught proof and restore every kind of period wooden window and door: casement windows, bay windows, gothic and arched windows, leaded lights, French doors, even timber conservatories.

Casements get compression seals suited to a hinged closing action rather than sliding brush pile: the right seal for the right movement.

Conservation areas and listed buildings

Because our seals are carried in new, replaceable staff and parting beads, with nothing routed into the original sashes or box frame, the draught-proofing is discreet and reversible.

Historic England’s Advice Note 18 says draught-proofing of windows will almost invariably be acceptable in a listed building, usually with only a negligible effect on its special interest.

If your house is in a conservation area but not listed, it’s rarely an issue: new beads are a like-for-like repair and don’t change how the window looks from the street, though councils differ, so ask yours if you want certainty. For wider works such as reglazing, check for an Article 4 Direction first.

For a listed building, the same advice note says listed building consent is unlikely to be required for draught-proofing, apart from rare exceptions such as windows of exceptional delicacy or ones that can’t be draught-proofed unobtrusively; reglazing is different, and consent is likely to be needed for that.

Can you double glaze draught-proofed sash windows?

Yes, and it’s the natural next step: draught proofing tackles the air gaps, and the glass is the other half of the story.

Our vacuum double glazing retrofit reglazes your original sashes with ultra-thin vacuum insulated glass around 8mm thick, 8–12 times more efficient than the single glazing it replaces, with draught-proofing, frame restoration and priming all included.

To take the vacuum unit, each sash is rebated deeper; what you keep is the original sash and its glazing bars.

If reglazing is on the cards at all, have it done in the same visit.

Reglazing runs around 30% more than restoration alone; leave it for a later job and you pay for the restoration a second time, because every sash has to come out again to be rebated deeper and rebalanced for the heavier glass.

Where we work

From Norfolk farmhouses to Kentish cottages, we restore and draught proof period timber windows across twelve counties: Essex, Cambridgeshire, Suffolk, Hertfordshire, Bedfordshire, Northamptonshire, Buckinghamshire, Norfolk, Kent, Surrey, Berkshire, and London, where our sash window repairs in London page covers the capital.

For a local example in detail, see sash window draught proofing in Essex, and the full list of areas we cover shows every town we travel to.

Frequently asked questions

How much does it cost to draught proof sash windows?

£260–£360 per window, fitted as part of a restoration project.

Where a window lands in that range depends on its size, the condition of the existing beads and how much overhaul it needs: bays with perished beads sit at the top of the range, sound bedroom sashes at the bottom.

Will draught proofing stop my sash windows rattling?

Yes, because rattle and draughts are the same fault. Sashes rattle because they sit loose in oversized channels, and wind moves them about.

The brush pile or acoustic foam seal in the new parting and staff beads holds each sash snug in its channel, so there’s nothing left to knock. On the first windy night, the silence is usually what you notice before the warmth.

Will draught proofing change how my windows look?

No. The seals are concealed inside new timber staff and parting beads, machined to match the originals and primed before fitting. With the window closed you cannot see a single seal, inside or out.

Sightlines, mouldings and all the architectural character of your period windows stay exactly as they were. The only visible difference is windows that sit properly in their frames.

How can I insulate my old windows without replacing them?

Draught proof them first, then reglaze the original sashes.

Most of what a period window loses goes out through air gaps rather than the glass, so new staff and parting beads with the brush pile built in close those gaps without changing how the window looks.

Then the glass: your original sashes can be reglazed with vacuum insulated units, each sash rebated deeper to take the unit, the sash and its glazing bars kept. Both happen in one visit, and neither is a replacement window.

Does draught proofing help with condensation?

It helps you control it.

Condensation forms when warm, moist air meets cold glass.

Draught proofing doesn’t warm the glass, but it replaces permanent uncontrolled airflow with ventilation you choose.

For persistent condensation on windows, pairing draught proofing with vacuum glazing warms the inner pane and tackles the cause.

If a room already struggles with damp, tell us at the survey and we’ll make sure it keeps the ventilation it needs.