Evaluation of settlement textures in terms of building energy, economic performance, and outdoor thermal comfort

https://doi.org/10.1016/j.scs.2020.102110Get rights and content

Highlights

  • A multi-scale approach was developed to evaluate the different settlement textures.

  • Considered energy and economic performances as well as outdoor thermal comfort.

  • Parametric analyses were conducted to guide sustainable urban neighbourhood designs.

  • The effect of design parameters was explored for temperate-humid climate region.

Abstract

Settlement textures have continued to exist for many years without any major changes in terms of the performance of the buildings or outdoor thermal comfort conditions. Radical changes in a settlement texture are only possible when the existing texture is completely demolished and a new settlement texture is built in place of the old one during urban redevelopment processes. Therefore, a multi-scale approach evaluating building component scale, building scale, and settlement scale was developed in this study to design settlement textures based on environmental and climate data. This approach intended to evaluate the energy and economic performance of the reference residential building in different settlement texture alternatives and to determine the effects of settlement texture alternatives on outdoor thermal comfort conditions. Additionally, the goal was to evaluate the existing thermal properties of building envelope components to improve the energy and economic performance of the reference residential building as well as to evaluate the use of trees on streets to enhance existing outdoor thermal comfort. In this way, mistakes in the construction of settlement textures affecting many occupants could be prevented, and the development of sustainable urban neighbourhood designs with efficient buildings and settlements would be possible.

Introduction

One of the most important indicators of technological, economic and physical developments in both developed and developing countries is the supply and use of energy. The rapid increase in energy use in urban areas, which consume the most energy, during increased urbanisation cannot be ignored. With the current increase in the population and urbanisation rates, it is estimated that global urban areas will increase three-fold compared to the beginning of the twentieth century (Seto et al., 2012), and two-thirds of the global population will be living in urban areas by 2050 (UN DESA, 2014). Moreover, urban areas account for three-fourths of global primary energy use and approximately 60 % of global greenhouse gas emissions (UN-Habitat, 2018). The fast growth of urban areas as well as the failure to establish an efficient energy plan has led to an increase in energy and environmental problems. The goal in architecture and urban planning in terms of energy and environmental problems is to meet the demands of people while protecting nature and the environment.

Accordingly, buildings are critically important in terms of energy efficiency, as they are responsible for 32 % of global energy consumption and one-fourth of human-induced CO2 emissions (IEA, 2013). The main ways for a building to save energy are passive heating, cooling, and natural lighting. Buildings that show optimum performance in these functions minimize the energy consumption of active systems to meet thermal comfort conditions and become energy and cost-efficient buildings.

All the studies on energy performance of buildings since the 1960s have claimed that evaluations of stand-alone buildings would not be sufficient, and interactions between buildings and other buildings in the neighbourhood to obtain more accurate results from analyses to evaluate the energy performance of buildings should be investigated (Rodríguez-Álvarez, 2016; Sanaieian et al., 2014). In the literature, overall climate conditions, settlement and building geometry, thermal properties of the building envelope, efficiency values of the energy systems, and occupant profiles are emphasized as important factors that affect the energy performance of buildings (Mitchell, 2005; Ratti et al., 2005; Salat, 2009). According to a study conducted by Baker and Steemers, a study by Carlo Ratti demonstrated that among these five independent factors that affect the final energy performance of a building, settlement geometry could cause a change in energy consumption of over 10 % (Baker and Steemers, 2000; Curra et al., 2020; Ratti et al., 2005).

However, as a result of decreasing green and open spaces with increasing urbanisation, increased motorised vehicle traffic and dense settlements, unfavourable thermal comfort conditions compared to rural areas have increased, especially in large cities. Therefore, outdoor thermal comfort is one of the most basic factors to evaluate the quality of the microclimate in cities. Including outdoor thermal comfort in the design stages is important to design sustainable urban neighbourhoods. Therefore, studies that investigate the effects of the design of settlement textures on micro-climate have also become more prominent in the last couple of decades. The geometrical parameter—which defines the relationship between building heights and spaces between buildings and is also known as the urban canyon, or aspect ratio, within the limitations of orientation—controls solar access and wind movements, manipulates microclimate data, and additionally affects thermal comfort conditions of the buildings within a settlement texture. Therefore, this ratio, which determines the relationships between buildings in sections of settlement textures, should be analysed in the design stage while considering the climate data. Oke (1988) is one of the first researchers to use the urban canyon concept, and in his study, he intended to offer alternatives that provide optimum conditions using the four most basic conditions (i.e. maximisation of shelter, maximisation of dispersion of pollutants, maximisation of urban warmth, and maximisation of solar access) when developing designs for outdoor climates.

A review of the studies in the literature showed that settlement texture design significantly affects both the building energy performance and outdoor thermal comfort conditions, which vary for different climate regions. However, the number of multi-scale studies that do not solely concentrate on building energy performance or only on outdoor climate conditions but investigate energy, economic performance, and outdoor thermal comfort conditions together and develop different alternatives to improve these performances remains insufficient. This study aimed to develop a multi-scale and comprehensive approach model on a settlement, building, and building component scale to understand the direct and indirect interaction of several settlement texture alternatives and a building’s energy and economic performance and outdoor thermal comfort in a temperate-humid climate region.

With a focus on urban scale, studies that focus on mutual interactions between buildings and settlement texture in a built environment rather than the conventional approach, which mostly deals with the improvement in thermal physical properties of the building envelope and energy systems mostly in the evaluation of the stand-alone building energy performance, have been increasing. The results of the studies show that the building’s energy performance is predominantly affected by the settlement texture and building form in terms of heat loss and solar access (Futcher and Mills, 2013; Hachem et al., 2011a; Hachem et al., 2011b; Ratti et al., 2005; Salvati et al., 2017; Vartholomaios, 2017).

However, the direct use of complex settlement textures and building forms in studies makes analysis of area-specific complicated interactions difficult and prolongs the time spent for analysis. Therefore, standard forms that simplify complex settlement forms by maintaining basic spatial parameters that are effective in the evaluation of the performance of settlements are used, or notional grids are developed. As standard forms, some simplified and archetype urban forms including pavilions, slabs, terraces, terrace-courts, and courts were developed by Martin and March Martin and March (1972) and used in many studies (Quan et al., 2014; Ratti et al., 2003; Taleghani et al., 2013; Vartholomaios, 2017). In studies where notional grids were developed to evaluate the performance of settlement forms, grid sizes and the distribution of blocks on the vertical and horizontal planes varied (Cheng et al., 2020; Nutkiewicz et al., 2018; Rodríguez-Álvarez, 2016; Rode et al., 2014; Vermeulena et al., 2018).

Another important point to consider in a meaningful analysis of the relationship between settlement texture and energy performance is which design parameter(s) will be used in the settlement scale. Nault et al. Nault et al. (2015) defined design parameters concerning the settlement scale in three categories: geometry-based, external solar and geometry-based, and full climate and geometry-based. The geometry-based group includes design parameters that are calculated based on settlement texture and building morphology. The second group includes design parameters that consider the level of solar exposure of exterior building surfaces depending on the settlement geometry (e.g. solar irradiation (kWh/m²)). The third group includes design parameters that consider climate and geometry data that require mostly complex simulations and more time (e.g. spatial daylight autonomy) Curra et al. (2020); Nault et al. (2015). Among these three groups, geometry-based design parameters can be calculated more easily, as the data is accessible and simple, and calculations do not require expert knowledge (Curra et al., 2020). The most common geometry-based design parameters are the aspect ratio (building height to street width) (Allegrini et al., 2016; Ali-Toudert and Mayer, 2006; Johansson, 2006; Ratti et al., 2005; Sanaieian et al., 2014; Strømann-Andersen and Sattrup, 2011; Vartholomaios, 2017), surface-to-volume ratio (Morganti et al., 2017; Oh and Kim, 2019; Ratti et al., 2005; Rode et al., 2014; Taleghani et al., 2013; Vartholomaios, 2017), ground space index (Morganti et al., 2017; Nault et al., 2015; Rodríguez-Álvarez, 2016), floor space index (Curra et al., 2020; Natanian et al., 2019a; Morganti et al., 2017; Rodríguez-Álvarez, 2016; Rode et al., 2014), and average building height (Cheng et al., 2020; Morganti et al., 2017; Rode et al., 2014).

In this sense, the aspect ratio, which is one of the geometric parameters used to simply define the relationships among buildings in the sections of settlement textures, has been investigated in many studies to understand the relationship between urban canyon designs and energy consumption. Ali-Toudert Ali-Toudert (2009) studied a building in different settlement textures using different building properties in three climate regions and determined that cooling decreased with deep street canyons. Strømann-Andersen and Sattrup Strømann-Andersen and Sattrup (2011) analysed settlement textures in northern Europe to investigate the effects of the height-width (H/W) ratio of settlement textures on heating, cooling, and lighting energy consumption; they concluded that the H/W ratio affected up to 30 % of total energy consumption.

It is also necessary to ensure urban comfort within settlement textures. Therefore, urban areas should be designed to have streets with shading to provide cool areas for occupants and to allow passive heat gain using solar radiation under necessary conditions. Bourbia and Awbi Bourbia and Awbi (2004) examined outdoor thermal comfort, which traditional and new settlement texture typologies in hot climate regions provide, and they measured the surface and air temperature on the streets in two different settlement textures in the city of El-Qued. According to their results, settlement textures in a hot climate region provide urban areas with better thermal comfort by minimising solar radiation with narrow streets and prevent the microclimate effect with low surface temperatures. Van Esch et al. Van Esch et al. (2012) found that 5-m changes in different street widths provided solar radiation gains of up to 19 % in winter and 25 % in summer in cold climate regions. Perini and Magliocco Perini and Magliocco (2014) investigated the effects of building density, different settlement textures, and different building heights to evaluate the role of the canyon effect in Milan, Genoa, and Rome. The results of the study demonstrated that the density and height of buildings in a city area influence the potential temperature, mean radiant temperature (MRV), and predicted mean vote (PMV) distribution; for most of the cases examined, a higher density resulted in higher temperatures and vegetation had higher cooling effects. Yin et al. Yin et al. (2019) developed a parametric model to investigate the effect of four main variables: settlement textures, canyon type (i.e. alley, arcade street, and boulevard), canyon axis, orientation, and the canyon aspect ratio (H/W) in southern China. The physiological equivalent temperature (PET) was adopted to assess pedestrian-level thermal comfort (PTC). According to the main findings, both arcade and green spaces had a significant cooling effect on pedestrians, especially on east-west oriented streets; proper PTC was achieved in the settlement with long east-west oriented streets; and the PTC in all streets dramatically responded only to a H/W ratio higher than 0.67.

All the above-mentioned studies further concluded a settlement texture design has a major effect on the energy consumption of buildings and outdoor passive thermal comfort in urban areas. Additionally, since settlement textures do not change for many years, settlement textures are accepted to have a long-term effect on the energy consumption of large building stocks in settlement textures. Considering that the urban redevelopment process quickly occurs, especially in developing countries, and that decisions about settlement and building designs in this process continue to affect outdoor thermal comfort for many years, an effective roadmap or procedural approach is essential to solve energy and environmental problems based on urban development dynamics. Only a few studies have evaluated the effects of settlement textures both on energy performance and on the outdoor environment on a multi-scale level (Barreiro et al., 2009; Natanian et al., 2019b). This study intended to fill this gap with a comprehensive and comparative approach suggestion that allows the study of the change in the micro-climate on a multi-scale level and its practical applicability using energy-related trade-offs and integrated cost analyses to identify suitable settlement texture alternatives. Therefore, the research question was based on an evaluation of effectiveness of design parameters in the design of settlement textures in terms of the energy and economic performance of buildings and outdoor thermal comfort conditions: what performance level can be achieved with each settlement texture design?

Section snippets

Methodology

The objective of this approach was to comparatively evaluate the design parameters that are important to re-institute the complicated balance between the settlement texture and the energy consumption of a building in an energy-efficient and cost-effective way. This approach also aimed to determine the level of the effect of settlement textures on outdoor thermal comfort performance with the use of different street sections. The multi-scale approach model developed for this purpose consisted of

Energy, cost, and outdoor thermal comfort analyses

Energy analyses concerning the final energy consumption and associated CO2 emissions were conducted to evaluate the energy performance of the reference residential building in each of the settlement texture alternatives. Life cycle cost (LCC) analyses integrated with energy analyses were conducted, and discounted payback periods (DPPs) were calculated to evaluate the economic performance of the reference residential building. Outdoor thermal comfort analyses were also conducted to evaluate the

Results

The level of the effect of the 30 settlement texture alternatives developed in accordance with the building scale and settlement scale design parameters on the energy and economic performances of the reference residential building and outdoor thermal comfort conditions was determined. Energy, cost, and outdoor thermal comfort analyses were then performed for the different alternatives developed on a building component scale and street scale. The results were compared with the existing

Conclusion

Considering the rapid increase in urban areas globally, the planning and developing of these areas in terms of efficient energy consumption and limited CO2 emissions have become important. However, the design parameters used to create urban areas, such as settlement texture, building form, building envelope, and landscape planning also impact the urban climate, which impacts the energy performance of buildings and the use of urban open spaces. Therefore, the relationship between settlement

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This study was supported by a grant from the Scientific Research Projects Unit of Istanbul Technical University under the Scientific Research and Development Support Program (Project No: 39956).

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