Durga Devi finds no relief after a day working in New Delhi’s sweltering summer , because her poorly ventilated home radiates trapped heat, leaving her bedroom as hot as 45 degrees at night. Campaigners are now documenting conditions in this densely packed area of India’s capital, home to some of the country’s poorest people, hoping to push policymakers to better protect vulnerable communities. “I prefer staying outside after work, because inside the house there is no relief,” said 45-year-old Devi, who lives in the cramped lanes of Delhi’s Sundar Nagri district. She spends eight hours a day working in a factory without a fan, only to return at dusk to stifling heat at home. The one-room house — like many in this part of the sprawling megacity of 30 million people — has concrete walls, low roofs and poor ventilation, which combine to trap heat during the day and keep the space oppressively hot throughout the night. Devi’s son Abhishek has been keeping a heat diary and tracking te...