In the aftermath of Hurricane Sandy housing is becoming scarcer. And with cold weather on the way, city, state, and federal officials are trying to assemble a pool of vacant houses to supplement New York City's shelter system. While many people have been clinging to their apartments despite not having heat or hot water, officials are worried that another wave of people, numbering in the hundreds if not the thousands, will seek shelter as temperatures fall. “We feel a real imperative to have something in place when the second surge comes,” said Matthew M. Wambua, the city’s housing commissioner. With the electrical outages and the encroaching winter season, many people are left wondering where, and how, they are going to stay warm.