According to the International Panel for Climate Change (IPCC), the greatest positive impact on reducing global climate change will come from changing the way we use energy in buildings. Building energy consumption has grown steadily, reaching levels of 20 – 40% of the total national energy consumption in most OECD countries. About 20-30% of this energy is lost through uncontrolled heat flows through the building envelope. The use of energy-efficient windows leads to a considerable reduction in the cost and environmental impact of indoor climate control.
Vacuum Insulated Glass (VIG) consists of two glass sheets with a thin evacuated gap between them (Figure 1). Establishing a vacuum (low gas pressure) environment between two glass panes reduces heat transfer through gas conduction and convection to near zero. Solder glass (a glass frit) hermetically seals the glass edges and is used to seal the pump out tube to the top glass sheet. Establishing a hermetic seal is essencial to have a high and stable internal vacuum. Radiative heat flow is significantly reduced by using transparent low emittance coatings on the internal glass surfaces. An array of support pillars helps to maintain the separation of the glass sheets and counteract the large forces caused by atmospheric pressure established over the glass surfaces. The stresses throughout the VIG structure are also affected by external loads such as thermal, wind and debris loads. Our Thermal and Mechanical Performance Calculators help to find optimal VIG design parameters.
The VIG research project has been running at the University of Sydney since 1989, when the first in the world practical thermally insulating sample of VIG was made by Stephen Robinson under Prof. Richard Collins’s supervision [1]. During the first decade, our group focused on fundamental research and prototyping. The achievements in this period include:
- determination of the stresses in the glass sheets due to pressure and temperature differences [4, 15, 20, 21, 30];
- development and validation of methods for calculating the heat flow through the VIG [22, 37, 38];
- development of a procedure for optimization of geometry and properties of the pillar array [22, 32];
- demonstration that time required to evacuate VIG internal volume is not a limiting factor in the production process [18, 46];
- development of a method for measuring the outgassing rates of relevant gas species [47];
- development of a method of long term and accelerated ageing measurements to estimate vacuum degradation rates [28];
- development of glass failure models to account for the sub-critical limit of crack growth [15 ,34].
The commercial VIG development started in 1994, when the University of Sydney and Nippon Sheet Glass Group (NSG) formed a strong partnership. In 1996, NSG launched the first commercial VIG product, SPACIA, used as an architectural window for residential and commercial buildings [45]. Even though the demand for VIG product was not strong at that time, in the following decade, the interest in VIG grew, with many realizing that this technology holds the potential to make a significant impact on heat loss control and comfort of windows in buildings.
Since Prof. Richard Collins’s retirement in 2000, the project has continued to grow and is still the world leader in fundamental VIG research and design engineering, as well as prototype and component testing. The project is strongly aligned with industry interests and works closely with numerous industry partners. We also provide know-how and facilities (link) to support the development of VIG product, VIG components, and the education of groups interested in the VIG technology.