Are building upgrades and neighborhood-scale microclimate modifications complementary?

In many countries, so-called 'green building' building codes are adopted that aim, inter alia, to reduce energy consumption for heating and cooling. Separately, local initiatives promote green infrastructure and increase the vegetated fraction of the surface as a response to climate change and global warming. The compound effect of both strategies was examined in a simulation study of an urban neighborhood in Tel Aviv. Using the CAT model, modified TMY files were generated that account for the urban effects of location, surface cover, and density in different building configurations. These files were then used to assess the climatic cooling potential (CCP) by night ventilation and as inputs for detailed computer simulation of building energy performance. Model outputs indicate that the nocturnal urban heat island will increase demand for summer cooling relative to the reference rural site, but this penalty will be more than offset by reduced winter heating, resulting in an overall annual saving of nearly 7% in a standard urban building. However, because the urban heat island will reduce the potential for cooling by night ventilation in summer, the prevalence of air conditioning use will increase. Peak electricity loads will be higher and buildings may be more vulnerable to potential loss of electric power during episodes of extreme heat. 'Green' buildings are more efficient than standard ones, but the shading effect of adjacent buildings in dense urban locations reduces their advantage. Implementing a strategy of extensive planting, so that a green surface fraction of 0.5 is obtained, results in a mean annual temperature reduction of about 0.3^oC and an energy saving relative to the current condition of about 2-3% in both standard and 'green' buildings. The study highlights the importance of comprehensive analysis of the complex interactions between neighborhood-scale modifications of the microclimate and upgrades to individual buildings.