Older buildings in Japan, such as Danchi (older apartment complexes) and Machiya (traditional townhouses), often rely on single-pane glass or traditional lightweight sash windows. This construction leads to significant heat loss in winter and heat gain in summer, causing high energy bills and chronic discomfort. Furthermore, the combination of poor insulation and high humidity causes persistent issues.

A full window replacement is often prohibitively costly, time-consuming, and—critically—may alter the building's original aesthetic, a major concern forhistoric or traditional structures.

Vacuum Insulated Glazing (VIG), or 真空ガラス (Shinku Garasu), is the powerful, non-invasive technology that solves this dilemma with two primary features:

• Slim Profile: The Non-Invasive Solution

  VIG units are incredibly thin (often as little as 6mm–8mm), which is comparable to single-pane glass. This allows them to be installed directly into most existing window frames and sashes. This is the key advantage for retrofitting, as it avoids the need for expensive, disruptive frame replacements (フレーム交換不要), thereby preserving the original design and aesthetic.

• Superior Thermal Performance & Energy Savings

  By creating an evacuated space (a vacuum) between the glass panes, VIG virtually eliminates heat transfer by conduction and convection. Its thermal insulation performance (U-value) is comparable to or better than standard triple-glazed units, providing outstanding energy efficiency (断熱窓 Dantotsu Mado). This immediately cuts the energy demand for heating and cooling, translating directly to lower utility bills and helping Japan move towards its 2050 carbon neutrality goal.

While VIG delivers superior thermal performance and preserves your building's look, its benefits go far beyond energy efficiency. In Part 2, we reveal how VIG eliminates the costly problem of condensation (結露Ketsuro), boosts your home's safety, and unlocks crucial government subsidies.