According to Grubb & Ellis Co.'s third-quarter report, there is seven million sf of empty class A space in its 77.3-million-sf inventory and 9.7 million sf vacant in the 64.4 million sf of class B space. Looking at it from an occupancy perspective, class A is 90.9% filled and class B, 85%. Class A rent averages $29.13 per sf and class B, $19.51 per sf. The report puts spec construction at 4.3 million sf.

Transwestern Houston's researchers peg class A occupancy at 92% in its 93.7 million sf while class B's 90.1 million sf is 87% filled. An additional five million sf is under construction or being renovated. The average class A rate is $20.25 per sf; class B, $16.10 per sf.

David Lee, Transwestern's vice president, says the statistics represent a classic demand for class B space in a rock-solid market. "The same, identical conditions occurred in our last boom market during the late 1990s," he tells GlobeSt.com. "Class A occupancies were well above 90%, rents started to increase and tenants who had an option to renew chose less expensive product." He believes that in the current cycle, class B office space, especially in the stronger submarkets, is poised for continued strong performance for the next couple years.