Thermal regulation enhancement in multi-story office buildings: Integrating phase change materials into inter-floor void formers

Addressing the thermal loss from building envelopes is a crucial challenge and requires the explo- ration of various mitigation strategies. This study employs comprehensive 3D computational fluid dynamics simulations to investigate the incorporation of various bio-based Phase Change Materials (PCMs) including CrodaTherm (CT) 19, CT21, and CT24W, within inter-floor void for- mers between the roof-floor boundary in multi-story office buildings to optimize energy manage- ment during inactive periods in one of the adjacent units. Aside from the PCM type, the void for- mer shape, its placement, and the combinations of PCMs and insulating layers are examined through heat flux and solid fraction plots as well as liquid fraction contours. Results highlight the exceptional performance of CT24W-integrated void formers, achieving a remarkable 36.74 % re- duction in the 48-h average heat flux in comparison with the case without void formers, and of- fering lower heat flux values than the scenario with insulating layers for 89.38 h (endurance time). Based on the findings, with identical PCM volumes, the semi-ellipsoid PCM-integrated void former provides 11.07 % lower heat flux and 27.56 % longer endurance time compared to the one with a spherical shape. The results underscore PCM integration as a superior strategy over standalone insulation for managing thermal loss between apartment floors.