Following a 20-month, $29 million renovation and expansion project, the Nantucket Memorial Airport has reopened its Memorial Terminal.

The renovation was planned to significantly upgrade the airport in all aspects, according to a statement from construction manager, Skanska USA Building.

The terminal was expanded by 23,000 square feet, including a 6,000-square-foot basement addition and 6,300 square feet of office airline space. All windows, roofing trim and siding were refurbished using much of the existing materials. New elevator and baggage handling systems were installed, and the electrical and fire alarms were upgraded. In addition, the airport’s first air conditioning system was added. New gift shop and car rental areas were also built.

More than 500,000 people fly in-and-out of the airport each year.

"We are thrilled to unveil the newly renovated terminal at Nantucket Memorial Airport," said Al Peterson, manager of Nantucket Memorial Airport. "It has now been modernized to improve the passenger experience and serve as a greener, more efficient airport that can act as a guiding light for future airport renovations of this size."

The terminal is one of the first in the country to run on an HVAC geothermal system, which extracts power from heat stored in the Earth instead of relying on fossil fuels, Skanska said in a statement.

The Massachusetts Aeronautics Commission funded $12 million of the project cost and the Federal Aviation Administration paid for $11.5 million. The remaining portion was paid for by Nantucket Memorial Airport.

Earth Tech Architecture, now AECOM, served as the project designer and designed both architectural and engineering components of the project. Jacobs, Edwards & Kelcey served as the owner’s project manager. The town of Nantucket is the owner and the Nantucket Memorial Airport Commission is responsible for the custody, care and management of the airport.