Overview

• Germany is enduring indoor temperatures above 30 °C, driving households without AC to experiment with the Flaschentrick hack
• Users fill 1.5-liter PET bottles with water, freeze them overnight and place them up high to release cold air as the ice melts
• In small rooms the method can lower local temperatures by up to 2–3 °C but the effect is confined to the bottle’s immediate vicinity and ends when melting stops
• Social media feedback is mixed, with some users reporting drops from 32 °C to 29 °C while others see no change after hours of use
• Each frozen bottle removes roughly 770 kJ—equivalent to 10–30 minutes of air-conditioning—and experts advise pairing the hack with passive shading or conventional cooling for sustained relief