In the first part of this paper, some of the newest design features of hot water district heating piping are described. Emphasis is on polyurethane preinsulated one-and two-pipe elements equipped with a polyethylene jacket pipe. The paper also deals with the newest developments in concrete culvert district heating lines, namely the preinsulated concrete culvert pipe elements with a metal sheet jacket.

In the second part of the paper a method for calculating the economic optimization of preinsulated district heating lines is described. The term “economic optimization” means that the sum of investment costs, heat loss costs, and pumping costs of the line during a certain period are minimized when the maximum heat output of the line is known. The optimization program is designed to answer the following important questions: What are the optimum flow-pipe dimensions, how great is the optimum heat conductance (or insulation thickness) and how do various factors influence the results obtained?

In the third part, installation practices for different pipeline systems are discussed. Emphasis is on compensating for thermal movements in pipelines. Also compensating or noncompensating methods are discussed.

In conclusion, some test methods developed in Finland are presented. Also, Scandinavian and European cooperation and standardization work in the field of district heating is discussed.