The vibe at Shawmut Design and Construction’s newly renovated Boston headquarters is more like a well-funded start-up than a 34-year-old general contracting firm.

Jumping to 59 on ENR’s national Top 400 Contractors list this year, up from 63 the previous year, Shawmut saw its revenue rise 22.6 percent in 2015 to $1.2 billion.