The selection of facilities to be replaced during a building retrofit can be challenging due to conflicting interests such as budget constraints, building minimum requirements, human comfort, and environmental goals. In order to assist decision-makers with the appropriate selection of facilities, this paper presents a multi-objective optimization model aiming at optimizing the retrofitting costs, energy savings, water savings, payback period, and points earned under the Leadership in Energy and Environmental Design (LEED) rating system. This work introduces green building certification as an objective for existing building retrofits. The benefits of an existing building retrofit and green building certification to the building owner includes reduced operating costs, carbon footprint, and improved air quality. The developed model considers a wide range of facilities and saving measures as retrofitting options for the energy and water efficiency credit categories of LEED. A case study of a hotel in South Africa is presented to demonstrate the feasibility of the proposed model and optimization approach. (C) 2017 Elsevier B.V. All rights reserved.