Bloomberg Businessweek is reporting that the budget for Apple's new "spaceship" campus has risen from $3 billion to "nearly $5 billion." Citing five anonymous sources, the publication notes that the stretched budget would make Apple Campus 2 more expensive than the World Trade Center complex currently under construction. The project was originally scheduled for completion in 2015, but the move-in date has now been pushed back to 2016 as architects Foster + Partners search for a way to cut the current cost by a billion dollars.

The new campus was announced back in 2011 at what was to be Steve Jobs' last public appearance. Even at $3 billion the budget for what is essentially an office complex was high, but Jobs believed the cost was justified as it could become "the best office building in the world." Speaking to the Cupertino City Council, Jobs said that "there isn’t a straight piece of glass on the whole building... and as you know if you build things, this isn’t the cheapest way to build them."

Seele, the German firm tasked with creating the curved glass exterior, says it's producing something like "six square kilometers of glass" for the building, noting that "normally we talk in terms of square feet." The company, which also makes the glass staircases that have become synonymous with Apple's retail stores, has doubled the capacity of its factory to complete the project.

Campus 2 is also planned as a "net-zero energy" complex. In addition to architectural energy-saving tactics such as advanced skylights and an airflow design that will help cool and warm the building, the campus will hold 700,000 square feet of solar panels, generating 8 megawatts of power. Although that's enough to power roughly 4,000 homes, Apple will still require additional power, and is said to be negotiating deals on solar- and wind-generated power to augment its supply. Apple didn't offer comment on Bloomberg's piece, but the publication seems confident that its sources are correct.