The History of Double Glazing in the UK

1960s

• In 1965, a pivotal shift occurred as the government implemented measures to safeguard future homes and their inhabitants by mandating construction standards in the Building Regulations Act. 
• Among these standards was a directive to adopt new technologies and materials to reduce energy expenses.
• At the same time, window experts introduced a ‘second window’ approach, replacing decaying wood and adding an additional glass layer to the original window. 

1970s

• It really wasn’t until the 1970s that double glazing became a major consideration in UK homes. 
• It still wasn’t a standard, though, because material prices were high, and there was no strict implementation of building codes.
• In the late 70s, aluminium double glazing was discovered, which was more cost-effective and low-maintenance than timber or steel frames. 
• The Glass and Glazing Federation (GGF) was established in 1977 to develop technical and safety standards in the glass industry.

1980s-90s

• Aluminium was replaced with warmer uPVC from Germany, the most cost-effective of all available materials.
• Georgian styles and woodgrain options revolutionised home aesthetics.
• Between 1979 and 1999, the adoption of double glazing in UK homes surged from 16% to 68%, significantly reducing internal condensation and creating a warmer, safer living space for British families.
• In 1997, the British Fenestration Rating Council (BFRC) was established to improve the energy performance of doors and windows.

2000s

• In 2002, the government released The Building (Amendment) Regulations requiring new and replacement windows to be double-glazed.
• FENSA (Fenestration Self-Assessment Scheme) was also established in 2002 to issue an official certificate to installers with energy-efficient doors and windows.

How Does Double Glazing Work?

Double-glazed windows feature an air gap between two glass layers, enhancing insulation against heat movement from outside to inside. This gap (typically between 5-12mm) is often filled with a gas like argon, chosen for its low heat conductivity, which further minimises heat loss. 

Using argon gas instead of air can increase the window’s insulation effectiveness by up to 30%. PVCu and aluminium frames, known for their durability and efficiency, are commonly used. In terms of the glass, they can be:

• float (flat finish)
• laminated (2 sheets), or 
• toughened (with heating tempering)

These features work well for three main homeowner concerns:

Saving energy

• Acoustic insulation is a poor conductor of heat, keeping the interior temperature stable regardless of outside conditions without relying on heating or cooling systems. 
• They also include a reflective e-coating on the inner side of each pane, designed to reflect heat back into the room, further enhancing their ability to retain warmth. 
• The Energy Savings Trust says replacing single-glazed windows with A-rated or A++-rated double-glazing in a semi-detached house can save between £175 and £235 annually.

Reducing noise

• Sound travels in waves, vibrating air and object molecules, with glass transmitting these vibrations to the other side when sound waves encounter it. 
• Double glazing dampens noise by absorbing energy and slowing vibration through the glass and Argon gas layer, slightly reducing sound intensity. 
• Disrupting sound waves with materials of varying thicknesses, such as different glass panes, is most effective in maximising noise reduction.

Reducing condensation

• The air around us contains invisible water molecules that condense into visible droplets when cooled to the dew point, leading to phenomena like steamy kitchen windows or bathroom mirrors. 
• Double-glazed windows combat internal condensation through a desiccant within the spacer bar to absorb moisture from the air trapped between the panes.

Technological Advances and Material Innovations

Throughout history, advancements in double glazing have been driven by the need to raise energy efficiency, especially during energy crises and instability. Innovators were also looking for better, more sustainable materials that could reduce manufacturing costs. 

Here are some breakthroughs that made double glazing the powerhouse it is now.

Electrochromic (EC) Glass

Electrochromic glass (also known as smart windows) can automatically block out sunlight without needing curtains or blinds. This glass works by using electricity to change how it looks and functions. 

When turned on, the glass can shift from clear to dark, adjusting how much light gets through and how effective it is at shading a room from the sun. This makes it a great option for big windows and spaces with a lot of glass, offering a built-in way to control light and heat from the sun.

It has a special coating that reacts when electricity is applied. This causes tiny metal particles in the coating to move to one side, creating a shaded effect. This technology is perfect for large glazed areas like skylights or tall windows where traditional shades or curtains wouldn’t work. 

• Research into electrochromism dates back to 1815, with Swedish chemist Jöns Jacob Berzelius demonstrating that tungsten trioxide changes colour when heated in dry hydrogen gas. 
• The term “electrochromism” was introduced in 1961 by American physicist John Rader Platt at Bell Laboratories, initially related to the colour changes under strong electric fields. 
• However, significant advancement in electrochromic technology happened in 1969, when scientist Satyen K. Deb experimented with an electric field applied to tungsten oxide, a breakthrough often considered the foundation of modern EC devices.

Low Emissivity (Low-E) Windows

These innovative windows, which became popular in the 1980s, are designed to let light in while keeping heat out during summer and retaining warmth inside during winter, helping to keep homes at a comfortable temperature. The US Department of Energy (DOE) notes that these special coatings can reduce energy lost through windows by 35%. 

Low-E windows have metallic coating on a plastic film between the glass layers, making them ‘spectrally selective’ (letting sunlight in while preventing heat from escaping). Although this metallic coating is almost invisible from the inside, it may give the windows a slightly mirrored appearance from the outside.

• These windows were developed in the 1970s because of the energy crisis in the US. 
• The DOE and Berkeley Laboratory in California worked with the window industry to tackle the issue of windows losing too much heat and energy. 
• They discovered a solution by combining efforts with the metal oxide coatings industry. 

Vacuum Glazing

Different types of double glazed windows vary in how thick the glass is, what kind of gas is used, and how the edges are put together. 

However, Vacuum insulated Glazing (VIG) is a bit different because it eliminates all air molecules between the two panels, creating a high pressure difference where external air presses the panes together. To counteract this and prevent the panes from bending inward and touching, micro-spacers, or small supportive pillars, are strategically placed within the vacuum glazing. 

VIG is especially good at keeping heat inside and reducing outside noise — making it much quieter inside. This technology is so effective that it can insulate a house up to five times better than standard double-glazing and even compete with triple-glazed windows while being lighter and less bulky. 

In the UK and North America, it’s often used in older buildings to improve insulation without changing how the windows look, known as ‘Heritage Windows.’

• The idea of VIG was introduced in 1913 by German scientist Zoller, but it was in the mid-1980s that significant research and development efforts resumed, notably in the US and Australia. 
• By 1996, the first commercial VIG product was launched in Japan, benefiting from the University of Sydney’s foundational research.
• By 1997, commercial production began, marking a significant achievement over eight decades after its initial concept. 

Triple Glazing

Triple glazing enhances energy efficiency by incorporating an additional glass pane and sealed space, along with low-E and low-iron panes to minimise heat loss and reflect warmth indoors. Its design, featuring spacer bars and argon gas-filled gaps, significantly boosts heat retention.

In the UK, triple glazing is still very rare, with the government admitting that it doesn’t have sufficient data on how many homes have it. However, a homeowner who invested £13,500 in triple glazing for their windows and doors reported a dramatic improvement in maintaining a consistent and warmer indoor temperature. 

Pending regulations in England may require windows to achieve a U-value (how easily heat can pass through windows) of 0.8 or lower, likely making triple glazing a standard for new constructions starting in 2025.

• Triple glazing was discovered in 1991 by scientists at Lawrence Berkeley National Laboratory, who patented a “thin triple-pane” glass window designed to significantly improve energy efficiency, potentially reducing heating costs by 39% and air conditioning costs by 28%. 
• The Berkeley team enhanced the window’s efficiency and lightness by inserting a slim glass layer sealed with an inert gas like krypton.
• Despite its innovative design, the breakthrough was not adopted due to its high cost and was forgotten. 
• But in 2019, the same Berkeley team resurrected the technology and found that the material is now one-eighth of its former cost. 

The Future of Double Glazing: Trends and Regulations

Even with all these developments, scientists continuously seek more resilient and flexible materials and manufacturing processes. Moreover, with the increasing shift to automated homes, double-glazed windows are about to get a lot thinner and smarter.

Self-Cleaning Glass Coating 

In 2016, University College London (UCL) researchers developed a window incorporating nanostructures that mimic the anti-reflective properties of moth eyes, enabling it to clean itself, save energy, and minimise internal light reflection. The technology uses a very thin layer of vanadium dioxide on the glass, a material chosen for its cost-effectiveness and availability, to control thermal radiation based on the outside temperature. 

This allows for the retention of heat during colder periods and the reflection of infrared radiation during warmer periods. This technology could reduce heating costs by up to 40%, making it particularly attractive for use in high-rise office buildings, but it also addressed the high maintenance costs associated with keeping building windows clean. 

The self-cleaning capability of the windows allows rainwater to form beads that roll off the surface, taking dirt and dust with them. 

Transparent Electrochromic (EC) Windows 

In 2021, Nanyang Technological University (NTU) researchers developed a revolutionary ‘smart’ window material that effectively manages heat transmission without blocking views, potentially reducing the energy needed for cooling and heating buildings. This material, intended for EC windows, can block a significant amount of the sun’s infrared radiation—the primary source of heat in sunlight—upon the flip of a switch. 

• Composed of a nanostructured mix, including titanium dioxide, tungsten trioxide, neodymium-niobium, and tin oxide, this composite can be coated onto windows, allowing users to control infrared heat passage electrically.
• The material can block up to 70% of infrared radiation while allowing up to 90% of visible light through, making it about 30% more efficient in heat regulation than existing solutions and more cost-effective due to its durability.
• Unlike traditional EC windows that darken to reduce light entry, NTU’s innovation selectively filters out unwanted heat while maintaining transparency.

The research team has expanded the technology’s capabilities by developing a system to control conducted heat, integrating magnetic carbon-based particles and thin films to regulate heat transfer through the window. 

Aerogel Glazing

Aerogel is an incredibly light solid formed by replacing the liquid part of a gel with air, resulting in a material similar to very light sand, making up about 99% of its structure. 

This unique composition gives aerogel an exceptionally low weight and makes it an outstanding insulator because it mainly consists of tiny, interlinked particles of silica (a type of sand) that take up only 3% of its space. Known as the lightest solid on Earth, aerogel is known for its top-notch insulating abilities. 

In 2023, University of Colorado Boulder researchers developed a transparent aerogel made from wood that could replace the air in double-glazed windows, enhancing their insulation to match that of walls. This could solve limitations in boosting window insulation, such as adding more glass layers or widening the air gap.

Environmental and Regulatory Drivers

Even with the advancements in double glazing technology, 23% of UK households still have pre-2002 models in 2023, which were found to be 50% less energy-efficient by the GGF. The organisation also said that 80 million windows must be replaced in the country to achieve the Net-Zero goals by 2050.

Because of increasing pressure to fulfil environmental pledges, the UK government is ramping up its regulations to encourage homes to transition to more sustainable improvements. One of the comprehensive regulations so far, The Future Homes and Buildings Standard, was launched in 2021 with the following rules:

• By 2025, new homes are to be highly energy-efficient, incorporate low carbon heating systems, and be prepared to achieve zero carbon emissions, with an expectation to emit 75-80% less carbon than current standards. 
• Starting in 2021, new homes will be required to generate 31% less carbon emissions to ensure the industry aligns with the forthcoming regulations. 
• Existing homes are not exempt from these advancements; they will face elevated standards, particularly in extensions and renovations, to enhance warmth and efficiency, including the mandate for energy-efficient replacements and repairs in windows, building services, and lighting.

To support this transition, the government provides financial help or grants for low-income households who want to update or replace their windows, with some grants covering as much as 100% of the costs.

Moreover, window installers and organisations are developing recycling schemes. For example, FENSA introduced a complementary uPVC recycling initiative for its Approved Installers in Scotland, Wales, and parts of England. 

This recycling program addresses the growing public concern over plastic waste by preventing window and door frames from ending in landfills. The scheme completes the ‘circular economy’ loop by transforming collected PVC-U windows and frames into recycled pellets, which are then used to create new glazing products.