An optimal model for a building retrofit with leed standards as reference protocol

Abstract

This research study presents a multi-objective optimization model aimed at optimizing the retrofitting costs, energy savings, water savings, pay-back period and points earned under the Leadership in Energy and Environmental Design (LEED) rating system. In order to assist the decision-makers (DM) with the appropriate selection of facilities, 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. The contribution of this research study is that the percentage energy and water savings of each retrofitting facility or measure is identified, and the LEED points obtained as a result of the energy and water savings is considered, and in the process LEED certification is obtained. The issue of limited available funds is also considered as the retrofitting project is implemented over several years, enabling the DM to reinvest savings from preceding years and reduce the initial investment. Consequently, the time value of money is considered by applying the discounted payback period (DPP). A sensitivity analysis is performed by analyzing the influence of the weighting factors applied to each objective function. The results reveal that the weighting factors have a great influence on the number of selected facilities, selected energy and water saving measures, and the project cost. A case study of a hotel in South Africa is presented to demonstrate the feasibility of the proposed model and optimization approach. The optimization results show the optimal number of selected facilities and measures for each year. The cost associated with the project ranges between $13k-$140k for each year respectively, and an increase in the percentage of energy and water savings is noted for each consecutive year. For the case studied, LEED gold certification level is achieved by the end of the project, and the payback period is 34 months.Hierdie navorsingstudie bied n meervoudige doelwit optimalisering model aan, gemik op die optimalisering van die installasiekoste, energiebesparing, waterbesparing, terugbetaaltydperk en punte verdien onder die Leierskap in Energie en Omgewing Ontwerp (LEED) gradering stelsel. Ten einde besluitnemers te help met die geskikte keuse van fasiliteite, neem die ontwikkelde model ?n wye verskeidenheid van fasiliteite en spaar maatreëls in ag as retrofit alternatiewe vir die energie- en waterdoeltreffendheid kredietkategorieë van LEED. Die bydrae van hierdie navorsing is dat die LEED puntebydrae van elke fasiliteit of maatstaf oorweeg word en LEED sertifisering in die proses verkry word. Daarbenewens is die bestaande modelle verbeter deur beide die LEED drempel en afmerkpunte te oorweeg. Die probleem van beperkte beskikbare fondse word ook inaggeneem deur die retrofitprojek oor n tydperk van n paar jaar te implimenteer en die besluitnemers sodoende in staat te stel om besparings van die voorafgaande jaar te herbelê en die aanvanklike belegging so te verminder. Gevolglik word die tydswaarde van geld beskou deur die toepassing van die verdiskonteerde terugbetalingstydperk. n Sensitiwiteitsanalise word uitgevoer deur die ontleding van die invloed van die gewigsfaktore op elke doelfunksie toe te pas. Die resultate dui daarop dat die gewigsfaktore n beduidende invloed op die die aantal gekose fasiliteite en die projekkoste het. n Gevallestudie van n hotel in Suid-Afrika word aangebied om die haalbaarheid van die voorgestelde model en optimalisering benadering te demonstreer. Die optimalisering resultate toon die optimale aantal gekose fasiliteite en maatreëls vir elke jaar aan. Die koste verbonde met so n projek wissel tussen $13k - $140k per jaar en n toename in die persentasie energie- en waterbesparing word gemerk vir elke daaropvolgende jaar. Vir die gevallestudie is die LEED goud sertifisering vlak behaal teen die einde van die projek en die terugbetalingstydperk is 34 maande.