Glass Windows Through Time: 2025 Edition

Few aspects of a building shape our experience of a space as much as its windows. They offer protection, let in natural light, and connect our indoor environments to the outside world. Yet, the window we take for granted today has been anything but ordinary throughout history. From unglazed roof openings in ancient times to high-performance glass solutions in modern skylights, windows are the result of centuries of experimentation, breakthroughs, and even serendipitous accidents.

In this updated 2025 edition of Glass Windows Through Time, we’ll explore key milestones, technological evolutions, and cultural shifts that have influenced window design—while also showcasing how we at Sunsquare carry forward these remarkable traditions with our own skylight solutions for contemporary living.

1. Early Windows (13th Century BC and Beyond)

The story of windows starts simply, with unglazed openings that served as vents for smoke and stale air. Archaeological evidence indicates that some of the earliest windows date back to around the 13th century BC—essentially holes in roofs or walls that were left uncovered or sealed with organic materials like animal hide, thinly scraped horn, or even paper in regions of East Asia.

Key takeaway:

• Ancient windows prioritised ventilation and basic illumination over clarity.
• Materials like paper (used in places such as China and Japan), horn, and even wooden shutters often replaced glass for the vast majority of people well into the Middle Ages.

2. Roman Windows (1st Century AD)

The Romans significantly advanced the idea of using glass in windows. It’s believed they first created glass panes in Alexandria, Egypt, using thick, imperfect slabs to keep out the elements. These rudimentary panes appeared especially in Roman bathhouses, where they sometimes sealed windows with thin panes of lapis to retain warmth and steam.

However, glass remained a luxury. Only the wealthiest homes and public buildings featured glass windows at this time, and the quality was far from the transparent, uniformly thick panes we enjoy today.

Key takeaway:

• Romans led the way in large-scale architectural uses of glass.
• Glass was predominantly a status symbol, restricted to affluent households and grand public spaces like bathhouses.

3. Stained Glass and the Middle Ages

With the decline of the Roman Empire, many of their glassmaking techniques disappeared in Europe for centuries. As a result, most medieval window openings were unglazed or covered with parchment, animal skin, or shutters.

By the High Middle Ages, stained glass became increasingly popular, particularly in churches and cathedrals. These awe-inspiring works of art—colourful narrative windows depicting biblical stories—ushered in a rich tradition of windows not just as functional openings but as vehicles for light, colour, and spiritual symbolism.

Key takeaway:

• Stained glass popularised the idea that windows could be both functional and artistic.
• Ordinary people still relied on cheaper seals like horn or shutters, reinforcing the exclusive nature of glass.

4. Tudor & Elizabethan Era: The Growth of Glassmaking

In the late medieval to Tudor period (15th–16th centuries), glass manufacturing techniques in Europe began to improve, spurred by developments in blowing, flattening, and forming glass cylinders. Gradually, glass began to filter into the homes of the growing middle class.

During Elizabethan times, large windows became a symbol of wealth and status. Prodigious homes, such as Hardwick Hall in England—famously “more glass than wall”—demonstrated just how coveted and showy substantial windows could be. Nobles away from their estates would sometimes remove or store their glass sashes for safekeeping, illustrating how expensive and prized glass was.

Key takeaway:

• Glass windows were still expensive, so partial glazing (only half the windows) was common for the upper middle class.
• Large panes of glass were equated with social standing and architectural prominence.

5. The Emergence of Sash Windows (17th–18th Centuries)

By the 1600s, sash windows—consisting of one or more movable panels—became widespread in Europe. Soon after, the vertical sliding sash window emerged as a hallmark of British design and quickly gained popularity in towns and cities. These windows could be held open at various heights, allowing more control over ventilation.

Meanwhile, different glass production methods, such as crown glass (flattening a blown bubble, reheating it, and spinning it to form a disk) and broad sheet glass (blown cylinders that were then cut and laid flat), were becoming more refined. Crown glass was relatively cheap and fairly effective, though it often had characteristic ripples and a ‘bullseye’ mark in the centre.

Key takeaway:

• Sash windows offered new levels of convenience and ventilation.
• Crown glass was the most economical method for large-scale window production until the 19th century.

6. Plate Glass and Floor-to-Ceiling Windows (Late 18th–19th Centuries)

Plate glass first surfaced around 1700, enabling thicker and smoother panes compared to crown glass. However, it wouldn’t dominate the market until the 19th century when industrialisation drastically cut production costs. The cylinder method of making sheet glass, alongside improved polishing processes, meant plate glass could be produced in ever-larger sizes.

Architects seized these opportunities to incorporate floor-to-ceiling windows in Regency and Victorian homes, particularly in urban townhouses. Such windows filled interior spaces with light and provided views of well-tended gardens or bustling streets—redefining the experience of interior living.

Key takeaway:

• Plate glass revolutionised window transparency, scale, and affordability.
• Large windows became more commonplace, reflecting industrial capabilities and middle-class aspirations.

7. The Float Glass Revolution (1950s)

Though early float glass experiments date back to the mid-19th century, it was Sir Alastair Pilkington in 1959 who perfected the modern float glass process. By floating molten glass on a bed of molten metal (usually tin), manufacturers could achieve consistently even thickness and a virtually distortion-free surface. This method remains the global standard for flat glass production, enabling the skyscrapers, panoramic windows, and extensive glazing we see in the modern world.

Key takeaway:

• Float glass provided the foundation for widespread glass usage in high-rise buildings and residential architecture.
• Uniform thickness and clarity drastically improved the aesthetics and structural potential of glazing.

8. Laminated Glass & PVC-U Systems

Around 1903, the French chemist Edouard Benedictus made a chance discovery—later perfected by others—that led to laminated glass (two sheets of glass with a plastic interlayer). This innovation greatly enhanced safety by ensuring the glass would hold together if shattered, paving the way for large-scale and more daring architectural designs.

In the late 1970s and early 1980s, PVC-U (unplasticized polyvinyl chloride) windows arrived in the UK, providing a lower-maintenance, weather-resistant alternative to traditional wooden frames. Alongside aluminium and timber-aluminium composite frames, these developments significantly expanded choices for homeowners and architects looking for improved insulation and design flexibility.

Key takeaway:

• Laminated glass improved safety and allowed for increasingly larger windows.
• PVC-U systems offered high durability and insulation, further democratising the use of glass in everyday homes.

9. Modern & Contemporary Windows: Going Bigger, Smarter, and Greener

By the late 20th century, windows were not merely a functional necessity; they became central to architectural style, energy efficiency, and sustainability. Insulated double- and triple-glazed units, low-emissivity coatings, and innovative frame materials drove a new era in building regulations aimed at improving thermal performance and reducing energy consumption.

In the 21st century, windows and skylights have become smarter still. Glass coatings can filter out harmful UV rays, self-cleaning surfaces reduce maintenance, and advanced glazing techniques drastically cut heat transfer while still letting in the sun’s warmth.

The Sunsquare Approach

At Sunsquare, we’re proud to be at the forefront of modern glazing innovation for roof windows and skylights. Our range—which includes the SkyView Fixed Rooflight, the Aero Electric Vent Rooflight, and the award-winning Smartsquare (the world’s first truly smart skylight)—embraces the best of the window revolution:

• Thermally broken aluminium frames to minimise heat transfer.
• Multiple polyamide insulation barriers for improved energy performance.
• Laminated inner panes as standard to enhance safety.
• Advanced electronic controls that can integrate with smart home systems (e.g., Alexa, Google Home, Siri), offering remote operation and weather-response features.

By combining the latest in structural engineering with centuries of glassmaking progress, Sunsquare’s skylights infuse natural light into any environment—whether it’s a loft conversion, modern extension, or bespoke commercial building.

10. What’s Next? Future Trends in Window & Skylight Design

Sustainability remains a driving force. As building regulations and energy standards become more stringent worldwide, demand for ultra-efficient glazing solutions will soar. Dynamic glass technologies, which tint or clear automatically based on sunlight and temperature, could become increasingly mainstream. Aerogel insulation, a NASA-pioneered material used by some cutting-edge manufacturers (including certain vertical window systems), might eventually find more extensive adoption in skylights, drastically improving thermal performance.

Additionally, the push for solar integration—where glass windows and skylights can harvest solar energy—remains on the horizon. Transparent photovoltaics are already in development, indicating a future where your windows could generate electricity without compromising on aesthetics.

Conclusion

From the earliest unglazed openings of the 13th century BC to the laminated, sealed, and high-performance windows of the modern era, the evolution of glass windows is a story of endless ingenuity, social aspiration, and technological breakthroughs. With every new leap forward—be it the Romans’ pioneering uses of glass or the Industrial Revolution’s democratisation of large panes—windows have shaped not just our buildings but our understanding of comfort, style, and connection to the outside world.

Today, at Sunsquare, we strive to carry this legacy forward by blending the latest manufacturing innovations with timeless design. Whether you’re seeking a sleek, fixed skylight like our SkyView, a vented model for fresh air, or a fully electric access rooflight for elegant rooftop entry, we’re here to help you reimagine what windows can do for your space.

Want to Know More?

If you’d like to learn how our Sunsquare skylights and rooflights can transform your home or commercial project, our expert team is on hand to discuss everything from design possibilities to building regulations.

• Call us on +44 (0)1922 714087
• Email sales@sunsquare.co.uk
• Or visit our contact page for more information.

Bring history, innovation, and your unique vision together—choose Sunsquare for skylights that stand the test of time.