Germany's DIY frozen bottle hack eases home heat during summer waves

German households are adopting a low‑cost cooling trick to combat high summer temperatures. The method involves filling a plastic bottle about one‑fifth full of water, freezing it overnight, and placing the frozen bottle on a high surface in a room. As the ice melts, it absorbs heat from the surrounding air, potentially lowering room temperature by one to two degrees Celsius. The technique works best when combined with other habits such as keeping windows closed during the hottest part of the day, drawing curtains, and ventilating early in the morning or late in the evening. Experts note that while the frozen bottle cannot replace air‑conditioning in extreme heat, it offers a simple, inexpensive way to make living spaces more comfortable on hot days.