Abstract The envelope thermal behaviour in dynamic conditions is becoming essential to assess the whole year energy performance of buildings. International Standards describe in detail the theoretical approach, but few examples of experimental analyses and procedures exist to determine the performance of materials and components in unsteady-state conditions. The work is aimed at filling this vacancy, describing a modification of hot box devices, which are generally designed for stationary measurements, but they could be successfully used also for time-dependent investigations. Two different methods are proposed: a hot box system where one-day period sinusoidal solicitations in terms of temperature and heat flow are imposed, and another type of boundary condition, with a faster impulsive thermal driving force. The former showed a good agreement with the expected theoretical results; the latter proved also suitable but suffered a lower accuracy, being characterised in turn by a significant reduction of the measurement time. It is also showed that hot boxes allow also more detailed investigations, such as infrared thermography imaging, to better analyse the thermal performance of the tested samples.