Production and distribution of domestic hot water in selected Danish apartment buildings and institutions. Analysis of consumption, energy efficiency and the significance for energy design requirements of buildings

Abstract The goal of this work has been to document the efficiency of domestic hot water (DHW) distribution systems and to propose more energy efficient and environmentally friendly solutions for DHW systems based on analyses of existing conditions. In the article, measurements from 13 apartment buildings and two institutions are presented, i.e. consumption of DHW, heat loss from circulation lines and efficiency of the DHW system. The heat load and the cooling of the district heating water for DHW are documented as well. Possibilities for improving the DHW system include new types of circulation pipes, which have the potential of a 40% reduction of heat losses. In addition to the reduction of heat losses inside the building, a low return temperature from the hot water system will have a large impact on the heat losses from the district heating network when the building is being heated by district heating. It is likely that the production and distribution of DHW in buildings will constitute a dominant share of both the present, and in particular, the future energy design requirements of buildings. The results of this project could influence not only future buildings, but also existing buildings when renovation of installations take place.