Irvine-based design firm LPA Inc., the largest architectural firm in Orange County, opened a new office in Dallas, its sixth U.S. location.

“Revenue in the San Antonio office has nearly doubled in the last three years of operation so the decision to expand our presence in Texas and serve a larger market was natural,” said Mark Oppelt, principal of LPA San Antonio.

The Dallas office has a capacity for 50 employees.

LPA creates energy-efficient environments in K-12 schools and colleges and in health care, corporate and civic facilities.

It reported two-year revenue growth of 61% to $71 million last year on the Business Journal’s list of the fastest-growing, midsize private companies.