Optimizing the thermal performance of double skin Façades in a cold climate with phase change materials and cavity ventilation

• Phase Change Materials enhance Double Skin Façades under Nordic climate conditions. • Ventilation strategies significantly influence the thermal performance of the façade. • High solar gains overheat façade systems even in cold climates • PCMs cut the DSF temperature by 15–24%, keeping it below ∼34 °C during the day. • Different PCM types reduce the heat flux from 6.5% to 9% at peak hours. Double Skin Façades (DSFs) emerge as an advanced façade technology to enhance thermal insulation and improve thermal comfort, particularly in office buildings. However, DSFs can experience overheating during the day or can underperform as a thermal buffer during nights and cold periods, particularly in cold climates. Such drawbacks can be moderated by integrating Phase Change Materials (PCMs) into the façade system, due to the added latent thermal energy storage. Ventilating the cavity has also proven to be a key element for thermal control. However, research connecting ventilation, PCM selection and shallow-angle irradiance in a Nordic context is currently underdeveloped. This paper fills the gap by addressing a DSF cavity of an office unit in a construction site in Helsinki, Finland. Detailed simulation models of the DSF unit, validated against field measurements, address both cavity and indoor air temperatures, and investigate different PCM types and façade ventilation options. It is found that integrating different combinations of PCM types and cavity ventilation strategies reduces the cavity air temperature from 15% to 24% during the day, always keeping it below the peak value (∼34 °C). The heat flux is reduced from 6.5% to 9% at peak hours, and the PCM-DSF system prevents the cavity from freezing in the morning and at night. Cavity ventilation thus confirms its crucial role in controlling the thermal environment inside the façade as well as indoors. These encouraging results are scalable to a general Nordic context for an energy efficient implementation of DSFs into building envelopes.