27 years of Spacia™: How the world’s first vacuum insulating glass is shaping a sustainable future

Spacia, launched in 1997, was the world’s first commercially viable vacuum insulating glass. A 0.2 mm vacuum layer is sandwiched between two panes of glass, providing exceptional insulation—much like a vacuum flask keeps hot or cold liquids at their temperature for hours.

Of course, without support, the two panes of glass would be pressed together by atmospheric pressure. To maintain the vacuum layer, “microspacers”—tiny metal pieces scarcely visible to the naked eye— are placed at 2 cm intervals.

The microspacers that prevent the two panes of glass from touching are held in place by pressure alone, without the use of adhesives. By dispensing with unnecessary materials, the glass can maintain its performance over a long period. This unique technology gives Spacia exceptional insulation performance—about four times that of standard single-pane glass and roughly twice that of typical double-glazed glass, which has become increasingly common.

Spacia, a testament to the global edge of NSG Group’s manufacturing technology, has led the field for more than a quarter of a century since its launch.

In Japan, except in Hokkaido and northern Honshu, most homes are fitted with single-pane sash windows. These spread widely during the rapid economic growth of the 1970s, when housing was in short supply, because they were relatively inexpensive, easy to mass-produce, lightweight, simple to process, and quick to install.

However, while single-pane glass windows keep out the rain and wind, they readily transfer heat and offer poor insulation. Since the 1990s, as energy efficiency became a priority, double- and even triple-glazed windows have also become more common outside cold-climate regions.

In Japan, the push toward carbon neutrality—reducing climate change impacts and protecting the environment—has created strong demand for highly insulating windows. In practice, however, replacing not only the glass but also the sash frames with ones suitable for double glazing is costly and time-consuming.

In this respect, Spacia offers a major advantage: it allows windows to be upgraded for better insulation more easily and at lower cost than conventional methods. Although it consists of two panes of glass with a vacuum layer, Spacia is thin enough to fit into existing single-pane window sashes. In other words, unlike double glazing, it does not require bulky sashes—only the replacement of the existing single pane of glass.

Replacing the glass alone takes only about 30 minutes per window panel. You simply disassemble the existing sash, fit in Spacia, and reassemble it. This approach improves window insulation not only in existing homes across Japan, but also in many commercial and public buildings.

Spacia is increasingly being used to enhance insulation in local government offices, hospitals, and nursing homes, where extended shutdowns would cause major disruption.

One example is Mitaka City Hall in Tokyo. During the 2011 renovation, Spacia was installed for all windows. The improved insulation enhanced the air conditioners’ cooling effect in summer and cut electricity bills in winter by roughly half. Thanks to the better insulation, the offices stayed warmer in winter, particularly at your feet, eliminating the need for additional personal heating devices.

The Kurume City Environmental Department building in Fukuoka Prefecture, over 30 years old, was renovated in 2021 and became the first existing building in Japan to achieve Net Zero Energy Building (ZEB) certification. ZEB certification is only granted to buildings that have the highest energy-saving performance rating in the Building-Housing Energy-efficiency Labeling System (BELS) and satisfy stricter requirements. ZEB-certified buildings are those with net zero energy consumption achieved through energy-saving measures, such as enhanced insulation, and use of solar power or other renewable energy. In Kurume, this was accomplished by improving the insulation of window openings with Spacia, installing solar panels, and updating aging air conditioning systems. Until this renovation, ZEB was considered practically attainable only in new construction, making this achievement all the more significant.

The former Japan Post Building in Kasumigaseki, Tokyo, is being renovated to serve as the Ministry of the Environment’s new office, with relocation scheduled for fiscal 2027. Spacia has been adopted, and a range of measures to ensure high environmental performance—including enhanced insulation—have enabled the building to achieve “ZEB Ready” certification, meaning its primary energy consumption has been reduced by over 50%. This project is expected to become a model for decarbonization in large-scale renovations and to influence other government ministries and agencies.

In addition, major homebuilders are planning housing products that fully incorporate Spacia, and leading restaurant chains have adopted it for their store windows. Strong performance in the BtoB market is helping drive business growth. Because Spacia can greatly improve insulation performance simply by replacing the glass, it is poised to become an essential technology for advancing the decarbonization of Japan’s building stock.

To achieve its Medium Term Plan “2030 Vision: Shift the Phase,” launched in fiscal 2025, NSG Group has defined a strategy focusing on the Four Ds—Business Development, Decarbonization, Diverse Talent, and Digital Transformation—as key areas of activity. Of these, “Decarbonization,” which contributes to carbon neutrality, aims not only to reduce emissions within the company but also to help realize a sustainable society through the company’s products. Spacia is expected to play an important role by improving the insulation of openings in office buildings, stores, warehouses, and other facilities, thereby enhancing energy efficiency and reducing CO₂ emissions.

NSG Group has set ambitious sustainability goals. For Scope 1 and 2, it aims to reduce greenhouse gas emissions by 30% by 2030 compared with 2018 levels, and has already achieved roughly half of that target. Scope 1 initiatives focus on decarbonizing the glass manufacturing process, while those for Scope 2 involve introducing renewable electricity. NSG Group has also newly established a reduction target for Scope 3, working with key suppliers to cut CO₂ emissions throughout the supply chain.

In light of the Japanese government’s 2050 carbon neutrality declaration, improving insulation in renovation of existing buildings will become an essential task. The importance of Spacia is expected to increase further in the future. NSG Group’s vacuum insulating glass technology, honed over many years, will surely serve as a key tool for solving the global issue of achieving carbon neutrality.