LYNN-Greater Lynn Senior Services (GLSS) formally re-opened its doors Thursday during a ribbon-cutting ceremony focused on the multi-million-dollar reconstruction recently completed at the 8 Silsbee St. facility.The building, home to the Lynn Senior Center and many related programs for the elderly, underwent major reconstruction over the past year, creating additional space on the upper floors and new quarters for its growing staff.”Completion of this project will dramatically improve our ability to meet the growing demand for services over the long term,” said GLSS Executive Director Ron Airey. “Our staff have waited a long time for this, and I couldn’t be happier with the outcome.”In addition to significant growth in the size of programs and staff over the past two decades, the aging Baby Boomer generation ? the first of which has already turned 60 years old ? will continue this demand trend forward, Airey said.GLSS employs a staff of more than 500 and uses more than 75 volunteers throughout its programs, according to spokesman Margaret Gilligan.Earlier this week, the remaining members of the agency’s Lynn staff who were displaced by the construction moved into the newly-renovated offices on the first floor. Other employees were relocated in phases during the summer.In addition to the headquarters staff on Silsbee Street, more than 200 are based out of the agency’s transportation headquarters in Peabody, Gilligan said.After leasing the Lynn building for 17 years, GLSS purchased it in 2000. Airey said the $4.5 million rehabilitation project represents a sizeable investment in a section of the city targeted as a primary revitalization zone. Lynn-based DeIulis Construction Co. was the primary project contractor.The construction was carried out in stages, with the last and most comprehensive involving a complete gutting of the third floor to create more than 19,000 square feet of raw space. Finish work related to the modernization of offices on the two lower floors was also recently completed. The first floor was designed to accommodate new programs, provide meeting space, and allow room for special services such as a nurses’ suite and hair salon.Each year, GLSS provides a broad range of in-home assistance services to over 1,500 home-care clients and more than 300,000 meals to senior citizens, many of whom are homebound, Gilligan said.The agency is also the Massachusetts Bay Transportation Authority contractor for the North Territory of “The RIDE,” providing over 400,000 rides annually to disabled persons of all ages who live in 23 cities and towns north of Boston. Through the range of services provided, 3,000 people depend on GLSS every day in its five-town service area of Lynn, Lynnfield, Nahant, Saugus, and Swampscott, Gilligan said.