Optimizing Cancer Care Environments: Integrating Indoor Air Quality, Daylight, Greenery, and Materials Through Biophilic and Evidence-Based Design

Abstract

The current study evaluates how effective the integration of evidence-based design (EBD) and biophilic design (BD) principles are in cancer healthcare environments. This study takes a step further from current biophilic applications in architecture and sheds light on the crucial role of material selection in improving patient well-being through improved indoor air quality (IAQ), natural light exposure, greenery, and material selection. To this end, a case study observation and semi-structured interviews with healthcare professionals and architects at King Hussein Cancer Center are conducted to develop a comprehensive design guide to help healthcare architects and designers implement environmental solutions tailored to patient needs. This study contributes to the growing body of research in healthcare environmental design and highlights the need for cancer-specific environmental design in therapeutic settings.

1. Introduction

Healthcare quality is a global concern that shapes health policy. According to the World Health Organization (WHO), health is not only the absence of disease or infirmity but aiming for complete well-being [1]. Building on this, scholars emphasize the importance of therapeutic environments, suggesting that the characteristics of the physical setting in which a patient experiences healthcare significantly influence the period of recovery or the adaptation to specific acute and chronic conditions [2,3,4,5].

Stemming from the EBD principles that improve healthcare settings through scientific evidence [6,7], healing environments extend beyond medical treatments; they must also support the psychological, emotional, and social needs of patients, families, and staff [8,9].

Recent trends in promoting therapeutic environments have led to a proliferation of studies that address the role of natural elements in healthcare settings to promote support for both physical and psychological recovery [6,8]. In their seminal work, Laursen et al. [10] stressed that the environment significantly influences patients with chronic illnesses who frequently attend hospitals. Therefore, effective health environments should consider such impact of the built environment, necessitating the selection and implementation of an appropriate theoretical framework to establish reliable evidence for its design, thereby facilitating the development of more effective health interventions.

Several theoretical attempts have been made to link the built environment to health and well-being. Preliminary theoretical work was undertaken by Ulrich [3], where the author demonstrates that patients with views of green spaces experienced shorter hospital stays and required less pain medication. Adopting this line, Stress Reduction Theory (SRT henceforward) [6,11] was developed in 1991 to elucidate the impact of natural elements on mental and physiological responses. The SRT adopted the biophilic hypothesis [7,12] and stressed that interaction with nature improves concentration and satisfaction [13]. The “biophilic design” (BD) approach is then developed as a framework for integrating natural patterns and processes into the built environment [7]. The BD approach suggests that greenery design helps patients with chronic illnesses in reducing psychological distress [14] and enhancing mental health [15,16]. Evidence-based design (EBD henceforth) [17,18] has also developed as a methodology for the design of healthcare facilities. The primary focus of EBD is the utilization of scientific data to enhance healing environments [19,20]. Similarly, the concept of “healing gardens” of [21] is delivered as an environment that promotes stress reduction and improves well-being via multiple restorative mechanisms. Along the same lines, Attention Restoration Theory [22,23] and therapeutic landscapes [24] all contribute to human attraction to nature and form the basis for understanding how healthcare environments influence health.

A few important themes emerge from the aforementioned evidence so far: First, the impact of built environment elements on physical recovery and improving comfort is now theoretically well-established [25]. In this vein, the aforementioned theoretical framework ascertains that those social and environmental factors, aside from physiological aspects, can enhance health when utilized effectively. Natural lighting, adequate ventilation, soothing colors, and BD contribute to stress reduction and improved emotional resilience. However, very few researchers utilized these in research questions, gathered data regarding the built environment’s effects on individuals in particular contexts, or reported findings. In fact, the research would have been more relevant if diverse populations and locations had been explored. Among the limited empirical studies, Blaschke [26] noted that the nature-based design improves the treatment experience of cancer care settings by providing access to natural elements indoors and through the outdoor spaces. Blaschke et al. [27] also recommend the natural elements recommended by patients themselves as a source of psychological comfort and a renewed sense of control during treatment.

Second, a notable limitation identified in the literature is the insufficient understanding of the specific mechanisms by which natural materials, natural colors, and biophilic elements affect human well-being in various environments. Tekin et al. [28] indicated that, although these features are classified as third-level priorities, it is essential to investigate their integration’s effects on cognitive, emotional, and physical responses across various contexts, including healthcare, education, and workplace environments. Most of the research on this vein has been mostly restricted to prioritize fresh air, light, and greenery. However, it has have not dealt with how patients room finishing material interact with these factors in such sensitive environment as cancer treatment environments. In fact, these studies would have been more interesting if they had examined the cost-effectiveness, scalability, and cultural adaptability of these features. Doing so will contribute to the practical implementation to facilitate user needs and sustainability objectives, and thus enhance recovery and optimize patient outcomes.

Last and most significantly, very little research has been found that surveyed the influence of built environment and health in one of the most serious health challenges of the twenty-first century: cancer ranking as the second highest cause of death globally [29]. An individual who has been diagnosed with cancer has not only the physical difficulties, but also the psychological and social complications which are associated with it [30,31,32]. Depression, anxiety, and adjustment disorders are among the conditions that are identified the most frequently [33,34]. It is important to note that approximately 30–35 percent of patients experience difficulties with their mental health while they are undergoing treatment for cancer [32,35]. Given these challenges, it is essential to explore environmental interventions that can mitigate the psychological burden of cancer.

As mentioned, interaction with natural environments would help in pain relief, reduced medication use, lower blood pressure, and faster recovery [26,36]. Furthermore, biophilic elements enhance emotional and cognitive well-being, alleviate stress and anxiety, and improve mood [15,37,38]. These aspects are especially crucial for cancer patients, who often undergo prolonged treatment with psychological distress, fatigue, anxiety, and depression.

Despite the increasing body of research related to therapeutic environments and BD, significant questions remain unanswered. First, what is the role of material selection and its influence on indoor air quality (IAQ), infection control, and patient comfort? The role of elements such as light and greenery is now well-established [39,40]. What influence material selection in therapeutic environments has remains unclear. Second, the extent to which the material selection as well as the natural elements help cancer-specific therapeutic environments, where patient needs vary by cancer type and treatment stage. Last but not least, existing EBD frameworks does not fully provide strategies for integrating BD principles into such sensitive environment as cancer treatment environments.

Against these backdrops, the paper attempts not only to validate the interaction be-tween BD elements (including air quality, daylight, greenery, and materials), but also the usefulness of such factors on the sensitive case of cancer patients’ well-being. The specific objective of this study is stemmed from two critical research gaps. These gaps covered the underexplored role of material selection in enhancing other biophilic elements in cancer centers. Moreover, it shed light on biophilic strategies based on cancer type and stage, providing insights into how several BD principles can be optimally integrated into healthcare settings especially on the unusual physiological and psychological needs of cancer patients.

To this end, a multi-method approach is utilised, integrating literature review, case study, and stakeholder interviews as detailed in the Section 3.

2. Literature Review

A growing body of literature has acknowledged the importance of the surroundings natural diversity (including, among others, the presence of natural sunlight, colorful plants, and a quiet setting) in promoting patient’s recovery [41].

BD is an important aspect of the therapeutic resources for cancer care environments specifically [24,42,43,44]. As noted by Tekin et al. [23], biophilic elements alleviate psychological stress and improve the patient-family experience. The results of surveyed sample drawn from Maggie’s Centers, which is designed specifically for cancer care, clearly highlight the centrality of nature-based strategies in cancer-focused architectural design. Similarly, in the study conducted at Sir Robert Ogden Macmillan Cancer Centre, Peters [8] highlight that the chemotherapy spaces center suggestively reduce photosensitivity and dizziness, offering calming natural views.

In their review of the studies that pronounced the beneficial effects of nature contact on immunity, Andersen et al. [45] conclude that nature contact may enhance the healing process for cancer patients. Equally, Blaschke [26] stressed the role of the natural contact in supporting resilience and stress reduction among cancer patients.

Ebaid [46] conduct a survey in two cancer centers in France and the Czech Republic and advocate to the role of BD in cancer healthcare facilities as it imposes health and comfort benefits for cancer patients of all ages, genders, and backgrounds. The study recommends a prioritization framework for BD interventions to enhance the design of cancer healthcare spaces, and thus to better address patients’ needs and improve their healthcare experience. The author, however, focus only on one category, namely “Nature in the space”, as a component of the 14 BD patterns [47]. Kellert and Calabrese [48] make attempt to extend BD beyond the mere presence of “Nature in the space”. Their work tends to cover three dimensions and 14 patterns arguing that neglecting these dimensions’ risks oversimplifies the potential of BD in healthcare contexts.

Few studies incorporated the benefits of biophilic architecture in healthcare organizations (hospitals, health centers) in general, and even fewer addressed the impact of incorporating the nature in the space design from the patient’s perspective for specific types of care, such as cancer facilities, resulting in a lack of implementation guidelines [28,46]. In addition, most of the research on Biophilia in healthcare regarding stress and comfort was conducted in the medical field and focused on measuring patients’ psychological responses. However, no research has established a systematic framework for implementing nature in architecture design patterns for cancer facilities from patients’ perspectives. Although some studies explored biophilic elements in healthcare [3,11], very few have addressed systematic frameworks for cancer facilities specifically.

From an alternative viewpoint, BD is more than just documenting all the requirements that can bring us into contact with nature or researching the specifics of designing with natural elements. However, the incorporation of natural components in general is not exclusive to BD; in fact, many of these factors are required and monitored in every design guideline. To achieve BD, the space must be able to accommodate the required criteria in a way that is harmonic for the user groups that are being targeted. The design of a biophilic garden encompasses more than just the presence of oxygenated fresh air; it also involves the presence of plants, water, and animals, besides the smells, freshness, colors, noises, textures, and sentiments that are evoked, such as a sense of mystery, prospect, refuge, or even danger. For cancer patients, such sensory dimensions of BD may enhance coping mechanisms by offering spaces of refuge and psychological restoration [49].

Existing BD frameworks lack effective advice, as their design guidelines do not distinguish the importance of each design parameter related to specific building programs and environments. BD frameworks can only be effective if customized to specific building purposes and contextualized geographically and culturally [50]. As Kellert et al. [47] argue, biophilic guidelines must be adapted to cultural and clinical contexts to achieve meaningful impact.

To promote and enhance health and well-being in cancer hospital settings, Tekin, Corcoran, & Gutierrez [28] delineate and prioritize the most significant BD characteristics. Their hierarchy of significance indicates that fresh air, light-sunlight, and greenery are paramount BD elements for users; thus, a designer cannot designate a space as biophilic if it lacks any of these essential parameters. Hung and Chang [51] established the concept of BD in healthcare centers and its relation to the sustainable development goals (SDGs) to support this finding [52]. They claimed that both Goal 3 and Goal 11 receive significant support from BD, while other goals also gain advantages from its implementation in various cases. Zhong et al. [16] also defined some priorities (such as air flow, daylight, plants, and landscape) in BD which can help reach many long-term goals in the SDGs. The data presented in

Table 1. Biophilic design and SDGs.

BD Elements	SDG 3: Good Health and Well-Being	SDG 11: Sustainable Cities and Communities	SDG 13: Climate Action	SDG 15: Life on Land
Fresh Air	Improves respiratory health, contributing to overall well-being.	Promotes healthier environments through improved air quality in cities.	Improves air quality and reduces need for energy-intensive air-conditioning.	Promotes sustainable urban environments through green infrastructure.
Light-Sunlight	Regulates circadian rhythms, improves mood, and supports faster recovery.	Natural lighting reduces energy use and supports sustainable building design.	Lowers carbon footprint by minimizing the need for artificial lighting.	Reduces environmental impact through energy savings.
Greenery	Reduces stress and enhances mental well-being, speeding up recovery.	Green spaces improve urban biodiversity and provide restorative environments.	Green infrastructure contributes to climate resilience.	Supports biodiversity and ecosystem health within and around healthcare environments.

are adapted from [51] and expanded with insights from [28] and the SDG’s that were essentially comprising fresh air, light-sunlight, and greenery as the most Relevant BD Elements in healthcare environments.

Although the aforementioned priorities aligned with sustainable development goals, they require further testing within cancer-specific healthcare contexts. Generally, hospital design for medical and non-medical spaces can help improve a patient’s recovery situation and well-being, as well as relieve staff stress [53]. Architectural structures, including both interior and exterior design, should consider such visitors’ needs to create a positive experience [54]. In cancer facilities specifically, such design considerations are critical as material choice and interior finishes directly affect infection control and patient safety.

Interior design features for healthcare well-being and healing include medical and non-medical furnishings. The finished materials and color schemes of the patient’s room have an impact on their healing and well-being [55]. Ulrich [56] analysed the power of flooring materials in healthcare settings on patients’ comfort. For immunocompromised cancer patients, selecting antimicrobial and hypoallergenic materials becomes not only a design choice but a medical necessity.

Joseph and Rashid [54] examined the associated materials, products, and chemicals used. The research pushes for moving toward a more sustainable approach, which could have a better influence on all stakeholders, including users, suppliers, and even the local community.

Kokulu and Ozgunler [57] showed the influence of building and interior design on the experience of patients. The transition to green materials encounters challenges through assessing materials’ specifications as green materials [58,59]. It is well-proven that interior design not only affects the patients’ experience, but also that of their families and friends when visiting patients in their hospital room [60]. Pradinuk [61] defined a green material as having green chemicals with 12 principles of green chemistry in production, without toxic chemistry, and being healthy to both people and nature.

Ismaeil and Sobaih [62] developed an assessment tool for enhancing the healing environment in healthcare buildings, especially interior finishing materials, based on sustainability standards to help decision-makers, interior designers, and client committees to identify the compatible interior materials’ specifications with the healing and non-infection environment to create a better experience for patients, staff, and visitors.

Kokulu and Ozgunler [57] concluded that the most suitable materials for human health were determined as the following: marble from natural and artificial (concrete) stone-based materials, natural wood from wood-based materials, aluminum from metal-based materials, polypropylene from polymer-based materials, and glass from terracotta-based materials.

In summary, the existing literature underscores the therapeutic potential of BD in healthcare settings, with consistent evidence for the benefits of IAQ, daylight, and greenery. However, three critical limitations remain: first, the role of materials is rarely integrated, despite its direct relevance to air quality, infection control, and patient comfort; second, few studies specifically address cancer care environments where patients’ needs vary by cancer type and treatment stage; and third, existing frameworks, such as the 14 patterns of BD [47], are often applied in a generic manner without contextualization to oncology settings.

Collectively, the presented evidence provides important insights for new research to validates and ex-tends core biophilic principles to cancer-focused healthcare environments, thereby sup-porting evidence-based, patient-centered design guidelines.

3. Research Methodology

The present study take advantage of integrating literature review, case study, and stakeholder interviews (multi-method approach) to shed light on how several BD principles (including air quality, daylight, greenery, and materials) can be optimally integrated into cancer patients’ well-being.

King Hussein Cancer Centre (KHCC) (Jordan’s largest oncology facility) in Amman, Jordan, is considered as a case study where the study conducted over the period between June 2024 and October 2024. The significance of the KHCC stemmed from its worth in the region as an innovative center for cancer treatment.

In order to evaluate the environmental features (IAQ systems, daylight access, greenery presence, and finishing materials used across the buildings) a customized checklist during the observations stage. Furthermore, during this observation stage field notes were collected alongside a spatial analysis of floor plans and photos with a particular attention paid to BD integration and spatial flow. The data were then synthesized thematically to evaluate the alignment between observed features and the principles of BD and EBD.

Next, the semi-structured interviews used to identify themes such as environmental comfort, patient needs, and biophilic priorities.1 A total of 12 participants, including 5 architects, 4 oncology healthcare providers, and 3 hospital designers were selected via purposive sampling based on their expertise in cancer facility design. During the scheduled interview (last for 30–45 min), the participants were asked how BD elements are perceived and prioritized across different cancer types and care con-texts.

The constancy of the findings is further enhanced by integrating the results of these stages with the data drawn from the literature review. Put simply, the results from observations stage were cross-validated through interview insights, and literature findings informed the interpretation. To control for bias, member checking was conducted with two participants to validate key themes. Finally, reflexivity was maintained throughout the analysis.

These results will provide further support for the development of design guidelines for cancer treatment centers in Jordan. These guidelines will focus on integrating both EBD and BD principles to create environments that enhance patient well-being through improvements in air quality, daylight, greenery, and materials.

Study Setting

The KHCC, Figure 1, contains three buildings built on an area of 108,700 sqm. The oldest building, known as the Nizar Al Naqeeb Building, was completed in 1997 as the main facility for KHCC that provide outpatient services and handle specific administrative tasks.

Twenty years later, two towers were initiated to enhance amenities and clinics. Namely; King Salman, established by King Salman bin Abdulaziz Al Saud, is a 14-floor inpatient tower dedicated to rigorous cancer treatment. Whereas Sheikh Khalifa, initiated by the Sheikh Khalifa Bin Zayed Al Nahyan, is a 12-floor outpatient tower serve as an educational center and houses Jordan’s first public stem cell and cord blood bank.

With around 7000 new patients being served annually, hospital admissions reaching a total of 14,000 cases and an estimated 250,000 outpatient clinic visits each year. Among KHCC’s these three buildings, the inpatient and outpatient towers most clearly exhibit BD features, as they both were inaugurated in 2017.

4. Results

4.1. Analytical Study

The first set of analysis highlight three essential BD elements prioritized by users. These elements include: fresh air, light-sunlight, and greenery, as well as the natural materials affecting IAQ. For the purpose of the analysis, a comprehensive matrix was developed to assess how these elements aligned with both observed user behaviors and EBD principles.

A notable relationship among the mentioned elements is revealed. Of particular interest is that the strategic use of daylight enhanced the perception of nearby greenery in non-clinical areas although natural and hypoallergenic materials contributed to improving IAQ. Unsurprisingly, no greenery was installed within patient rooms due to strict infection control policies. Nevertheless, natural elements were incorporated into adjacent lounges and external view corridors, offering visual and psychological benefits without compromising clinical safety.

The proposed framework (in Section 5) will be further detailed the benefit of these elements in BD.

4.2. Case Study: KHCC

The therapeutic advantages stemmed from connecting patients to nature seems exceedingly apprehended while designing KHCC. The latter is clearly evident in the extensive incorporation of natural light, carefully selected materials, and the presence of greenery visible throughout the structures. The elements in question not only meant to enhance visual appeal, but it simultaneously contributing to the psychological and physiological well-being of patients. The center aligns its architectural approach with therapeutic principles through the integration of BD. This alignment is crucial to minimize stress, promote relaxation, and improve a sense of tranquility that is vital for patient recovery. This view was echoed by one architect by emphasizing that the orientation of patient rooms toward garden courtyards was deliberate; it changes how people heal. This was reflected in the integration of greenery in courtyards, window views, and patient lounges.

Observational data provided a tangible understanding of the interaction between the built environment and the needs of cancer patients, complementing the findings from literature reviews and semi-structured interviews.

4.3. Observation and Semi-Structured Interviews with Architects, Oncology Healthcare Providers, and Hospital Designers

The findings from site observations are presented below according to the four main BD elements: IAQ, daylight, greenery, and materials.

4.3.1. Indoor Air Quality (IAQ)

As shown in Figure 2, the KHCC buildings employ double-glazed windows measuring 12X10X12 mil with UV protection to create a visually comfortable environment for both patients and staff while preventing the entry of harmful outdoor air, allergens, and contaminants by prohibiting window openings. “We avoid any living plants in patient rooms; air filtration is a priority, and any volatile organic compounds (VOCs) source is a risk” explained one of the ventilation engineers.

To further ensure high indoor air quality, a central Particulate Monitoring System (PMS) is in place. This PMS is feed with the specific needs of patients based on their cancer type and treatment level to detects contaminants detects contaminants and adjusts the mechanical air ventilation. Beside the PMS, the facility maintains strict temperature and humidity controls to enhance comfort. Here, an advanced air filtration system is implemented to protect immunocompromised patients, particularly those undergoing chemotherapy. This filtration system effectively removing harmful particles from the air and reducing infection risks. At the same time, indoor plants are not permitted in patient rooms due to their potential to introduce infection risks and allergens, as well as their interference with the air filtration system through the release of VOCs. These systems collectively ensure a sterile yet comfortable healing environment, tailored to the immunological needs of cancer patients.

4.3.2. Daylight

Aligning with BD principles, the healing environment by providing ample natural light is also considered in the KHCC by incorporating skylights along the hallways (see Figure 3). The natural light positively influences patients’ moods, reduces stress, and supports mental health through in regulating circadian rhythms, aiding recovery, and boosting immune function. It’s also influencing patients’ moods by fostering a connection to the outdoors.

In contrast, blackout curtains are strategically placed in corridors to manage light exposure effectively, especially on the south-west façades that receive direct sunlight. Additionally, large windows in the family lounge, oriented towards the north-west, allow for indirect sunlight, creating a warm ambiance that minimizes reliance on artificial lighting during the day. The considerate design aimed to promotes a less clinical atmosphere and provides relaxing spaces that support both patients and their family.

4.3.3. Greenery

The building is designed with green views, as shown in Figure 4, particularly evident in the north-west elevation and through the entrances of both towers. This greenery helps in reducing stress and anxiety. According to BD research, exposure to greenery aids recovery by lowering cortisol levels, promoting relaxation, and enhancing immune function. In addition to green view, the healing garden, located on the east side of the center, serves as a vital space for both children and adults. This garden aimed at facilitating activities that benefit physical and mental health. In fact, engaging in activities like walking not only improves blood circulation but also alleviates muscle weakness associated with cancer treatments, while sensory experiences in nature provide a much-needed respite from the confines of therapeutic environments. To further enhance the atmosphere, colorful and green paintings adorn the corridors, offering an allergen-free alternative to potted plants. These natural artworks evoke outdoor experiences, aligning with BD. Blaschke [26] highlights the role of visual nature cues in reducing anxiety in immune-sensitive environments.

4.3.4. Material Selection

During the semi-structural interviews with the architects and engineers, they mentioned the high importance of the material selection of the interior design of the cancer centers. They also highlighted its strong relation with the indoor air quality and the efficiency of the daylight. Material selection at KHCC was guided by four main criteria: VOC emissions, light reflectance, antimicrobial properties, and sustainability.

The cancer center has been thoughtfully designed with materials that prioritize air quality and patient comfort, particularly for those with compromised immune systems (refer to Figure 5). Rockfon ceilings are designed to emit very low levels of VOCs, which is important for a good air quality in the cancer center where patients may have compromised immune systems. White Rockfon ceiling panels are crucial for reflecting daylight; they can reflect up to 86 percent of available light. Rockfon stone wool ceiling panels contain up to 42 percent recycled materials and primarily are made from abundantly available basalt rock [63]. The use of linoleum flooring, also low in VOC emissions, benefits from the natural antibacterial properties of linseed oil, promoting hygiene [64,65]. Additionally, cherry wood cladding contributes to thermal insulation and sound absorption, creating a quieter and more stable indoor atmosphere [66], while its low-emitting nature ensures safety for patients. Thanks to their a low VOC emissions and antimicrobial treatments, the modular carpet tiles further boost the hygienic environment through inhibiting bacteria and mold growth [67]. Besides the carpet, the cubical curtains are seen as antimicrobial and flame retardant. This help in reducing the risk of healthcare-associated infections [68,69]. Porcelain cladding, made from natural raw materials, is non-porous and resistant to stains and bacteria, while also reflecting light to enhance natural illumination and minimize reliance on artificial lighting. Lastly, Corian countertops, known for their versatility and non-porous surfaces, not only resist dirt and bacteria but also contribute to the overall aesthetic by enhancing natural light, thus fostering a dynamic and innovative interior space [70]. The selection of such materials illustrates a deliberate alignment between BD intent and EBD infection control measures.

4.4. Semi-Structured Interviews with Staff

The next stage involves conducting semi-structured interviews with oncologists, architects, and designers at KHCC. This interview aimed at gaining in-depth insights into how the spatial environment influences cancer care outcomes. Specifically, the aim is to identify how BD and EBD elements are perceived and prioritized across different cancer types and care contexts.

The main results are summarized as follows:

• Air quality: Lung cancer patients are highly sensitive to the air quality; in their early stages they might not feel as acutely affected by air quality and may prefer fresh air via windows or any outdoor access. However, in the late stages, patients become more sensitive to poor air quality. As a result, filtered and purified air would be more critical for comfort in these stages. Leukemia and immune-sensitive patients have compromised immune systems due to their treatment, making them more vulnerable to infections. Environments with very strict air quality controls would be preferred in late stages. “Late-stage patients often ask for purified air or specific room types”, one oncologist noted.
• Daylight: Skin cancer patients need to avoid direct exposure to sunlight due to increased sensitivity to UV radiation. Furthermore, interviewees mentioned that daylight exposure on breast cancer patients is closely linked to improved mood and reduced depression and anxiety. Both types in early stages may still be active in spaces that are directly exposed to daylight. In late stages, patients might be confined to their rooms; as a result, large windows with controlled daylight options and views of nature can have a positive impact on their mood and mental well-being. “For skin cancer patients, we designed rooms facing north or shaded areas”, explained an architect who was interviewed.
• Greenery: Gastrointestinal cancer patients experience a lot of stress and discomfort because of their overall physical well-being. Such symptoms are noticed in hematological cancer patients who cannot spend time in large communal outdoor spaces but could still benefit from visual engagement with nature. In early stages, patients are still able to walk through green areas or even past green walls to feel the connection with nature. Nevertheless, in late stages, where patients are bedridden, green views from windows are required. Some procedure rooms and some inspection rooms have green views on the ceilings to provide a sense of peace and emotional relief.
• Material: Interviewees confirm that patients with sensory sensitivities, such as neurological cancer patients and the bone cancer patients, experience pain, making them more sensitive to hard surfaces or uncomfortable furniture textures, especially in their late stages when they spend extended periods in bed or seated. Materials that are antimicrobial, non-porous, and visually warm are essential for improving the air quality.

These findings shed light on how the built environment interacts with cancer patients’ physical and emotional needs, considering on their type and stage of cancer. These findings form the basis for EBD recommendations aimed at creating therapeutic environments that address the diverse and evolving needs of cancer patients throughout their treatment journey.

5. Discussion

The current investigation contributes to the ongoing debate on the role of BD and EBD principles on the cancer patients’ healing environment. In this vein, prior studies have been widely apprehended several environmental factors as the IAQ, daylight exposure, greenery, and materials as key factors. The study distinguish itself by asking important questions about the importance of using natural materials in cancer centers. Further, how such materials have a strong connection with the other three elements. Another crucial question in this research involved the nuanced relationship between cancer type, disease stage, and environmental needs, highlighting the necessity for tailored biophilic strategies [14,15,16].

The results of this study demonstrate that early-stage and late-stage cancer patients have distinct environmental requirements. Also, the different types of cancer necessitate a more dynamic and patient-centered approach to therapeutic healthcare design. Another finding that stands out from the results is that IAQ is a fundamental component of healing environments, mainly for patients with lung cancer, leukemia, and other immune-sensitive conditions.

Patients in early-stage treatments expressed a need for clean and filtered air, which is extremely important for minimizing allergens and pollutants. On the other hand, late-stage patients, especially those undergoing intensive treatment such as bone marrow transplants, for example, require highly controlled IAQ conditions, including a HEPA filtration system and sterile environments, so as to minimize the infection risk [71,72]. These results corroborate the findings of a great deal of the studies. For example, Park and Mattson [36] found that improved ventilation and filtration significantly reduced perceived stress among cancer inpatients. Similarly, Blaschke [26] emphasized that patients undergoing immunosuppressive treatments are particularly vulnerable to airborne pathogens, highlighting the need for strict environmental control.

Compared to global benchmarks in EBD, the use of HEPA filtration and sealed room systems is not widespread. However, unlike some western hospitals that allow controlled natural ventilation in early-stage cases [37], KHCC adopts a more conservative policy due to regional epidemiological considerations, due to a combination of factors, including higher rates of certain communicable diseases, seasonal respiratory infections, antimicrobial resistance patterns, and variable environmental air quality.

This research also highlights the material selection role in IAQ management. It has been confirmed that the presence of low-VOC materials significantly reduces the indoor air pollution, supporting the previous literature that links material selection to respiratory discomfort and immune responses [62]. These results suggest that the IAQ should be customized based on cancer type and stage, to certify that patients receive appropriate environmental support.

Natural daylight promotes circadian rhythm regulation, psychological comfort, and patient recovery. Nevertheless, this study highlights the need for daylight exposure strategies based on the cancer type. For instance, breast cancer patients across all stages benefit from controlled daylight exposure, which is important to reduce their stress level and enhance their mood. Conversely, skin cancer patients require indirect daylight to minimize the UV risk; this highlights the need for shading devices and filtered light solutions [73,74]. Berman et al. [37] link exposure to daylight with cognitive performance and reduced chemotherapy fatigue. Furthermore, other factors, including the building orientation and window placement, are thought to be critical in optimizing daylight exposure, which supports EBD literature.

Healing gardens and indoor and outdoor green views seems to be an essential for stress reduction and emotional well-being. For instance, patients with gastrointestinal and hematologic cancers prefer spending their time in healing gardens so they can walk and interact directly with nature.

Consistent with the attention restorative theory, the findings suggests that contact with the natural environment enhances cognitive functioning and emotional resilience [22,23]. However, this study, based on the KHCC case study, highlighted the infection control challenges associated with greenery in cancer centers in general. For immunocompromised patients, direct physical interaction with plants was deemed high risk; in the KHCC case, plants had been replaced by artificial nature representations as an alternative BD strategy. DeJean et al. [38] found that virtual and artistic representations of nature can elicit similar relaxation responses to real greenery. These findings suggest that, in highly sterile environments where live plants are prohibited, integrating nature-themed artworks and access to exterior green views can serve as effective alternatives. Future healthcare designs, particularly in oncology, should consider the incorporation of virtual or representational forms of nature as standard BD elements to support patient well-being without compromising infection control.

Material selection in therapeutic cancer environments emerged as a crucial yet unexplored factor. It contributes to both sensory experience and health outcomes in profound ways. Some cancer patients experience some sensory sensitivities, especially those who are treated by chemotherapy; soft and natural materials provide comfort and a stress-relieving environment. Additionally, immunocompromised patients require antimicrobial, hypoallergenic, and easily cleaned materials, ensuring a sterile yet non-clinical atmosphere [62]. Moreover, the integration of natural textures and biophilic materials such as wood and stone, for example, enhance the patients’ psychological well-being, which reinforces the theory that a built environment should evoke a connection to nature [25]. The results of this research underline the need for evidence-based material selection which considers both functional and psychological aspects in healthcare design. Further, it underscores the need for tailored design strategies that account for differences in cancer types and treatment stages. Designers should move beyond generic healing environments and instead implement adaptable biophilic features to respond to the evolving physiological and psychological needs of oncology patients. Considering these findings, this research contributes new insights by demonstrating that the environmental interventions must be tailored based on cancer type and stage, and material selection plays an essential role in cancer patients’ recovery. Also, biophilic strategies need to extend beyond greenery to include sensory-friendly materials and adaptive daylight systems, as illustrated in the research guideline in Figure 6.

6. Limitations

While this study presents valuable insights, its results are limited by the KHCC case study with reference to other cases in different countries from the previous literature, which may restrict generalizability. Future research should conduct multi-cancer centers studies to validate the proposed design guidelines.

Another limit was not having interviews with patients due to KHCC policies, which may limit the depth of user experience insights. A future study may investigate long-term patient outcomes to assess the sustained impact of biophilic interventions. Future multi-center studies could compare BD implementation across diverse cancer contexts, besides considering cultural and climatic contexts.

To minimize potential knowledge bias, the thematic findings were re-evaluated by three independent experts from the architecture field who reviewed the interpretive themes. Their feedback ensured triangulation and reduced the influence of the primary researcher’s perspective. As a researcher in architectural design and healthcare, my interpretation of the data and my conclusions may be influenced by my professional background and my interest in environmental and spatial factors. The potential of biased is controlled through reviewing the results by experts from various fields. Furthermore, a systematic analytical approach was employed to ensure greater objectivity.

7. Conclusions

The main goal of the current study was to determine intersection of BD and EBD in the context of the cancer center healthcare facilities. In detail, the paper shed light on how indoor air quality (IAQ), natural light, green spaces, and materials influence the experience of the patients who use the cancer centers in different facilities. The study take advantage of integrating literature review, case study, and stakeholder interviews (multi-method approach). This study has identified that environmental design priorities in oncology vary by cancer type, treatment stage, and functional space. The relevance of results is furthered maintained using a customized design framework that addresses these specific needs while maintaining clinical safety standards.

Ultimately, this work strengthens the urgent need for human-centered and context-sensitive healthcare design and lays the foundation for future interdisciplinary research and multi-site validation.