PITTSBURGH - The overseers of the 112-year-old Phipps Conservatory and Botanical Gardens knew the Victorian glass house needed to offer more than flower shows if it were to survive another century.

The conservatory had been treasured by generations of Pittsburghers since industrialist Henry Phipps had it constructed in 1893 for $110,000. But despite their fondness for the "crystal palace," few residents visited it except when the conservatory was hosting one of its seasonal flower shows.

In a plan that Phipps had hoped would increase attendance, boost revenues and improve amenities, the conservatory began a $36.6 million project to build a new welcome center, tropical forest exhibit, greenhouse production space and other additions. Phipps' overseers also had another goal: to make it one of the most ecologically friendly conservatories in the nation, according to the executive director, Richard Piacentini.

The completed welcome center uses wind-power energy and is topped by a green space. The exhibit space will use a vented roof, energy blankets and an asymmetrical design to cool and heat the space. Unlike its old greenhouses, Phipps' new production houses won't rely on huge, energy-wasting fans to control their temperatures.

Most public gardens of Phipps' size have plans to improve their facilities or build additions if they haven't started the projects already, said Dan Stark, the executive director of the American Association of Botanical Gardens and Arboreta. The conservatories and botanical gardens also want to be ecologically responsible as they grow, he said.

Before Phipps took on its current construction project, the public garden was notable because of its size and its design. The building was designed by Lord and Burnham of Irvington-on-the-Hudson, the firm that designed the New York Botanical Garden, and it remains one of the largest conservatories in the nation.

The greenhouses leaked. Managers relied on massive exhaust fans to cool the glass buildings. The conservatory's entrance, which was rebuilt in the 1960s, was cramped and ugly.

Phipps' trustees also realized most patrons visited the gardens for about an hour three times a year - and that attractions needed to perpetually change if attendance were to be increased, Piacentini said.

Phipps began its multimillion-dollar expansion in September 2003 and the first phase of the project, a 10,885-square-foot welcome center, opened this spring. The eight production houses are to open later this year, while the tropical forest exhibit space is expected to open the end of 2006.

The welcome center features a cafe that sells organic or locally grown food and a gift shop that won't sell products made of tropical wood. Eventually, the center will be cooled by air drawn through underground tunnels, Piacentini said.

Plans are in the works for a phytoremediation garden, which would feature plants that can draw toxins from the ground. There's also been talk about a natural water processing plant that could double as an education center.

While all these projects should draw attention to Phipps, it should save the conservatory some money, too, Piacentini said.

"By the time that it's done, it's going to be the most energy-efficient conservatory in the nation," he said.