Diarmuid Justin McSweeney

Diarmuid “D” J. McSweeney, M.A., M.B.A., 84, of Lakewood Ranch, FL passed into the arms of his Almighty Father on February 26, 2025 surrounded by family. He was predeceased by his parents Dr. Christopher J. McSweeney and Evelyn M. (Donegan) McSweeney, and first wife Jennifer (Leonard) McSweeney. He is survived by his loving wife of 40 years, Sydney (Heller) McSweeney of Lakewood Ranch, his three children Helen McSweeney Corley (David) of Huntersville, NC, Kristin Leigh Lighttiser of San Francisco, CA, and Matthew David Lighttiser of DeBary, FL, his six grandchildren David Donegan Corley (Michaela), Jennifer Marie Brasington (Will), Sarah Jean Tesar (Cole), Aidan Joseph Corley, Samuel Matthew Lighttiser, and Lauren Irene Lighttiser, and by his many cousins in Cork and Dublin, Ireland.

Diarmuid was born in Dublin, Ireland on May 13, 1940. In his youth he spent much time sailing in Cork with his cousins during the summer months. Diarmuid graduated from Glenstal Abbey boarding school in County Limerick. He subsequently graduated from Trinity College, Dublin where he received his Bachelor’s and Master’s degrees in Physics. He was taught by Professor Walton, who won the Nobel Prize for splitting the atom in 1951. While in the science halls at Trinity, Diarmuid met his first wife Jennifer (Jenny) Leonard who was pursuing Chemistry. Diarmuid was very active as captain of the Trinity Sailing Club, racing Fireflies, and as captain of the Table Tennis Club. Diarmuid and Jenny married in 1963 after settling in Buckinghamshire, England for their new jobs. Diarmuid began his pioneering career in prismatic lighting with GEC.

After the birth of their daughter, Helen, and as the political and economic climate changed in England, he accepted a position at Holophane, a lighting company in Newark, Ohio. He decided to ”try it for a year”, moving his family to Newark, then Granville, Ohio, beginning a 40 year career with Holophane Corporation, well known for design and manufacturing of Prismatic Luminaires, and later becoming

a division of Johns Manville and then Acuity Brands. Diarmuid expanded his business expertise by earning an MBA from Xavier University, Cincinnati, Ohio with classes in Columbus. During his career, he became Director of Research and Development, Director of International Operations (Australia), Director of Marketing, and Director of the Lighting and Vision Center. He was the inventor of, and granted letters patent for, a ceiling system while working for Johns Manville Corporation. Diarmuid also served on the Board of Directors of the Jim H.McClung Lighting Research Foundation, Inc.

A few years after the death of his first wife, Diarmuid met Sydney on Valentine’s Day. Quickly realizing they were an ideal match, an opinion shared by their many friends, they married two years later in Granville, Ohio. Diarmuid was devoted to Sydney, to their three children, Helen, Kristin, and Matthew and their six grandchildren. Diarmuid and Sydney did life well together; supporting each other’s careers and their children’s activities and goals, traveling for work and pleasure, and serving their communities and professions.

Diarmuid was a member of the Illuminating Engineering Society of North America and was president of the Buckeye Section of IES in Columbus. As a member of IESNA, he served on many committees, including the Progress Committee, which included the production of the Progress Report. He served as IES president for the 1996 - 1997 term. He was later honored as a Fellow of IES (FIES) for his outstanding contributions in the lighting field and was also presented with the IES Louis B.Marks Award in 2006. He participated in Lightfair every year.

After his successful career at Holophane, Diarmuid co-founded Green Lighting Supply with his son Matthew, which continued a lifelong mission to develop sustainable and efficient lighting solutions.

A devout Catholic, Diarmuid was a member of The Church of St. Edward the Confessor in Granville, OH, Saint Joseph Cathedral in Columbus, OH, and Our Lady of the Angels in Lakewood Ranch, FL. He was well known for being one of the head ushers at OLOA, especially during the holidays.

Diarmuid was a Rotarian for over 46 years with perfect attendance and was a Paul Harris Fellow. He served as Rotary President in Granville, OH and helped to start a Rotary club in Pataskala and New Albany, OH, where he lived. In Lakewood Ranch he served as sponsor chair for the annual Lakewood Ranch Rotary Club Food and Wine Fest, securing a major benefactor which allowed the club to issue more grants within the community. He served on the New Member Committee as well as the Ways and Means Committee. In Newark and Granville he served on the Board of Directors of First Federal Savings and Loan.

Diarmuid loved sports and spent decades with a racket in hand playing tennis, table tennis, platform tennis and later pickleball. He enjoyed skiing with Sydney in Colorado for several years. His original sailing passion and skill crossed the Atlantic with him, and he built a sailboat, which he raced in his early years in Ohio. Although he didn't grow up with American college football, Diarmuid became a huge fan of Ohio State University (OH-IO) and Notre Dame. He always supported his children’s passions in horses, sailing, and boating and fishing. Diarmuid greatly enjoyed his activity and friends at the Royal St. George Yacht Club, Dún Laoghaire, Ireland; Leatherlips Yacht Club, Granville Tennis Club, New Albany Country Club, all in OH; Lakewood Ranch Country Club, FL.

He enjoyed traveling around the world with Sydney to various countries in Europe (especially Ireland) and to Guatemala, Australia, New Zealand, Cayman Islands, across the United States and Canada, and cruising in the West Indies and Greek Isles. Diarmuid often pointed out the luminaires he designed while traveling here and abroad. (It is well known that Lighting professionals are always looking up). They also attended the annual IES Conference, held in a different city each year, and developed many lifelong friendships. For many years they looked forward to joining their friends at the annual Past Presidents’ and the Past Presidents’ Spouses’ luncheons.

His family is extremely thankful for the love, care, and respect he received at Arden Courts Memory Care in Sarasota where Diarmuid so enjoyed walking the grounds.

A funeral Mass will be held Monday, March 10 at 11:00 AM at Our Lady of the Angels church, Lakewood Ranch, FL. Visitation will be held the prior day, Sunday, March 9 from 2:00 - 4:00 PM at Robert Toale & Sons Celebration of Life Center in Lakewood Ranch (Bradenton). Interment and service will be held in Granville, Ohio at a later date to be announced.

In lieu of flowers, the family suggests donations be made to Mass General CAA Research (https://www.angiopathy.org/support-us), Rotary International (https://my.rotary.org/en/donate), or Our Lady of the Angels (https://www.olangelscc.org).