From proportions and style to material, placement and detail, the choice of window carries more weight than many realise — not just in how a house looks, but in how it lives. ‘It’s difficult to overemphasise the importance of fenestration. Even subtle changes can completely alter the feel of a building,’ says Rupert Cunningham, director at Ben Pentreath. ‘Their proportions, shape, size, how they are framed, how deeply recessed they are, what they are made of and even what colour they are painted — all these factors matter.’
The history of windows traces back to the earliest forms of shelter. The first examples were little more than holes in walls, covered with timber shutters or animal hide treated with oils to admit light while keeping out the weather. The Romans were the first to use glass architecturally, although it was reserved for important buildings and offered limited clarity. For centuries, glass was made in small, uneven pieces — spun or blown, then joined with lead. This gave rise to the multi-paned windows now associated with medieval churches and Tudor houses.
It wasn’t until the Georgian era that larger, clearer panes became possible, thanks to techniques developed in France and industrialised in Britain. Further advances in the Victorian period allowed for even larger sheets of glass, fewer glazing bars, and improved transparency. By the 20th century, windows had evolved from functional necessity to design feature, with the Art Deco movement embracing bold, steel-framed styles. The float glass process, developed in the 1950s and which creates flat, even panes, made expansive windows a hallmark of modern architecture.
Today they come in all shapes and styles, but sash windows are perhaps the most common in Britain and certainly the most recognisable. Unlike casement designs, which open outward on hinges, sash windows slide vertically. They consist of two glazed panels set one in front of the other within a frame. Each moves within vertical grooves, counterbalanced by weights attached to cords concealed inside the frame. One of the key advantages of this type of window is ventilation. Opening both sashes allows warm air to escape from the top while cooler air enters below, creating a gentle through-draught during the warmer months. This is a familiar benefit, but there are other reasons why sash windows remain a fitting choice, especially in Georgian and Victorian homes.
‘Traditionally, all houses would have had timber windows, and these are as much a part of their identity as any other period feature,’ says Richard Dollar, managing director of The Sash Window Workshop. ‘When walking down the street, you can easily spot one that hasn’t been sympathetically replaced, as it will stand out for all the wrong reasons.’
Rupert expresses a similar view: ‘We’ve all seen a nice house from a distance, only to discover, to our horror, that the historic sashes have been torn out and replaced with plastic ones. They’re proportionately correct but materially repugnant. Similarly, we often see houses where the original sashes, subdivided by glazing bars, have been binned by the Victorians in favour of single-pane sashes that give the building a peculiarly blank and vacant appearance. As an architectural designer, a huge amount of my time is spent thinking about, as well as drawing and detailing, windows.’
Timber has long been the material of choice for period homes, valued not only for its natural feel but also for its longevity. ‘We recommend using Accoya wood,’ says Richard, ‘as it is highly durable and stable, meaning it requires minimal maintenance.’ But wood isn’t the only route. Metal frames — particularly in bronze — are becoming increasingly popular for their strength and versatility. ‘Many of our clients choose bronze for its distinct warmth and evident quality,’ says Architectural Bronze. ‘While other products are simply covered in a bronze-coloured, powder-coated finish, real bronze is a manganese brass with a rich colour that blends seamlessly with even the most contemporary or historic of homes. As a non-ferrous metal, bronze is also highly resistant to corrosion and develops its own natural patina over time, requiring little upkeep and offering both strength and elegance.’
Deciding whether to restore or replace windows depends largely on their condition, and the answer often lies somewhere in between. ‘Historic windows should be refurbished wherever possible,’ says Rupert, who recommends starting with draught-proofing and reinstating shutters if they’re still in place. At home, he uses discreet acrylic panels fixed with magnetic tape as temporary secondary glazing: ‘they come off easily in spring.’
In many cases, if the frames are sound, replacing the sashes alone can improve energy efficiency with minimal disruption. A simple adjustment to the glazing pattern can also have a surprisingly strong visual impact. Swapping a two-over-two sash for a six-over-six (glass panes), for instance, can better suit the proportions of a Georgian-style façade. With more glazing choices available today — including slim-profile double glazing, secondary glazing and restoration glass — it’s possible to improve thermal performance while preserving the look of the originals. Full replacement, however, may be necessary when damage is extensive or earlier repairs have built up over time.
Planning requirements also come into play, particularly for those living in conservation areas or listed buildings. Regulations can affect what is permitted, from materials to glazing patterns and the appearance of frames. These constraints may limit certain options, but they also help preserve the architectural rhythm of streets and neighbourhoods, where windows form a defining part of the streetscape.
Glazing can also be used inside the home to shape space and bring in light where solid walls might otherwise make things feel closed. Partitions between kitchens and pantries, for example, can introduce flow without sacrificing definition. On a larger scale, it can provide remarkably adaptable family rooms, breakfast areas, or places to read and relax.
Thoughtful window design depends on context. For James Thurstan Waterworth, success lies in how windows respond to their setting — whether framing a view, softening a street-facing room or opening a space to the garden. ‘In a London townhouse, the back and front serve different purposes,’ he says. ‘At the front, especially on the lower floors, it’s about balancing light with privacy. Sheers, curtains, the way you dress the window — all of that shifts the atmosphere. You can elevate an otherwise unremarkable space or make it deeply cosy.’
At the back, the view becomes central. ‘There’s nothing quite like that feeling of being connected to nature,’ he adds. ‘In a period house, I’ll usually keep sash windows. They just feel right. But if there’s a contemporary extension, I might suggest something cleaner and more open. It strengthens the connection with the garden and lets the outside in.’
