Measuring Local Climate Effects of Institutional Gardens in Budapest

Abstract

Climate change significantly affects the well-being of urban populations. Thus, there is an increasing need for public green spaces in cities, as biologically active surfaces play a critical role in modifying the urban climate—cooling temperatures and providing shelter. Some institutional gardens, like cemeteries and hospital gardens, are hidden treasures: they are open but excluded from citizens’ mental maps, while usually having a rich green mass. This article aims to explore these hidden green surface elements, presenting their advantages and disadvantages by measuring their local climate effects. Three institutional gardens located in different urban environments were selected for analysis in the sample area of Budapest to explore how the surrounding built-up areas of the city modify the urban climate. The climate analyses were prepared with the ENVI-met climate simulation program. In the case of both hospital gardens and cemeteries, our studies show that their green spaces have great potential to increase the sense of comfort for both users of the green spaces and inhabitants of the neighborhood. In densely built-up urban areas, it is particularly important to involve institutional green spaces in public use, because with appropriate development they can contribute to cities’ adaptation to climate change.

1. Introduction

With the growth of the world’s population, urbanization processes have accelerated in the last few decades. The number and proportion of people living in cities with a population of more than 500,000 is increasing year by year [1]. Due to the increasing intensity of urbanization, cities are characterized by a specific urban climate: modified radiation, water balance, air circulation and temperature conditions. This has a number of negative effects on the environment and on the population. One of the main problems is the increase in the urban heat island (UHI) effect, which, coupled with the longer and more frequent heat waves in the region, can cause a number of health problems for urban dwellers. Changes in the urban climate are partly reflected in the incidence of mental and psychological illnesses and partly in physical illnesses, which are also reflected in mortality and morbidity data [2,3,4].

Climatological research shows that negative climatic effects in cities can be most effectively compensated for and improved by natural and semi-natural elements of the urban green infrastructure [3,5] and the creation of urban water surfaces [5].

Green infrastructure elements have the following two main scales of impact on the urban climate.

Microclimatic impact: A specific climate is created within the green space, which positively affects the well-being of those who use and occupy the green space. This is closely linked to the concept of accessibility, as the more people can visit them, the more people can enjoy the positive microclimatic effect of green spaces.

Mezo- and macroclimatic effect: The microclimate created within a green space has an impact on its environment, improving the climatic conditions of its surroundings and thus positively influencing the well-being of those who do not use the green space (e.g., cooler air flows out of the green space, its green mass provides shade for the surrounding streets, the more humid air makes the environment more pleasant, initiates urban air circulation) [6].

The climate-modifying effect of green surfaces depends on the type of green infrastructure element. The local climate modification effect is mainly important for green space elements that are frequently used by more visitors and for longer periods of time, while the meso- and macro-climatic effect is more important for the surrounding neighborhoods. The key aspects that influence the mezo- and macroclimatic effect are the size, shape, location, and design. On the local level, microclimatic aspects are more complex and interrelated.

Urban green infrastructure elements can be divided into two main categories in terms of use: those that can be used by the wider community and those that do not allow public use. Green spaces that are open to the public can be used by citizens with or without restrictions. Ownership can fundamentally determine a green space’s microclimatic impact: while the role of community-owned green spaces in the local urban climate is inevitably great, the effect of privately owned green spaces is very much dependent on the owner. That is the reason why privately owned green spaces that are opened up for the community, such as institutional and office gardens, are important hidden treasures from the local climate point of view (

Table 1. Grouping of the green spaces by ownership and community exploration (authors’ edit).

	Green Spaces Not Openable	Green Spaces with Limited Possible Public Access	Green Spaces Open to the Public
Public property: state, municipal, ecclesiastical and other organization	Specific institutional gardens (for example, belonging to the army)	Public parks, public gardens, institutional gardens	Public parks, public gardens, streets, urban squares, public green spaces
Private property: individual or legal person	Private gardens	Office gardens	Public parks belonging to private investments

).

The World Health Organization has developed guidelines for the minimum ratios of urban green space and green area based on urban climate analysis, and it has set the primary criteria for the amount of green space at 50 m² per capita on average and at 9 m² per capita for community use [7]. On the list of European cities, Budapest (6 m² per capita) is in the middle based on its green spaces and water surfaces per capita [8]. Cities with a high green space ratio are also at the top of livability lists, so it can be said that the presence of green space is a very important aspect for a city to become a good place to live, in addition to other sociological and cultural aspects [9]. Moreover, a lot of research shows that active green spaces not only improve people’s physical and mental health but also promote social inclusion and boost real estate prices [10,11,12].

Besides the quantitative indicators, the World Health Organization’s standard does recommend a uniform distribution allowing 300 m accessibility of green spaces [7]. It is usually the case that cities have large green spaces in the urban periphery, such as urban forests, that significantly increase the minimum ratios of a city. These areas are outside the 300 m accessibility zone for the inner parts and therefore do not fulfill the even distribution of urban green.

Previous research has already addressed the potential of institutional gardens to improve the accessibility of green space in denser urban areas [13]. Large institutional gardens, such as cemeteries and hospital gardens, especially in a city center location, can be great assets from the ecological, functional and economic point of view [14]. In addition, the network of institutional gardens—especially if they are open to the public—is highly valuable and can greatly increase the distribution, which can enhance overall urban well-being. One great example is the OASIS project in Paris, which exploits exactly this fact in the case of schools [13,15,16].

The potential for green space development in an institutional garden is primarily influenced by the advantages and disadvantages (in terms of use, cost, safety, and regulations) that the opening up brings to the institution and the community. The historical structure of the institution, its entrances, its links to the urban fabric and the social relationship with the institution are particularly important aspects to review when considering community use. Some institutional gardens have a long history of public use (e.g., university gardens, botanical gardens, museum gardens, or gardens of cultural centers) [13]. Although cemeteries and memorial gardens have always been visited throughout history, there is a mental barrier that prevents developments toward alternative recreational use, even for historical cemeteries [17]. In some countries and cultures, such as Hungary, the gardens of hospitals and health care institutions are relatively little visited, although the fence is more mental than physical [18].

These institutions can be considered hidden treasures from the community-use perspective and therefore they have great potential to contribute to the well-being of city dwellers through their microclimatic and macroclimatic effects [5]. We primarily used climate simulation methods to demonstrate the value of these gardens in mitigating the urban environment’s climate impact.

Climate simulation methods have only become widespread in the last decade due to computer developments, although centuries of experience has shown the local environmental-conditioning effects of green spaces. Instrumental measurements of the extent of the conditioning have also only been available in the last few decades. To convince decision-makers involved in today’s green infrastructure development strategies, it is essential that landscape architects not only make empirical predictions but also present the significance and benefits of various landscape interventions in a quantified and accurate forecast, so that the return on investment of the various interventions can be planned.

To investigate the role of conditioning, we have partly chosen urban climatological studies that influence human comfort, since in physical terms human well-being is basically determined by the state of the environment around us. The more pleasant the climate is, the more comfortable we feel.

In Hungary, research on ecology, urban climatology, settlement ecology and green spaces began to take off in the 1960s, and the extent of the so-called conditioning effect of green spaces, their role in reducing temperature and increasing humidity—mainly depending on the size and the area of the green space—and in modifying urban and local air circulation systems, or in the regulation of air quality, is now being investigated [19]. In the 1990s, based on international research, human comfort and comfort climate also played an increasingly important role in landscape architecture [20].

The first empirical bioclimate indices were published in the 1930s [21]. Urban planners and landscape architects were mainly able to find out about the results of their work on the basis of their measurements and empirical research, including how the microclimates of certain green areas and interventions were shaped from a climatological point of view, and on the basis of these they could predict how the implemented projects would affect the climate of the environment and what impact they would have on human well-being and comfort. A number of studies have looked at the impact of different landscape elements on the micro-environment and used the proportions of these elements to estimate the beneficial impact of planned green spaces. The positive impact of open spaces and green spaces on human comfort has been studied and analyzed by many researchers, not only in the context of the whole but also in terms of individual landscape elements (plants, pavements, built elements) [19,22].

In the course of the human climate research that has been accelerating since the 1980s, numerous definitions of human comfort have been developed, perhaps the best known of which is “the perception of temperature comfort is a positive opinion (satisfaction) that expresses our attitude towards the temperature conditions of our environment” [21]. In this research, we used one of the most widely used rational indices based on the energy balance—the term physiologically equivalent temperature (PET). The PET is the temperature of a standardized fictitious environment in which the body produces the same physiological responses (skin temperature, sweat rate) to maintain the energy balance as in the complex conditions of the real environment [23]. The PET index can nowadays not only be calculated on the basis of measured results but also be used by a number of computer modeling programs, and it has thus become a key element of settlement planning, as interventions can be almost exactly prologized.

Dutch research has shown that the urban local climate can be better visualized on bioclimatological maps (potential air temperature, radiation, wind, humidity) than on classical meteorological maps. The PET map shows in detail how the physical equivalent temperature (PET) varies in urban areas. For example, in densely built-up areas, the heat stress is high; in open areas, near water and in tree-covered parks, lower temperatures are observed, even though the potential air temperature hardly changes due to convection [24,25].

In our research, we have used potential air temperature maps for the climate simulation analyses, as they provide a good indication and illustration for the layperson of the impact of vegetation on climate prediction. We also performed a physical equivalent temperature (PET) simulation based partly on the potential air temperature, which the literature shows to be a more sensitive, multi-component analysis.

For the simulations, we used the climate simulation software ENVI-met, which models and simulates the micro-, meso-, and macroclimatic effects of each selected case study site at a given time and under given conditions. ENVI-met, although used mainly for urban climate modeling at larger scales, can be applied at this scale as well.

2. Materials and Methods

2.1. Case Study Selection Method

For our research, we chose Budapest as the sample area because it is the only real metropolitan city in Hungary where the negative effects of urban problems, such as climate impacts, are also prevalent [26]. Within Budapest, institutional gardens are well-researched fields [13,18,27]. Several research studies have already examined the different types of institutional gardens in Budapest in terms of their development history, spatial distribution, ecological potential, and functional development potential, and the challenges and difficulties of opening them up for the community.

Within institutional gardens, we focused on cemeteries and hospital gardens because of their relatively high ecological value and potential community use. These institutional gardens usually have a larger lot size and compact shape, and they are typically open to the public but underused. Mental barriers are significant: developing recreational functions or placing equipment that serves other functions than the original is controversial in Hungary. Because of the expansion of the city, historical gardens now appear in the heart of the city, creating great ecological potential for the locals. The rich, mature vegetation is usually in high contrast with the neighboring densely built-up areas (Table 2). These institutions are owned by the state, the local government or religious bodies—not the private sector—which is more favorable when it comes to influencing the design or changing the usage and opening them up to the public.

These characteristics make them both exciting areas for investigation. Their better maintenance and proper development can greatly contribute to enhancing urban well-being by validating the local climate modification effect.

Table 2. Comparative analysis of hospital gardens and cemeteries (authors’ edit).

Hospital Gardens		Cemeteries
Typically large	Lot size	Typically large
Typically large	Proportion of green	Typically large
Usually compact, separated by buildings	Shape of the green element	Compact and linear
Not even	Distribution in the city	Not even
Yes	Appear in dense urban set-up	Historical ones
Owned by the state, municipality or religious bodies	Ownership	State or church governance
Sometimes have recreational equipment but only for inside users	Recreational activities	Minimal recreational use

Table 2. Comparative analysis of hospital gardens and cemeteries (authors’ edit).

Hospital Gardens		Cemeteries
Typically large	Lot size	Typically large
Typically large	Proportion of green	Typically large
Usually compact, separated by buildings	Shape of the green element	Compact and linear
Not even	Distribution in the city	Not even
Yes	Appear in dense urban set-up	Historical ones
Owned by the state, municipality or religious bodies	Ownership	State or church governance
Sometimes have recreational equipment but only for inside users	Recreational activities	Minimal recreational use

As can be seen in Figure 1, both hospital gardens and cemeteries appear in various urban settings within Budapest. Their location is not completely even but rather diverse in terms of the surrounding urban structure. As the surroundings of the green element significantly and fundamentally influence the microclimatic effect, we differentiated three main types of urban environment:

• Urban core zones are the densest urban areas with mixed use, having more than two-story high buildings predominantly attached to each other. These areas are usually the downtown areas of metropolitan cities, sometimes even the historic parts. These neighborhoods are the most exposed to the urban climate because of the high proportion of inactive surfaces: paved and built-up surfaces’ heat retention capacity is very high, but their water retention capacity is low. These areas are generally lacking in green space, but if there is green, it occurs in blocks, without longitudinal, connecting elements.
• Transitional urban zones are general urban areas with medium built-up density, mostly residential but still mixed use. The biologically active and inactive surfaces have a more or less equal proportion. In this zone, green infrastructures have both block and longitudinal elements, and they are usually rich in public green spaces.
• Sub-urban residential zones have the lowest built-up density in the city. Residential use accounts for the majority with a loosely built structure, often with stand-alone buildings. In this zone, the biologically active surfaces are clearly larger than the inactive surfaces; however, here, the majority of the green infrastructure is privately owned, which often causes a shortage of public green spaces and both distribution and accessibility problems in the area.

Figure 1. Budapest’s cemetery gardens (green) and Budapest’s hospital gardens (orange) (authors’ figure based on the Budapest Environmental Assessment 2024 [28]). Selected case study sites: 1. Budafok Cemetery, 2. Péterfy Sándor Street Hospital, and 3. National Centre for Spine Medicine.

Figure 1. Budapest’s cemetery gardens (green) and Budapest’s hospital gardens (orange) (authors’ figure based on the Budapest Environmental Assessment 2024 [28]). Selected case study sites: 1. Budafok Cemetery, 2. Péterfy Sándor Street Hospital, and 3. National Centre for Spine Medicine.

The categories were chosen based on several studies [29,30] and the researchers’ own experiences. Each one of the selected case study areas is located in one of the different types of urban environment: the Péterfy Sándor Street Hospital is located in the urban core zone, the National Centre for Spine Medicine in the transitional urban zone, and the Budafok Cemetery is located in the sub-urban residential zone.

Another important criterion for the selection of the case study sites was the type of built-up structure within the lot. The cemeteries have a relatively uniform structure in terms of the built-up area and green space ratio, despite the fact that the green cover of the cemeteries is constantly changing due to the continuous burials, so the choice of the case study site was mainly determined by the location. For hospitals, we selected each of the two historically significant types of built-up areas: one having a pavilion structure (Péterfy Sándor Street Hospital) and the other one having a block building (National Centre for Spine Medicine) (Figure 2).

2.2. Introducing the Case Studies

2.2.1. Budafok Cemetery

The oldest part of today’s Budafok Cemetery, the so-called Old Cemetery, was created in the mid-19th century by extending an earlier, now-dismantled cemetery. The first official burial took place here in 1887, but some graves had already been established in the area before that. The Old Cemetery was primarily used by the Swabian families of Budafok for the construction of crypts, but the extension of the cemetery to the northwest also provided space for simpler graves. The funeral home was built in the late 1920s according to the design of Lajos Bathó. In the 1930s, another separate section was added to the cemetery, which was incorporated into the former cemetery by the 1960s. The cemetery also includes a small Jewish cemetery enclosure, which was used until the 1950s. The cemetery is now surrounded by a loosely built-up urban fabric of detached houses, and no further expansion is possible. The Old Cemetery, with its valuable and beautiful crypts, and the old trees planted in the early 20th century, has become a site to be protected [31].

According to the Budapest Environmental Status Report, the cemetery’s green surface index value was 58 in 2020, decreasing to 52 in 2024. The most stable and important elements of the cemetery vegetation are the trees and the tree lines. The first planned afforestation of the Budafok Cemetery took place in the first two decades of the 20th century, when tree alleys were planted along the main roads [31]. Most of the tree lines survived the Second World War, and the 1967 aerial photograph shows a significant tree population in both the Old Cemetery and the expansion areas. During this period, the main alleys ran freely, with the post-construction graves currently in the middle of them having been created after the regime change in 1989 (Figure 3).

A detailed, publicly available survey of the cemetery’s tree population was carried out in 1995 [32], which showed that there were 403 trees in the cemetery’s tree lines and 51 trees within the parcels. At that time, the double tree line in the longitudinal axis of the cemetery and the Japanese acacia tree alley by the mortuary, as well as the double linden tree between parcels 20/1 and 20/2 in the Old Cemetery, were highlighted as valuable tree stands. In 2025, 30 years after the previous survey, a site visit found that the central tree line had become significantly incomplete and that most of the Japanese acacia tree alley by the mortuary had been felled to create a new parcel and urn walls. Only the linden tree line in the Old Cemetery has survived in its majority, although here 4 of the 24 small-leaved linden trees previously recorded have been felled (the stumps are still visible in the area). The lack of trees means that there is virtually no shade in the summer in most of the parcels (Figure 4).

2.2.2. Péterfy Sándor Street Hospital

The first buildings of the hospital were built around 1890, with a one-story brick pavilion design [33]. Then, in two phases between 1931–32 and 1940–42, the new block building was built, with two symmetrical wings. The new building is 6 stories high, with a sophisticated design in keeping with the spirit of the times [34].

Several service buildings were added to the courtyard, eliminating much of the garden between the pavilions. The process of building is clearly visible on the maps and aerial photographs (Figure 5).

The aerial photo from 1963 clearly shows that there is an ornamental fountain in the courtyard, preserved in an archival photo as well [35], but today, only the basin of the fountain is visible, as the associated putto statue has disappeared over time. Parking had already appeared in the inner courtyard in those days, but due to the intensive development, it was not very significant for the time being, only visible next to the main building.

The demolition of the service buildings in the early 2000s did not increase the green areas, but typically, the parking area. After the demolition of the large service building behind the pavilion buildings in 2006–2007, a recreation area was created, which resulted in an increase in the proportion of green areas.

In 2009, a new complex of buildings with underground parking appeared in the courtyard, but unfortunately, this did not eliminate surface parking, and in fact, it only resulted in the displacement of parking, often sacrificing green surfaces. In 2006, parking on the edge of the ornamental garden changed from parallel to perpendicular, and new parking stalls were also created between the pavilion buildings with crushed stone paving [36].

The paving and furnishings of the garden are mixed, neglected and in poor condition, and some of the ornamental plants have died out (Figure 6).

The garden as a whole is characterized by extensively managed grass areas with almost no shrubs or perennials. The tree canopy coverage, on the other hand, is good, but the trees are old and partly neglected, partly composed of invasive species along the margins.

2.2.3. National Centre for Spine Medicine

The first building of the Garrison Hospital was built in 1869 according to a design by Dodier. A new, modern wing was added in the late 1930s. During the Second World War and the Soviet occupation, both parts of the building completely deteriorated [37]. The old wing was demolished in 1950, while the new wing was rebuilt according to the design of József Schall [38].

Based on the aerial photographs and historical photos (fortepan.hu), the hospital was surrounded by a large garden, where not only the patients convalesced but also the children from the neighborhood used to come and play.

In the 1960s, there was a decorative plaza in front of each of the two entrances to the building, and an ornamental fountain or statue may be visible in the eastern part of the garden in the aerial photograph (Figure 7).

The parking feature appeared in the 1970s, by which time the new modern cross-wing had been completed. The proportion of the enclosure increased, the vegetation decreased, and with it, the ornamental function of the garden, too. In keeping with the design guidelines of the time, an employee tennis court was added. The 1996 aerial photograph clearly shows that one of the southern entrances has been removed, so that the decorative paving there has been removed and replaced by parking on the south side of the hospital building.

Today’s development follows the existing layout, but the garden has lost even more of its function. New paved areas have also been added to the Alkotás Street side of the building, where parking has also been added, resulting in the building being completely disconnected from the surrounding green spaces. The statue that was there in 1989 has now disappeared, and the resting area has been pushed back to the western side. The tennis court on the site has been converted into a parking lot since the early 2000s.

Only the quality of the paving on the western side of the garden suggests that there has been an attempt to create a resting area over the last decade, but both the furniture and the lighting are inadequate and outdated (Figure 8).

The vegetation in the garden has only two layers: the significant tree canopy and the degraded lawn surface below. Shrubs are only occasionally found here and there, and they are also masses of shrubs, with practically no ornamental value.

Along the main roads, invasive species are usually seen, while the inner areas of the garden are characterized by mature ornamental trees [39].

2.3. Climate Simulation Methods

Our research methodology was based on the analysis of the physical equivalent temperature (PET) maps and potential air temperature (PAT) using the climate simulation software ENVI-met [40,41]. ENVI-met is primarily an urban climate simulation program, but it is increasingly used to simulate the local climate of smaller spaces and built-up areas [42,43,44]. For the climate simulations, aerial and space images were used as basic data to create three-dimensional models of the objects to be investigated in a defined raster. The three-dimensional models were then used to simulate the climatic conditions and their variation at a given time on a hot summer’s day, under given meteorological conditions and for a given geographical location, using the climate simulation part of the microclimate modeling software ENVI-met. The simulation program took into account the short- and long-wavelength radiation, shading, evaporation from plants and other surfaces, dynamic surface temperature and water and heat exchange in the soil. The data were used to determine the potential air temperature (PAT) conditions, relative humidity and wind conditions, which were analyzed at different times.

The simulation software is linked to a biometeorological simulation software component, BioMet, which is able to generate physical equivalent temperature (PET) data and maps using microclimate data [40].

The heat sensation and its alteration are represented by the PET index. The human climate model was performed on an average middle-aged human. The climate data and the biometeorological data obtained for a given time point were plotted on a map and compared in different ways. The PET maps provided the most important data as they took into account all the climate factors (wind, temperature, humidity, radiation, mean surface temperature).

Climate modeling can be used to investigate how open spaces and green areas, vegetation, pavements or built structures and their green surfaces are involved in shaping the local microclimate and whether they can influence the climatic conditions of the environment and thus human well-being.

We took into account the following ENVI-met simulation parameters and optimization methodology for institutional gardens.

Meteorological configurations:

Boundary conditions were derived from Energy Plus Weather (EPW) data for Budapest to capture the peak seasonal conditions. Summer air temperature parameters: a typical hot summer’s day, initialization at 12:00–14:00 (ensuring high temperature): lowest nighttime temperature 22 °C, highest daytime temperature 34 °C. Wind parameters: northwest direction (315°) at 2.5 m/s—prevailing breeze pattern verified against Budapest Airport meteorological data (WMO:12843), enhancing convective cooling.

Material specifications:

Pavements: light concrete (albedo 0.35) for graves vs. dark concrete (albedo 0.10) for walkways and for the car routes—critical for radiative heat differentials. Soil: loamy type (40% sand, 40% silt, 20% clay) representing uncovered areas, a typical choice of soil within the ENVI-met options. Buildings: default walls with moderate insulation, due to lack of site-specific insulation data, which is a basic option within ENVI-met.

Vegetation modeling:

Deciduous trees (15 m height, LAI = 2.5, sparse canopy, option within ENVI-met Vegetation category) account for Budapest’s mixed species (e.g., Acer platanoides, Tilia cordata). This simplification enables replicability but ignores species-specific transpiration rates, root–soil moisture interactions and seasonal phenology changes.

Grid configuration—this was varied between gardens due to the differences in size:

By the hospitals: cell size Dx = 2 m, Dy = 2 m, Dz = 2 m optimized for computational efficiency. By the cemetery: cell size Dx = 8 m, Dy = 10 m, Dz = 2 m optimized for computational efficiency while resolving tree–canopy interactions (Δz < 1/3 canopy height).

Spatial structure, plan layout:

The current model of the hospitals was created based on aerial photos from Google Maps in 2020. Based on this, we determined the paved and vegetated areas and the canopy cover. These were then verified through site visits. When developing the optimized plan, we took into account the functional characteristics and requirements of hospital gardens. We increased the canopy cover, optimized the ratio of green and paved surfaces, favored pavements with higher albedo, and recommended the installation of water features and green roofs (Figure 9, Figure 10 and Figure 11, Table 3).

In the case of the cemetery, since the proportion of built-up areas and pavements there is less modifiable, the only change was the planting of trees along the walkways. A total of 40 Acer platanoides trees were marked in the proposed model.

Figure 11. Budafok cemetery: (a) existing garden model, and (b) proposed garden model (authors’ figure created with ENVI-met 4.4.5 software using Google Maps photo).

Figure 11. Budafok cemetery: (a) existing garden model, and (b) proposed garden model (authors’ figure created with ENVI-met 4.4.5 software using Google Maps photo).

In addition to the map representations, the changes are also presented in the table below (Table 3).

Table 3. Comparison of spatial data of existing models and proposed models of the sample areas (authors’ edit).

	Péterfy Sándor Street Hospital		National Centre for Spine Hospital		Budafok Cemetery
	Current status	Planned status	Current status	Planned status	Current status	Planned status
Land area	22,637 m2	22,637 m2	23,170 m2	23,170 m2	22,637 m2	22,637 m2
Buildings	39%	39%	17%	17%	39%	39%
Paved surfaces	41%	32%	48%	34%	41%	32%
Vegetation-covered surfaces	20%	29%	35%	48%	20%	29%
Canopy coverage	15%	30%	35%	51%	15%	30%

Table 3. Comparison of spatial data of existing models and proposed models of the sample areas (authors’ edit).

	Péterfy Sándor Street Hospital		National Centre for Spine Hospital		Budafok Cemetery
	Current status	Planned status	Current status	Planned status	Current status	Planned status
Land area	22,637 m2	22,637 m2	23,170 m2	23,170 m2	22,637 m2	22,637 m2
Buildings	39%	39%	17%	17%	39%	39%
Paved surfaces	41%	32%	48%	34%	41%	32%
Vegetation-covered surfaces	20%	29%	35%	48%	20%	29%
Canopy coverage	15%	30%	35%	51%	15%	30%

Our methodology did not cover the validation of results; rather, it only analyzed the simulations produced by the program. This is because the ENVI-met program is continuously monitored by its developers to ensure its validity, and numerous studies have been conducted on the reliability of the program’s simulations [45,46].

3. Results

Microclimatic data is most commonly characterized by the air temperature, but this does not provide a complete picture of the microclimate. Therefore, in the case of more complex spatial changes, it is worth examining the climate modification (PET) affecting users, as this provides a more complete picture of the changes in human well-being. As the differences are large and incomparable, we have analyzed them separately.

3.1. Potential Air Temperature Change (PAT)

A potential air temperature change was only observed in the local climate of the case study areas, mainly where vegetation has increased significantly or where the covered area has decreased.

For the Péterfy Sándor Street Hospital, the potential air temperature (PAT) changes inside the garden averaged a decrease of 1.17 °C. Due to the relatively large paved surfaces of the courtyard, the decrease was below this value in several places. Due to the building structure, the small opening to the street is not sufficient for convection. The potential air temperature decrease in front of the buildings is mainly due to street trees (Figure 12, Table 4).

A large potential air temperature (PAT) decrease was observed in the middle of the garden due to the reconstruction of the fountain. Moving water can produce significant potential air temperature (PAT) differences of up to 6 °C. This can be seen in the cross-sectional figure, and it is clearly visible that the reconstruction of the fountain causes a significant potential air temperature (PAT) (0.3–1.35 °C) and physical equivalent temperature (PET) drop (4–14 °C), not only horizontally but also vertically (depending on the air movement of the one meter water column up to a height of 10–12 m) (Figure 13).

The potential air temperature change (PAT) in the case of the National Centre for Spine Medicine exceeded 2 °C, which is a significant result in terms of air convection. In the inner garden area, an intensively covered core area with a relatively small pavement ratio could be created, while the radiating surface of the buildings is moderate compared to the size of the whole area, and these two factors produced positive results. This form of development also has a more favorable potential air temperature (PAT) reduction effect on the surrounding area, as the hospital garden is connected to the urban fabric on both sides, and the favorable topography and fencing design allow cooler air to flow out into the surrounding areas (Figure 14, Table 4).

In the case of the Budafok Cemetery, where it would be possible to add only an increased number of trees, the potential air temperature change in summer is significantly smaller. The establishment of tree lines and the planting of 40 trees resulted in an average potential air temperature decrease of 0.34 °C in summer, mainly in the vicinity of the walkways (Figure 15, Table 4).

Figure 15. Simulation of the potential air temperature (PAT) in the garden of Budafok Cemetery during summer: (a) existing garden model, and (b) proposed garden model (authors’ figure created with ENVI-met).

Figure 15. Simulation of the potential air temperature (PAT) in the garden of Budafok Cemetery during summer: (a) existing garden model, and (b) proposed garden model (authors’ figure created with ENVI-met).

Table 4. Minimum and maximum potential air temperature (PAT) values and the change in the potential air temperature (PAT) between the original and proposed conditions during the summer period for each sample area (authors’ edit).

	Original Condition		Planned Condition		Maximum PAT Values in a Given Area (See Figure 12, Figure 13, Figure 14 and Figure 15)
	Min. PAT values	Max. PAT values	Min. PAT values	Max. PAT values
Péterfy Sándor Street Hospital	28.96 °C	32.54 °C	23.94 °C	32.29 °C	−6.06 °C
National Centre for Spine Medicine	30.10 °C	32.66 °C	29.19 °C	32.25 °C	−2.24 °C
Budafok Cemetery	31.09 °C	34.13 °C	30.18 °C	32.00 °C	−2.13 °C

Table 4. Minimum and maximum potential air temperature (PAT) values and the change in the potential air temperature (PAT) between the original and proposed conditions during the summer period for each sample area (authors’ edit).

	Original Condition		Planned Condition		Maximum PAT Values in a Given Area (See Figure 12, Figure 13, Figure 14 and Figure 15)
	Min. PAT values	Max. PAT values	Min. PAT values	Max. PAT values
Péterfy Sándor Street Hospital	28.96 °C	32.54 °C	23.94 °C	32.29 °C	−6.06 °C
National Centre for Spine Medicine	30.10 °C	32.66 °C	29.19 °C	32.25 °C	−2.24 °C
Budafok Cemetery	31.09 °C	34.13 °C	30.18 °C	32.00 °C	−2.13 °C

For the Budafok Cemetery, a simulation for the winter period was also carried out, which illustrates that the cooling effect of vegetation in summer is replaced by a heating effect generated by vegetation in winter. The simulation shows that the average daily mean air temperature increase reaches +0.23 °C (Figure 16).

3.2. Physical Equivalent Temperature (PET)

The observations and values of the microclimatological studies (potential air temperature, wind, potential humidity) are summarized in the PET, i.e., the physical equivalent temperature maps, which clearly show that the reduction of the physical equivalent temperature (PET) between the planned and existing situations in the hospitals has been achieved in both cases. The physical equivalent temperature (PET) reduction can be as high as 20 °C in cases where the canopy growth is significant (Figure 17c). This contributes greatly to the well-being of users.

There is a big difference in the impact of different installations on the human climate of the environment. In the enclosed area, although the physical equivalent temperature (PET) improved, this was not noticeable in the urban fabric due to the tall buildings—see the south side of the Péterfy Sándor Street Hospital (Figure 17, Table 5).

Figure 17. Physical equivalent temperature (PET) simulation of the garden of the Péterfy Sándor Street Hospital in summer: (a) existing garden model, (b) proposed garden model, and (c) comparison of the two models (authors’ figure created with ENVI-met).

Figure 17. Physical equivalent temperature (PET) simulation of the garden of the Péterfy Sándor Street Hospital in summer: (a) existing garden model, (b) proposed garden model, and (c) comparison of the two models (authors’ figure created with ENVI-met).

For the National Centre for Spine Medicine, due to it having a more open urban structure around it, a slight macroclimatic effect on the human climate of the surrounding streets can be observed (Figure 18, Table 5).

In the case of the Budafok Cemetery, the physical equivalent temperature (PET) change is mainly observed under the tree canopies, which due to the shading of the trees.

In addition to the map representation, the values recorded in the table illustrate, quantify and convincingly depict the climatological change in the difference in condition of the existing and planned garden’s green space, the positive impact on human well-being and the local climate modification effect of different building complexes (Table 5).

Table 5. Minimum and maximum physical equivalent temperature (PET) values and the change in the physical equivalent temperature (PET) between the initial and design conditions during the summer period for each case study area (authors’ edit).

	Original Condition		Planned Condition		Maximum PET Values Change in a Given Area Unit (See Figure 17 and Figure 18)
	Min. PET values	Max. PET values	Min. PET values	Max. PET values
Péterfy Sándor Street Hospital	29.57 °C	57.00 °C	28.43 °C	56.20 °C	−22.60 °C
National Centre for Spine Medicine	29.89 °C	57.80 °C	29.05 °C	56.80 °C	−20.00 °C

Table 5. Minimum and maximum physical equivalent temperature (PET) values and the change in the physical equivalent temperature (PET) between the initial and design conditions during the summer period for each case study area (authors’ edit).

	Original Condition		Planned Condition		Maximum PET Values Change in a Given Area Unit (See Figure 17 and Figure 18)
	Min. PET values	Max. PET values	Min. PET values	Max. PET values
Péterfy Sándor Street Hospital	29.57 °C	57.00 °C	28.43 °C	56.20 °C	−22.60 °C
National Centre for Spine Medicine	29.89 °C	57.80 °C	29.05 °C	56.80 °C	−20.00 °C

4. Discussion

Our models have clearly shown that the significance of the potential impact on the air temperature and human comfort of institutional gardens with restricted use is inversely proportional to the surrounding built-up area: the more densely built-up the urban context wherein the institutional garden is located, the greater the temperature differences compared to the surrounding area that can result from climate-conscious improvements. In the case of the Budafok Cemetery, which is located in a sub-urban residential zone between detached houses with significant green gardens, the difference is considered minimal compared to the surrounding blocks, whereas in the case of the hospitals, the difference between the ambient and institutional area climate is greater in areas of temporary or densely built-up areas.

Institutional gardens that are open to the community have a number of functions (parking, traffic, transport, etc.) that need to be served and therefore the proportion of green surfaces can only be increased to a limited extent, so it is of paramount importance that this is performed in a planned way with maximum efficiency [48,49]. A measurable increase in human comfort caused by the green coverage could mostly be detected within the lot or in the immediate surroundings of the institutional gardens studied. Despite the fact that there is little measurable difference in temperature compared to the surrounding areas, visitors to the hospital and cemetery gardens report that they are significantly more comfortable in these areas on a hot summer’s day than in their surroundings. This is mainly due to the shading, as the short-wave radiation from the atmosphere is less affected in areas covered by trees, and the shading also reduces the irradiance of the ground surface, so that the radiation it absorbs and the long-wave radiation it returns is weaker. The evaporation provided by plants also has a beneficial effect on the microclimate, as the energy used in evaporation reduces the thermal energy of the environment and indirectly slightly reduces the potential air temperature. And last but not least, the difference in air temperature in the area covered by the larger vegetation, which is barely perceptible to humans, also induces air movement, which also leads to a physical equivalent temperature (PET) improvement in users.

Hospital gardens and cemeteries have different alternatives to improve green coverage and thus human comfort. In cemeteries, the main option is to vegetate the paths between the graves. As most cemeteries do not set rules for graves, individual taste and financial means determine the design of the graves. The covering of graves with headstones is now very common in urban cemeteries, but in the long term, when new graves are built, the planting of a mantle instead of a cover may be required by cemetery regulations. This would significantly reduce the proportion of paved surfaces within the cemetery. The proportion of green space within the cemetery can also be further improved by planting trees within the plots, with the necessary space being provided by the omission of a grave.

In hospital gardens, the paving can be rationalized to a large extent by displacing parking from the plot or by creating underground parking, and so the green areas can be increased significantly, but also, paving with lower albedo or permeability can reduce long-wave radiation, which can result in a more favorable thermal environment. In general, there is scope to increase the woody plant cover within the site, so that by greatly increasing the canopy coverage or using water features, the climate can be influenced favorably. In our research, we found similar results to models run for other institutional gardens [48,50].

While ENVI-met simulations offer high-resolution microclimate insights, the key limitations require acknowledgment.

Biological simplification: Single-tree species modeling ignores elements like interspecies competition for light/water, root zone heterogeneity affecting soil moisture, and species-specific drought resilience (critical during heatwaves). These biological factors, even though they are very minor and can help replicability within the program, can be improved within the program in a more complex analysis and further studies.

Material uncertainty: The default building albedo and insulation as a typical option within ENVI-met may deviate from actual cemetery structures. For example, historic limestone crypts could reduce wall temperatures by 2–3 °C versus the modeled values.

Extreme weather gap: The EPW data represents the current climate and excels at it, but it fails to capture millennial trends (e.g., 50-year heatwaves), sudden climatic events and compound events (heat + drought) and urban moisture feedback (irrigation limitations during water restrictions).

Absence of in situ measurements during peak events introduces uncertainty: ENVI-met’s radiative module has known ±1.5 °C errors for shaded areas [41,51].

Furthermore, this research has shown that the method used, the ENVI-met program, is suitable for measuring the climate-modifying role of landscape architecture interventions in institutional gardens, and this opens up a new perspective for planning and planning theory. Based on research on similar topics, it is clear that, in addition to ENVI-met, other programs may be needed to clarify the local climate-modifying effects of institutional green spaces. A possible further development could be, e.g., 3D grid profile analysis [52].

5. Conclusions

Across Europe, more and more cities, such as Rotterdam, London and Rome, are using ENVI-met for climate modeling to create cities more resilient against the effects of climate change. In addition to large-scale analyses, ENVI-met can also be useful for the climate-smart design of smaller green spaces [43,52,53,54].

In Budapest, ENVI-met has also started to be used in the planning of public spaces to predict the expected local climate change, but these studies have been limited to public spaces. Our studies have shown that the deliberate transformation of institutional areas, especially in densely built-up parts of the city, can have a significant impact on the human comfort of inhabitants [55].

In our research, we typified the green infrastructure elements in Budapest based on their use, the surrounding built environment and their impact on the local climate. We have found that even those specific green infrastructure elements (hospital gardens, cemeteries) have a significant impact on the local climate and human comfort, the use of which currently faces strong mental barriers in Hungary. In the case of both hospital gardens and cemeteries, our studies and computer models clearly show that their green spaces have great potential to increase the sense of comfort for both users of the green spaces and inhabitants of the neighborhoods.

We modeled the impact of consciously modified study areas (pavements, vegetation) on the potential surface temperature and human comfort. The simulations can help to improve the climate-conscious long-term planning of institutional gardens in order to reduce the urban heat island effect and thus the negative health impacts on city dwellers.

Based on our research, we would recommend continuing the work and expanding it to additional areas or other case studies, which would allow for broader validation of the importance of these institutional gardens.

Climate modeling with the ENVI-met program is essential for green space developments, especially in dense urban areas. It can be used to decide on the climate impact of individual developments, the strategy for green space development, and the climate efficiency of landscape architecture interventions. The quantified data predicted based on the simulation provides objective and convincing evidence for decision-makers, thereby promoting green space development that supports urban well-being.