How anthropogenic heat affects air temperature of naturally ventilated apartments

Natural ventilation is an important resource to cool down indoor areas at sub-tropical areas. However, within a high density urban context, anthropogenic heat from a mechanical cooling system, such as an air-conditioning unit, could have significant impact on the thermal environment at naturally-ventilated indoor areas. Prof Yuan Chao and his team conducted a study to investigate the importance of building design to mitigate the negative impact of these anthropogenic heat effect.

Titled 'external page Impact of Anthropogenic Heat from Air-Conditioning on Air Temperature of Naturally Ventilated Apartments at High-Density Tropical Cities;, Prof Yuan, external page Ruixuan Zhu, external page Shanshan Tong, Shuojun Mei, and external page Wei Zhu focused on a residential neighbourhood. They aimed to develop evidence-based strategies to improve residential building design to mitigate the negative impact of anthropogenic heat.

Conducting a parametric study using validated Computational Fluid Dynamics (CFD) models, they investigated the impact of various design parameters, like building typology, floor elevation, apartment location, and heat emission source location on the indoor air temperature increment (∆T).

The research outputs indicate that ∆T could be significant at public housing areas, and these insights highlight how building design plays an important role. First, ∆T is generally higher at slab residential buildings compared to high-rise residential buildings. Secondly, lower ∆T at slab buildings with courtyards does not means better indoor thermal comfort, because lower ∆T is caused by poor natural ventilation. Thirdly, the apartments located at the windward side of courtyard could have much higher ∆T than the ones at leeward side. This means that, when organising hybrid ventilation for the buildings with courtyards, selecting the right ventilation direction to prevent heat entering the indoor areas from the courtyard is important. Fourthly, significant increment of ∆T with increasing floor elevation is observed at slab buildings. Finally, changing heat source locations from the windward to leeward side did not seem to decrease ∆T, but putting the heat sources at the façade parallel to the incoming wind or rooftop could be very helpful.

The above research outputs enable architects and planners to assess the current heat risk and take the necessary actions regarding locating air-conditioning placement and building design.