Progressing urbanization and climate change are interacting processes that require comprehensive actions to minimize their negative effects. Particularly significant are the challenges related to the intensity of threats of the progressive dispersion of housing construction along its communication routes (urban sprawl) and the increasing socio-environmental fragmentation of urban areas [1
]. These threats often result from a lack of knowledge and in-depth analysis at the local level, starting from a single building, through housing estates, and ending in the areas of basic territorial units; i.e., municipalities. Therefore, this article analyzes the improvement of energy efficiency in urban areas, starting from individual households in buildings (including multi-family buildings) located in quarters characterized by similarity of structure and intensity of development.
Urban areas, which gather more than half of the world’s population [4
], have a steadily increasing share in global energy consumption, and all indications are that this trend will not change. At the same time, cities are centers of innovation, engines of development and economic growth, and provide the necessary services to their residents. Energy consumption in urban areas results directly from their function, the way buildings are used, and the increasing time we spend in them. Also, It results from the growing demand for services (including construction), and the need to ensure and maintain thermal comfort in buildings.
To reduce energy consumption in cities (reduce environmental pollution) at a supranational level, a new development path has been proposed for cities based on their adaptation to climate change: the report, Urban Adaptation to Climate Change in Europe in 2016. Transforming Cities in a Changing Climate [5
] is an overview of the actions that can be taken to adapt cities in Europe with the future challenges faced by cities due to the effects of climate change. The proposals relate to changes in spatial planning at the local level, and in the buildings, designs to make cities more economical, less energy-consuming, safe, and more attractive to their residents. The growing popularity of design methods that create buildings with low energy consumption (low energy, passive, zero, and plus energy buildings) [7
], as well as new technologies using renewable energy (not increasing greenhouse gas emissions), such as photovoltaic panels, solar collectors, wind turbines, and heat pumps significantly improve energy efficiency. The work of a research team from Kuwait [10
] showed the possibility of transforming a public utility building into a zero energy building by introducing as a source of energy, photovoltaic systems mounted on a roof in three energy scenarios (energy savings of over 1400 MWh per year, while reducing CO2
emissions by over 700 tons per year). Energy scenarios have also been used in a study of residential buildings. By indicating the possibility of using solar energy to transform residential homes into zero energy, profitability in terms of emissions can be achieved in less than two years [11
]. Baljit et al., when analyzing the efficiency of photovoltaic syfigurestems for roofs and walls of buildings also indicated the need to integrate the technology of erecting buildings with these systems. At the same time, they postulate that economic aspects and climate conditions should be considered as a priority when designing construction objects [12
The wind energy potential is currently used mainly in coastal and submontane areas as well as in open areas with favorable conditions [13
]. It is worth emphasizing, however, that technologies are being developed to obtain wind energy in built-up areas. Rezaeiha et al. indicated in research the possibility of using wind turbines with vertical axes in the urban environment, adapted to changing wind directions (common in built-up environments) [14
]. Systems for properly designed heat pumps are another way to generate energy in urban areas. They allow heat transfer to the building from the surrounding air (also moist) and energy gain during the day and at night [15
]. Combining early, at the design stage, conventional energy sources and energy obtained from renewable sources immunizes systems against climate change. Bagheri et al. for that purpose proposed the creation of urban hybrid renewable energy systems that through optimal planning, will allow the use of energy on a neighborhood scale, taking into account the real-time of the electric load of the city [16
]. An interesting solution proposed in Polish work [17
] is the creation of energy cooperatives based on local communities that produce energy using renewable energy sources and use it for their own needs. Such local policy increases social and environmental awareness and can improve the quality of residents’ lives.
Energy efficiency is constantly increasing in newly designed buildings and is improving in existing ones, where, along with changes in the living standard, the following are created: thermomodernization, changes in the heating method and preparation of hot water, and replacement of equipment and lighting. Programs for the above improvements are most often associated with benefits from support (also financial) programs. There are many possible changes and improvements, and each brings different benefits, so what is the possibility of choosing the optimal variant? It should also be remembered that the programs have different recipients—building owners, users using RES (renewable energy source), electricity producers, users of some technology or obtaining a specific consumption rate, prosumers, organizations related to environmental protection, etc. Also, not all changes can be made in all locations (some depend on climate, wind strength, thermal water temperature, distance of the power network and others that can be effectively identified using geoinformation tools). There are also significant differences between types of buildings and energy consumption and production profiles and the months in which they reach their maximum values. The greatest impetus for energy efficiency measures is undoubtedly economics. The question, therefore, remains whether policymakers have sufficient knowledge and information about the economic benefits of using energy efficiency improvements [18
Energy demand monitoring in cities is the task of municipalities, which while implementing the spatial policy (at the lowest level) of the country, should strive to limit the use of energy and greenhouse gas emissions [19
]. The local government decision-makers need effective tools to achieve this goal, which will support making decisions regarding both spatial planning and low-energy building design, as well as introduce renewable energy sources into urban areas. The article aims to develop an innovative system supporting the decision-making process in local government institutions, which uses multi-criteria analysis and GIS (geographic information system) (DGIS – decision support system for GIS). Multi-criteria analysis and mathematical methods of its implementation in practical issues related to construction and improvement of energy efficiency are currently a very dynamically developing field of knowledge. To assess the energy efficiency of low and zero energy buildings, Hu, in the article [20
], proposed the use of life cycle and multi-criteria analysis. In this way, he identified additional benefits related to a building’s energy efficiency, such as improving human health and protecting the environment. Using the method he developed to assess the relationship between building and energy consumption, environmental impact (smog, global warming, ozone reduction), water (acidification, eutrophication), and human health, he found alternative construction and material solutions with low environmental impact have a more beneficial effect on human health but do not always correlate with energy savings over the building’s life cycle. Launay et al. proposed the use of multi-criteria analysis to optimize interseason solar energy storage to meet the energy needs of residential buildings. The authors analyzed storage systems in terms of meeting the demand for heating and hot water [21
]. Kozik et al. present the method of selecting the most advantageous material solutions supported by the multi-criteria analysis method. In their work, they described a method for selecting the best thermal insulation and thermo-modernization of buildings for a potential investor [22
]. They also wrote about the possibility of using multi-criteria analysis for the energy performance of a building or group of buildings in an article by Ziembicki et al. In addition to energy performance, the authors recommend an energy source concerning CO2
emissions and predetermined construction investment costs [23
]. They conducted their own research based on data on the energy efficiency of various types of buildings located in Polish cities. Ouria [24
] presents research on the use of solar energy in cities and buildings, taking into account many geographical and climatic factors, aimed at estimating the potential. The author analyzed the decisive factors in the assessment of solar energy: geographical parameters, climatic factors, types of radiation, analysis of building geometry, and building orientation. Research results indicated the possibility of increasing the solar energy potential in the city with to the use of appropriate orientation and geometry of individual buildings.
Supplementing multi-criteria analysis by GIS tools allows for spatial analyzes, enables quick identification of changes and determining the impact extent of decisions related to space. Multi-criteria analysis techniques based on GIS are used, among other things, to determine the optimal building location, endangered or protected area locations, or areas designated for various investments.
The article [25
] is an example of a combination of decision methods and the GIS system. It presents the method of choosing the location of the investment (municipal waste incineration plant) in terms of the principles of sustainable development. Feyzi et al. analyzed environmental, economic, and socio-cultural criteria and applied, using a geographical information system, the final weights to each of the adopted criteria. The results obtained indicate the possibility of using the proposed solution by decision-makers who want to make decisions by the principles of sustainable development. Similar results were obtained in their research by Arabameri et al. They used multi-criteria decision analysis based on GIS for developing the methodology used by decision-makers and managers to plan preventive measures and reduce damage caused by erosion [26
]. An interesting combination of the presented approach was proposed by the Erbaş et al. hybrid method supporting the decision making process regarding the location and construction of vehicle charging stations [27
]. The methodology of making decisions regarding the determination of optimal locations for wind farms was also presented in [28
], in which three location scenarios were analyzed—each contained a different set of restrictions. The construction of scenarios supporting GIS with multi-criteria analysis has allowed the creation of decision models that can be easily implemented in other areas and updated if there is a change in the provisions related to spatial planning and location of such investments. Optimal development of space was also analyzed by Özceylan el al. Taking into account 13 geographical criteria in their research, they proposed the best location of a freight village among 20 alternative solutions [29
]. The problem of urban development and the vulnerability of urban structures to threats is more widely presented by Ghajari et al. [thirty]. The authors proposed to examine the physical susceptibility of buildings to external factors (14 vulnerability criteria were defined, and a standard environment for each of them was generated in the GIS environment) and pointed to the need to reduce the risk of threats to buildings. It seems that it is advisable to help with choosing the variant, scenario, and selection criteria for individual decisions dependent on local authorities because they should reduce the vulnerability of urban areas to physical hazards and mandate the obligation to conduct sustainable spatial policy and urban development [30
The innovation of the proposed system is to provide decision-makers with the option of using multi-criteria analysis supported by GIS to improve the energy efficiency of buildings in urban areas. The use of GIS methods allows the visualization and analysis of many alternative development scenarios and optimal selections, which positively affects the decision-making process. Although, as mentioned above, there are already studies that use multi-criteria analysis methods based on GIS data, there is still a gap in the use of the proposed methods to determine the energy efficiency potential of urban areas taking into account technological, economic, urban, and social criteria. The proposed decision support system DGIS, was tested in select quarters of Zielona Góra, a medium-sized city, located in Poland (Europe).
The energy consumption visualization of urban buildings, in the private and public sectors, can be a powerful tool to increase behavior related to economic optimization but also environmental protection. Visualizing trends, information, and the dynamics of changes can enrich recipients with new knowledge to avoid improper workload and resources; e.g., in the selection of heating systems, investing in energy efficiency measures and renewable energy sources, and in new development projects [18
]. The article presents a decision support system using multi-criteria analysis and GIS, which allows mapping the results of analyzes in the city space. The article proposes innovative control of the decision-making process (depending on the level of decision-makers and appropriate transmission of media to them—the GIS tool) in a way that allows achieving the highest possible energy savings. GIS technology support guarantees quick visualization of results in a real environment, allowing for analysis of variants; i.e., a practical guide for decision-makers.
The structure of the article is as follows: Section 2
describes the materials and methods used. In that section, in addition to the assessment of the decision-making and how to make decisions about ways to improve energy efficiency in urban areas, it presents the possibility of implementing the DGIS. Part 3 presents the results and discussion, which are the result of the case study analysis of buildings in the city of Zielona Góra. The conclusions are contained in Section 4