An A-rated efficiency rating and low maintenance were probably far from Englishman Robert Hooke’s mind when he designed and created the first sash windows.

Hooke, who was Surveyor to the City of London and chief assistant to Christopher Wren, helped rebuild London after the Great Fire in 1666. The first sash window to appear in the England was fitted in Ham House, on the banks of the River Thames, in the 1670s.

And his window design has stood the test of time. Sash windows continue to have an upper and lower sash that slides vertically to open. The movable casing that holds the glass panes is actually called the “sash” and in the original design they were made of wood.

The weight of the glazed panel is balanced by a steel, lead or cast iron sash weight or counterweight concealed in the window frame. The sash weight is connected to the window by a cord or chain that runs over a pulley at the top of the frame,

It is not hard to understand their appeal. Sash windows were used throughout homes in the Victorian and Georgian eras and are particularly suited to houses with a classic period appearance.

The biggest advantage of sash windows is the air circulation they generate. By opening the bottom and top of the window, so they overlap in the centre, cool air will come in through the lower opening while allowing warm air to leave from the top opening. By opening just the top of a kitchen window will let any smoke made from cooking escape.

Tim Cork, the MD of You Choose Windows warns: "Original sash windows, however, were invariably made from wood. This can create problems for homeowners with original sash windows because they can become difficult to open."

This happens because Britain’s wet weather causes the wood frame to swell or because friction has caused a wear spot.

If your sash windows are showing signs of age and decay, do not force the window open. This will either cause it to jam or even break the glass panes.

Many homeowners consider replacing their original wooden frames with modern uPVC sash windows, but what if your home is a listed buildings, in a Conservation Area or has a leasehold agreement with stringent management conditions?

How to maintain sash windows

If the sash is stuck, gently raise the bottom sash all the way up and then apply beeswax at the point where the window has jammed. Then repeat the same steps for the upper sash.

If the paint on the wooden frames of your sash window needs renewing, first remove the old paint from the glazing bars. Care needs to be taken when doing this because older paint typically contains lead.

Next, repaint by first applying masking tape to the window panes and use a small brush for the glazing bars. Once the paint is dry, remove the masking tape and wash the glass panes.

Sash windows can become drafty over the years but products such as felt stripping can cure this problem.

With regular care and maintenance sash windows can last for many years without needing replacement. There are many products available to make them very energy efficient and by leaving them in place your home will maintains its historical value.

How to choose a replacement sash window

There are occasions when sash windows will need replacing. If you choose to replace the wood frames with modern uPVC sashes, you will benefit from enhanced heat retention and nominal maintenance.

Most uPVC sash windows are made to measure and come with weather-resistant seals and A-rated Argon filled glazing, ensuring optimal energy efficiency.

And jammed windows will no longer be a problem. The sliding motion of uPVC frames is assisted by hidden spring mechanisms for smooth movement. Each sash should also have a built-in tilt function for easy cleaning. 

Also read about: The Advantages of Installing Double Glazed Windows