Historic Windows – The Future?

Where original windows survive in domestic buildings in the UK these often date back to around the late mediaeval period, in other words around the 15th and 16th century. At that time only the wealthiest property owners could afford glass in windows. Therefore, most windows were merely openings with shutters. Some had oiled skins etc., to infill them but it would not have been usual to find them filled with glass. In higher status buildings one sometimes found an oriel window, but most were simple forms of a mullion window.

The window openings were formed in positions that seemed practical and fell within the frame structure and panels. They were sometimes symmetrically placed, but more often not. Many were small, as it was necessary to keep the weather out and heat in. However, there are examples of larger windows, particularly to the main hall, or significant rooms within a building.

Examples of various forms of windows can be seen in places such as Little Moreton Hall.

As the national economy and social stability improved in the 16th century there was a gradual increase in the ability of the middle and lower classes to afford glass. We start seeing the infilling of windows with glass in or around the 16th century and thereafter. At that time the production of glass meant that large panes were difficult to create, and windows would generally have been formed with small panes and each piece of glass held in place by lead. Although many of these panes would have been inset directly into the timber, there is evidence that some would have been in a metal frame.

Of course, these are generalisations and refer to the middle and lower order houses. It was always the case that the wealthy could afford better and there are many examples of larger houses containing glass from an earlier period. There are of course also examples of significant glass used in some notable buildings such as Hardwick Hall.

It is often said that windows are the eyes of a building and when standing before Hardwick Hall with the sun shining on the windows one begins to appreciate the truth of this statement. The irregularities in the glass and the small planes result in a glistening surface that gives the impression of eyes blinking in the sunlight.

The same effect cannot be achieved with modern flat glass and many so-called replica windows failed to achieve this glistening that is often seen in older windows.

During the 16th and 17th centuries there was increasing international trade and whilst there had always been influences from abroad, this was a period where it is notable that influences from foreign lands were seen in our buildings.

Apart from the more obvious impact of the classical orders of architecture (in particular Palladian style), one starts to see greater symmetry and proportions of windows that reflect classical proportions and in particular the golden ratio. More specifically, we see a new style of window being used and that is the sash window. As is typical with most foreign influences, the sash window was adapted and has become a unique English feature in buildings over the centuries.  An early example of the use of sash windows can be found at Chatsworth House.

As the manufacture of glass changed and improved it was possible to form larger panes of glass. Nonetheless, these were not so large that windows could be glazed in a single sheet. Therefore, the windows were subdivided by glazing bars and again this was usually in classical proportions.  The result was what is often regarded as ‘Georgian’ windows.

Recognising the extremes of weather experienced in the UK, the use of shutters was not lost, but incorporated into the design of many windows, usually internally, but sometimes externally.

In 1696 the Window Tax was introduced.  Although applied to all houses, it was intended to tax the wealthy and houses with more than 10 windows were taxed the most.  The Tax applied in various guises through to 1851, when it was repealed. One consequence of the Tax was the  design of buildings with blank and false windows in order to maintain architectural symmetry, etc., but without creating a taxable window.

Through much of the 18th and 19th century domestic buildings of all levels tended to be designed with sash windows to principal openings and casement windows reserved for the lesser openings, serving utility and other areas.

Then came the Arts and Crafts movement that looked back to the mediaeval period and reinterpreted some elements and design of those buildings. This often included the use of casement windows with quarrels of glass set in lead into a metal casement, usually set into a timber subframe.

Therefore, by the early 20th century there was a greater variety of window styles in the architectural designs of buildings. Also, through the 19th century there had been changes in the production of glass meaning that larger panes could be produced. This affected the style of windows in that glazing bars were no longer necessary. This resulted in a significant change to the appearance of windows.

Of course, many houses retained their earlier windows and the variety and changes were often only seen in new houses and where existing buildings were extended or altered.

During the 19th century, improved transportation (mainly by railway) meant that materials could be taken to all parts of the country. Towards the end of the 19th century and into the 20th century we see a significant reduction in regional variation. Although ‘design books’ had been in use for a couple of centuries, it becomes very noticeable how the improved transportation combined with use of design books resulted in a reduction in variety of style in architectural design.  In many ways this suited the rapid mass development seen in the last quarter of the 19th century.  Hence why many estates of terraced houses across the country have very similar features including styles of windows.

The changes in glass production and the ability to create very large panes/sheets of glass had an impact on window design, because the windows were no longer restrained by the size of glass that could be used.

In the 1910s an Essex based company set out to create metal framed windows and within a fairly short period of time Crittall windows were being widely used. One of the significant advantages of the Crittall window was that metal could easily be bent into shapes in a way that other materials could not, or at least it would be difficult to achieve the same curves, etc., in other materials This happened at about the same time that a new architectural movement was occurring and that was Art Deco. The combination of the technology and design resulted in some of the magnificent sweeping curved bays and design details that we often associate with art deco buildings.

Such windows are often ruined by trying to install replacement straight windows into what was a curved bay.

In the mid 20th century there was a growing trend in DIY, and increasing home ownership meant that owners wanted to put their own character into a building.  This often involved changing the windows. In attempts to get more light through smaller window openings there were many ‘picture’ windows formed.  We also saw many sash and casement windows removed to be infilled with large glass sheets.  This resulted in the many ‘picture’ windows we see from the 1960s and 1970s.

As the 20th century progressed there was an increasing desire to minimise heat loss through windows and a different driver arose to see major changes in how windows were regarded and dealt with.  This resulted in the installation of double glazing.  Many destroyed the character of the building, often ignoring proportions and any attempt at being sympathetic in style.

Picture windows below and double glazed windows above.

The foregoing has set out a brief overview of how windows have developed and how they are significant in the design of any building.

In the present day we have the benefits of a wide range of materials and technology that enables us to create windows of a significant variety. However, one problem remains. Older windows are now recognised as being poor insulators for buildings and a significant area where there will be heat loss.

In recent decades windows have become a primary focus for upgrading buildings in terms of thermal performance. The results have often seen the complete removal of old windows to be replaced with modern double glazed units. Earlier double glazed units were poor in terms of replicating any form of historic detail for windows and whilst there have been significant improvements in this regard, a replica windows still fails to capture the charm of original windows.

There is also the question of sustainability and embodied energy. One has to appreciate that the original window would have taken materials and energy to create. By simply destroying it we are losing that embodied energy unnecessarily and using yet more energy for its replacement.

Of course, if a window has deteriorated to the point of its replacement being inevitable, then a suitable replacement has to be found. However, in many instances lack of maintenance and regular redecoration are the simple causes of such deterioration and, therefore, could be avoided. Also, too frequently, we see the whole window ripped out and replaced when only a small amount of rot has been detected. We seem to have lost the ability to repair, but instead have taken on the approach of replacements and renewal.

From energy and sustainability points of view it is surely better to repair and maintain an existing window than to replace it?

However, if an older window is to be retained how can it be upgraded to provide better thermal performance?

We find that there are increasing technologies that enable us to install improved draught proofing and secondary glazing, which all help upgrade a window without its replacement.

This article is not intended to discuss these issues, merely to raise awareness. However, I and my fellow directors who run the successful Building Conservation Summer School, have organised a two-day window conference. The conference will look at the history of windows and glazing, methods of repair of various types and a look at how upgrading could be undertaken. There will also be consideration of planning issues, particularly relating to listed building consent. Mindful of the fact that sometimes a window might have to be replaced, there will be a look at what might be available for sympathetic replacement.

In light of increasing concern about global warming and energy consumption, as well as the problems of fuel poverty and the drive to improve the energy performance of buildings generally, this conference is timely. It also follows on from the recent guidance published by Historic England (https://historicengland.org.uk/advice/technical-advice/retrofit-and-energy-efficiency-in-historic-buildings/modifying-historic-windows-as-part-of-retrofitting-energy-saving-measures/). The conference draws upon some of the leading people in their specific fields.

This is an opportunity to hear about best practice when it comes to upgrading historic windows and avoiding unnecessary loss of what some might consider the glistening eyes of our historic buildings. Reserve the date: 22nd and 23rd September 2023.  Further information and ticketing will be published in due course.

Let me know if you might be interested in attending.

Stephen Boniface

7th February 2023

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