Due to their very low thermal conductivity, Vacuum Insulation Panels (VIPs) have recently seen a fast development and an increasing penetration in building thermal insulation market.However, there is still a lack of knowledge about their performance when actually applied in buildings. In fact, the thermal bridging effects that occur in VIP junctions are not easily evaluable while produce a reduction of the global thermal performance. In this paper, the linear thermal transmittances related to VIP junctions considering different joint materials between VIPs panels and different wall configurations were assessed through a 2D numerical analysis. Finally, through a quasi-steady state simulation, a parametric building case study was analysed, with the aim to evaluate the influence of the thermal bridging effects on the overall building energy need.The results shows that the thermal bridging effect due to VIPs assemblies have not a negligible influence on the overall building energy performance

In this paper a numerical analysis aimed at evaluating the thermal performance of vacuum insulation panels (VIPs) at the building scale is presented. This technology has seen considerable development over the past few years, gaining increasing penetration in the building insulation market. However, it is important to evaluate correctly the thermal bridging effect that occurs when the VIPs are coupled with joints at the building scale. To this purpose, the linear thermal transmittances of different VIP assemblies inserted in several wall configurations were assessed through a bidimensional numerical analysis. Moreover, to evaluate the influence of thermal bridges on the building energy need, quasi-steady-state simulations for a parametric building module were performed. A simple empirical model was finally built to estimate the linear thermal transmittance from basic input variables. The study demonstrates that thermal bridging effects that occur when VIPs are jointed are never negligible and they could have an important impact on the building heating energy need.

Solar Air Heating Façades (SAHF) can exploit solar radiation to partially fulfil the building heating and ventilation demand. This study was developed starting from an experimental campaign on a full scale fan-assisted SAHF applied to an outdoor test cell (TWINS) located in Torino (Italy). The data gathered from the monitoring activity were used to validate a white box model, developed in EnergyPlus. An axial fan drives the airflow through the façade; therefore, the supplied air temperature can be controlled by changing the fan speed. For this purpose, a PID (Proportional Integrative Derivative) controller was developed. This study demonstrates that the application of different control strategies significantly affects the façade overall performance and behaviour. Results highlight that the system can reach an average seasonal solar efficiency of up to 30%. Furthermore, by operating the system in heating-mode only and controlling the supply air temperature at 25°C, the system operates for 30% of the heating season, while at 40°C the system can provide fresh pre-heated air with an higher exergy level for the 10% of the winter period. Fan-assisted SAHF represent a valuable retrofit strategy solution in all buildings that present space limitations for the installation of centralised ventilation systems, helping to address the nZEB target requirements.