Environmental Design Innovation in Hospitality: A Sustainable Framework for Evaluating Biophilic Interiors in Rooftop Restaurants

Abstract

Biophilic design (BD) has become one of the most critical design approaches for improving the user experience and sustainability in hospitality settings. This paper examines how Biophilic Design Elements (BDEs) can be integrated into the interior architecture of rooftop restaurants and how the presence of BDEs can enhance guest satisfaction and restaurant operations. The study is based on the Nature Preferences Theory (NPT) and Dynamic Capabilities Theory (DCT), creating a framework that explores the relationship between biophilic principles and measurable user outcomes, as well as design innovation. A mixed-methods design was employed, where qualitative insights gathered from a Delphi panel of interior design and hospitality professionals were integrated with quantitative data collected through guest surveys. The study suggested that some high-performance BDEs, which are natural materials, utilise daylight, greenery, and water, as well as culturally embedded design motifs. The results indicate that users are positive about an environment with principles of well-being, authenticity, and sensory connection with nature. Researchers focused on context-sensitive, flexible, and low-cost strategies that are adaptable to rooftops in developing urban cities. The study is significant as it presents real-life biophilic design methods applicable in hospitality environments atop buildings and demonstrates how they may align with the Sustainable Development Goals (SDGs). The suggested framework applies to both academic studies and the industry, focusing future designs on nature, user experience, and operational sustainability.

1. Introduction

Environmental consciousness has adopted sustainable design and operational strategies in the hospitality industry, shifting towards environmentally friendly building methods. Ref. [1] shifts to green innovation ideas that pursue the aim of reducing environmental impact while strengthening operational efficiency [2]. Thus, achieving sustainability objectives has particularly recognised the role of architecture and design in hotel spaces, as well as the industry as a whole. This recognition has become more evident in recent decades [3]. The global demand for interior architecture in hotels is significant in shaping guest experiences and promoting overall well-being, while minimising the environmental footprint [4]. It is also key to sustainable and human-centred architectural design practices within hotel facilities [5,6].

BD, which seamlessly integrates natural elements such as greenery, natural lighting, and water features into built environments, has spurred a significant emphasis on enhancing human well-being and productivity [7]. In the hospitality sector, where differentiation and guest satisfaction are key competitive factors, the integration of BD can improve operational flexibility and innovation [8,9]. This trend has led to growing interest in the interior architecture design of hotel facilities to positively impact occupants’ health, foster well-being, and support sustainable tourism practices [10,11]. Through applying BDEs in the interior architectural design, rooftop restaurants, with their unique open-air environments, serve as ideal case studies for this implementation that not only bring benefits to guests but also contributes to the uniqueness and sustainable image of a hotel or restaurant. Such a strategic approach offers unique opportunities to integrate BDEs that elevate the dining experience while contributing to United Nations Sustainable Development Goals (SDGs), including Goal 3: Good Health and Well-being, by promoting environments that embrace and improve psychological and emotional wellness through exposure to nature; Goal 11: Sustainable Cities and Communities, by optimising rooftops for functionality and sustainability; and Goal 12: Responsible Consumption and Production, by encouraging the use of eco-friendly materials and practices in design and operations [12]. These practices aim to develop restorative and stimulating environments, aligning directly with the principles of Nature Preferences Theory (NPT) [13], which enables guests to recover from daily stressors and replenish their cognitive and emotional resources. Further, the application DCT provides a valuable framework for understanding how the hospitality industry can effectively adapt and respond to emerging trends in design and consumer preferences by integrating BDEs [14]. These practices develop an extraordinary understanding of how hotels can effectively adapt and respond to emerging trends in design and consumer preferences by integrating BDEs, creating a memorable experience for their guests, while enhancing operational sustainability, thus achieving competitiveness in a specific market segment [15].

Although, there is a growing interest in the integration of BD in hospitality settings, the application on dining environment attributes remains under-researched. Firstly, the current literature mainly covers application of BDEs in homes or workplaces, and there is a lack of knowledge about how BDEs might be implemented in restaurants to meet guests’ needs and sustainable management objectives [16], which addresses the importance of future research in the field for a nuanced understanding of the contribution of BD to customers’ behaviour in the context of rooftop restaurants in hotels. There is limited literature available for understanding the combined effects of BD engagement with NPT and DCT to stimulate guests’ delight and the behavioural intentions of the customer in the interior architecture design of open-air hospitality settings, like a rooftop restaurant. As for the previous studies, the majority of them have not attempted to explain the application of BD in ever-changing environments that are as radically experiential as rooftop restaurants [17]. Secondly, the successful implementation of BD requires not only expertise in BDEs, such as natural shapes and patterns, natural light, plants, and water features, but also a deep understanding of guest engagement and the perception of natural elements in such spaces [18]. The further examination of BDEs within the context of rooftop restaurants and hospitality environments, in both theoretical and applied senses, remains unexplored. Thirdly, the idea of participative design, which involves guests, staff, and designers in the design process to incorporate as many (BD) features as possible [19] in such settings, remains unexplored. Fourthly, there is a lack of consideration for the current trends in interrogating BDEs that may require sustainability, focusing more on a luxurious image with no consideration for the SDGs [20]. Fifthly, while the potential of rooftop restaurants to create both restorative and stimulating environments is recognised, the application of NPT and DCT in this context remains underexplored [14]. Moreover, the application of BD in open-air eating settings raises new questions because such environments are vulnerable to similar stressors coming from the urban environment and climate fluctuations [21].

This study aims to fill the research gap in demonstrating the combined effects of BD engaged with NPT and DCT, highlighting the efficacy of BDEs in reconnecting guests with the natural world and impacting both physical and psychological attributes [17]. Simultaneously, it examines how BDEs interact with NPT and DCT aligned with SDGs as a vital part of fostering sustainable practices and addressing the deep understanding of guest engagement and the perception of natural elements in an open-air space such as a rooftop restaurant [10] to maintain the successful implementation of BD. Furthermore, The current study claims, to the author’s knowledge, to be the first study to conduct such an investigation of the two theories, as well as BD’s consequences on the interior architecture design of open-air hospitality settings like rooftop restaurants, seeking the integration of natural elements to enhance well-being, behavioural intentions, and operational sustainability in hotel restaurants [22] through a participative design approach involving guests, staff, and designers, to create an experimental design proposal engaging BD and responsive to the study aim and guest preferences, and foster sustainable behaviour within urban environment, and climate fluctuations [23].

The study culminates with vital contributions by filling the gap in the existing literature that addresses the integration of BD in the interior architecture of rooftop restaurants in the hospitality sector. More specifically, this paper examines the synthesis of NPT and DCT in determining how the dynamic and experiential context of open-air hospitality settings, such as rooftop restaurants, can be [24]. A design proposal is introduced as an experimental methodology to explore a particular rooftop restaurant design, initiating the concept and identifying the best environmental features for guest comfort. The results will provide additional insights into the lack of research on BD in the hospitality context, particularly concerning its applicability in enhancing guest preferences and the enhancement in the dynamic capabilities in the hotel industry’s sensitivity to new trends in design [17], customers’ preferences, and adopting the growing market challenges [25]. As a result of employing NPT and DCT, the study will present a different view of environmental psychology, design approaches, and organizational performance in the hospitality industry towards operational sustainability [2,3].

To this end, this study provides insightful practical implications for interior architecture designers or managers of hotels and restaurants. The outcomes are expected to extend the existing knowledge of BD in hospitality and bring a fresh approach to linking BDEs, interior architecture design, and hospitality practices with broader sustainability objectives, thereby enhancing guest satisfaction, fostering positive business outcomes, and responding to global trends such as wellness and sustainability. Thus, it stimulates a rooftop restaurant presence on the sustainable design platform, enhances customer delight, increases revenues, and, ultimately, contributes to the long-term success of the hotel [26,27].

2. Literature Review

2.1. Biophilic Design (BD) in Interior Architecture

BD is based on people’s inclination to feel a connection with nature and incorporates the relationship between natural attributes, such as plants, water, light, and sound, to create fields [28]. Studies have demonstrated that contact with nature in the interior has physical and mental health benefits, decreases stress, and boosts mood and cognitive performance [29,30].

BD has been found to enhance customer satisfaction in the hospitality industry, particularly in the hotel sector, fostering repeat patronage and promoting trust and perceived quality of service [26,31,32]. The most interesting opportunities to incorporate biophilic elements are rooftop restaurants, which may feature green roofing, water-related elements, flowerbeds, and animal housing, thereby transforming the experience of being in nature [32,33]. Such interventions relate to serving guests well, in addition to being in line with the sustainability goals (SDGs), as well as serving as a marketing tool for competitive positioning, aligning with the sustainability goals (SDGs).

The use of BD in rooftop restaurants can positively impact emotions and thoughts, and these natural stimuli also have a positive impact on feelings and thoughts. This aligns with the recommendations of NPT, implying that natural stimuli have a positive impact on emotions and thoughts, and that this setting is best suited to prevent burnout [30,34]. At the same time, DCT underpins the notion of BD as having an ability to enhance the adaptability and strategic differentiation of hotels, resulting in efficient operations and environmental sustainability [35]. Hence, BD can have experiential and strategic values (see Figure 1).

Although comparative case studies may also be relevant for yielding cross-contextual information, the present research has intentionally focused on a primary, in-depth study of a single real case: the Four Seasons Hotel, Alexandria. Such a decision is necessitated by the inadequate documentation of rooftop-specific BD initiatives, which are likely to be similar to the research context in terms of environmental, cultural, and economic conditions. It was considered to incorporate loosely aligned or non-regional case studies; however, this approach was avoided because it would generalise the research to the extent of further diminishing the specificity and applicability of the findings.

Instead, the literature conducted at the international level is used to develop a conceptual framework, which is backed by direct empirical evidence based on professional viewpoints (via the Delphi method) and the views of guests, providing very contextualised and actionable conclusions. This strategy also enhances the internal validity in the research without being overly broad in scope, thereby maintaining focus on the central ideas of the investigation.

2.1.1. Biophilic Design Elements (BDEs)

Based on the principles of Stephen R. Kellert, BD is focused on matching the built environment with human preferences for nature, which offers the possibility of integrating natural elements, patterns, and processes into the design [19]. The model of Kellert (created between 2004 and 2008) includes six underlying components: the features of the environment, the nature of shapes and forms, the patterns and processes of nature, light and space, the connections to places, and the human–nature relations that have evolved [18]. The principles help designers to include more than 70 specific features that enhance health, well-being, and environmental balance [36]. These design strategies, organised into six foundational elements, provide a robust framework for integrating nature into built environments. These elements are fundamental for designing settings that promote health and human bonding with the natural environment [10]. Incorporating BDEs into architectural spaces has emerged as a transformative approach to fostering human connection to nature and sustainability [3].

Within the framework of rooftop restaurants in hotels, such aspects help create restorative environments, full of sensory experiences that enhance the guest experience and sustainability [3]. Adding positive regional materials and allusions to culture, BDEs promote both aesthetic attraction and personal connections, thereby stimulating a positive intent to interact with the environment and encouraging a desire to revisit it. The selection of biophilic strategies is made in a project context. When designed strategically, BDEs can plunge into the ecosystem and provide a pliable, yet sustainable, adaptive structure in interior architecture design [36].

2.1.2. Biophilic Design Framework by Kellert

The synthesis of Stephen R. Kellert’s framework that explains the issues of integrating biophilic concepts into architecture is laid out as follows: In his framework, six important points are (1) environmental characteristics, (2) organic shapes and contours, (3) organic patterns and processes, (4) light and space, (5) place-based relationships, and (6) evolved human–nature relationships [18,37]. The components provide a design creator with an organised guide to achieving an innate human inclination towards the natural environment through architecture. As applied to rooftop restaurants, the plan can be used by Kellert to achieve both visual and sensory stimulation by integrating actionable recommendations on implementing a Biophilic Design Element (BDE) that facilitates not only visual and sensory stimulation but also fosters and encourages emotional comfort and environmental awareness. The framework of the hypotheses design of this study will be matched with the model proposed by Kellert to ascertain that this study indicates a concise theoretical connection between the incorporation of nature in interior architecture and customer well-being within the hospitality context.

2.1.3. Browning’s 14 Patterns of Biophilic Design

Building on the developments by Ryan et al. [29], a list of 14 biophilic design patterns was created, systematically organised into three broad themes: Nature in the Space, Natural Analogues, and Nature of the Space. These trends offer evidence-based tactics that align environmental stimuli with the desired health or mental outcome, thereby aligning environmental stimuli with the intended health or mental outcome. An example of such features includes visual connections with nature, non-rhythmic tactile sensations, and prospect and refuge zones that promote feelings of relaxation and positivity and can enhance cognitive capacity. These patterns can be operationalised in hospitality settings, with particular reference to rooftop restaurant settings, where the spatial design aims to maximise restorative and emotionally stimulating experiences for guests. The inclusion of the patterns presented by Browning in this research yields a more nuanced examination of how design can influence behaviour, satisfaction, and well-being through complex, context-sensitive surroundings.

2.1.4. Geometrical Theory of Salingaros

The way Nikos Salingaros [38] reflects upon the issue of biophilic design is related to the psychological appeals of natural geometry, fractals, and human-scaled space constructions. According to his theory, within a space that exhibits complexity and harmony, such as those found in nature, there would be a neurological reaction in the brain, resulting in the immediate relaxation of the mind and emotional stability. In rooftop restaurants, these principles are reflected in the organic arrangement and patterns, rhythmic textures and elements, and a sound-reactive environment that guests enjoy. Biophilic geometry is a concept that Salingaros employed, which also favourably augurs cultural and contextual design adaptations, underscoring the fact that geometry and structure may influence user satisfaction and the long-term adherence to a premise subconsciously. This paper references his facts to assess the role of geometric clues and natural proportions in enhancing the spatial quality and authenticity of design in hospitality interiors.

2.2. Theoretical Lens

This paper explores the connection between BD, which is associated with BDEs, and its impact on the experience of guests and operational efficiency in rooftop hotel restaurants with BDEs, as well as its influence on the guest experience and operational efficiency in rooftop hotel restaurants within the hotel industry [2]. It uses two theoretical perspectives, namely, NPT, which emphasises the restorative project advantages of natural systems on guests, and DCT [25], which promotes the capacity of the hospitality industry to embrace changing design requisites and clientele demands [17]. In combination, NPT and DCT create a holistic system for planning how biophilic interior design could achieve both functional and aesthetic objectives [30] as well as how it could contribute to personal well-being and be in balance with the Sustainable Development Goals (SDGs).

2.2.1. Nature Preferences Theory (NPT)

Theories related to psychological health and nature have been categorised into three main areas: cognitive psychology, emotional psychology, and evolutionary psychology [38]. NPT addresses the inherent tendency of people to select and appreciate the natural environment based on evidence from evolutionary psychology related to cognitive psychological health. According to NPT, human beings who have chosen the right environments have survived longer and had more successful births than others and have transmitted to us the tendency to prefer such environments [39].

NPT is derived from the concept of evolved biophilia, which posits that people have an inherent preference for natural settings [40]. According to this theory, the human preference for certain natural places can be explained by the fact that such places were important for survival in the past. That is why this theory claims that people naturally prefer particular natural areas, because their ancestors’ lives depended on values associated with specific surroundings [41].

In light of the NPT as a theory that affects human health through the human–nature connection, the present cross-sectional study postulates a general positive relationship between psychological well-being, cognitive functioning, and self-reported positive effects with interaction with nature [30,42,43]. It suggests the influences that affect the satisfaction of the hotel’s guests and their future recommendations to others, linking them to the SDGs, thereby positively impacting the SDGs and, in turn, positively affecting the hotel’s financial performance (See Figure 2). The main key benefits for rooftop restaurants based on NPT are that designers of hotel spaces have started to include BDEs into their interior architectural designs by applying natural materials, plants, views, and lighting in the rooftop restaurant, adopting restorative experiences, aesthetic preferences, and multi-sensory engagement.

Moreover, all the BDEs are experienced and perceived using the various human senses of touch, sight, smell, taste, and sound. All human senses are highly important; however, vision is the most significant sense for recognising the natural environment and how people respond to it using other senses. When the human sense of vision sees natural elements, it produces several reactions in the human body. It should also be noted that aesthetically appealing elements that are found in nature interest the human mind and provoke human curiosity, passion, and creativity; hence, when the human has no contact with the natural world in visuals, the feeling results in tiredness and dullness in a built environment and space, which, in some extreme cases, may lead to abnormal psychological behaviour in the human body. To the extent that the NPT helps incorporate biophilic interventions that are incidental attractions for guests due to their innate biology, it proposes designing environments that allow guests to meet their inherent desire to be surrounded by nature, thus promoting people’s health and enjoyment [44].

According to this theory, rooftop restaurants can design aesthetically inviting and calming spaces for their guests while making a statement about their position in the highly competitive restaurant and hospitality industry. This theory-based approach to the peat business emphasises the importance of high satisfaction in the hospitality industry. The implications of the NPT aspects for rooftop restaurants foster engagement, and promoting a brand identity. The fact that rooftop restaurants potentially implement BD solutions corresponding to NPT means that nature-related designs are consistent with promoting a brand identity and they can strengthen their sustainable and pro-guest, environmentally friendly image. Finally, they sustain aesthetic appeal through natural textures, forms, and ornaments, which, in return, enhance the perception of the visual–sensory space quality [45]. This, in turn, increases the number of visitors, making guests feel comfortable and psychologically drawn to visually pleasing places [46].

2.2.2. Dynamic Capabilities Theory (DCT)

This theory emphasises the intense focus on creating the necessary and desired change in response to the changing requirements of the marketplace for new knowledge [14]. BD potentially adds to this, since differentiation and guest satisfaction are strategic components in this competitive industry [26]. Nevertheless, BD also involves a deeper understanding of design principles, as well as an awareness of the individual guest’s experience and their perceptions of nature in space [10]. Therefore, the application of BD can also be seen as a dynamic capability to address and develop the hotel’s capabilities to efficiently [35] incorporate new design values for improving the guest experience and satisfying a growing customer concern with the environment (see

Table 1. DCT aspects in relevance to BDEs and application in interior architectural design of rooftop restaurants.

BDEs (Outlined by Kellert)	DCT Perspective	Design Application in Rooftop Restaurant
Environmental Features	Hotels can sense guest demand for sustainable, nature-integrated designs and respond by implementing greenery and water features. Seizing opportunities: Green rooftop environments differentiate hotels, attracting eco-conscious and wellness-seeking guests.	Rooftop gardens and water features offer dual benefits of aesthetic appeal and psychological restoration, aligning with sustainable tourism trends.
Natural Shapes and Forms	Reconfiguring interiors to include organic forms demonstrates a hotel’s ability to adapt to modern design trends, enhance guest experiences, and contribute to a unique brand identity.	Curved furniture and flowing pathways enhance visual appeal and emotional connection. Dining furniture with decorative features resembling leaves or waves can foster a subconscious connection to nature. Incorporating curved seating tree-like structures not only enhances visual appeal but also improves guests’ emotional connections to the space.
Natural Patterns and Processes	Hotels sense and seize opportunities by integrating dynamic elements to create visually dynamic and engaging spaces. Reconfiguring design processes to accommodate changing patterns ensures that guest experiences remain fresh and relevant.	Incorporating natural textures and seasonal decorations creates a dynamic environment. Incorporating natural stone textures and seasonal floral arrangements provides an aesthetically rich and engaging dining experience. Reflective surfaces align with guest preferences and reinforce brand identity.
Light and Space	Hotels that reconfigure spaces to maximise natural light and openness respond to sensed trends for environmentally friendly and wellness-oriented design. These elements reduce operational costs and create memorable guest experiences.	A rooftop with large windows overlooking a city skyline or the sea, coupled with shaded areas for comfort, strikes a balance between openness and protection. Rooftops with open seating provide both functional and emotional benefits, enhancing guest satisfaction.
Place-Based Relationships	This approach strengthens the hotel’s competitive position by appealing to travellers seeking authentic experiences through the integration of local culture and materials.	Incorporating Alexandria’s native plants, such as date palms, and utilising local limestone in the design enhance authenticity and aesthetic appeal. Using cultural motifs and region-specific materials fosters a sense of place and belonging, resonating with both local and international guests.
Evolved Human–Nature Relationships	Hotels reconfigure experiences by integrating sensory elements that enhance guest well-being, aligning with the principles of sustainable tourism.	Installing a small water fountain and tactile surfaces, such as stone walls or wooden furniture, creates a multi-sensory environment that resonates with nature.

). DCT engages with BD, emerging as a competitive advantage that can help establish an adaptation to evolving market demands and integrate sustainability [1].

Together, these theories provide a comprehensive framework for integrating BD in rooftop restaurants. While NPT explains why biophilic elements resonate with guests [44], DCT addresses how hotels can effectively implement these elements to enhance guest experiences and sustain competitive advantages [15].

Table 2. Table 2 illustrates the comparative analysis and relevance of Dynamic Capabilities Theory (DCT) vs. Nature Preferences Theory (NPT).

	Dynamic Capabilities Theory (DCT)	Nature Preferences Theory (NPT)
Feature	Tends to highlight the internal opportunities for BD and the need to evolve, adapting to changing market trends and use nature to gain competitive advantage.	Highlighting guest experience, discussing how BD meets essential human needs for exposure to nature.
Focus	Assessing and sustaining competition. Recognising and utilising assets in order to sustain a competitive edge in the hotel.	Individual decision and psycho-acceptance in environments incorporating natural elements.
Primary Outcome	Better operational activities in response to customer trends, higher organisational efficiency, and a competitive advantage.	Higher occupancy rates, less levels of stress, and a sense of feeling connected to the location.
Application In Interior Architectural Design Of Rooftop Restaurants	Adaptive designs and flexible layouts can be introduced in harmony with sustainable concepts to create a unique experience for guests.	Organic interiors and natural designs that accommodate guests’ urge to be surrounded by nature.

illustrates the comparative analysis and relevance of DCT vs. NPT

2.3. Sustainable Development Goals (SDGs)

It is very important to know how much depletion has occurred due to the emergence of the modern built environment in order to know how much sustainable and contemporary green design plays a big role in remedying measures for the environment and the wellbeing of humans [47,48]; however, sustainable design has been noted to mainly focus on the development of methods and frameworks, which have an impact on the environment to the least possible extent, resources which are used sparingly to provide enough to cater to the biophilic. Thus, the net benefit of primarily focused green and sustainable buildings [36] is the very little and insignificant contribution to the achievement of BD goals; therefore, biophilia has been referred to as the missing link in the approaches of sustainable building designs [49]. Awareness of the principles of implementing the elements of BD will be helpful in pursuing the best practice of sustainable biophilic design. Figure 3 illustrates the entire correlation and interior solutions for enhanced design practices in rooftop restaurants.

Since BDEs in rooftop restaurant interior architecture have been investigated, it is evident that such strategies have a direct relationship with multiple SDGs, thus merging sustainability goals with nature-informed architectural designs. The interior architectural design of rooftop restaurants with BDEs enhances several SDGs by synchronising sustainability goals with nature-inspired design concepts. Thus, it is possible to state that all six elements of BD are linked to the corresponding SDGs, as the style contributes towards the global ultimate goals [20].

The incorporation of BDEs into the interior architectural design of rooftop restaurants in the hotel industry may enhance the following specific SDGs: SDG 3, which aims to create a restorative environment that is healthy for both guests and staff, both physically and mentally; SDG 8: Employment, which states that achieving equality, decent employment, and improved work conditions for workers can lead to better outcomes among employees and others; and SDG 11: Sustainable cities and communities [12].

Hence, BD plays a key role in developing a sustainable and climate-proof urban fabric [47]. From an energy usage perspective, the influence of this purpose is manageable for hotel rooftop restaurants, and there is a likelihood of incorporating sustainable materials into its design solutions (SDG 12: When designing the rooftop restaurant, sustainable and locally available materials were used, supporting the concept of responsible consumption and production; and SDG 13: Climate: Biophilic designs can utilise energy conservation measures, hence contributing to climate action). This analysis links the implementation of BD to the contribution to broader SDGs [47].

3. Methodology

The proposed study employs a mixed-methodology approach, which involves the use of both qualitative and quantitative measurements to assess the relevance of applying BDEs to NPT and DCT within the context of rooftop hotel restaurants [22]. The Delphi methodology was applied to the qualitative stage, where experts were employed in a two-round, purposive, and face-to-face discussion aimed at identifying and ranking high-impact BDEs in support of the Kellert framework [7,10,18]. Such an expert-led process made the selection process of biophilic applications deep and credible in contexts. The quantitative part consisted of a guest satisfaction survey, which, due to its nature, piloted user perceptions and provided the opportunity to measure the influence of biophilic qualities on environmental quality, comfort, and total experience. By combining the two techniques as shown in Figure 4, it was possible to gain an overall sense, which can be described as a combination of theoretical background and experience. Such a two-step scheme promotes the verification of design tactics [50] by ensuring the coherence of professional advice with end-user feedback, and contributes to the creation of harmonised, market-competitive, and sustainable targets for user-oriented hospitality spaces [5].

Although this study is exploratory in nature, the mixed-methodological design was based on Delphi interviews with experts on the topic and quantitative responses from users of rooftop hospitality buildings, which allowed for consistent and significant correlations between BDEs and key performance indicators within rooftop hospitality buildings [51]. Expert and guest respondent perspectives were triangulated to provide rich, contextual specific biophilic features which influence spatial experience, emotional well-being, and perceived operational value.

In the light of this intertwining of qualitative depth and quantitative trends, the paper advances a hypothesis that can be used to test the same in the future: incorporating BDEs such as use of natural materials, daylight, and plant features has a strong benefit, in that it increases user satisfaction and the sustainability of operations of rooftop hospitable setting.

The hypothesis is based on two theoretical frameworks: the theoretical perspective of NPT, which focuses on the realisation of innate human affinity to nature, and DCT, which emphasises adaptive innovation as a determinant of organisational performance. Literature also supports this finding in the article by Gillis et al. [52], which revealed positive psychological and physiological effects of nature exposure, including mood improvement, decreased stress, and increased cognitive activity. According to Ryan et al. [29], natural elements possess a restorative value, and biophilic environments can enhance user satisfaction and emotional attachment. The hypothesis can also be viewed as a direct correlation of the observed data (see Table 1 and Table 2 and Figure 2, Figure 3 and Figure 4), with experts and users assigning the same high priority to these features.

Through the formulation of such testable propositions, the research moves beyond the descriptive undertaking to provide a theoretically evidence-based avenue for conducting the research. It also promotes the creation of measurement tools and indicators that will enable better quantification of the contribution of BD in improving the quality of experience, as well as the operational strength of hospitality settings.

3.1. Delphi Method

The Delphi method is an effective methodology related to identifying the most effective biophilic dimensions, elements, and attributes of BD framework adapted from Kellert [7] in improving the design of rooftop restaurants in hotels through qualitative analysis and prospective assessment of multidimensional topics to come up with design recommendations supported by expertise to develop restaurants that enhance guest experience and achieve sustainability [50].

The expert panel is an integral component of the Delphi method, which employs a mixed-methodology approach to explore BDEs from a qualitative perspective [53]. The panel gathers experts in interior architecture, academic staff members, PhD holders, MSc researchers, hotel management, experts in environmental psychology, and scholars with more than 10 years of working experience in related fields, as they are expected to offer broader scope for considering the BDEs outlined by Kellert [18] in the interior architectural design of rooftop restaurants.

Table 3. Expert panel.

Expert’s Information	Classification	Number	Percentage
Gender	Male	8.0	53.30
	Female	7.0	46.70
Education	College/University	3.0	20.0
	Master	10.0	66.70
	PhD	2.0	13.30
position	Director/Dean/	7.0	46.70
	Managerial	8.0	53.30
Working experience	11–15 years	2.0	13.30
	16–20 years old	6.0	40.0
	21–25 years old	7.0	46.70
Total		15.0	100.00

illustrates the expert panel. This way, the data sources guarantee the comprehensiveness of the approach, where theoretical knowledge is complemented with actual practice.

The expert panel engages 15 professionals with practical and academic experience. Through two rounds of face-to-face open discussions, these experts provided comprehensive insights from theoretical, practical, and experiential perspectives, identifying biophilic elements [53], determining their application in rooftop restaurant design, and highlighting opportunities and challenges [50]. This process of experts’ open discussions is a well-established method for gathering in-depth knowledge from experts in the field. The data obtained from this panel contributed to the identification of the most current design and marketing management factors [54]. The outcomes from the expert panel include the identification and prioritisation of key BDEs, as well as the exploration of challenges and opportunities related to maintenance, cost, and feasibility, with specific reference to creativity and contextual relevance to cultural and geographical locations, ensuring designs are relevant and blend in with the surroundings. See Figure 5, which illustrates the entire Delphi procedure.

Round 1 is conducted through an open-ended question to explore the overall knowledge of experts with biophilic design, definition, and application to rooftop restaurants in hotels, with its existing trends in the interior architectural design of rooftop restaurants, the relevance of the rooftop interior architectural design to hotel location and local culture, and the anticipated challenges and opportunities associated with applying BD in hotel environments. The open discussion is conducted in a face-to-face manner, ensuring direct engagement. It begins with a brief overview of BD in rooftop restaurants, followed by open-ended questions that allow experts to elaborate freely and share any additional thoughts [53]. The Round 1 open discussion was recorded using an audio tool with the expert’s consent. See

Table 4. Round 1 questions for open discussion in the Delphi method.

	Open Discussion Questions for Expert Panel (Round 2)
(1)  Overall Knowledge and Existing Trends	1. Are you familiar with biophilic design and elements?
(2)  Environmental Features	2. What are the environmental elements you recommend for interior architectural design of rooftop restaurants in a coastal city like Alexandria?
(3)  Natural Shapes and Forms	3. What specific biophilic features would you like to see in a rooftop restaurant?
(4)  Light and Space	4. What role does natural lighting play in creating an inviting and energy-efficient rooftop environment?
(5)  Natural Patterns and Processes	5. Do you consider orienting the design to provide panoramic views of the city or sea important?
(6)  Place-Based Relationships	6. Do you believe that the interior architecture design of rooftop restaurants can incorporate Alexandria’s regional identity, such as native plants, cultural patterns, and local materials?
(7)  Evolved Human–Nature Relationships	7. How likely are guests to revisit a rooftop restaurant that fosters a strong connection with nature?
8. What opportunities exist for incorporating biophilic design into rooftop restaurant design to enhance operational efficiency and promote sustainability?

, which shows Round 1 questions for open discussion in the Delphi method.

Round 2 developed a new open discussion, containing refined questions derived from general patterns and concepts, based on experts’ responses from Round 1, to promote consensus and organise the findings into clear themes. Refer to

Table 5. Round 2 questions for open discussion in the Delphi method.

	Open Discussion Questions for Expert Panel (Round 2)
Overall Knowledge and Existing Trends	1. How do you perceive the role of biophilic design in creating a unique identity for your rooftop restaurant in Alexandria? 2. Do you believe that integrating natural elements, such as plants and water features, enhances the guest experience?
(1) Environmental Features	3. Does your rooftop restaurant currently incorporate any environmental elements, such as greenery, water features, air quality, or natural materials? 4. How might introducing environmental features, such as vertical gardens or reflecting pools, affect your operational considerations, such as maintenance or costs?
(2) Natural Shapes and Forms	5. Do you think that nature-inspired geometry in the design, such as curved seating, irregular patterns, and flowing lines in the layout, would effectively enhance the aesthetic and functionality of your rooftop design?
(3) Light and Space	6. Have you considered using open, spacious design layouts that allow guests to fully embrace the environment? 7. How can you control natural light, especially within a rooftop (for instance, skylights, glass walls, or large windows)? 8. What about installing dynamic lighting systems that adjust according to the presence of sunlight? Do you think such ideas for the rooftop restaurant are suitable?
(4) Natural Patterns and Processes	9. How could integrating patterns inspired by nature, such as organic forms or textures, be considered in the interior design of the rooftop restaurant? 10. Would it be possible to introduce dynamic experiences that incorporate seasonal changes, such as rotating seating arrangements or live plant displays reflecting seasonal shifts, or lighting effects that mimic the natural changes between day and night?
(5) Place-Based Relationships	11. Is it important to use local materials and plants, cultural motifs, and design elements (e.g., patterns inspired by local art) that reflect the identity of Alexandria in the design?
(6) Evolved Human–Nature Relationships	12. In your opinion, how likely are guests to revisit a rooftop restaurant that fosters a strong connection with nature?
13. Are there any additional biophilic design elements or considerations you believe should be prioritised in rooftop restaurant design?

, which presents the Round 2 questions for open discussion in the Delphi method. The questions were administered to delve into the design aspects of the most influential biophilic elements, dimensions, and attributes of BD framework adapted from Kellert [18] design of rooftop restaurants (e.g., natural light, natural materials, and plants), the relevance of the rooftop interior architectural design to hotel location and local culture (e.g., indigenous plants or heritage-inspired forms), and the anticipated challenges and opportunities associated with applying BD in hotel environments (e.g., cost, impact of the environment on job performance and mood, and maintenance). In addition to contributing to the sensory experience that fosters revisits and rooftop restaurant recommendations [55].

After two rounds of face-to-face open discussions and conversations, the analysed final results are summarised into a clear list of recommendations for biophilic restaurant design, focusing on ideas that received the highest levels of consensus from experts. The Delphi method data and criteria remained unchanged at all times during these operations.

3.2. Guest Questionnaire

Ambience is vital in the hospitality industry because customers tend to seek a favourable physical environment and a pleasant experience. Several studies on the servicescape in the hotel industry demonstrate that the feelings and behaviours of guests depend on the atmosphere and, in turn, indirectly affect the context of the environment [56]. Second, the physical environment has a drastic impact on customers’ consumption experience. [57] posited that the physical environment could influence avoidance behaviour. These studies also highlighted the importance of the spatial environment in influencing guests’ behaviour, emphasising the significance of the spatial environment in shaping guests’ behaviours [56].

In this phase, the questionnaire instrument is designed to focus on the themes and concepts prioritised through the Delphi method, as outlined by Kellert in the six BDEs: Environmental Features, Natural Shapes and Forms, Natural Patterns and Processes, Light and Space, Place-Based Relationships, and Evolved Human–Nature Relationships [18]. This instrument offers an inexpensive data collection method that yields reliable results—the questionnaire is self-distributed on-site after obtaining permission from hotel management. The guest group consisted of 70 Egyptian guests and tourists who had stayed in the five-star Four Seasons hotel in Alexandria, Egypt, within the past six months. The guests experienced dining at Kala Restaurant and Bleu Lounge. Two dining venues deliver extraordinary food service experiences that reflect Alexandria’s seafront charm, even though they do not rest on the rooftop. Both Kala Restaurant and Bleu Lounge offer connections to nature and natural lighting features through their design and location. The guest group’s emotions and observations during the rooftop restaurant dining experience are considered. The questionnaire employs a Likert-scale rating system, multiple-choice questions, and open-ended questions. The collected data were analysed using SPSS v24. Refer to

Table 6. The results of guest questionnaire.

Gender	Men	44 (62.9%)	Women	26 (37.1%)
1. What is your age group?	21–30	31–40	41–50	51–59
	30 (42.9%)	19 (27.1%)	21 (30.0%)	-
How often do you visit rooftop restaurants?		Rarely	Occasionally	Frequently
		1 (1.4%)	19 (27.1%)	50 (71.4%)
The questions			Mean	S.D.
Element1: Overall Knowledge and Existing Trends
1. How important is the dining environment in your decision to visit a rooftop restaurant?			4.543	0.557
Element2: Environmental Features
A. How much do the following features enhance your dining experience?
(1)  Greenery (e.g., plants and vertical gardens)			4.543	0.582
(2)  Water features (e.g., fountains and reflecting pools)			4.500	0.608
(3)  Natural materials (e.g., wood and stone)			4.514	0.531
B. Would the presence of lush greenery and water features make you more likely to revisit a rooftop restaurant?			4.571	0.554
Element3: Natural Shapes and Forms
(1)  How important are organic shapes (e.g., curved furniture and flowing pathways) in creating an inviting atmosphere?			4.586	0.525
(2)  Do natural forms and textures (e.g., wood grain and irregular patterns) positively influence your comfort in a dining space?			4.571	0.527
Element4: Natural Patterns and Processes
(1)  How much do you value seasonal elements (e.g., changing foliage and seasonal flowers) in enhancing the aesthetic of a rooftop restaurant?			4.471	0.583
(2)  To what extent do dynamic patterns in design (e.g., water ripples and natural lighting changes) affect your dining experience?			4.386	0.666
Element5: Light and Space
(1)  How important is natural lighting in creating an inviting ambiance for dining?			4.586	0.551
(2)  How much do you value open spaces and panoramic views in rooftop restaurant design?			4.614	0.519
Element6: Place-Based Relationships
(1)  How important is it for the design to reflect the local culture and environment (e.g., indigenous plants and cultural motifs)?			4.629	0.516
(2)  To what extent do cultural and site-specific elements enhance your sense of connection to the space?			4.614	0.519
Element7: Evolved Human-Nature Relationships
(1)  How effective are sensory elements (e.g., water sounds and tactile textures) in reducing stress during your dining experience?			4.443	0.629
(2)  Would an environment designed to connect guests with nature encourage you to recommend the rooftop restaurant to others?			4.586	0.525

, which presents the results of the guest questionnaire.

3.3. Summary of the Mixed Methodology

For this study, qualitative and quantitative data were used, allowing an in-depth investigation of BDEs in the interior architecture of rooftop restaurants serving the hospitality industry. The Delphi method was implemented for the qualitative part, with a panel of 15 experts in interior architecture, hotel management, and environmental psychology participating in two rounds of meetings [58]. By using this method, the expert panel was able to gain overall knowledge about BD and identify the main BDEs that consider environmental attributes, light, and space, as well as links to the place for the rooftop restaurant in Alexandria, Egypt. The second phase followed a questionnaire format, administered to 70 people who had enjoyed rooftop dining experiences at the dining spaces that adopted BDEs in the case study hotel. We used the questionnaire to discover how guests preferred certain areas, how they felt, and what they intended to do when facing particular elements of the BDEs. The survey revealed that having nature nearby leads to guests being happier, more comfortable, and more inclined to suggest or revisit the space [19]. According to the findings, what experts say aligns with what guests think, proving that it is a worthwhile way to improve the well-being, cultural relevance, and sustainability of spaces on rooftops for hospitality. More natural aspects in space led to greater satisfaction, improved comfort, and a stronger desire to return or recommend the area to others. In addition, combining theoretical principles of Nature Preference Theory (NPT) and DCT with this two-pronged process, BD was proven effective as a strategy in interior architecture that can integrate the expertise of the designers with the input from users. These findings provide a helpful guide for the study to put biophilia ideas into practice and transition from concept to design. The application of both practical expert knowledge and user feedback has made it possible to transfer what was explored in theory and through mixed-methodology approach into new designs, with practical implications for the study. This approach aims to improve well-being, maintain cultural relevance, and ensure interior design through mixed-methodology approach, ultimately enhancing the study’s practical implications. This aims to improve well-being, maintain cultural relevance, and maintain interior architectural sustainability for rooftop restaurants in the hospitality sector.

4. Practical Implication

To this end, the study provides insightful practical implications for interior architecture, provide an understanding of how they play a role in hotels and restaurants. The time methodology used, which included a Delphi study and guest questionnaires, has provided a strong basis for transforming our research into practical design ideas. Architects, hoteliers, and specialists in environmental psychology, through the Delphi method, agreed on how adopting BDEs can optimise a lively and successful interior design for rooftop restaurants. At the same time, the survey revealed details about what users liked, what they experienced, and what they intended to do while dining on the rooftop. They have both proven that BD works for rooftop restaurants and guarantee that the study’s recommendations are based on sound theory and ready to be used in practice. The next part translates these findings into useful insights for architects, interior designers, and developers of hospitality on how to create rooftop dining spaces that are visually appealing, uplifting, reflective of the local culture, and practical. As a result, the design proposal from the study will rest on a solid combination of real-world experience and theory. Natural components (daylight, organic forms, vegetation, and a view of the natural landscape) should be brought up. The UD principles guarantee accessibility, inclusivity, and social equity. Such aspects not only enhance spatial quality, but also lead to emotional wellness and the subsequent higher satisfaction of the guests.

Firstly, on-site observation is conducted to explore restaurants with access to a rooftop related to the case study and observe their interior design preference in terms of BD. Secondly, a design proposal is introduced as an experimental intervention methodology process, initiated by conceptualising the concept and developing an interior architectural solution that incorporates the best environmental features for guest comfort. The results will provide additional insights into the lack of research on BD in the interior architecture of rooftop restaurants in the hospitality context, particularly concerning its applicability in employing NPT, by the means of the human–nature connection [44], and the enhancement in the dynamic capabilities in the hotel industry to generate new trends in design [35], customers’ preferences, and adopting the growing market challenges towards operational sustainability [22].

For the case study, the Four Seasons Hotel in Alexandria, Egypt, was selected. Using the six BD patterns developed by Kellert, the observation examines rooftop dining venues at the hotel, offering an important yet limited insight into hospitality services in Alexandria, a coastal city. The experimental design is introduced and documented as a design proposal based on the collected data with regard to the interior architecture design theme of the hotel. The combination of the mixed methodologies provides a holistic view of the effective practice of implementing biophilic interior architecture to improve rooftop restaurants of hotels with broader sustainability objectives.

The outcomes from the design proposal can directly test the effect of BDEs on the guest experience of the rooftop dining space at the hotel and evaluate the natural elements in the rooftop space to deliver an exceptional luxury hospitality experience. Moreover, the proposed design can serve to enhance the practice of BD for rooftop restaurants throughout hotels across the city of Alexandria. To make it even more applicable to the real world, the major findings were identified and operationalised into practical design solutions including the examples, including the incorporation of a connection to the seating areas, the maximum utilisation of daylight via skylights, and utilising local materials, to be used by scholars researching in the field and practitioners in the hospitality industry alike.

The selection criteria will include a restaurant that is located on the rooftop of the Four Seasons Hotel and others that have a direct connection with nature, examining Stephen R. Kellert six principles of biophilic design: environmental features, natural shapes and forms, natural patterns and processes, light and space, place-based relationships, and evolved human–nature relationships. A design approach for guests is presented, with a focus on enhancing sustainability practices that utilise all aspects of the rooftop concept, design development, and zoning to strengthen the environmental attributes and capture guests’ preferences and feedback [59]. In addition to combining the fundamentals of Nature Preference Theory (NPT) and DCT with what experts say with what guests think from the mixed-methodology approach, this selection criterion forms a reliable base to bring biophilic ideas to interior design [60]. With a scarce precedent in the region, the proposed rooftop biophilic solutions focused on cost-effectiveness, flexibility, and compatibility with existing buildings. The considerations of experts and user surveys prescribed minimum structural interventions. This hands-on project enhances transferability to other hospitality settings, particularly in growing cities.

4.1. Study Area

The Four Seasons Hotel Alexandria at San Stefano lies in the heart of Alexandria, Egypt. It stands as a luxurious seaside base, located within a 10-minute walking distance of the Royal Jewellery Museum. The Library of Alexandria is approximately 9 km away, and the historic Lighthouse of Alexandria is located approximately 12 km away. Travellers seeking relaxation alongside cultural discovery will find perfection in the Four Seasons Hotel Alexandria, situated directly on the Mediterranean coastline. From every corner of the hotel, guests can enjoy panoramic beach views since the establishment rests directly along the seafront. Refer to

Table 7. Study Area.

Site	Case Study Photo	Rooftop Spatial Features
Four Seasons Hotel (5-Stars Hotel)

, which shows the selected study area. The hotel offers refined accommodation, relaxation, and Mediterranean cultural experiences, along with a variety of amenities, including four refined restaurants, three sophisticated bars, and a relaxed café. Guests enjoy four upscale dining options, all with breathtaking views, without the need for a separate rooftop dining space.

4.2. On-Site Observation

The on-site observation of the selected case study restaurants is conducted to capture details of any rooftop restaurants included, as outlined in Stephen R. Kellert’s six principles of biophilic design: environmental features, natural shapes and forms, natural patterns and processes, light and space, place-based relationships, and evolved human–nature relationships [18,30]. See

Table 8. On-site observation to study area.

	Spatial Features	BDEs	BD Features
Kala Restaurant	Situated on the third floor, Kala Restaurant provides diners with views of the Mediterranean Sea, allowing natural light to enhance the dining ambiance.	Environmental Features	The restaurant achieves its coastal theme through blue accents and palm plants which provide a relaxing environment.
		Light and Space	Extensive views of the sea establish the main linkage to nature which brings natural lighting into dining spaces to improve the dining experience. The biophilic principle of bringing nature into architecture finds expression in the building design through Mediterranean Sea view windows.
	Bleu Lounge has an outdoor space “terrace” where guests can enjoy views of the coastal nature. Bleu Lounge strategically integrates biophilic design elements (BDEs) to deliver an authentic Alexandria beachfront experience for its guests.	Environmental Features	The built-in contact with natural elements creates stronger sensory reactions which accede to the principles of biophilic design.
		Light and Space	An open interior architectural design at the lounge provides maximum access to natural light, where sunlight streams easily into the space. Its open-air venue delivers functional lighting conditions that strengthen guests’ connection to outside elements and enhance the feeling of the sea breeze and hearing Mediterranean sounds beneath the natural daylight.
		Natural Shapes and Forms	Bleu Lounge stands out through its naturally inspired, curved seating arrangements, which harmonise with the organic elements of nature. The round and flowing seating configurations create physical and emotional connections which enhance both quality and social interactions.
		Place-Based Relationships	The interior design concept at Bleu Lounge draws from city flair natural materials and design elements.

, which shows the on-site observation study area. These observations are made on photographs and notes. Due to this detection, the potential and shortcomings of restaurants in hotels were brought to light in terms of biophilic design. Hence, the physical environment plays a significant role in consumer psychology.

The presence of two dining venues, Kala Restaurant and Bleu Lounge, delivers guests extraordinary food service experiences that reflect Alexandria’s seafront charm, even though they do not rest on the rooftop. Kala Restaurant and Bleu Lounge are open-air, technically rooftop in their structural positioning, and exist in a simulated rooftop environment. Their inclusion demonstrates a limited number of BD venues dedicated solely to rooftops in Alexandria, providing meaningful insight into BD in elevated hospitality spaces. Kala Restaurant, located on the third floor, showcases locally sourced seafood in a family-friendly setting, where guests can admire Mediterranean Sea views from its elegant surroundings and savour the authentic taste of Alexandria’s culinary heritage. The restaurant spaces present woodwork and ornamental ceilings that contribute to a grandiose atmosphere. Extensive sea views provide natural light to the dining areas and serve as the primary connection to nature in the space. The exposed Mediterranean Sea view aligns with biophilic principles that require built environments to blend outdoor natural settings into interior architectural solutions.

While Kala Restaurant may not be utilising the six BD patterns developed by Kellert, the interior architectural design of Kala incorporates a thoughtful integration of natural views, elements, and materials, as seen in Table 8, Photos 1 and 2. This contributes to BDEs, fostering a connection to the natural environment.

Bleu Lounge operates as an outdoor space adapted from the hotel’s design, evoking the special essence of Alexandria’s ambience, as seen in Table 8, Photos 3 and 4. Guests at Bleu Lounge can savour sunset beverages in a location that showcases the Mediterranean Sea view and features a waterfall. Multiple biophilic elements appear throughout the lounge’s structures. Water moves naturally through as a biophilic component because it creates both auditory and visual elements that clients appreciate. Outdoor guests engage with natural elements because the lounge exists as an open-air establishment that connects people directly to local sea breezes and sunlit surroundings. The lounge maintains a biophilic atmosphere through its existing features, although there are no details about the use of natural elements and vegetation.

In summary, the hotel lacks a dedicated rooftop restaurant; however, it offers several restaurants that provide remarkable views across various sites. Both Kala Restaurant and Bleu Lounge offer connections to nature through their design and location. Kala offers guests sea views alongside natural lighting features, which comprise its BD and Bleu Lounge, creating a biophilic experience through its outdoor elements and water features.

4.3. Experimental Design

Exploring BDEs within rooftop restaurant interior spaces constitutes a significant example of human–nature improvements [28]. In this context, the design proposal is based on interior architectural solutions that deliver strong experimental control; thus, researchers modified the rooftop area within the hotel plan by exploring BDEs within rooftop restaurant interior spaces. The study employed reflective measurement items copied from earlier research to ensure validity in the study framework. This experimental design proposal combines the outcomes of both qualitative and quantitative approaches, drawing on the experiences of experts and the feedback of guests, to demonstrate that BD is a worthwhile way to enhance the well-being, cultural relevance, and sustainability of rooftop spaces in hospitality. Aligning the theoretical concepts of Nature Preference Theory and DCT with the mixed-methodology approach to move toward practical uses, a strong basis for using biophilic ideas in interior architectural design of rooftop restaurants is revealed, providing useful guidance and tips, with a focus on design, using suitable materials, landscaping, and cultural styles, for improving resilience and quality of rooftop restaurants for architects, hoteliers, and planners.

The experimental design proceeds through two distinct phases: the Conceptual Design phase, followed by the Schematic Design Phase. Each phase of the design process drew from the Promoting Brand Identity objective and the intentions of guest satisfaction, as well as consent to NPT and DCT, aligning with sustainability metrics and an environmentally friendly image. These guidelines, along with supplementary considerations, help designers incorporate nature in the design of the spaces that merges creative ideas with scientific principles.

The conceptual design phase is where the thoughts and ideas are translated into sketches. The design proposal concept during the preliminary stage draws inspiration from sea waves, concerning the hotel’s location and Alexandria as a Mediterranean city, which defines environmental goals through natural design elements. See

Table 9. The concept inspiration from sea wave for the design proposal.

The Conceptual Design Phase

which shows the inspiration from sea waves. This natural metaphor enabled the creation of the design proposal and relied on both static and dynamic elements of aesthetic quality, such as peace and balance, alongside fluid interior components within the rooftop restaurant. Such integration of local cultural references and environmental characteristics not only contributes to the maintenance of the space identity, but also results in a closer emotional bond with both visitors and local people. Context creates sensitive design approaches that increase the complexity, resulting in better overall acceptance and success of hospitality environments. This creative inspiration to design solutions had a positive impact on interior design suggestions, leading to the brainstorming of seating zones and furniture selections [61].

The Schematic Design phase is where the conceptual design approach turns toward a variety of cuisines and languages. However, the language is unclear. This phase is conducted to offer goals and explore solutions through interior planning and furnishing, ending with a biophilic 3D rooftop restaurant. A flexible zoning system emerged through the application of rational thinking to restaurant requirements, facilitating compliance with the requirements and facilitating the creation of the organisation. A linear circulation system fits the space’s rectangular configuration properly. The selection of furniture depended on the number of blocks, the intensity of use, and the placement and arrangement of furniture, and faces a choice between compromising aesthetic quality and ambience scenes, along with transparency control, which affects the connection between the interior and exterior.

Refer to

Table 10. Table 10 illustrates the experimental design proposal as the practical implication for the study.

BDEs	The Experimental Design Proposal
Environmental Features
Natural Shapes and Forms
Natural Patterns and Processes	.
Light and Space
Place-Based Relationships
Evolved Human–Nature Relationships

for the experimental design proposal, which outlines the practical implications for the optimising of features in BDEs, vertical gardens, and walls that contain ferns, ivy, and succulents, as well as lower vines, which are expressed as a combination of greenery and water features as focal points, alongside visual display fields, which occur either vertically or horizontally to establish clarity while also generating interest through natural and artistic elements, as well as furniture layout and organisation. As seen in Table 10, the indoor–outdoor flow, paired with plant life, water elements, and other natural elements, will lay the foundation for a design that aligns with a biophilic application in restaurants and hotels, offering unique advantages. The achievement of the interlock and overlap between lines, as accessing forms is easily signified, is characterised by high fluidity and harmony. The final restraint involved partitions as researchers attempted to eliminate the differences between the regular geometry of a given interior space.

The study of natural patterns and processes in BDEs included natural materials and textures interventions, as seen in Table 10. The combinations of wood panelling, stone floors, and expansive glass elements will provide guests with an authentic experience of natural surroundings. The Natural Shapes and Forms in BDEs are strengthened through furniture choices that include wooden tables, along with chairs and lounge seating areas. The design proposal incorporated recycled and sustainable elements, including bamboo furniture and locally sourced stone, to minimise environmental impact.

Natural and artificial lighting provided a strong sense of light and space in BDEs [28], as shown in Table 10. Natural lighting during the day and ambient lighting at night, combined with panoramic views and natural ventilation, create a sense of rhythm and well-being for guests in ways that align with BD’s principles of matching building environments with natural cycles. The extensive open design of the proposal merges natural spaces with artificial structures to create an environment where landscapes appear to blend seamlessly into architecture. The outdoor foundation gives patrons full Mediterranean Sea vistas while keeping guests in direct contact with their coastal surroundings. The unobstructed nature of this space allows guests to observe endless horizons, perceive the fresh sea air, and hear the water elements in motion. Different seating levels within the design expand spatial interaction since they create multiple viewpoints that direct users to explore and experience both built spaces and natural surroundings.

See Table 10 for optimising a place-based relationship. The design proposal included palm trees, bamboo, and lemon trees, as they provide rooftop shade and a sense of peacefulness. Surfaces featured symbolically rich, curved formations that delivered comfortable areas for enjoyment, accompanied by creative forms inspired by originality and novelty, which maintain evolved human–nature relationships.

5. Discussion and Conclusions

The research findings explained the approach of BD for the interior architecture design of rooftop restaurants since they operate primarily outdoors. The study presents schematic guidelines derived from the research outcomes of NPT and DCT combined [29] in terms of BDEs, which include significant components such as lighting, air, water, plants, shapes, colour, and supportive gardens [28]. Moreover, the mixed-methodology approach, which combines both qualitative and quantitative methods, yields strong biophilic strategy results. These findings are relevant to the literature review on physical designs, informed by an experimental design approach that links scientific linear thinking with design artistic elements [62]. The researchers generated a design proposal that modified the rooftop area within the hotel plan by conducting a strong experimental exploration of BDEs within rooftop restaurant interior spaces to create sustainable environments that support hotel owners and guests.

The research implies that these meaningful natural elements create a better perceived value for customers. Rooftop restaurants benefit from this perspective, as their tiered structures provide an ideal setting for sustainable design features that include organic garden styles, combined with potted plants and vertically translated facade installations, along with natural landscape integration [28]. The documented therapeutic effects of plants culminate in creating superior experiences for their guests. Restaurants that rely exclusively on views or sunlight should adopt vegetation features that researchers consider more likely to create beneficial emotional responses that align with guest identity, while potentially boosting revisits [55]. These findings align perfectly with rooftop restaurants, especially in the hotel industry, as they demonstrate how green elements represent an essential design element that can be implemented through garden layouts, potted plant choices, vertical wall plantings, and natural landscaping elements [60]. Through verified evidence of plant-based relaxation and pleasure, rooftop dining spaces can create superior dining environments for their customers [39]. Customer experiences benefit most when vegetation replaces standard view-based or sunlight-based decorations, as plants produce more positive emotional effects and align with guest preferences [57].

The research also made clear that design, together with lighting and colour, works as a strong determinant in moulding guests’ emotional reactions. Restaurants located on rooftops should utilise open-air dining, complemented by mood-enhancing lights and earth-toned colours and blues, to create a sense of safety and comfort for their guests [30]. Rooftop dining perception is elevated through a combination of warm lighting bulbs, natural materials, and biophilic-themed decorative elements that create a relaxing and fully immersive dining atmosphere.

Rooftop restaurant establishments that achieve aesthetic perfection with integrated natural elements will boost the per-guest revenue they earn by providing comfortable, aesthetically pleasing, and relaxing surroundings [10]. Local materials, patterns, and motifs should be used to fortify the authenticity and cultural resonance of the rooftop restaurant design. These factors not only contribute to the spatial identity, but they also foster an emotional attachment in its users. Context-sensitive design strategies improve not only the outcome of guest satisfaction but also sustainability. Sustainable research indicates that designers need to produce fresh solutions that minimise the impact on the hospital-sector users, who are likely to modify their behaviour and preferences [5]. BD succeeds as an effective solution because it requires both adaptability and context specialisation [63]. A rooftop restaurant interior design should integrate user-oriented principles by taking into account seasonal factors, local plants, and diverse sensory elements such as aromatic herbs, leaf movement, and organic textures. Hotel brands can enhance guest loyalty by creating environments that cater to people’s desire for natural experiences and private retreats [55].

The study concluded that BD featuring greenery presents itself as a strategic business opportunity for rooftop restaurants, as it delivers improved customer experiences alongside an increase in social outcomes. The outdoor environment, such as rooftops, allows for the implementation of research-based, practical methods, which produce meaningful impacts [50]. As such, plants had an improvement on guests’ quality of life. Moreover, the current study demonstrated that the attributes of BD are vital in driving a positive consumer response. Moreover, training programs, stakeholder engagement, and awareness campaigns should accompany design processes to support the consistent and sustainable application of biophilic principles, reflecting both expert guidance and user expectations.

6. Limitations for Future Research

In the study we conducted, several limitations are noted in order to provide useful suggestions for future investigations in sustainability and biophilic design for hospitality spaces. Future studies should adopt a comparative case study of various rooftop dining settings and different geographic contexts. The value of the study lies in its thorough examination of the biophilic interior approach to creating rooftop hospitality spaces; however, the use of an exclusive case study on a luxury hotel setting imposes limitations on the study. The guest design profile of a luxury setting might lean more towards a design-conscious and receptive audience, and this likely affected the attitude beyond the knowledge of the study regarding user experience and revisit intention. Nonetheless, future scholars could work to extend the methodology to further hospitality typologies and areas, as well as to incorporate more diverse perspectives from users, which combines specific applications. Furthermore, it is important to investigate scalable, flexible, and cost-effective biophilic strategies that can facilitate practical implementation under varying operational and environmental conditions. These future directions will promote the real-life applicability and generalizability of the framework to a broader hospitality design setting. According to the Theory of Planned Behaviour (TPB), individuals’ behavioural intentions vary across cultures and within different organisations [64]. For this study, data from guests were collected at one specific time using a cross-sectional design. Therefore, it is unable to show which factors have a direct impact or will continue to do so in the long run. Long-term research could better explain the ways BD influences guests over a period. Future longitudinal studies should be conducted in order to monitor how behaviour changes and experiences outcomes over time, as well as intervention-based studies that can provide a proximate understanding of how BD can have a long-term positive effect in hotels. In the context of understanding how nature and architecture are combined, biophilic design is key. This study, however, overlooked how technologies could enhance this approach. Additional studies should investigate virtual and augmented biophilic experiences, as noted by [65], who observe that generative AI and new technologies are having a significant impact on hospitality design and customers’ interactions within hotels. Additionally, since these participants were staying at a luxury hotel, the results may be influenced by the socio-economic background of the individuals staying there. More varied sampling from all demographics is required to determine the attitudes of various market groups toward BD, which would help examine consumer behaviour towards BDEs.

In addition, even though BD is about mental and physical well-being, it does not always consider physical access and social inclusion. Accessibility, inclusivity, and social equity are guaranteed by the UD principles. Works like the BD Matrix from [66] confirm that much of BD and Universal Design (UD) use are incompatible, if their focus and aims are not the same. Using colours and UD helps create a pleasant, relaxing, cohesive atmosphere, even if the focus, methods, aims, and approaches are not the same. This proves how best to utilise BD for inclusive goals, affecting guest intentions, mainly among those with physical, mental, or sensory challenges. Future studies can also be improved with using subjective user responses (e.g., survey of satisfaction, interviews, and perception of well-being measures) combined with the objective (e.g., behavioural observation: time of stay, locomotion, and usage frequency, and emotional responses: heart rate variability, skin conductance, and facial expression analysis) to capture the entire picture of the BD intervention impact. This should be examined with participants across a variety of geographic locations and hotel types in order to broaden the findings and confirm the relevance of BD strategies in different contexts.