Hines, the Houston-based international real estate firm, has started construction of a downtown Houston skyscraper, one of the largest “spec” office projects being built in the world.

The Hines project, 609 Main at Texas, will be a 48-story, 1,050,000-square-foot office tower at the corner of Main and Texas streets in Downtown Houston, catty-cornered from the Rice Hotel lofts. The new Hines office tower was first reported by CultureMap in an exclusive story in March of 2011.

Hines started out to build a slightly smaller skyscraper, but the high demand for office space encouraged Hines to build a larger building instead, says George Lancaster, senior vice president of corporate communications for Hines.

Lancaster says Hines is “in discussions with major tenants, none yet signed, but very pleased with their reaction to the product. It will definitely be a significant Hines trophy building in terms of form and function.”

A “spec” or speculative project means the developer is starting construction without a tenant committed to leasing it, and spec office projects have been a rarity in commercial real estate in recent years. A spec of this magnitude demonstrates Hines has a significant amount of confidence in the economy. But Houston’s energy business has been expanding and generating growth in other sectors for several years and increasing the demand for office space.

Houston, with 82,000 new jobs last year, led the nation in job growth and housing starts in 2013.

Office occupancy is exceptionally high in Houston and rents are rising. The Energy Corridor in west Houston has a Class A office occupancy rate of 99 percent.

Downtown occupancy rates are high in Houston office towers. The Houston CBD vacancy rate is 9.2 percent in overall and 7.5 percent in Class A, according to CBRE.

Hines says that construction is expected to take 36 months, with delivery scheduled for February 2017.

609 Main at Texas is being developed by the Hines CalPERS Green development fund, a partnership that focuses exclusively on developing sustainable office buildings throughout the United States certifiable through the U.S. Green Building Council (USGBC) Leadership in Energy and Environmental Design Core & Shell program. This same partnership developed the BG Group Place, another new office building on Main Street that is nearly 100 percent leased.

609 Main at Texas is pre-registered LEED, and is expected to attain Gold or Platinum certification upon completion. In short, this means the building will be very green, very energy efficient.

Located at the southeast corner of Main and Texas where a McDonald’s once stood, HCG has owned the full-block site, known as Block 69, since 2008. Site preparation, including the demolition of an existing abandoned building, began in November 2013.

“609 Main at Texas will set a new standard for Houston’s Class A space, with its combination of world-class architecture, state-of-the-art amenity-rich office space in an irreplaceable location,” says Hines senior managing director John Mooz. “We are excited to develop our next landmark structure in Houston.”

Designed by Pickard Chilton, 609 Main at Texas’ north and south facades will extend skyward, culminating in a diagonal crown, creating a new, highly visible Downtown landmark. The narrower east and west facades will be slightly recessed, and the subtly faceted exterior façade will be clad in floor-to-ceiling glass with brushed-stainless-steel accents. Vertical blades will be incorporated in the east and west facades, enhancing the tower’s silhouette and offering solar shading.

D.E. Harvey has been selected as the general contractor, Hines said.

The high occupancy and rental rates have injected a lot of energy into the downtown office market. Crescent Real Estate Holdings just announced last week that it is starting 6 Houston on a spec basis. Crescent’s project will be a 30-story, 600,000-square-foot building located on Block 95, bounded by Rusk, Caroline, Walker and San Jacinto streets.