Sash window draught proofing fits hidden brush seals around both sashes, so air, dust and rattles stay out. We remove the sashes, rout grooves, fit the seals and rebuild the window. Overhaul and draught proofing together cost £188 per window. A five-year guarantee covers our labour and the system.
Why draught proof a sash window
Traditional sash windows need a small gap to slide. However, over a century or more, that gap grows. Wind finds it, dust follows it, and the sashes rattle at night.
So draught proofing closes the gap without changing the window. It is a small, reversible change to timber you already own. We repair first and seal second, because seals only work on a window that closes properly.
If you want to compare options, our guide to draught proofing versus secondary glazing sets out what each one fixes. In many period homes, draught proofing is the cheapest place to start, since it fixes the most common fault.
What it costs
Overhaul and draught proofing is £188 per window. For that price we take the sashes out and fit a seal system on every perimeter. We also fit new sash cords, new timber profiles and new hardware.
We also supply a Brighton fastener free of charge. It pulls the meeting rails more firmly together. As a result, the window closes tight and the latch works as it should.
However, some windows cost more to do. Very large sashes, difficult access and repairs all change the price. Our costs page lists every rate. We always quote in writing before we start.
Does it save money on heating
Draught proofing should lower your heating bill, because warm air no longer leaks out round the sashes. The size of the saving depends on your home, your boiler and how draughty the windows are now.
For that reason we do not promise a pound figure. Some websites claim hundreds of pounds a year, but we could not source a figure like that, so we do not repeat it. Instead, judge the benefit by comfort first. A room without a cold draught is one you can heat to a lower temperature.
There is one money fact we can source. HMRC’s VAT Notice 708/6 says the installation of draught stripping in residential accommodation is zero-rated from 1 May 2023 to 31 March 2027, and that it reverts to the 5% reduced rate from 1 April 2027. However, the notice applies this to installation, and it treats work done alongside other jobs as either one supply or separate supplies. Because of that, ask how the rate applies to your own quote.
Why nylon brush seals
We use nylon because cotton-based pile breaks down far too quickly in a window that moves every day. We find nylon holds up far better, so the seals keep working.
The amount of nylon in a window is small, too, because it is a thin line of fibre in each groove, not a whole plastic frame. For many homeowners, that is a fair trade for years of sealed windows.
The noise bonus
Sealing the gaps also cuts some noise. However, it will not match double glazing. Even so, it makes a real difference to a room on a busy London road.
For example, some clients keep their original single glazing and add draught proofing and heavy curtains. That costs far less than new glazing. If you want more, read about double glazing existing sash windows as a second step.
How we install the system
Every window follows the same steps.
- We remove both sashes and the staff and parting beads.
- We plane the sashes where needed, so they run true.
- We rout precise grooves into the frame and the sash edges.
- We fit nylon brush pile inside the grooves, where it stays invisible when the window is shut.
- We re-cord, re-balance and rebuild the window, then fit the Brighton fastener.
Because the sashes are out, this is the best moment for other work. We can replace tired cords, fix timber and change glass. Our sash cord replacement service fits neatly alongside it. The full package is our sash window overhaul.
When rattles are the real problem
Rattling does not always come from seals, because worn beads, shrinkage and loose sashes can all cause it. Our article on why sash windows rattle explains how to tell which one you have. If a window needs timber repair as well, our sash window repairs service covers it.
Get a quote
First, tell us how many windows you have and send a few photos through the contact page. We offer a free site visit and a written quote. We cover all Greater London postcodes and often work just outside the M25, Monday to Friday, 08:00 to 18:00.