Optimization Of The Urban Microclimate For Building Energy Demand And Thermal Comfort Under Climate Change

Abstract

Buildings in the EU are responsible for 40% of energy consumption and 36% of GHG emissions. This means that a major contribution from the construction and building sector is required to achieve the climate neutrality targets set by the European Green Deal. Conversely, the issues of energy poverty, energy inefficiency in buildings, urban heat island (UHI) and climate change are the challenges the built environment faces that impede the progress towards carbon neutrality. The potential of retrofitting strategies in improving the building performance is simulated using weather files from rural stations neglecting the impact of UHI. This leads to over-evaluation of the performance. Due to this approach, the impact on heating demand, probable increase in cooling energy demand due to future climate change and negative consequences of improvement in envelope such as worsening of indoor and outdoor thermal comfort are often not accounted for. This study proposes a tailored workflow to progressively study the challenges faced by urban planners and building energy modellers using the latest tools such as Urban Weather Generator (UWG), ENVImet, Ladybug Tools and EnergyPlus. Firstly, the study uses reference and RCP 8.5 2050 weather files to evaluate annual building energy demand with and without UHI influence. Secondly, the potential benefit of envelope retrofitting combined with UHI is simulated as an 18% decrease in annual heating energy demand under reference and extreme climate conditions. While the minimum effect of envelope retrofitting is observed on cooling energy demand, the improvement in urban microclimate shows a strong premise for tackling the cooling needs and the challenges of outdoor and indoor thermal comfort. Assessing the potential of research-backed planning strategies, the study demonstrates that for the design day of 21st July, the peak cooling energy demand will increase by 120% from reference climate to future extreme climate. Continuous canopies of dense trees along with hedges and reflective roads with an albedo of 0.4 can reduce this increase to 77%. Furthermore, the daily averaged indoor operative temperature is reduced by 1.9 °C. Similarly, thermal comfort measured as static PET shows improvement from extreme stress to moderate heat stress and strong heat stress at 13:00:00 and 17:00:00 on 21 July measured at 2 meters from the facade. Further assessment of dynamic comfort shows a significant decrease in the range of change of comfort i.e., from +12 to +3. The findings urge the research and planning community to investigate holistically the impact of different variations of urban green infrastructure and reflective materials to combat the issues of energy poverty and thermal comfort under extreme climatic conditions.