bow window

How to Replace a Sash Window Cord

A traditional pair of sash windows make a great match for older properties – and some newer ones, too.  They incorporate one or more movable panels (or ‘sashes’) which can be slid up and down to open and close the window.  These panels are counter-balanced by weights, which hang on cords concealed by the window frame.  What happens when one of these cords snaps?  The sash gets stuck.

Replacing these cords can be a little fiddly, and so once you’ve got the window open, you’ll want to swap them all at the same time.  And, while you’re at it, you might as well install insulation brush strips around the sashes.  Brushes will keep those pesky draughts at bay and safeguard the overall performance of your window.

Let’s consider how the job might be done.

1.      Assemble your tools

Before getting started, you’ll want to be sure you’ve a few items to hand.  These include:

  • A filling knife
  • A flat-head screwdriver
  • A volunteer
  • Some nails
  • A hammer
  • New cords. Waxed cotton is best: it’ll move smoothly and will last for ages.

2.      Remove the sashes

From the inside of the building, prise the beading from the frame using either a knife or flat-head screwdriver.  You’ll then be able to lift out the inner sash and see into the compartments that house the weights.

The covers will flip open with a little encouragement from your screwdriver – but if they’ve been painted over, you’ll need to cut them out.  Between the two sashes is another layer of beading.  Remove it in the same way and free the sash.

3.      Remove the old cord

Having disassembled the window, you’ll be able to remove the old cords.  Before attempting this, cut the weights off the end using scissors.  Having freed the cord, you’ll be able to easily pull it out.

4.      Install the replacement cord into the outer sash

Get your volunteer to hold one end of the new cord, and then feed it over the pulley beside the outer sash channel.  Once you’ve pushed it around, you’ll see it dangle on the other side.  Pull it down and tie it securely to the weight.  Now repeat the procedure on the other side.

For the cord to be the right length, the outer sash should be a few inches above the windowsill when the top of the weight hits the pulley.  Get your volunteer to hold it in position and then pull the cord until you hear the weight impact the pulley. Then, secure the cord into the cord grove using a nail.  Trim away any excess and then replace the central beading.

5.      Install the replacement cord into the inner sash

Next, you’ll want to install your replacement cord into the inner sash.  Attach the new cord with nails in the same way.  This time, the cord is the right length if the weight is at the top of the channel when the sash is all the way down.

6.      Put everything back together

Your final task is to reassemble the window.  Replace the weight covers first, tapping them into place with your hammer.  Then, replace the sashes and the beading.  If any have been damaged during removal, they’re inexpensive and widely available.  Check everything’s working properly, and apply a coat of paint if you feel it necessary.

Looking for new windows for your home? Browse our sliding sash or conservation windows or find out about our handmade bespoke windows.

Want to learn more about sash windows? Check out our other posts:

How to Paint a Sash Window (without it sticking)

Sash Windows: uPVC or Timber?

How to Fix a Sash Window that Won’t Stay Open

wooden windows

Argon vs. Krypton vs. Xenon in Windows

When it comes to energy efficiency, windows are notoriously vulnerable.  Given a chance, they’ll drain the heat out of your home and into the great outdoors, far faster than brickwork and doors.

Of course, this isn’t a new problem, but in recent years better solutions have entered the market.  Of these, double-glazing is the best-known.  In a double-glazed window, two glass panels are placed parallel with one another, with a layer of insulating gas sandwiched in-between.

The precise makeup of this gas has changed over the years.  When the technology first appeared in Victorian Scotland, manufacturers used ordinary air.  During the middle of the 20th century, manufacturing techniques became more sophisticated, and the air was replaced with a vacuum.  Inside a modern double-glazed window, however, you’re likely to find one of three noble gases: namely argon, krypton or xenon.  Take a look at the periodic table, and you’ll find them stacked on the right-hand side.

But what are the practical differences between these gases?  Why is argon used in double glazing instead of air?

Why Argon in Windows?

Argon gas windows represent, in most situations, the optimal balance between performance and cost.  If you shop for double-glazed windows, you’ll tend to find that they feature argon alongside low-emissivity glass, and thereby drop heat gain during summer while keeping the interior cosy during winter.

Argon offers a thermal conductivity around a third lower than ordinary air, for only a marginal increase in cost.  Treated well, argon-filled double-glazing will last for more than two decades, losing only a fraction of its performance over the years.

Are Argon Filled Windows Worth It?

In most cases, argon-filled windows are an obvious choice.  Having said that, some circumstances might call for a more expensive, high-performance gas.

Why Krypton in Windows?

Krypton represents something of a middle-ground between argon and xenon.  It’s more expensive than the former, but less so than the latter.  It’s yet to overtake argon as the industry standard, on account of its higher price, but this might well change in the future, should manufacturing techniques become even more sophisticated.

Krypton-filled double-glazing tends to be thin.  Indeed, if krypton is used in a wider gap than, say, 20mm, convection currents will begin to form that transfer heat from the interior of the window to the exterior.

In old buildings, cavities were filled with single-paned windows, meaning there might not be sufficient room for a thicker argon-filled window.  You might therefore consider krypton-insulated windows as a means of preserving the aesthetic of the building while enhancing the insulation.  It’s worth considering the potential difficulties inherent in obtaining planning permission for a double-glazed window in a period property, since the difference in pressure between the two sides will generate a bowing effect on the glass.  This can undermine the appearance of the property from the outside.  That said, this drawback is common to every sort of double-glazing – not just krypton-filled windows.

If you don’t have any such space-restrictions to worry about, then you might cram multiple layers of krypton gas into the same window.  Triple-glazed krypton-insulated windows incorporate three panes of glass, the middle of which will interrupt the convection currents we’ve just discussed.  In the UK, such windows are installed only rarely, since temperatures don’t often dip low enough to justify them.  If you’d like to go down this route, however, krypton is worth considering.

Are Krypton-Filled Windows Worth It?

It’s difficult to state with certainty whether krypton-filled windows justify their price-point, as the answer will depend on your aims.  Most in the building industry will view them as an extravagance, but if you consider energy efficiency to be important, krypton might well prove tempting.

Why Xenon in Windows?

Let’s take a moment to consider trends in the world of architecture.  A modern skyscraper has a surface area made almost entirely from glass, and they’re not an exception – courthouses, swimming baths, service stations and office buildings across the country are increasingly transparent.  The advantages of this approach are obvious: glass allows more natural light into an interior, and helps us to see the world outside.

But how can architects incorporate such large expanses of glass without compromising the energy efficiency of the building?  One answer comes in the form of xenon.  Xenon-filled windows are a relatively recent innovation, and sit at the forefront of glazing technology.  They’ll insulate wonderfully.  But this performance comes with a price tag to match.

Xenon gas windows are therefore permitted in exceptional circumstances only.  If a business wants to achieve LEED certification for their headquarters, for example, then xenon might just be a way to do it.  Some residential circumstances might also warrant the use of xenon-filled double-glazing – but these are rare.

Are Xenon-Filled Windows Worth It?

The short answer is: probably not.  Xenon’s eye-watering price puts it out of reach of all but the most ambitious homeowners.  That said, if you’re planning your dream property, and you’d like to incorporate a lot of glass, then the performance of xenon might make it worth considering.

So What Should You Choose for Your Windows:  Argon, Krypton or Xenon?

When it comes to energy efficiency in double-glazed windows, the three gases could accurately be labelled as ‘Good, Better and Best’.  A denser gas will perform better as an insulator, but this performance comes at a cost.

Your choice of window will, to a large extent, depend on your personal tastes and circumstances.  For most of us, the insulating qualities of argon will be more than sufficient, and the cost of the more effective materials will outweigh their advantages.

Looking for new windows for your home? Browse our sliding sash or conservation windows or find out about our handmade bespoke windows.

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