In recent years, passive houses have become a familiar term, and nouns such as ultra-low energy consumption buildings, nearly zero energy consumption buildings, and zero energy consumption buildings have also appeared frequently. How to distinguish them? Briefly speaking, taking the building energy consumption level in the early 1980s in China as the benchmark, if the building energy consumption is reduced by 82.5%, the requirements for passive ultra-low energy consumption buildings (passive houses) will be met; if it is reduced by more than 86%, it is a nearly zero energy consumption building; if it does not consume energy and can even export energy outward, it is a zero energy consumption building. (For details, see "How to Distinguish Ultra-Low Energy Consumption/Nearly Zero Energy Consumption/Zero Energy Consumption Buildings").

The nearly zero energy consumption demonstration building of the China Academy of Building Research (CABR), completed in 2014, is an important project of "China-US Clean Energy Cooperation" and represents the highest level of the development of national building energy conservation technology in China. In 2016, it won the 21st Century Green Building Award; in 2017, it won the exemplary award of the China Habitat Environment Award; in 2018, it was rated as the China's "Top Ten Best" energy-saving practice project by the National Development and Reform Commission. This is a landmark building. Its completion and use are of special and great significance for the development direction of building energy conservation in China.

Adhering to the principle of "passive priority, active optimization, economic and practical", as a national nearly zero energy consumption demonstration project, this building integrates and displays 28 world-leading building energy conservation and environmental control technologies. The "passive priority" principle means that walls and exterior windows with extremely high thermal insulation performance must be used, which is a prerequisite for ensuring the nearly zero energy consumption goal of the building. The exterior windows of the project use the vacuum laminated insulating glass with built-in blinds (5T + 27A blinds + 5TL + V + 5T) produced by Xinliji Company. The heat transfer coefficient of the whole window is 1.0 (W/m2·K), and the shading coefficient is adjustable between 0 and 0.4. A total of 800 square meters of vacuum glass is used.

Since it was put into use in 2014, it has been eight years. Recently, the leaders of Xinliji Company led a team to pay a return visit to the nearly zero energy consumption demonstration building to understand the actual application of vacuum glass. The operation management and technical support team of the demonstration building introduced the relevant situations such as the indoor environment and operation energy consumption.

1. Comfortable indoor environment

 During the cooling season, the room temperature in the demonstration building is between 25-27℃, with an average of 26.5℃. During the heating season, the room temperature is between 20-23℃ during working hours. The average room temperature in the building is 21.5℃, which is very in line with the requirements of human comfort for temperature. The results of the questionnaire survey on the indoor environment show that the satisfaction rate for temperature is 85.72%, and the satisfaction rate for noise is 90.48%. Due to the use of vacuum glass, the weighted sound insulation can reach more than 40 decibels, which effectively isolates outdoor noise.

2. Actual operating energy consumption
The nearly zero energy consumption demonstration building has remarkable energy-saving effects. The annual building operating energy consumption meets the design target of 25 kWh/(m2·a), which is only 20% of the average energy consumption of ordinary office buildings in Beijing, and the energy saving rate reaches more than 80%. Compared with similar projects in Beijing as a benchmark, this project saves 78 kWh of electricity per square meter per year and reduces carbon dioxide emissions by 225 tons per year.

3. Stable performance of vacuum glass
After eight years of use, there is basically no vacuum failure in the vacuum glass, ensuring the thermal insulation performance and project demonstration effect, and also providing valuable data support for the service life of vacuum glass, which can be evidenced by the basically stable operating energy consumption data in each year. The performance verification and service life of vacuum glass need to be verified by time. Regular return visits, continuous tracking and attention will provide the answer.

Approximately 50% of the energy consumption of buildings is lost through doors and windows. Improving the thermal insulation performance of doors and windows is the most important and direct way to reduce building energy consumption. The application of vacuum glass can significantly reduce energy consumption and carbon emissions in the building operation stage, help the development of nearly zero energy consumption buildings in China, and is also the perfect embodiment of the principle of "passive priority, economic and practical".
In 2020, China put forward the dual carbon goals. Ultra-low energy consumption buildings are expected to become a product form widely recognized in the new residential building market. "Standard leading, advanced planning, and long-term benefits" may become an increasingly widely accepted building design and construction concept.
On September 1, 2019, China's "Technical Standard for Nearly Zero Energy Consumption Buildings" GB/T51350-2019 was officially implemented, which clarified specific specifications for the development of nearly zero energy consumption buildings. The next stop in the development of ultra-low energy consumption buildings is nearly zero energy consumption and zero energy consumption buildings. Zero carbon emission buildings are expected in the future.