Who invented the sash window and what are its virtues? Why did builders not adopt the inward-opening

Who invented the sash window and what are its virtues? Why did builders not adopt the inward-opening French window, which is simpler and more easily cleaned?

• MOST probably, sash windows were not 'invented' but developed from the simpler horizontal sliding sash (known today as the 'Yorkshire' sash). They are supposed to have come from Holland in the seventeenth century. However, W. Horman, in his Vulgaria , printed in 1519, writes: 'Glasen wyndowis let in the lyght . . . I have many prety wyndowes shette with levys goynge up and down.' They were first used conspicuously at Chatsworth in 1676-80 and then in 1685 at the Banqueting House at Whitehall, designed by Inigo Jones, where they replaced the original casement (i.e., side-hung) windows. They became exceedingly popular; earlier windows were replaced with sashes, and sashes were used almost exclusively in new buildings, from cottages to palaces, throughout Britain and the colonies, until early this century. This phenomenal 250-year success story is due to the many excellent qualities of the sash window. For instance, the opening of the window can be finely adjusted, down to a narrow gap at the top or the bottom or both, giving good control of ventilation with little danger of rain blowing into the room. A 'French' window or inward opening casement is very vulnerable in this respect, and would be quite unsuited to British weather. The sash, being hung from each of its top corners, rather than from the side as with a hinged window, is less likely to distort under its own weight. This has several consequences. Less distortion means longer life: there are many sash windows still serviceable after 150 years or more. Imagine a 150-year-old plastic window! Casement windows need wider components for stiffness. Larger casement windows need two lights (the moving parts) which necessarily meet side by side in the centre and so, from the visual point of view, give a strong central vertical emphasis. The wooden structure of the sash, on the other hand, can be made with thinner sections, giving more light and a more delicate appearance, and could be vertically divided into three panes, harmonising with the classical style and so becoming the principal feature of the graceful and elegant buildings of the Queen Anne and Georgian periods. Sash windows are less highly regarded today than they were, but they are very much victims of their longevity; that rattling, draughty but unopenable old window may well have functioned beautifully for the first 100 years of its life; but in refusing to die gracefully has become the victim of inexperienced tradesman and heavy-handed DIYers. A new plastic window will need replacing entirely in about 20 years; in the same period a new sash window will probably only need new cords, if that.

  Jacob Butler, Joiner, Bonsall, Derbyshire.

• Further to the above, ventilation is superb with a sash window. Hot air in a room rises; this creates lower pressure towards floor level drawing in fresh air from outside through the bottom of the sash, and the hot air is pushed out of the top of the sash. Even with just a tiny bit open top and bottom, you can get naturally-powered ventilation, without a gale rushing through the room, or even creating a noticeable draught. And you can lock them slightly open very easily, so you get burglar-proof ventilation.

  John Rymell, Stepney