Boston-based Synergy Investments paid $45 million for One Liberty Square in September 2023, a 17 percent decline from its last sale in 2013. Photo courtesy of Google Maps

As real estate markets monitor a reset of office building values, a Boston Financial District building traded for 17 percent below its 2013 acquisition price.

Boston-based Synergy Investments paid $45 million for One Liberty Square, a 176,241-square-foot office building completed in 1924, from Clarion Partners. The sales price equates to $255 per square foot.

The building is 84 percent leased, according to Newmark capital markets which represented the seller.

Class B office rents in Boston already have started to decline after big increases in vacancies since 2020, averaging $55.25 per square foot on a gross basis at the end of the second quarter, according to CBRE data. Class B and C rents declined 0.3 percent and the availability rate rose to 24 percent.

Net effective rent, which takes into account tenant concession packages and free rent, has dropped 12 percent for new lease deals since 2020, CBRE said in its second-quarter market report.

The class B sector in Boston’s central business district has over 188,000 square feet of negative leasing absorption in 2023, according to CBRE data.

Along with uncertainty about future leasing demand, owners of older office buildings in Boston face potential costly capital expenditures to reduce fossil-fuel-based building emissions to comply with the Building Emissions Reduction and Disclosure Ordinance.

The transaction is a rare investment sale for the downtown office sector in 2023, following Azora Exan Capital’s recent acquisition of 7 Post Office Square for $41 million.