This research develops an aqueous electrically switchable electrochromic building envelope for the building thermoregulation. First, comprehensive experiments were conducted to demonstrate the benefits of Cu-aqueous electrolytes. The nonflammability and lower cost (79.3% reduction of electrolyte price compared with Ag-DMSO) provided by the aqueous electrolyte contribute to a safe and economical smart building envelope. By removing the Br 3 -/Br -redox couple, the metal deposition shows a non-volatile tunability with significant thermal emissivity contrast (0.85 in the atmospheric transmittance window range). The low-e state in mid-IR can be maintained for 5.5 hours without significant decay under the open circuit condition. Since the aqueous electrolyte is less harmful to the working electrode, the device can switch between heating and cooling modes 1800 times with only 21% degradation in emissivity contrast, which exhibits significant improvement for long-term durability.