The all-conquering air conditioner

“The last — ay yi yi — three and a half to maybe five years, it seemed that I’ve either lost tolerance of sleeping in the heat or it’s just been hotter,” said Susan Krummann, who lives outside Portland. She’s the service manager for a heating and air-conditioning company there. But she, of all people, gave in to an installation only in late June. “I’m 55, and I deserve a little comfort,” she said.

Decades after air-conditioning made much of the Sun Belt livable, it has now become standard nearly everywhere. Eighty-six percent of new single-family homes in the Northeast are now built with it; 94 percent in the Midwest are. Parts of the United States whose historical development never depended on air-conditioning increasingly resemble the regions whose growth wouldn’t have been possible without it.

“Air-conditioning is reaching where it hasn’t reached before,” said Don Prather, the technical services manager with the Air Conditioning Contractors of America. “It’s been moving north and northwest, in every direction.”