Combined power and heat generation is state of the art to enlarge the energy usage of fuels above the level of producing electricity only. Therefore, in any case district heating is a simple and effective energy saving tool and for distribution plastic jacket pipes are used. For even larger reduction of pollution and carbon dioxide emission integrating solar power stations into district heating systems is one option. Plastic jacket pipes for district heating consist of a steel medium pipe with rigid polyurethane foam as insulation material and polyethylene casing. These pipes have to withstand stresses caused by the thermal elongation during heating and cooling cycles. Such stresses have to be transferred to the surrounding, which is in the most cases soil as compacted sand bed. Due to the specifics of solar radiation a fast change in high and low power output can happen e.g. during cloud movement. This is directly transferred into increasing number of load cycles causing cyclic stresses to specifically the rigid polyurethane foam. There is little known about the behavior of such rigid polyurethane foams under cyclic stresses over time. First attempts to characterize this kind of foams by using both static and dynamic testing combined with thermal and climate ageing had been performed. The results of such tests will be discussed and the testing scenario for the respective plastic jacked pipes presented.