Wall assemblies U-value calculation in test buildings using constant power heating

Building envelopes under various climates behave differently, in this paper the actual thermal transmittance or U-value of five different wall assemblies are evaluated and compared with values, calculated using standard EN ISO 6946. The experiment is carried out in five test buildings with equal spatial orientation, the same ceiling and floor assemblies as well as the same windows and doors mounted in each building. The thermal transmittances for these partitions are assumed to be well known and therefore, by knowing temperature difference and heat sources inside the building, the thermal transmittance of wall assembly can be calculated. It is shown that for small buildings the corner effects are of great importance and therefore a more precise calculation of them are done.