Effect of dynamic characteristics of building envelope on thermal-energy performance in winter conditions: in field experiment

Research about building strategies for energy saving is taking a growing interest worldwide. New solutions for building envelopes require increasingly sophisticated investigation to analyze the thermal-energy in-field dynamic response of constructions. Moreover, in-lab experiments are difficultly able to represent real environment boundary conditions. In this paper, effect of dynamic properties of building opaque envelope is investigated in winter conditions through an extensive continuous monitoring campaign of a dedicated experimental field. The field consists of: two fullscale buildings, an outdoor weather station, and two indoor microclimate stations. The two buildings were designed with the same stationary envelope characteristics, but different envelope technologies, materials and, therefore, different dynamic properties. Nevertheless, following Italian regulations about building energy performance in winter, they should behave the same. With the purpose to verify this hypothesis, a continuous long-term comparative monitoring is developed. The results only partly confirm that simplified hypothesis. In fact, in winter, while the two buildings exhibit equivalent long-term energy behavior, a weak difference is registered in terms of air temperature in free-floating, transient, and operative HVAC systems’ regime. Additionally, non-negligible discrepancies are registered in terms of mean radiant temperature, indoor humidity and internal-external envelope surface temperature, given the different transpiration rate of the two envelope systems and different solar reflectance values of the roofs.