# Analysis of Climate-Oriented Researches in Building
## 3 Results and Discussion
### Results of Cluster Analysis
#### 3.2.1 Cluster 1--Mitigation of the Effects of UHI and Cooling of Buildings  
The first cluster includes a total of 24 investigations (Table S1). These include general methodologies for energy conservation in buildings, techniques for mitigation the various effects of urban heat islands (UHI), the improvement of outdoor thermal comfort in UHI conditions and techniques for reducing energy consumption for cooling in buildings. The first and oldest works of this cluster were focused on the idea of energy conservation. They analysed the application of cool-roof energy conservation techniques for non-residential and commercial buildings in different cities and in different climate zones, showing energy simulation results [58; 59]. Subsequently, studies appeared that focus on the search for optimal bioclimatic architectural strategies [89] as well as the optimal design of residential building envelop systems [90], all of this with the general aim of reducing energy consumption in housing and improving indoor thermal comfort. Mitigation techniques were developed, ranging from cool-roofs, green roofs and green facades, to the application of phase change materials (PCM) for building envelopes and the search of the optimal PCM for different cities and climate conditions. These generally show an evolution from field studies of the thermal effect and the radiation balance of various UHI mitigation techniques to complex computational simulations of the energy saving potential, considering indoor thermal comfort. Thus, in 2010, a paper was published on the search for optimal building shapes [91] with the main purpose to mitigate the effect of UHI using simulation with the ENVI-Met tool, which showed that the shape of buildings can improve ventilation in the streets, and the use of green-roofs, will help mitigate the effect of UHI. In this respect, research on techniques for mitigating the effect of UHI was subsequently carried out. Thus, in 2011, based on Energy Plus simulations in six ASHRAE climate zones in the USA, it was determined \"that white and green-roofs are effective strategies for UHI mitigation\" [92]. In Italy, based on field experiments and computer simulation, a numerical model for calculating the thermal resistance of green roofs was presented [93]; finally, numerical models were developed for calculating the thermal resistance of green facades [94]. Continuing with the application of UHI mitigation techniques in countries such as the USA and Australia [95], the use of PCMs in building envelopes, which can generate potential annual energy savings of 17-23%, is emerging [96]. In this regard, it has become clear that \"PCM performance highly depends on the weather conditions, emphasising the necessity to choose different PCMs at different climate zones\" [97]. More recent work focuses on finding optimal PCM melting temperatures for different cities and climate zones [98], as well as combining the use of PCM with indoor thermal comfort models in energy simulations [99]. This cluster also includes two publications that address the study of outdoor thermal comfort in UHI conditions, as well as the development of methods to mitigate the thermal and energy effects of UHI [100, 101]. In both investigations, the authors point out the importance of the urban wind environment for outdoor thermal comfort in two cities located in different climate zones. By 2017, estimates were already being made of the effect of green roofs on outdoor/indoor temperature and cooling demand under four different climate conditions and urban densities with ENVI-met and Energy Plus tools [102]. In this sense, studies have evolved from focusing solely on the dwelling to an analysis of buildings with an aspect of interaction with the urban environment, e.g., on the scale of streets and neighbourhoods.