French homeowners paint windows with chalk to combat summer heat

French residents are coating their windows with chalk as a heat‑mitigation tactic. The chalk layer reflects sunlight, reducing indoor temperature rise. This low‑cost method emerged in response to unusually warm summer conditions. Homeowners report noticeable cooling benefits after applying the chalk. The practice is easy to implement and can be removed when temperatures fall. Researchers note that the technique complements other passive cooling strategies. The approach has attracted media attention as a creative climate‑adaptation measure. The story appeared in a BBC Future article in June 2026.