Renovation Strategies for Green Spaces in Aging Residential Communities in Cold Regions to Enhance Carbon Sequestration and Wellness

Abstract

This study explores renovation strategies for green spaces in aging residential communities in cold regions, with a particular focus on enhancing carbon sequestration capacity and residents’ well-being. Under the framework of the “dual carbon” goals, a combination of literature analysis and resident surveys reveals that (1) the existing layouts of green spaceand plant selections have not fully considered their carbon sequestration potential, leaving significant room for optimization; (2) low outdoor temperatures, the lack of heating facilities, and monotonous winter landscapes contribute to reduced green space utilization, limiting outdoor activities and diminishing the health benefits of green spaces; and (3) the integration of glass sunrooms with renewable energy systems, such as photovoltaic power generation, can effectively improve winter green space utilization, regulate micro climates, and enhance vegetation-based carbon sequestration while also providing residents with comfortable spaces for social interaction and wellness activities. The findings indicate that scientifically optimizing green space layouts, selecting plant species with high carbon sequestration potential, and incorporating climate-adaptive architectural designs can significantly enhance the ecological value of green spaces and residents’ quality of life. It is recommended that future community renewal initiatives integrate green technologies, policy support, and interdisciplinary collaboration to promote low-carbon and livable urban development.

1. Introduction

In the context of global climate change, China has become the world’s largest emitter of greenhouse gases, assuming significant responsibility for carbon reduction efforts [1]. The country has pledged to peak carbon dioxide emissions before 2030 and achieve carbon neutrality by 2060. As major contributors to carbon emissions, cities play a crucial role in realizing these “dual carbon” goals. Although urban areas occupy only 2% of the Earth’s surface, they accommodate 50% of the global population, consume 85% of the world’s resources and energy, and generate 85% of global carbon emissions [2]. Against this backdrop, urban renewal has emerged as a key strategy for reducing carbon emissions and promoting sustainable urban development. Among these efforts, the low-carbon renovation of old residential areas is particularly significant due to its long-term environmental impact [3]. By 2022, China’s urbanization rate had reached 65.22%, marking the later stages of rapid urbanization [4]. Urban development is now shifting from expansion and new construction to optimizing existing urban infrastructure. In 2020, the General Office of the State Council issued the “Guiding Opinions on the Comprehensive Advancement of Renovation Work for Old Urban Residential Communities”, underscoring that renovating old residential areas is both a livelihood project and a developmental priority. The initiative aims to improve living conditions, especially in communities with outdated facilities, functional deficiencies, poor environments, or urgent renovation needs. The Chinese government currently classifies renovation projects into three categories: basic, improvement, and enhancement. Basic renovations focus on upgrading public and essential infrastructure to ensure residents’ safety and basic living needs. Improvement projects include environmental upgrades, supporting infrastructure enhancements, energy efficiency improvements, and the installation of elevators, improving residents’ convenience and quality of life. Enhancement projects focus on expanding public service facilities, such as elderly care, childcare, and healthcare services, to further improve residents’ well-being. The renovation of old residential areas is closely linked to achieving the dual carbon goals in the building sector. Currently, carbon emissions from urban residential buildings in China total 891 million tons, accounting for 40% of total building-related emissions [5]. Therefore, advancing the low-carbon renovation of these areas is crucial for sustainable urban development. Carbon reduction in old residential communities primarily involves upgrading building fabrics and modernizing energy consumption systems, including heating, cooling, and lighting. In terms of building fabrics, all renovated communities now comply with the latest energy-efficient design standards, significantly reducing emissions. Regarding energy consumption systems, carbon emissions are lowered by adopting cleaner heating sources (e.g., utilizing industrial waste heat) and installing energy-efficient devices such as LED lighting. Consequently, research on reducing energy consumption and carbon emissions in existing residential communities through building fabric upgrades and energy system improvements has reached a high level of maturity.

In addition to building renovations, green space renewal has gained increasing attention for its role in enhancing urban living environments. Green spaces not only improve microclimates but also contribute to climate change mitigation through their carbon sink function [6]. However, current green space renovations in residential communities primarily focus on basic landscaping, such as laying lawns and creating simple green divisions. These approaches often neglect the impact of green space layout and plant community composition on carbon reduction and resident well-being [7,8]. This oversight fails to maximize the ecological potential of green spaces and their climate benefits. First, in terms of green space layout, strategic planning can significantly enhance carbon sequestration capacity. Studies by Zhang et al. [9] and Pulighe et al. [10] indicate that well-designed green spaces not only increase carbon sequestration and mitigate climate change but also reduce the urban heat island effect, thereby lowering overall energy consumption. However, many existing renovation projects fail to integrate carbon reduction objectives into their design, limiting their effectiveness in emission reduction. Second, plant selection in many projects remains arbitrary, failing to prioritize species with high carbon sequestration potential [7]. Ignatieva et al. [11] pointed out that many designs still heavily rely on lawns, which have low carbon sequestration capacity and contribute little to urban carbon reduction. In contrast, plant diversity directly influences climate regulation and public health benefits. Demuzere et al. [12] highlighted that carefully curated plant compositions can enhance carbon sequestration, regulate microclimates, and improve residents’ well-being. Additionally, Mills et al. [13] emphasized that diverse plant species play a crucial role in improving air quality and fostering psychological restoration. Beyond layout and species selection, climatic conditions significantly affect the carbon sequestration potential and usability of green spaces. Byrne and Sipe [14] noted that green spaces in cold regions are often underutilized in winter due to inadequate design considerations. Raihan [15] further observed that plant selection in these regions tends to prioritize cold-resistant species, which often lack esthetic appeal during winter, reducing their attractiveness to residents. Additionally, heavy snow and ice frequently render green spaces inaccessible, limiting their usage. Cold climates also affect plant activity, as lower temperatures and reduced sunlight significantly diminish plant functions, thereby weakening the ecological benefits of green spaces. Hunter et al. [16] reported that during winter, the effectiveness of green spaces in regulating urban microclimates declines. Han et al. [17] noted that diminished plant activity in winter not only weakens ecological functions but also negatively affects residents’ mental well-being. The lack of greenery and monotonous winter landscapes can lead to a sense of alienation, reducing outdoor activities. When temperatures drop below freezing, residents tend to avoid outdoor spaces, adversely impacting both physical and mental health. Vanos [18] highlighted that reduced outdoor activity particularly affects children and the elderly, potentially exacerbating symptoms of seasonal depression. Lai et al. [19] further demonstrated that decreased outdoor engagement in winter negatively impacts social interactions, diminishing the role of green spaces in fostering community cohesion.

To address these challenges, researchers have proposed various strategies. Chenyang et al. [20] suggested that green space designs in cold regions should incorporate windbreaks and heating facilities to encourage outdoor activities during winter. Dvorak and Volder [21] emphasized the importance of selecting cold-resistant plant species with esthetic value to maintain visual appeal year-round. Jamei et al. [22] demonstrated that spatial design adjustments, such as adding shading elements or optimizing wind flow, can enhance user experiences in green spaces. Furthermore, technologies such as green roofs and vertical greening can improve the ecological and esthetic functions of urban green spaces during winter. Berardi [23] highlighted that integrating sunrooms or heated walkways into green spaces can significantly enhance comfort and increase their utilization during cold seasons.

While green space renovations in aging residential communities meet basic resident needs, significant deficiencies remain, particularly in carbon reduction and ecological performance. The lack of scientific plant community selection and optimized spatial configuration not only constrains the carbon sequestration potential of these green spaces but also diminishes their positive impacts on residents’ health. These issues are particularly pronounced in cold regions, where reduced plant activity during winter, low utilization rates of green spaces, and decreased outdoor activities among residents result from the combined effects of climatic conditions, inadequate facilities, and management challenges. Future renovation efforts should prioritize ecological design principles by (1) optimizing green space layout patterns, (2) scientifically selecting plant communities (including cold-tolerant species with high carbon sequestration capacity), and (3) improving infrastructure such as windbreaks and heating facilities. Such integrated approaches would comprehensively enhance the ecological benefits, winter usability, and social value of these renovated green spaces.

2. Literature Review

A systematic literature search was conducted on the Web of Science, CNKI, and Scopus using the keywords “microclimate”, “plant carbon sink”, and “green space renovation”. An initial retrieval yielded 300 records. After the removing 50 duplicates, 250 records remained for title and abstract screening. A total of 100 papers were excluded due to irrelevance to the research focus. Subsequently, 150 full-text articles were assessed for eligibility, with 80 further excluded based on predefined criteria, such as lack of relevance to cold-region communities or absence of carbon sequestration data. Ultimately, 70 articles were included in the final review. The main content of the selected papers was analyzed, revealing that the existing studies primarily discuss the layout of green spaces, plant species, and the outdoor activity needs of residents in existing residential communities from the following five perspectives: (1) the impact of green space layout and plant species on the microclimate of residential communities; (2) the influence of green space layout and plant species composition on the carbon sink capacity of residential communities; (3) the impact of green space layout and plant species on the rehabilitation and health of residents; (4) the role of green spaces in air quality and human well-being; and (5) the outdoor activity demands of residents during winter.

2.1. The Impact on Microclimate of Residential Communities

The spatial distribution, form, and area of green spaces play a crucial role in regulating the microclimate of residential communities, such as temperature, humidity, and wind speed. Xiao et al. [24] investigated the green space layout in Suzhou Industrial Park and found that a 10% increase in green space coverage can reduce the average ambient temperature by 0.3 °C. When water bodies are integrated with green infrastructure, the cooling effect is further enhanced, with a maximum temperature reduction of 1.2 °C in the surrounding environment. Deng et al. [25] discovered that greenery along roadsides positively impacts wind speed reduction and temperature regulation. Specifically, a 10 m-wide green belt was found to optimize cooling efficiency, reducing road surface temperatures by approximately 2.1 °C. Zhang et al. [26], in their study of subtropical urban parks, showed that large green spaces effectively block sunlight and provide substantial transpiration, thereby regulating air temperature and humidity. Yu et al. [27] found that park areas with tree canopy coverage ≥60% exhibit an average temperature reduction of 1.8–3.3 °C and a humidity increase of 8–14%.

The composition of plant species is also essential for microclimate regulation in residential communities. Hami et al. [28] emphasized that green spaces with a high leaf area index (LAI > 3.5) can increase air humidity by 10–15%, effectively improving thermal comfort. Moreover, Li et al. [29] explored the impact of different plant species configurations on microclimate regulation in small green spaces, revealing that areas with large-canopy tree coverage demonstrate a temperature reduction of up to 3.2 °C and a humidity increase of 12%. Furthermore, the water body + vegetation configuration shows optimal cooling performance, achieving temperature reductions of 4.1 °C. Bao et al. [30] noted that the canopy structure, density, and arrangement of different plant species play distinct roles in temperature regulation. Dense tree species provide significant shading, thereby reducing the impact of solar radiation on the local climate.

In cold regions, winter microclimate regulation is particularly crucial. The selection of cold-tolerant plants and the rational planning of green space layouts can effectively improve the winter microclimate of residential communities. Nie et al. [31] demonstrated that park green spaces with high-density vegetation (>70% coverage) exhibit significant cooling effects, reducing air temperatures by 2.1–3.6 °C, while those with medium-density vegetation (30–50% coverage) show more modest reductions of 0.8–1.2 °C. Li et al. [32] emphasized that even small green spaces, through the rational design of plant species, can have a significant impact on the local microclimate, particularly in cold seasons, where they can effectively reduce wind chill effects.

Overall, the regulation of the microclimate in residential communities through green space layout and plant species is multifaceted. Proper green space planning and plant selection can effectively improve the temperature, humidity, and wind speed of residential communities, especially under cold climate conditions, and scientifically designed green space layouts help mitigate wind chill effects and enhance residents’ comfort.

2.2. The Impact on the Carbon Sequestration Capacity of Residential Communities

In addition to its impact on the microclimate, the layout of green spaces and the composition of plant species also have a significant effect on the carbon sequestration capacity. Ariluoma et al. [33] demonstrated that residential yard vegetation can store 0.9–3.2 kgCO₂/m², highlighting the potential of small-scale urban green spaces in carbon sequestration. This finding aligns with the research by Zhang et al. [34] on urban parks in Beijing, which pointed out that tree density is a key factor in determining carbon sequestration efficiency, with grasslands contributing relatively less.

In cold regions, the structure of plant species is closely related to their carbon storage efficiency. Dong et al. [35] mentioned that optimizing residential green space layouts could enhance carbon sequestration by 15–30%., especially when the combination of trees and shrubs increases the carbon storage in soil. Additionally, Cui et al. [36] found that in Harbin’s cold climate, a 10% increase in green space density boosted carbon sequestration capacity by 8.5% while reducing land surface temperature by 1.2 °C. Ariluoma et al. [37], through their study of green spaces in Helsinki residential areas, found that different plant combinations had a significant impact on carbon sequestration efficiency. The combination of trees and shrubs had a higher carbon storage potential than grasslands alone. Furthermore, research by Jiang et al. [38] and Tuck et al. [39] further supported this view, showing that different plant species communities have significant effects on atmospheric CO₂ concentrations, with trees and shrubs particularly effective in reducing CO₂ levels. Yang et al. [40] studied vegetation restoration on the Loess Plateau and found that increasing plant functional diversity enhanced carbon storage by 21–35%. This conclusion is consistent with the findings of Huo et al. [41], which suggested that urban community landscaping could contribute 5–12% toward carbon neutrality goals, with optimized greening further strengthening carbon sequestration.

In addition to the structure of the green space, plant selection is also crucial for improving carbon sequestration efficiency. Qiu et al. [42] analyzed forest ecological networks and projected that China’s forest carbon sink capacity could increase by 25–50% through ecological optimization. In cold regions, Xu et al. [43] found that subalpine plants, such as coniferous trees and cold-resistant shrubs, exhibit higher carbon sequestration capacity. These plants can effectively photosynthesize and store carbon even under low-temperature conditions. Similarly, Zhang et al. [9] studied urban green spaces in China and found that coniferous trees have notable carbon sequestration capabilities, whereas grasslands and shrubs are relatively less efficient in carbon sequestration.

Overall, the layout of green spaces and the composition of plant species have a significant impact on the carbon sequestration capacity of residential communities in cold regions. Through scientific planning of tree and shrub combinations and optimizing the layout of green spaces, the carbon sequestration efficiency in cold regions can be significantly improved. This conclusion provides theoretical support for optimizing carbon sequestration in green spaces in cold regions and serves as a reference for future urban planning.

2.3. The Impact on Residents’ Rehabilitation and Therapy

The design of green spaces can significantly enhance residents’ physical and mental health. Davern et al. [44] emphasized that well-planned green spaces contribute to well-being, ecological diversity, and stress reduction, particularly when incorporating elements such as trees and water features. In cold regions, the selection of cold-resistant plants and the design of green spaces should accommodate seasonal variations. Rappe [45] found that gardening activities in cold climates improve the subjective well-being of elderly residents, while Erbino et al. [46] reported that green spaces in winter provide essential outdoor environments that help regulate residents’ emotions.

Plant species play a vital role in psychological and physiological rehabilitation by offering visual and tactile stimuli. Hall and Knuth [47] noted that sensory interactions with plants not only improve mood but also promote physical recovery through gardening. Different plant types, including trees, shrubs, grass, and flowers, serve distinct rehabilitative functions. For instance, flowers and shrubs alleviate psychological stress through color and fragrance. Coutts and Hahn [48] proposed that plant diversity in green spaces is directly linked to psychological recovery, particularly in cold regions, where species selection should prioritize resilience while maintaining seasonal visual appeal. Wheeler et al. [49] further highlighted that green spaces alleviate stress and support long-term mental health recovery by providing tranquil natural environments, even under extreme weather conditions.

To maximize the wellness benefits of residential green spaces, their design should incorporate diverse plant species and functional layouts. Semeraro et al. [50] suggested that a combination of trees, shrubs, and flowers enhances sensory experiences and ecological functions, fostering year-round therapeutic benefits. Gardens [51] recommended incorporating plants, water features, and ergonomic outdoor furniture to create environments conducive to psychological and physical recovery. In cold regions, adding warm outdoor resting areas and windbreak structures can encourage wintertime outdoor activities. Souter-Brown [52] further emphasized the importance of designing green spaces that accommodate the needs of various age groups, particularly the elderly and children. Additionally, Chang et al. [53] suggested that increasing plant diversity and incorporating shading structures can improve rehabilitative environments and encourage outdoor engagement.

2.4. The Role of Green Spaces in Air Quality

Beyond their visual and tactile rehabilitation benefits, the layout of green spaces and plant species significantly influence air quality, which in turn affects residents’ health. Numerous studies have demonstrated the ability of plants to remove various air pollutants [54,55,56,57]. Research indicates that each year, 100–115 trillion tons of carbon are converted into biomass through photosynthesis [58], a process that sustains atmospheric oxygen levels and provides the energy essential for life on Earth [59].

Since the Industrial Revolution, atmospheric CO₂ concentrations have risen sharply from 280 ppm to over 380 ppm, with projections suggesting levels could reach 700–1000 ppm by the end of this century [60]. However, Berkeley Lab [61] reported that in recent years, atmospheric CO₂ levels have stabilized as plants have absorbed increasing amounts of carbon. The Conversation [62] estimated that terrestrial plants currently sequester approximately 25% of carbon emissions from human activities. Milcu et al. [63] further highlighted that plants can remove more CO₂ from the atmosphere than previously assumed. In a study of 55 office spaces, Tarran et al. [64] found that rooms with three or more potted plants exhibited a 10% reduction in CO₂ levels in air-conditioned buildings and a 25% reduction in non-air-conditioned buildings. Similarly, Pegas et al. [65] observed that classrooms with plants in Aveiro, Portugal, maintained lower CO₂ concentrations than those without.

Plants also improve air quality by intercepting particulate matter (PM) [66,67]. At the local scale, central areas of urban forest patches exhibit significantly lower PM concentrations than forest edges [68]. McDonald et al. [69] reported that increasing tree cover in the West Midlands of the UK from 3.7% to 16.5% led to the removal of 110 tons of PM₁₀ annually. In Glasgow, expanding tree cover from 3.6% to 8% resulted in a 2% reduction in PM₁₀ concentrations, equivalent to nearly 4 tons per year. Nowak et al. [70] found that trees in Syracuse and Atlanta removed between 4.7 and 64.5 tons of PM_2.5 annually. In Greater London, urban tree canopies eliminate approximately 852–2121 tons of PM₁₀ each year [71], while across the United States, urban trees remove an estimated 214,900 tons annually [72]. In addition to direct PM removal, trees indirectly lower PM concentrations by modifying air temperature and influencing building energy consumption. For example, trees reduce cooling energy use by lowering temperatures and shading buildings, thereby decreasing power plant emissions [73,74,75]. Thus, plants contribute to air purification through both direct filtration and indirect energy conservation.

Beyond particulate matter, plants also reduce chemical air pollutants such as volatile organic compounds (VOCs), ozone, nitrogen oxides (NO_x), and sulfur oxides (SO_x). Tarran et al. [64] demonstrated in laboratory experiments that plants significantly reduce VOC concentrations. Papinchak et al. [76] reported that rooms containing plants such as snake plants, spider plants, and golden pothos exhibited higher ozone removal rates than rooms without vegetation. Rogers et al. [77] found that plants are highly effective at absorbing nitrogen dioxide (NO₂).

Given these benefits, indoor plants are increasingly recognized for their role in enhancing energy efficiency and improving indoor air quality. As noted earlier, plants aid in the removal of indoor air pollutants, including PMs, VOCs, and CO₂. Many studies, particularly those conducted in controlled environments, suggest that plants can effectively purify indoor air. Wolverton et al. [78] demonstrated that plants significantly reduce air pollutants in small, enclosed laboratory settings. Wood et al. [57] found that in sealed rooms, plant-based air filtration reduced benzene and hexane concentrations by 80% and 70%, respectively.

However, field studies suggest that laboratory findings may not always translate to real-world conditions. Dingle et al. [79] conducted a study in an office building in Perth, Australia, and found no significant change in formaldehyde levels when 5 or 10 plants were introduced. Only with 20 plants did formaldehyde concentrations decrease by 11%. Similarly, a field study by the Landscape Contractors Association and Health Building International in Arlington, USA, found no measurable reduction in pollutant concentrations in rooms with plants [80], though the number of plants used was not reported. Wood et al. [81] conducted another field study in Sydney, Australia, and observed that VOC levels in rooms with plants fluctuated, sometimes being higher and sometimes lower than in rooms without plants.

Thus, different studies have reached contradictory conclusions. On the one hand, laboratory experiments indicate that plants can effectively remove air pollutants. On the other hand, field studies suggest that their impact on air quality in real environments is limited. Two key factors may explain these discrepancies. First, most laboratory studies are conducted in small, controlled spaces with a high density of plants, creating an environment conducive to pollutant absorption. To achieve similar effects in real settings, a significantly larger number of plants would be required. If only one or two plants are placed in a large space, their impact on air quality is negligible. Second, in real environments, pollutants are continuously emitted from building materials and human activities. In some cases, pollutant release may exceed the plants’ capacity for absorption. Human activities also introduce dynamic fluctuations in indoor air quality, limiting the time available for plants to effectively remove pollutants. In contrast, laboratory studies often introduce pollutants in a single instance and monitor their decline, leading to results that may not accurately reflect real-world conditions.

Girman et al. [82] noted that field studies often suffer from methodological limitations, as few account for the influence of ventilation systems, indoor pollution sources, and human activity, making it difficult to assess the true effectiveness of plants in removing air pollutants. However, some field studies suggest that plants can improve indoor air quality. Pegas et al. [65] compared classrooms with and without plants in Aveiro, Portugal. In a 52.5 m² classroom where six plants were introduced, CO₂ concentrations decreased from 2004 ppm to 1121 ppm. Additionally, the classroom with plants exhibited VOC concentrations during class hours that were four times higher than those in the plant-free classroom, suggesting an interaction between plant activity and pollutant dynamics. Tarran et al. [64] found that potted plants effectively reduce VOC concentrations in real environments and lower CO₂ levels by approximately 10% in air-conditioned buildings and 25% in naturally ventilated spaces. Meattle [83] conducted a large-scale study in a 4600 m² office building with over 1200 potted plants and observed a reduction in health issues among occupants. Compared to buildings without plants, the incidence of eye irritation, respiratory problems, headaches, lung damage, and asthma decreased by 52%, 34%, 24%, 12%, and 9%, respectively. These findings suggest that plants can contribute to air purification in real environments, but further research is needed to determine the most effective plant species and the optimal quantity required for passive pollutant removal.

However, air pollutant removal by plants—such as CO₂ absorption via photosynthesis and O₂ release—is a complex process influenced by environmental factors including temperature, CO₂ concentration, and light intensity. Different plant species have varying photosynthetic rates, making it challenging to establish precise guidelines on the number of plants needed to effectively reduce CO₂ levels and enhance oxygen production. Additionally, while studies have demonstrated that certain plants can remove VOCs, they often report pollutant reduction as a percentage rather than quantifying the mass of pollutants removed per plant over a given time period [82].

In summary, the design of green spaces and the selection of plant species play a critical role in enhancing the rehabilitative and therapeutic benefits of residential environments. Through scientifically informed planning and rational plant selection, green spaces can improve air quality and provide continuous health benefits throughout the year.

2.5. Outdoor Activity Demands of Residents

In cold regions, extreme climatic conditions—particularly low temperatures and high wind speeds—limit residents’ outdoor activities. Xiong et al. [84] found that areas with abundant sunlight are more popular in winter, as solar exposure effectively raises local temperatures and enhances thermal comfort. Lu et al. [85] reported that wind speed significantly influences residents’ willingness to engage in outdoor activities, with higher wind speeds leading to decreased participation. Yin et al. [86] emphasized that winter outdoor space design in cold regions must account for temperature and wind speed, as both factors directly impact outdoor comfort and activity duration.

Consequently, numerous studies have explored strategies to mitigate wind speed and increase outdoor temperatures in residential communities during winter. Li and Liu [87] highlighted that optimizing wind control measures in outdoor spaces across China’s cold climate regions can significantly improve thermal comfort, thereby encouraging outdoor activities. Weerasuriya et al. [88] studied “cold wind environments” and proposed that design optimizations to reduce wind exposure can enhance residents’ willingness to be outdoors in cold climates. Ge et al. [89] demonstrated that optimizing the layout of buildings and green spaces in China’s cold climate regions improves outdoor thermal comfort, providing more suitable spaces for outdoor activities. Yang et al. [90] further investigated adaptive thermal comfort design, suggesting that in dry, cold regions, urban planning should prioritize increasing sunlight exposure while minimizing wind speed, particularly when selecting and designing outdoor activity areas. Wu and Zhang [91] proposed that optimizing building envelopes and outdoor space layouts can effectively reduce wind speed and increase localized temperatures, thereby extending residents’ outdoor activity time. Hu et al. [92] and Zhang et al. [93] emphasized that installing wind-protected outdoor seating and other facilities can enhance residents’ willingness to spend time outdoors during winter. Additionally, Guo and Bart [94] suggested incorporating sun-exposed areas and outdoor heating facilities into urban design to further improve thermal comfort.

Overall, outdoor space design in cold regions must comprehensively address the impacts of low temperatures and wind speed on residents. By implementing strategies to reduce wind exposure, increase solar radiation, and provide comfortable amenities, outdoor activity participation can be significantly enhanced. Future designs should integrate residents’ behavioral patterns and offer more functional, adaptable outdoor spaces tailored to cold climates.

2.6. Research Gap Identification

Although existing studies have extensively explored the low-carbon renovation of urban residential communities, they have primarily focused on the transformation of building structures and energy consumption systems, such as reducing carbon emissions through energy-efficient building designs and new energy-based heating systems. However, the carbon sequestration capacity of residential community green spaces and their integrated role in health and wellness performance have not received adequate attention. Current green space renovation plans mainly address basic needs and neglect the scientific layout of green spaces and the organization of plant species, which are crucial for enhancing carbon sequestration potential and promoting health benefits for residents.

In particular, in cold regions, issues such as low green space utilization, reduced plant activity, and decreased outdoor activities among residents during winter further diminish the role of green spaces in improving microclimates and promoting health and wellness. Therefore, there is a lack of systematic technical strategies and empirical studies regarding the comprehensive renovation of green spaces in urban residential communities in cold regions, leaving a significant research gap. The key issues are as follows:

(1)

Insufficient green space layout and plant species design: In the renovation of urban residential communities, there is inadequate consideration of green space layout and plant species composition; in particular, there is a lack of focus on how to update green spaces from the perspectives of carbon sequestration potential and health and wellness functions.

(2)

Low green space utilization in cold regions: In cold regions, low winter temperatures and reduced outdoor activities result in a significant decrease in green space utilization. Existing studies have not effectively addressed the outdoor activity needs of residents during winter.

(3)

Lack of systematic technical strategies and empirical studies: There is a lack of integrated renovation strategies and empirical studies aimed at enhancing the carbon sequestration capacity and health and wellness performance of green spaces in existing urban residential communities in cold regions, creating a clear gap in the research.

2.7. Research Hypothesis

According to the literature review, to enable the green spaces and plant species in residential communities located in cold climate zones to fulfill their roles in health and wellness, carbon sequestration, and air purification, several requirements must be met. First, there must be a sufficient number of plants. As indicated in Section 2.4, studies have shown that a few pots or individual plants are insufficient to improve air quality. Second, the plants must be able to survive the cold winter conditions. Third, the plant species composition must be appropriate. The third requirement is relatively easy to achieve once the first two are met. However, to satisfy the first and second requirements, it is necessary to mention sunrooms. Sunrooms, through transparent enclosures that capture sunlight and store heat, provide a suitable growing environment for plants. The origin of sunrooms can be traced back to ancient Rome, where transparent materials, such as mica and glass, were used to construct structures known as “solaria”, designed to capture and store solar energy to aid plant cultivation [95]. During the Renaissance, European aristocrats introduced similar architectural structures into their estates, known as “greenhouses”, to protect rare plants, particularly by maintaining favorable growing conditions during the winter months [95]. By the 19th century, with the advancement of glass manufacturing technology, sunrooms gradually became a fashionable architectural element, used in private residences and public buildings not only to protect plants but also as indoor spaces to enjoy natural light.

In China, the widespread use of sunrooms began in the 1980s. The earliest sunrooms were primarily applied in agricultural production, such as greenhouse farming, to increase the yield of vegetables in cold regions during winter. Through sunrooms covered with transparent glass or plastic materials, solar energy enters the greenhouse during the day, providing sufficient light and heat for the plants. Sunrooms are able to provide appropriate temperatures for plants during the winter, extending the growth cycle of crops such as vegetables. According to Ma et al. [96], sunrooms not only improve crop yields but also significantly save energy. Evans et al. [97] pointed out that the use of multi-layer glass in sunrooms significantly improved the thermal insulation performance of greenhouses, while reducing energy consumption.

Since the 1990s, with economic development and advances in building material technology, sunrooms began to be applied in residential buildings in cold regions, although they were primarily concentrated in rural residences [98]. During this period, the design of sunrooms was relatively simple, with the sunroom placed on the south side of the residence to enhance the building’s insulation performance [99]. Sunrooms in rural residences not only improved the indoor thermal environment during winter but also provided extra space for families, which could be used for drying, storage, or simple indoor activities. In addition to agricultural use, sunrooms were also widely applied in flower cultivation. By utilizing solar heating, sunrooms provided an optimal growing environment for flowers, extending their growth period [100].

In modern urban residential communities, sunrooms are rarely found. However, some communities use glass constructions to enclose the escape openings of underground parking garages, effectively creating sunrooms (Left in Figure 1). These sunrooms are typically intended to shield the underground parking garage entrances from wind and rain and do not serve as spaces for residents’ activities. Nonetheless, during the cold winter months, people still have a need for outdoor social activities. As a result, residents, especially the elderly, can be seen gathering in these sunrooms, dressed in heavy clothing, engaging in recreational activities (Right in Figure 1). This observation confirms the conclusions of the previous literature review: in winter, residential communities in cold regions are unable to provide comfortable outdoor environments for residents’ outdoor activities, and the outdoor activity needs of people during the winter are not being met.

The reason people gather in the pedestrian evacuation exits of garages, covered by glass canopies, to interact is mainly due to the sunroom’s ability to absorb solar heat during the day, ensuring that the interior of the sunroom maintains a relatively comfortable temperature in cold weather [101,102]. However, relying solely on the sunroom to provide daytime temperature regulation is insufficient to address the low temperatures during the night and on rainy days. Therefore, photovoltaic heating technology has become an important supplementary measure. Fugate [103] highlighted the application of photovoltaic systems in sunrooms, which collect solar energy during the day and release heat at night, providing a constant temperature for plant species. Steen et al. [104] emphasized the energy storage function of photovoltaic systems, noting that the electricity stored in photovoltaic panels during the day can be used to power heating lights in the sunroom at night, providing the necessary thermal support for plants. Schiller [105] discussed the establishment of zero-energy greenhouses using solar energy to improve the efficiency of greenhouse flower cultivation. Peng et al. [106] propose an integrated low-energy ventilation system, which significantly improves the indoor environment of elementary school classrooms in cold climate regions by combining earth–air heat exchangers, fans, and plant sunrooms. The results show that the system maintains classroom temperatures between 15 °C and 27 °C and relative humidity between 30% and 80% throughout the year, with energy consumption only 12% of that of traditional heating and cooling systems. The integrated ventilation system proposed in this study provides significant support for the solution presented in this research.

However, the existing research on sunrooms has mainly focused on agricultural production, flower cultivation, and rural housing. There is limited research on their application in urban residential communities, and no case studies have been found that use sunrooms as activity spaces for residents in urban residential communities.

Based on the above discussion, this study proposes the following hypothesis (Figure 2 and Figure 3): in residential communities, the construction of sunrooms, coupled with a new energy photovoltaic system, is proposed to address the issues of unreasonable green space layout and plant species configuration, as well as low green space activity, in cold regions during the winter. This approach aims to meet the demand for outdoor activity spaces during winter and fulfill the requirements for the health and wellness benefits of plants.

The solution shown in Figure 2 involves constructing a sunroom on the ground level of the residential community, within which plants are placed. During the day, the sunroom absorbs solar heat to warm the air inside, providing an appropriate temperature for people and ensuring optimal conditions for plant growth. At night, due to the low outdoor temperatures in winter, it is necessary to use a photovoltaic power generation system with an energy storage device to heat the sunroom, maintaining a temperature suitable for plant species to thrive. However, the issue with Solution 1 is that the ground-level sunroom can interfere with the views and light access of residents in lower floors.

The solution shown in Figure 3 proposes establishing the sunroom in the underground space of the residential community. The top of the sunroom is equipped with a photovoltaic-integrated transparent system. The operating principle is consistent with that of the solution shown in Figure 2. However, the issue with Hypothesis 2 is that it would occupy space in the underground parking garage. Both the solution in Figure 2 and the solution in Figure 3 need to consider the following series of issues during implementation:

2.7.1. Space Demand for Sun-Rooms from Residents

The population size within a residential community directly influences the required spatial scale of the sunroom. Areas with a larger population demand a larger sunroom to accommodate more residents for leisure, social interaction, and activities. Additionally, the sunroom should not merely serve as a space that provides sunlight but should also integrate leisure, social, and ecological functions. During the design process, consideration should be given to whether the sunroom should be divided into multiple areas, offering seating, activity zones, and plant areas. The distribution and size of these functional zones should be adjusted according to the anticipated number of users and the types of activities. Thus, to ensure that the sunroom is comfortable for use and not too cramped, factors such as the residential community population, expected number of users, and activity types should be taken into account.

2.7.2. Plant Species Ratio Suitable for the Sunroom, Meeting Residents’ Health and Wellness Needs

The plant species ratio should fully consider the dual focus on carbon sequestration and health, while also adapting to the characteristics of low temperatures and insufficient light. A variety of plants should be selected to meet both ecological and health needs. For carbon sequestration, cold-resistant, low-light-tolerant plants with strong photosynthetic capacity should be chosen, such as large-leaf plants (e.g., rubber tree, monstera) and climbing plants (e.g., golden pothos) [36,37,40,41,42,43]. These plants are well-suited for indoor environments in cold climates. Additionally, a multi-layered combination of tall cold-resistant plants (such as dracaena) and low-growing herbaceous plants not only improves carbon sequestration efficiency but also enhances the visual layering of the space. From a health perspective, it is important to consider the positive psychological effects of plants. Cold-resistant, esthetically pleasing plants with soft colors, such as lavender and gerbera daisies, can help alleviate stress and reduce seasonal depression in cold climates [47,49,53]. Furthermore, plants with good air-purifying functions, such as devil’s ivy, spider plant, and snake plant, can absorb harmful substances like formaldehyde, improving indoor air quality [54,55,56,57]. To address indoor air dryness during the winter, hydroponic plants or ferns (e.g., maidenhair fern) can be added to effectively increase humidity and improve the comfort of the living environment. Consideration should also be given to both daytime and nighttime conditions. The sunroom will be used during both day and night. Particularly at night, plants that release oxygen (such as snake plant and aloe vera) should be included to mitigate the issue of oxygen consumption and carbon dioxide emission by certain plants, maintaining the oxygen concentration in the air.

2.7.3. Indoor Environment of the Sunroom Suitable for Plant Growth and Resident Activities

When designing the sunroom, temperature, humidity, air quality, and light optimization technologies should be comprehensively considered. Regarding temperature, the use of high-efficiency thermal insulation materials and sealed structures can reduce heat loss, while the installation of an intelligent heating system (e.g., underfloor heating or air-source heat pumps) can maintain the room temperature within a suitable range. Heat storage devices or thermal storage walls can be used to adjust diurnal temperature variations. For humidity control, automatic humidifiers, hydroponic systems, or indoor water features can maintain humidity within an optimal range, with ventilation designs preventing excessive humidity and mold growth. Regarding air quality, a fresh air system and air purifiers should be installed, complemented by air-purifying plants like spider plant and devil’s ivy, which filter pollutants and supplement oxygen. Light optimization should be achieved through high-transparency glass and intelligent shading systems to fully utilize natural light, with full-spectrum LED plant lights used when sunlight is insufficient, ensuring both plant and resident lighting needs are met.

2.7.4. Use of New Energy Devices

In the regulation of the sunroom’s indoor environment, the integration of new energy technologies such as photovoltaics can effectively address the energy needs for heating, ventilation, humidity, and air quality management, while enhancing the system’s sustainability. Photovoltaic power generation can provide clean electrical power to support heating systems (e.g., underfloor heating, heat pumps) and ventilation, humidification, and air purification devices. The energy can be stored using energy storage systems to meet nighttime operation needs. The adoption of building-integrated photovoltaics designs can simultaneously achieve lighting and power generation, with an intelligent energy management system dynamically allocating energy to optimize the operation of environmental control devices. Additionally, photovoltaic-thermal integrated systems can supply thermal energy, reducing reliance on traditional energy sources and lowering carbon emissions, contributing to the green development of the sunroom.

2.7.5. Deconstruction or Disassembly of the Sunroom

During the summer, spring, and some parts of the fall, there may be no need for the sunroom to provide a comfortable environment for activities. Therefore, the sunroom design should consider modularity for convenient disassembly, such as using lightweight, high-strength materials (e.g., aluminum alloy frames and removable glass panels) that facilitate storage and reuse. If disassembly is not feasible, consideration should be given to incorporating a movable design, such as sliding doors, folding windows, or retractable roofs, allowing the sunroom to be completely opened during seasons when it is not needed. This creates a seamless connection with the outdoor space, enhancing ventilation and preventing indoor temperatures from rising due to enclosure. Such a design not only reduces the hassle of disassembly but also preserves the multifunctionality of the sunroom. Furthermore, consideration should be given to integrating smart devices, shading systems (e.g., adjustable shading curtains, intelligent photovoltaic films), and efficient natural ventilation designs (e.g., skylights, convection vents) to address potential overheating issues, ensuring the normal growth of plants and the comfort of residents’ activities.

3. Research Methodology

This study employs a combination of qualitative and quantitative methods, including field research of case studies, ecological model construction, and experimental comparisons, to comprehensively explore the ecological, health, and economic benefits of green space system renewal strategies in existing residential communities in cold regions. Figure 4 presents the technical roadmap of this project.

3.1. Case Study Survey

This study focuses on the utilization of green spaces in cold climate regions. Accordingly, a residential community located in Tai’an City, within China’s cold climate zone, was selected as the research subject for investigation. Figure 5 shows the site map of the community (left) and the simplified model diagram (right). The community consists of 7 buildings, ranging from 13 to 18 stories, with a plot ratio of 1.5, and a total of 293 households. Block 1 and Blocks 3–7 are 13 stories each, while Block 2 is 18 stories. Figure 6 illustrates the layout of the community. As shown, there is a large central green space between Building 1 and Building 2, covering an area of over 4000 m². Additionally, there is another concentrated green space of 2700 m² to the south of Buildings 6 and 7. Apart from these, there is a hard-paved activity plaza located at the center of the community, between Buildings 2 and 3.

The residential community has been in operation for over 15 years. During the winter, the plants generally wither, exhibiting low vitality, and there are no large-scale plant species. Outdoor activities are also scarce (Figure 7), and there is an urgent need to improve the winter activity and health functions of the green spaces. To understand the residents’ needs for outdoor activity areas and greenery functions during the winter, a survey was conducted.

Based on a preliminary literature review and expert consultation, the survey questionnaire was designed in three sections. The first section focuses on residents’ basic personal information and their demands for outdoor activity areas and plant species in winter. The second and the third sections investigate residents’ awareness and evaluation of green space renewal, specifically understanding their opinions on how the outdoor environment, especially green spaces, should be designed or renovated in the residential community. The three sections of the questionnaire were designed in a progressive manner, guiding respondents to articulate their genuine perspectives on residential green spaces, thereby providing reliable data for this study. The survey questionnaire is shown in

Table 1. Survey on green space renewal in residential communities.

Section 1: Basic information
Q1	What is your gender?
	Male☐			Female☐
Q2	What is your age range?
	18–30	30–39		40–49		50–59	≥60
Q3	What is your occupation?
	Office workers☐	Freelance☐		Retirees☐		Students☐	Others☐
Q4	How long have you lived in this community?
	1 year<	1–3 years		3–5 years		≥5 years
Section 2: Utilization of green space in residential communities
Q5	How often do you usually go out to green spaces?
	Daily	1–2 times a week		3–4 times a week		Very few	Never
Q6	What activities do you mainly carry out in green spaces? (multiple choice)
	Walking□	Rest□		Exercise□		Social□	Others□
Q7	Do you spend less time in green spaces during the winter?
	No□			Yes□
Q8	If yes, What makes you reduce your activities in green spaces in winter? (multiple choices)
	Temperature is too low□	Green space lacks heating facilities□		Green space landscape is monotonous□		Green land covered with snow □	Others□
Section 3: Understanding and requirements for green space renewal
Q9	How satisfied are you with the green space in your current residential area?
	Very satisfied□	Satisfied□		General□		Dissatisfied□
Q10	Do you think green space renewal is helpful to your health?
	Yes□			No□
Q11	Do you feel the positive impact of green space renewal on your mental health?
	Yes□			No□
Q12	What is the most important area to improve in winter outdoor activity venues? (Multiple choice)
	Providing more shelter□	Providing heated seats or warming spots□	Strengthening green space maintenance□	Providing more light areas□	Improving landscaping for winter greenery□	Adding heated walkways or warm rest areas□	Others
Q13	What are your requirements for the landscape of winter green space?
	More greenery□	Richer colors□		Better views and lighting□		Scene design with seasonal plants□	Others□
Q14	Do you think it is feasible to build an outdoor sunroom as a venue for winter activities and exchanges?
	Feasible☐			Not feasible☐
Q15	What facilities in the sun room do you think will increase your enthusiasm for outdoor activities in winter? (multiple choices)
	Winter fitness facilities□	Rest area□		Warmer walks□	Community gardening□	Organizing outdoor group activities□	Others□
Q16	What do you think is the appropriate size for a sunroom?
	2 m2 per person☐	4 m2 per person☐		6 m2 per person☐		8 m2 per person☐	≥10 m2 per person☐

. A random sampling method was used in this study to select the samples, ensuring the representativeness of the sample and minimizing selection bias. The survey targets included residents of different genders, ages, and occupations within the community, thus reflecting the opinions and needs of the general population. Based on a preliminary survey, it was determined that the total number of permanent residents in the case study community is approximately 419. With a 95% confidence level and a 5% margin of error, the required sample size for this study was calculated to be 201 participants. The survey was conducted over a one-month period in December 2024. A total of 212 questionnaires were distributed, and 209 valid responses were collected. For the collected data, this study primarily employs descriptive statistical methods to present the distribution of responses for each question and identify residents’ key expectations for green spaces in winter.

3.2. Experimental Study and Simulation

Based on carbon sequestration models (such as forest carbon sequestration models and urban green space carbon sequestration models), combined with remote sensing imagery data and Geographic Information System (GIS) technology, a carbon sequestration benefit evaluation model for the residential community’s green space is established. The model simulates and evaluates the impact of different plant species community structures on carbon sequestration efficiency. The specific calculation formulas are shown in

Table 2. Carbon sequestration calculation model formulas.

	Formula	Description
Plant carbon absorption [107]	${\mathrm{C}}_{\mathrm{a}\mathrm{n}\mathrm{n}\mathrm{u}\mathrm{a}\mathrm{l}}=\mathrm{B}\times \mathrm{R}\mathrm{G}\mathrm{R}\times {\mathrm{f}}_{\mathrm{c}\mathrm{a}\mathrm{r}\mathrm{b}\mathrm{o}\mathrm{n}}$	Cannual represents the annual average carbon sequestration (tons/year). B represents the biomass of the vegetation (tons), which can be calculated based on the plant’s volume, density, and growth rate. RGR is the Annual Relative Growth Rate of the plant, typically a species-specific value. fcarbon is the carbon content ratio in the plant (usually between 0.45 and 0.50).
Soil carbon storage in green spaces [108]	${\mathrm{C}}_{\mathrm{s}\mathrm{o}\mathrm{i}\mathrm{l}}=\mathrm{S}\mathrm{O}\mathrm{C}\times \mathrm{A}\times \mathrm{D}\times \mathsf{\rho }$	Csoil represents the soil carbon stock (tons). SOC is the Soil Organic Carbon Concentration (units: tons of carbon per ton of soil). A is the area of the green space (m2). D is the soil carbon storage depth (m). $\mathsf{\rho }$ is the soil density (tons per m3).
The total carbon sink benefit formula	${\mathrm{C}}_{\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}}={\mathrm{C}}_{\mathrm{a}\mathrm{n}\mathrm{n}\mathrm{u}\mathrm{a}\mathrm{l}}+{\mathrm{C}}_{\mathrm{s}\mathrm{o}\mathrm{i}\mathrm{l}}$
Carbon sink efficiency [109]	${\mathrm{E}}_{\mathrm{c}\mathrm{a}\mathrm{r}\mathrm{b}\mathrm{o}\mathrm{n}}={\displaystyle \frac{{\mathrm{c}}_{\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}}}{\mathrm{A}\times \mathrm{T}}}$	Ecarbon represents carbon sink efficiency (t/m2·yr). A represents the total area of green space (m2). T represents time (yr).
The integration of remote sensing and GIS data [110]	${\mathrm{C}}_{\mathrm{v}\mathrm{e}\mathrm{g}\mathrm{e}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}={\mathrm{V}}_{\mathrm{C}}\times \mathrm{B}\times {\mathrm{f}}_{\mathrm{c}\mathrm{a}\mathrm{r}\mathrm{b}\mathrm{o}\mathrm{n}}$	Vc is the canopy cover rate, expressed as a percentage (%)

.

3.3. Design and Application of Sunroom

In the case study’s residential community, small-scale sunrooms were established, and different types of plants were selected for planting experiments. The survival rates, carbon storage capabilities, and esthetic effects of various plant species were compared during the cold season. This study aims to explore the potential application of sunrooms in cold climates, along with calculating and evaluating their thermal energy effects, quantifying their contributions to carbon sequestration and wellness performance. Figure 8 presents the proposed design schemes for potential sunrooms in certain areas of the case study’s residential community.

4. Results and Discussion

4.1. Survey Results

Figure 9 and Figure 10 present the survey results for questions 1–4 of the questionnaire. It can be observed that the gender distribution among the community residents is relatively balanced, with 48% male and 52% female. Regarding age, 35% of the residents are between 18 and 30 years old, 27% are between 30 and 39 years, 17% are between 40 and 49 years, and 11% are between 50 and 59 years, while 10% are 60 years or older. These data indicate that the community is primarily composed of a middle-aged and young adult population. In terms of occupation, 55% of the residents are office workers, 12% are freelancers, 23% are retirees, 5% are students, and 5% have other professions, reflecting a higher proportion of working individuals and retirees in the community. As for the duration of residence, 36% of the residents have lived in the community for more than 5 years, 21% have lived there for 3–5 years, 26% for 1–3 years, and 17% for less than 1 year. This shows that most residents have settled in the community for an extended period, indicating a strong dependence on and demand for the community environment.

Figure 11 and Figure 12 present the survey results for questions 5–8 of the questionnaire. In terms of green space usage, the survey shows that most residents regularly use the community green spaces. Overall, 43% percent of residents visit the green space 1–2 times per week, 20% visit 3–4 times per week, and 13% visit daily. However, 13% of residents rarely visit the green space, and 10% never visit it. The primary activities include walking (70%) and resting (57%), while exercise (33%) and social activities (23%) are also involved.

Despite this, the frequency of green space activities significantly decreases in winter. Seventy-three percent of residents reported reduced green space activities during winter, with low temperatures (65%) being the main reason. Other contributing factors include the lack of heating facilities in the green spaces (33%), monotonous landscape (13%), and snow cover (20%). These factors result in a significant decline in the willingness to use green spaces during winter, highlighting the impact of winter environmental conditions on residents’ use of green spaces.

Figure 13, Figure 14, Figure 15 and Figure 16 present the survey results for questions 9–16 of the questionnaire. It is evident that residents have a relatively low level of satisfaction with the current green space, with only 10% of residents expressing strong satisfaction, 27% expressing satisfaction, 40% considering it average, and 23% expressing dissatisfaction. Nevertheless, 67% of residents believe that the renovation of green spaces is beneficial for health, and 85% feel that such renovations have a positive impact on mental health.

In terms of improving outdoor activity spaces during the winter, residents have provided several suggestions. Among them, 60% of residents hope for better maintenance of green spaces, 47% support the addition of shading facilities, 40% wish for heated seats or warm resting areas, 37% suggest improving the winter plant landscape, and 33% would like to see more sunlit areas. Furthermore, regarding the winter green space landscape, 50% of residents want more plant species, 40% seek richer colors, 30% desire improvements in visibility and lighting, and 37% hope for the inclusion of seasonal plants in the landscape design.

As for the construction of sunrooms as winter activity spaces, 87% of residents find this feasible, with the primary desire for the sunroom to offer resting areas (53%), winter fitness facilities (47%), and community gardening activities (40%). Regarding the size of the sunroom, 40% of residents believe 4 square meters per person is ideal, while 33% consider 6 square meters per person suitable. Overall, the residents’ demand for green space renovation and winter activity spaces is focused on providing a more comfortable and warm environment, with particular attention paid to the suitability of winter activities and the maintenance of green spaces.

4.2. Discussion

In this study, the analysis of the literature review and the results from the resident survey provide important evidence for further exploring how to enhance the carbon sequestration capacity and wellness benefits of green spaces in aging residential communities in cold regions through green space renovation. The literature review and survey results not only mutually corroborate each other in theory but also offer practical guidance for the design and renovation of relevant green spaces.

From the literature review, it is evident that the utilization of green spaces in cold regions is generally low, especially in winter. Due to lower temperatures and reduced sunlight, plant growth activity significantly declines, leading to a sharp reduction in the carbon sequestration capacity and ecological functions of green spaces [16,17,18]. These phenomena are highly consistent with the survey results. In this study, residents generally reported that in the cold season, the esthetic effect of green spaces is weak, particularly when snow covers the area or during extreme cold weather, leading to a significant decline in green space usage. As a result, residents are reluctant to enter green spaces during the winter, which affects their utilization rate. Therefore, the “low winter utilization” and “decline in plant activity” mentioned in the literature review align with the findings of the resident survey, further confirming the common issue of winter green space usage in cold regions.

Additionally, the literature review emphasized the role of green space layout and plant species design in enhancing ecological benefits. A well-planned green space layout can not only increase carbon sequestration effects but also reduce urban heat island effects, thereby improving energy efficiency. In the resident survey, most participants expressed a desire to see more evergreen trees or cold-tolerant plants planted in green spaces to ensure the esthetic appeal and usability of green spaces during winter. This aligns with the study carried out by Dong et al. [35], who demonstrated that urban green spaces with diverse native plant species can enhance carbon storage by 15–30% in cold climates. The proposed plant configuration of this study mirrors their identified high-performance species.

The hypothesis proposed in this study primarily revolves around scientifically planning green space layouts, selecting high-carbon-sequestering plants, and integrating sunrooms and new energy systems to enhance the carbon sequestration capacity and wellness functions of green spaces in cold regions. The survey revealed that many residents suggested that green space renovations should consider incorporating plants with strong carbon sequestration potential and good winter landscape effects, such as evergreen trees and cold-resistant shrubs. This is consistent with the hypothesis put forward in this study.

Sunrooms can introduce a large amount of natural light and use solar energy for greenhouse effect heating, creating a warm and comfortable living environment or one for activities. They have multiple benefits in green space renovation. Firstly, they can increase the utilization rate of green spaces in winter. The cold climate conditions in winter limit the use of green spaces in cold regions, but sunrooms absorb solar energy to provide warm indoor spaces for residents, allowing them to enjoy natural light, air, and views inside the sunroom. In the literature review, many studies have verified the aforementioned advantages of sunrooms [101,102,106]. The survey showed that over 60% of residents would use green spaces more in winter if a sunroom were included in the green space design. Secondly, sunrooms provide a warm environment that enhances plant activity in winter, thereby improving the carbon sequestration capacity of green spaces. Lastly, sunrooms offer residents a space for intimate contact with nature, contributing to wellness benefits. Therefore, sunrooms not only increase the utilization rate and ecological benefits of green spaces but also provide additional assurance for residents’ physical and mental health, making a significant contribution to social welfare.

The findings of this study offer actionable insights for policymakers and urban planners aiming to enhance green space performance in cold-region cities. First, municipal governments should prioritize funding mechanisms for sunroom-integrated green space renovations in aging communities, particularly through subsidies for photovoltaic systems to offset initial costs (e.g., feed-in tariffs or tax incentives). Second, urban design guidelines should mandate multi-layered plantings with high carbon-sequestration species (e.g., conifers and cold-tolerant shrubs) in public green spaces, as our results demonstrate their dual ecological and wellness benefits. Third, planners should adopt seasonal adaptability standards for outdoor spaces, requiring windbreaks, heated pathways, or modular sunrooms in climates with harsh winters. These measures align with China’s ‘dual carbon’ goals while addressing residents’ demand for year-round usable green spaces.

While this study focuses on China’s cold regions, the findings may be transferable to other cold-climate urban environments (e.g., Canada, Northern Europe, or Russia) with necessary adaptations. For plant species selection, the proposed high-carbon-sequestration species (e.g., conifers, cold-tolerant shrubs) share similar functional traits with boreal species commonly used in other cold regions, though local biodiversity assessments would be essential to ensure ecological compatibility. The carbon sequestration efficiency of sunroom-enhanced green spaces could be comparable across regions, as the photosynthetic capacity of cold-adapted plants under controlled environments follows similar physiological principles globally. However, variations in solar irradiance (e.g., lower winter sunlight in Arctic cities) and heating demands (e.g., extreme lows in Siberia) may require adjustments to photovoltaic system sizing or insulation standards.

5. Conclusions

This study explores the potential for enhancing carbon sequestration and health benefits in the renovation of existing residential green spaces in cold-region cities under China’s “dual carbon” goals. Through a comprehensive literature review, resident surveys, and hypothesis validation, the research systematically examines existing challenges and proposes innovative solutions.

The literature review and survey results indicate that scientific planning of green space layouts and optimization of plant community design are crucial for improving the ecological and health benefits of residential green spaces in cold regions. The literature analysis reveals that a rational combination of trees and shrubs significantly enhances carbon sink capacity, whereas monocultural lawns have limited carbon sequestration effects. Additionally, plant diversity not only improves the microclimate (e.g., regulating temperature and humidity, reducing wind speed) but also promotes residents’ mental and physical well-being through visual and sensory stimulation. However, the low temperatures in cold regions during winter lead to decreased plant activity and monotonous landscapes. The lack of windproof and warming facilities further restricts the efficiency of green space utilization, with 73% of residents reducing outdoor activities in winter for this reason. Resident surveys further confirm this challenge: 65% of respondents attribute reduced winter activities to low temperatures, 33% cite the lack of heating facilities as a major obstacle, and 20% highlight the impact of snow cover. Notably, despite low resident satisfaction with existing green spaces (only 37%), 85% recognize the positive psychological effects of green space renovation, and 87% support the construction of sunrooms as winter activity spaces, with clear functional preferences (53% favor rest areas, while 47% prefer fitness facilities). These findings provide critical insights for green space renovation in cold regions, suggesting that optimizing plant configurations and improving winter facilities (e.g., sunrooms) can simultaneously enhance carbon sequestration benefits and residents’ health and well-being. The hypothesis validation demonstrates that constructing sunrooms in residential areas of cold regions, combined with photovoltaic-assisted heating systems, effectively addresses key issues related to reduced plant activity and resident activity needs during winter. While ground-level sunrooms provide optimal lighting and heat retention, their design must balance potential impacts on daylight access for lower-floor residents. Underground sunroom solutions, though mitigating visual obstruction, face challenges related to the occupation of garage space. Regarding plant configurations, the study confirms the necessity of employing cold-resistant, high-carbon sequestration species (e.g., Monstera deliciosa, Ficus elastica) alongside therapeutic plants (e.g., Lavandula angustifolia, Sansevieria trifasciata) in a multi-layered arrangement, complemented by nocturnal oxygen-releasing plants (e.g., Sansevieria trifasciata, Aloe vera) to ensure round-the-clock air quality. A modular design is recommended to enable seasonal conversion of sunrooms, integrated with intelligent temperature control systems (e.g., underfloor heating/heat pumps) and photovoltaic energy storage technologies to optimize energy utilization. Additionally, building-integrated photovoltaics should be incorporated to balance lighting and power generation needs. These measures not only enhance the year-round carbon sequestration efficiency and health benefits of green spaces but also provide a scalable technological pathway for low-carbon residential renovation in cold regions.

Several limitations of this study should be noted. First, the research focuses on a single typical residential area in China’s cold regions. While representative, caution is required when generalizing the findings to other climate zones or urban forms. Second, the estimation of plant community carbon sequestration is primarily based on theoretical models, lacking empirical monitoring data; future research should establish long-term carbon flux observation systems for validation. Moreover, the proportion of elderly respondents (10%) in the resident survey is relatively low, which may limit a comprehensive understanding of the needs of special demographic groups. Future research should focus on the following directions: First, long-term monitoring of sunroom applications in residential areas is necessary to quantify their comprehensive benefits in carbon reduction, energy conservation, and resident health improvement. Second, the adaptability of green space renovation technologies under different climatic conditions should be explored, with an emphasis on developing complementary technologies such as adjustable shading systems and rainwater recycling. Third, interdisciplinary collaboration should be strengthened by integrating expertise from architecture, landscape ecology, and environmental engineering to develop intelligent management systems for precise regulation of sunroom environmental parameters. Finally, further exploration of the economic implications of green space renovation is needed, including cost–benefit analyses, return on investment, and the role of policies in facilitating these transformations, such as subsidy mechanisms and regulatory framework optimization. These studies will provide more systematic and scalable solutions for urban renewal in cold regions and beyond.