## Vacuum Insulated Glazing (VIG) and Aerogel Glazing ### Overview [[Vacuum Insulated Glazing and Aerogel Glazing]] represents two distinct yet complementary [[Advanced Glazing Technologies]] engineered to achieve exceptionally low U-values, significantly enhancing the [[Thermal and Optical Performance Metrics|thermal performance]] of building envelopes. VIG leverages a high vacuum to eliminate gaseous heat transfer mechanisms, while aerogel glazing utilizes the nanoporous structure of aerogel to suppress convection and conduction within an inert gas-filled cavity. Both technologies are critical for meeting stringent energy efficiency mandates in modern [[International Building Codes and Energy Standards|building codes]] and contribute substantially to [[Operational Energy Savings and GHG Reduction Potential]]. ### Technical Details #### Vacuum Insulated Glazing (VIG) VIG consists of two or more [[Glass Substrates and Composition|panes of glass]], typically 3-6 mm thick, separated by a narrow gap (e.g., 0.1-0.3 mm) from which air has been evacuated to a high vacuum level, typically below 0.1 Pa. This vacuum virtually eliminates [[Emissivity and Radiative Heat Transfer|heat transfer by convection and conduction]] through the gas, leaving only radiation as the primary heat transfer mechanism. To mitigate radiative transfer, at least one internal surface of the vacuum gap is coated with a [[Low-Emissivity Coatings Types and Application]]. To maintain the precise vacuum gap against atmospheric pressure, an array of small, high-strength [[Insulated Glass Units and Spacers|support pillars (spacers)]] are strategically placed between the glass panes. These spacers, often made of stainless steel or ceramic, typically have diameters ranging from 0.3 to 0.5 mm and are spaced 20-50 mm apart. The perimeter of the VIG unit is hermetically sealed, often using low-melting-point glass frit, solder glass, or metal seals, which must withstand significant differential pressure and thermal cycling. Getter materials are frequently incorporated to absorb residual gases and maintain the vacuum over the product's lifespan. Typical [[U-value Calculation and Measurement Standards|U-values]] for VIG units range from 0.5 to 0.8 W/(m²K), significantly