## Dynamic Glazing: Electrochromic and Thermochromic ### Overview Dynamic glazing technologies represent a significant advancement within [[Advanced Glazing Technologies]], offering the capability to modulate [[Thermal and Optical Performance Metrics|optical and thermal properties]] in real-time. This adaptability allows for optimized daylighting, glare control, and solar heat gain management, contributing to enhanced [[Operational Energy Savings and GHG Reduction Potential|building energy performance]] and occupant comfort. These systems are crucial for achieving stringent performance targets outlined by [[International Building Codes and Energy Standards]]. The two primary categories discussed here are electrochromic (EC) and thermochromic (TC) glazing. ### Technical Details #### Electrochromic Glazing Electrochromic glazing operates on the principle of [[Glazing Manufacturing Processes|reversible electrochemical reactions]] within a multi-layered [[Low-Emissivity Coatings Types and Application|thin-film stack]]. A typical EC device comprises five layers: two [[Emerging Glazing Materials and Coatings|transparent conductive oxide (TCO) layers]] (e.g., Indium Tin Oxide, ITO, or Fluorine-doped Tin Oxide, FTO), an electrochromic layer (e.g., tungsten trioxide, WO3), an ion conductor layer (e.g., lithium perchlorate in a polymer matrix), and an ion storage layer (e.g., nickel oxide, NiO, or iridium oxide, IrO2). When a low DC voltage (typically 1-5 V) is applied across the TCO layers, ions (e.g., Li+ or H+) reversibly intercalate into the WO3 layer, causing a change in its electronic structure and thus its optical absorption spectrum. This process darkens the glass, reducing both [[Solar Heat Gain Coefficient and Solar Transmittance]] (SHGC) and [[Visible Transmittance and Light-to-Solar Gain]] (VT). Reversing the voltage extracts the ions, returning the glass to its clear state. Switching times range from minutes (e.g., 5-20 minutes for a typical 1 m² panel) depending on panel size and desired optical density. EC glazing can achieve VT ranges from approximately 60-70% (clear) down to 1-5% (dark), with corresponding SHGC reductions from ~0.40 to ~0.09. #### Thermochromic Glazing Thermochromic