# Heat mitigation through window insulation and AC use > Live situation record from CLSTR: https://clstr.news/situations/heat-mitigation-through-window-insulation-and-ac-use > Updated: 2026-08-22T02:51:56.000Z. Sources: 4. Developments: 2. Methods for mitigating indoor heat using aluminum foil and air conditioning have been highlighted as practical responses to rising temperatures. Initial reports suggest that applying aluminum foil to the exterior of windows can act as a reflective barrier, bouncing back up to 97% of solar radiation and potentially lowering indoor temperatures by three to five degrees Celsius. Additionally, experts recommend maintaining air conditioners at 24–26°C and cleaning filters to improve efficiency and health. As heatwaves persist, the use of aluminum foil is increasingly viewed as an emergency measure. While it serves as a thermal shield by increasing a window’s albedo, architects caution that it is a superficial, short-term solution. They warn that placing foil on the inside of the glass can be a “critical mistake” that creates a greenhouse effect, potentially worsening heat levels. For more effective long-term temperature reduction, experts emphasize the importance of external solar protections, such as shutters or panels placed outside the window. ## Timeline ### 2026-08-22: Aluminum foil on windows serves as emergency heat protection Using aluminum foil on windows can serve as an emergency heat shield during heatwaves, but experts warn that placing it inside the glass can worsen temperatures due to the greenhouse effect. 4 sources. https://clstr.news/cluster/aluminum-foil-on-windows-serves-as-emergency-heat-protection ### 2026-08-05: Aluminum foil window hack and proper AC settings help reduce indoor temperatures Aluminum foil on windows reflects most sunlight, dropping room heat by 3‑5 °C, while proper AC settings (24‑26 °C, good airflow, clean filters) enhance comfort and save energy. 6 sources. https://clstr.news/cluster/aluminum-foil-on-windows-reduces-indoor-heat --- Cite as: Heat mitigation through window insulation and AC use. CLSTR, https://clstr.news/situations/heat-mitigation-through-window-insulation-and-ac-use