As heat waves get worse, air conditioning has come to feel like a must-have even in parts of the U.S. that historically haven’t needed it. Those who live in public housing are especially vulnerable to the heat — they’re not just low-income, but also disproportionately older, people of color, chronically ill and often living in hotter neighborhoods that lack shade from tree cover. And yet even as extreme heat becomes more common, it remains a struggle for many tenants to get AC.