As the city looks for ways to contain its ever-growing housing problem, historical and architectural experts say New York's religious institutions become targets for elimination to make room for the new guard.

Over the past few decades, hundreds of churches, synagogues, mosques and other houses of worship have been shut down due to higher costs and declining attendance only to be replaced by condos, small shops and, in one case, a nightclub.

Although some of these buildings retain a facade or some other physical remain of their religious presence, preservationists say their absences create a void.

"Every time something like this happens there can be a cause for concern and introspection of the changes in the neighborhood," said Andrew Berman, the executive director of the Greenwich Village Society for Historic Preservation.

Experts say it is hard to calculate how many religious institutions are in danger because such decisions come from their respective orders.

In many cases, their closures aren't announced until the eleventh hour.

Last fall, the Archdiocese of New York announced about two dozen churches would close in the Bronx, Manhattan and Staten Island as part of a massive consolidation of parishes due to dwindling attendance and rising costs.

The Church of St. Elizabeth of Hungary at East 83rd Street is one of those endangered parishes and parishioner Kal Chany has led efforts to save it with an online petition and a formal appeal to the Vatican.

Chany said the 122-year-old building is home to the tristate area's deaf community, so closing it would have a devastating effect. "They've got no other place to get together," he said.

Marianna Mott-Newirth, the president of Town & Village Synagogue at First Avenue, can relate.

Her synagogue is one of the few left in the East Village, which had more than 100 Jewish places of worship in the early 20th century.

Mott-Newirth said the 200-year-old building has roof and foundation issues but her members have worked to find ways to keep the building viable.

"We as a synagogue have had to reinvent ourselves," she said.

Colin Cathcart, an architect and associate professor of design at Fordham University, said religious buildings in the city are the few major examples of long standing history traditionally impervious to the constantly changing cityscape.

"One thing that [closing places of worship] does is that it cuts off the community from its past," he said.

Berman said the pain is most acute in instances such as St. Ann's Church on East 12th Street, where the facade remains in front of NYU's Founders Hall dorm.

"I think people are glad that the building was preserved and reused, but they would have preferred if they were not reused for luxury condos, but instead maybe a communal gathering space," Berman said.

The same story happened with St. Vincent De Paul Church in Williamsburg, which was converted into the Spire Lofts, a 40-unit dwelling, last year.

Cathcart noted that sometimes new development can bring dynamic new history with it; the Church of the Holy Communion building on Sixth Avenue, for example, had a second life as the Limelight club from 1982 until 2007, before later becoming a marketplace.

The city's Landmarks Preservation Commission has designated 143 religious institutions as individual landmarks, and there are more located in landmarked districts. "Our approach to saving these buildings has been to collaborate with religious organizations to arrive at solutions that benefit them and the public interest," the commission's executive director Sarah Carroll said in a statement.

One possible solution, Cathcart advised religious institutions facing closure, is to reach an agreement where a congregation could share space with new housing.

St. Stephens and St. Martin's Episcopal Church in Bedford-Stuyvesant will take that approach.

Although the 146-year-old building will be demolished to make room for a five-story, 41-unit apartment building, Notias Construction agreed to build a new church on the lot.

Pierre Downing, a representative for the Flushing-based developer, said church leaders worked closely with his team, which had no qualms about fitting the community's needs into the construction plans.

"The church was in dire need of a new structure. We weren't thinking about the negative impacts when it comes to profit," he said about the new church.

Preservationists hope that other developers take a similar approach elsewhere.

"It is somewhat vexing that we are losing so many of our houses of worship either for their original purpose or some other purpose," Berman said.