A Study on Utility of Retrofit that Minimizes the Replacement of Heat-Source System in Large Offices

Abstract

In a general building retrofit process, the reinforcement of insulation performance or air-tightness in walls and windows are conducted to reduce the maximum cooling and heating load of buildings. A heat source consists of heat-source equipment and water-pipe systems, which are replaced with high-efficient specification materials. Most of them are simply replaced with the same capacity as the previous heating equipment. This study aims to investigate matters required for decision making in a retrofit plan, such as conducting an investigation of the maximum load reduction in buildings obtained by the retrofit and the capacity of heat-source equipment that reflects the reduction, and the re-use or replacement of the water-pipe system, etc. in advance. This study verified that when the capacity of heat-source equipment was reduced, the pipe diameter of the water-pipe system was also decreased, but if existing pipes were re-used, the transportation power of the pump was reduced due to the reduction in flow velocity. The changes in maximum cooling and heating load through retrofit were quantitatively verified compared to that of the initial design of the building based on previous study results, and flow rates of cool and hot water were determined by re-calculating the capacity of the heat-source equipment. Using the results, the water-pipe system was re-designed, and the annual transportation power of the pump was calculated through simulations. The calculation results verified that the transportation power decreased by up to approximately 10% when oversized pipes were re-used from the existing water-pipe system. Additionally, when the capacity of the heat-source equipment was decreased, reasonable measures considering remodeling, construction duration, and cost were derived.