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HomeMy WebLinkAboutBridge Bowman Executive Summary Section 1.0: Executive Summary The goal of themechanicallifecycle engineering economic analysis isto asses the performance of various mechanical systems in comparison to a baselinemechanical system. Each option is compared to the baseline system to determine the lowest combined savings over a 25 year cycle to determine the most advantageous system considering electrical costs, gas costs, maintenance costs, and initial construction costs. By comparison of each option to the baseline system, the optionwith the greatest total life-cycle savings is generally recommended. To further enhance controllability and overall system performance,additional options should be considered that will enhance year round temperature control and comfort at a possible marginal increase in capital cost. Section 1.1: Mechanical System Analysis 1.1.A: Baseline Mechanical System –Classroom Unit Ventilators and Constant Volume Air HandlingUnits(Replacement in Kind) Hot water coil unit ventilatorsserving the academic and support areas Exhaust fans and existing ductworkto remain and be cleanedfor classroom unit ventilator ventilation Gas-fired roof mounted heating and ventilating unit serving the auditorium/gymnasium Gas-fired heating/direct expansion cooling constant volume roof mounted air handling unit serving the administration areas Hot water coil indoor heating and ventilating unit serving the cafeteria Hot water coil indoor heating and ventilating unit andsplit system dx cooling units serving the computer classrooms Hot water coil indoor heating and ventilating unit serving the interior teacher offices Hot water coil indoor heating and ventilating unit serving the library Limited use of fintube radiation, convectors,and unit heatersin entryways, corridors,and storage areas Two-pipe hot water distribution systemserving unit ventilators, fintube radiation, hot water coils, and unit heaters (2) 2,000 MBH high-efficiency gas-fired condensing boiler power plant Hot water primary pumping with variable frequency drives Direct digital controls throughout 1.1.B: Mechanical System Option One–Classroom Unit Ventilators with Demand Control Ventilation and Constant Volume Air Handling UnitswithDemand Control Ventilation (Current Schematic Design) Hot water coil unit ventilators with demand ventilation controls serving the academic and support areas Exhaust fans and existing ductwork to remain and be cleanedfor classroom unit ventilator ventilation Gas-fired roof mounted heating and ventilating unit withdemand ventilation control serving the auditorium/gymnasium Gas-fired heating/direct expansion coolingconstant volume roof mounted air handling unit with demand ventilation control serving the administration areas Hot water coil indoor heating and ventilating unit with demand ventilation control serving the cafeteria Hot water coil indoor heating and ventilating unit with demand ventilation control and split system dx cooling units serving the computer classrooms Hot water coil indoor heating and ventilating unit with demand ventilation control serving the interior teacher offices Hot water coil indoor heating and ventilating unit with demand ventilation control serving the library Limited use of fintube radiation, convectors, and unit heaters in entryways, corridors, and storage areas Two-pipe hot water distribution systemserving unit ventilators, fintube radiation, hot water coils, and unit heaters (2) 2,000 MBH high-efficiency gas-fired condensing boiler power plant Hot water primary pumping with variable frequency drives Direct digital controls throughout 1.1.C: Mechanical System Option Two–CentralVentilation System with Energy Recovery, Variable Air Volume Air Handling Unit,and Constant Volume Air Handling Units with Demand Control Ventilation Multiple ceiling-mounted diffusers at approximately 200-300 CFM (2 per classroom, 1 per support area) inthe academic, interior teacher offices,and support areas Dedicated overhead galvanized ventilation distribution system feeding each diffuser 100% outside air gas-fired rooftop unit with energy recovery wheelproviding ventilation to the academicand support areas Wall-mounted fintube radiation located along the exterior wallin the academic, interior teacher offices, and support areas Gas-fired roof mounted heating and ventilating unit with demand ventilation control serving the auditorium/gymnasium Gas-fired heating/direct expansion cooling variable air volume roof mounted air handling unit with variable air volume diffusersserving the administration areas Hot water coil indoor heating and ventilating unit with demand ventilation control serving the cafeteria Hot water coil indoor heating and ventilating unit with demand ventilation control and split system dx cooling units serving the computer classrooms Hot water coil indoor heating and ventilating unit with demand ventilation control serving the library Limited use of fintube radiation, convectors, and unit heaters in entryways, corridors, and storage areas Two-pipe hot water distribution systemserving fintube radiation, hot water coils, and unit heaters (2) 1,200 MBH high-efficiency gas-fired condensing boiler power plant Hot water primary pumping with variable frequency drives Direct digital controls throughout Required architectural work for classrooms ductwork, structural supports, and acoustical screens for rooftop units 1.1.D: Mechanical System Option Three –CentralVentilation System with Energy Recovery, Variable Air Volume Air Handling Unit, and Constant Volume Air Handling Units with Demand Control Ventilation Multiple ceiling-mounted diffusers at approximately 200-300 CFM (2 per classroom, 1 per support area) in the academic, interior teacher offices, and support areas Dedicated overhead galvanized ventilation distribution system feeding each displacement diffuser 100% outside air gas-fired/direct expansion cooling rooftop unit with energy recovery wheel providing ventilation to the academic, and support areas Wall-mounted fintube radiation located along the exterior wallin the academic, interior teacher offices, and support areas Gas-fired roof mounted heating and ventilating unit with demand ventilation control serving the auditorium/gymnasium Gas-firedheating/direct expansion cooling variable air volume roofmounted air handling unit with variable air volume diffusers serving the administration areas Hot water coil indoor heating and ventilating unit with demand ventilation control serving the cafeteria Hot water coil indoor heating and ventilating unit with demand ventilation control and split system dx cooling units serving the computer classrooms Hot water coil indoor heating and ventilating unit with demand ventilation control serving the library Limited use of fintube radiation, convectors, and unit heaters in entryways, corridors, and storage areas Two-pipe hot water distribution systemserving fintube radiation, hot water coils, and unit heaters (2) 1,200 MBH high-efficiency gas-fired condensing boiler power plant Hot water primary pumping with variable frequency drives Direct digital controls throughout Required architectural work for classrooms ductwork, structural supports, and acoustical screens for rooftop units 1.1.E: Mechanical System Option Four –CentralVentilation System with Energy Recovery, Variable Air Volume Air Handling Unit, and Constant Volume Air Handling Units with Demand Control Ventilation Multiple ceiling-mounted diffusers at approximately 200-300 CFM (2 per classroom, 1 per support area) in the academic, interior teacheroffices, and support areas Multiple four-pipe two coil heating and cooling fan coil units, 100% recirculation air serving the academic, interior teacher offices, and support areas Dedicated overhead galvanized ventilation distribution system (primary air ducted directly to fan coil unit andsupply ductwork on discharge of fan coil unit) 100% outside air gas-fired/direct expansion cooling rooftop unit with energy recovery wheel providing ventilation to the academic, and support areas Wall-mounted fintube radiation located along the exterior wallin the academic, interior teacher offices, and support areas Gas-fired heating/direct expansion cooling roof mounted air handlingunit with demand ventilation control serving the auditorium/gymnasium Gas-fired heating/direct expansion cooling variable air volume roof mounted air handling unit with variable air volume diffusersserving the administration areas Hot water coil heating/chilled water coil cooling indoor air handling unit with demand ventilation control serving the cafeteria Hot water coil indoor heating and ventilating unit with demand ventilation control and split system dx cooling units serving the computer classrooms Hot water coil heating/chilled water coil cooling indoor air handling unit withdemand ventilation control serving the library Limited use of fintube radiation, convectors, and unit heaters in entryways, corridors, and storage areas Two-pipe hot water distribution systemserving fan coil units, fintube radiation, hot water coils, and unit heaters Two-pipe chilled water distribution systemserving fan coil units and chilled water coils (2) 1,200 MBH high-efficiency gas-fired condensing boiler power plant 60 ton high-efficiency air-cooled chiller power plant Chilled and hot water primary pumping with variable frequency drives Direct digital controls throughout Required architectural work for classrooms ductwork, structural supports, and acoustical screens for rooftop units Section 1.2: Mechanical System Analysis Conclusion Thereplacement in kind classroomunit ventilatorsystemisselected as the baseline system since it results in thelowestinstalled cost system.Unfortunately,the selection may resultin overall ownership coststhat in some cases are higher as compared to the alterative systems primarily relating tothe increased annual operating costswhile also compromising the thermal comfort of the building.The option comparison of each alternative system to the baseline assesses the benefits of differentsystems with potentially reduced combined operating costs and improved thermal comfortwith the goal of selecting the system with the highest ownership savingsover the 25 year study period. Annual electrical and gas consumption iscalculated thru theresultsof athermal dynamic heat transfer analysis utilizing Department of Energy (DOE-2)/eQuest software with allarchitectural data provided by Design Partnership of Cambridge Architects. Utility cost data for electricity and gas were obtained from published rate tables provided by the local electrical and gas providers. The“Building Life-Cycle” analysis includedfuture worth of each system option considered using standard industry discount, inflation,andinterestrates. Our observations of the Mechanical System Payback Summary suggest that option one,a classroom unit ventilator system with demand control ventilation, represents the most cost effective solution by yielding an approximate $77,424savings over the 25 year study periodwith a5 yearpayback. It shouldbe noted that the baseline, option one, and option two are heat only systems (with the exception of the administration and computer room areas) and will not provide the thermal comfort conditions of options three and four.