What Is the Minimum District Heating Supply Temperature in Residential Buildings in Norway?

Abstract

High temperature district heating systems are connected to high losses, therefore, new district heating systems have lower temperatures. In Zero Emission Neighborhoods (ZEN) the heat demands are reduced and 4th generation district heating (4DH) solutions opens as a solution to provide the heating demands with lower transmission losses. However, district heating (DH) has to cover demands in new, renovated and old buildings connected to the supply. Therefore the supply temperature cannot be reduced without further consideration. One strategy to cover demands is to connect older buildings with higher temperature requirements on the supply pipe and the new/renovated buildings on the return pipe. A second strategy is to use local boosters (at building level), e.g. heat pumps or boilers, in a low temperature DH network, to supply the buildings that require high temperature supply (old radiators, leaky envelopes…). Either way, the fundamental constraint is what is the minimum heating supply temperature in different building types? In turn, this holistic approach will map the minimum DH supply temperatures that the heating demands of all the buildings forming the ZEN can be covered. This paper analyzes for the case study of residential buildings in Norway according to the archetypes defined in the Tabula/Episcope projects. The focus of this paper is on single-family houses of the seventies. Each case is subdivided based on energy performance (original, standard renovation and ambitious renovation). The buildings were simulated in IDA Indoor Climate and Energy (IDA ICE). The effect of renovation on the achievement of thermal comfort levels compared to minimum supply temperature is studied.