Architectural Lighting Simulations as a Method to Evaluate Emotions on Cultural Heritage Building Facades

Abstract

This research concerns the exterior lighting of historic buildings and cultural heritage monuments. Its objective is to organize a methodology for the study of facades, to record the individual or grouped morphological and decorative elements of the facades, and to organize the steps to achieve a presentation of different ways of lighting these elements. This presentation is made by an experimental digital lighting simulation, leading the researcher to discover the relationship between light and the architectural element being illuminated. Finally, the results of the simulations are evaluated by experts in the field of lighting, who attest to the emotions generated by the observation of the different lighting scenarios, while an attempt is then made to synthesize these results on an entire building facade, to determine whether this synthesis of the individual lighting effects is practicable. The analysis of the results reveals the trends in each lighting scenario, leading to a variety of emotions, whether they arise from a specific morphological element or from the entire facade.

1. Introduction

In the history of humanity, a lot of work and enjoyment are completed after sunset, but artificial lighting was not the focus of human creativity, which has excelled in many other areas. But when the shift occurred, during the industrial revolution, it happened quickly, and it seemed like an interminable voyage from today’s brightly lit streets and buildings to our ancestors’ evenings, when they were lit by candles and oil lamps. In fact, it was only a few decades ago [1].

In ancient Greece, there was no artificial outdoor lighting, either public or private, and each man and his traveling companions needed a lighting vessel, such as a torch or lychnos (oil lamp), for the night. Private outdoor permanent illumination was known to exist during the Roman era, as evidenced by Pompeii and Herculaneum [2]. Oil lamps were installed in wall niches or windows of shops, residences, and public buildings to give appropriate lighting for the exterior. Despite the lack of public street lighting before 1788, it is likely that something comparable was happening in Rome [2]. Cities in Asia Minor, Syria, and North Africa, including Alexandria, had public fixed outdoor lighting throughout late antiquity [3]. In addition to their weapons, night watchmen in medieval England carried torches, which served the dual purposes of illuminating their path and drawing attention to the presence of law enforcement. The houses’ doors were shut by the evening bell ringing, and anyone found wandering the street without a torch was immediately suspected and frequently taken into custody [4]. Similar regulations requiring citizens to carry torches when walking around in the nighttime were in place in several European cities, including Paris [5], Lyon [6], Leicester [4], and others. In the 16th century, Paris [7] and New York [8] made the first attempts to provide permanent public lighting in their bigger cities. Public illumination remained essentially on private property until the 19th century. Since the 19th century, technological advancements have joined light “islands” into single lighting networks, increasing the dispersal of light beyond these borders. Gaslight at the start of the 19th century and electricity at the end of the century marked the beginning of the public lighting revolution [9]. Up to the turn of the 20th century, it attracted attention as a sign of innovation. However, interest in it quickly decreased due to its rapid technological development, its widespread use, and its tendency to become a key component of public life.

In recent years, we have been talking about architectural lighting that promotes the qualities of an element and tries to connect it with its environment. Architectural lighting is categorized and addressed to three different categories: historical buildings and places of historical interest, modern structures (modern buildings, bridges, etc.), and urban spaces (squares, parks, liquid elements, etc.). Moreover, it is primarily considered by UNESCO [10], but it is also commonly accepted that historic buildings are important and should be highlighted. Architectural lighting can play a key role, as it can contribute to the promotion of the building as a landmark and is an essential component of any architectural project for building restoration, since it has the potential to enhance the surrounding region or the environment in which the building is located. It can be used for a variety of things, including fostering a feeling of security and safety, enhancing a building’s aesthetics, generating entertainment through event planning, and—above all—disconnecting from the natural light cycle. The installation and specification constraints that limit lighting design decisions, resulting from legislation at the national level or from UNESCO and ICOMOS in a more international context [11,12,13], are a challenge for facade lighting in historic and listed buildings, which every designer must work through in order to achieve the best results [14]. The complex geometry and decorative elements found on the facades of historic buildings [15,16,17], combined with the flexibility of applications and results offered by artificial lighting today, lead to the emergence of new issues and obstacles. Aside from luminous performance, however, it is equally important to improve how it works and the impact it has on several factors. These factors are economic, psychological, and social ones, which are related to energy efficiency, light pollution, human well-being, and aesthetics, respectively [18,19,20,21,22,23].

For all the above reasons and combined with the additional difficulty of non-flexibility in setting up mockups on the facades, 3D lighting simulation is now not only considered necessary, but also needs to follow a specific methodology and techniques, as indicated in various reports [24,25,26,27], in order to include all the specifications that have been defined for these buildings and to have exhausted every alternative solution before the final implementation.

The aim of this research is to create a methodology for the lighting of buildings and monuments of cultural heritage. This publication presents a part of the methodology concerning historic buildings and the processes that need to be performed in order to produce results that are carefully and thoroughly grounded in the holistic requirements, characteristics, and factors that define historic buildings. During the progress of the research, parallel studies and surveys, published previously, had to be carried out at various steps of the research to verify the process and make its progress achievable. These studies concerned issues such as the analysis of the characteristics and morphological elements of historic buildings, considerations and methods of reducing and dealing with the light pollution produced by different lighting scenarios, the correlation of the characteristics of the various software to be used in the research, as well as the elaboration of the methodology on the projects of a specific architect [21,22,28].

This publication focuses on a case study that emerged from the database of the methodology and concerns the emotional impact of the visual effect of different lighting scenarios. However, the final goal of the methodology is to further enrich the database and to complete a framework with verified results through which researchers can consult, obtain ideas, and compose lighting scenarios for cultural heritage buildings.

2. Materials and Methods

2.1. Historic Building

In Europe, historical and theoretical approaches around the end of the 18th century raised awareness of the necessity to conserve structures that were built in the past and had unique architectural worth. This requirement stemmed from the wish to use architecture to maintain each nation’s unique identity [29]. The term “monument”, which goes back to Homer, represents the element that recalls something or that recalls something in memory. This term is from “μνάομαι-μνώμαι” (mnáome-mnóme) and thence to “μιμνήσκω-μιμνήσκομαι” (mimnísko-mimnískome); in Latin, this term is “moneo” and “monumentum-monument” [30]. After the middle of the 20th century, this concept was extended to cultural goods and cultural (archaeology, architecture, industry) and natural heritage. All human achievements whose protection and preservation are deemed necessary for the spiritual balance, quality of life, and cultural identity of people in the present and in the future are now considered cultural heritage. Cultural heritage includes those buildings which are classified as ’historic’ and have a spiritual and symbolic content, historical significance, and architectural value [31].

The criteria for classifying a building as “historic or listed” have been established in recent years. For instance, a structure cannot be classified as historic in the United States unless it is at least 50 years old. However, there are some exceptions, such as in New York City specifically, where the 30-year mark is applied [32]. Although there are regional variations, the overall framework for examination is universal. The National Register of Historic Places in the United States has set standards for the districts, sites, buildings, structures, and artifacts that exhibit the integrity of location, design, setting, materials, workmanship, feeling, and association, which are indicative of the quality of significance in American history, architecture, archeology, engineering, and culture. These places

“(a) … are associated with events that have made a significant contribution to the broad patterns of our history; or

(b) that are associated with the lives of persons significant in our past; or

(c) that embody the distinctive characteristics of a type, period, or method of construction, or that represent the work of a master, or that possess high artistic values, or that represent a significant and distinguishable entity whose components may lack individual distinction; or

(d) that have yielded, or may be likely to yield, information important in prehistory or history” [33].

Similar to that, UNESCO’s “Operational Guidelines for the Implementation of the World Heritage Convention” define cultural heritage as “groups of separate or associated buildings which, because of their architecture, homogeneity or their position in the landscape, are of outstanding universal value in terms of history, art or science”. Historic buildings must additionally meet other criteria in order to be approved for placement on the UNESCO World Heritage List. Nominated properties shall therefore

“(i) represent a masterpiece of human creative genius;

(ii) exhibit an important interchange of human values, over a span of time or within a cultural area of the world, on developments in architecture or technology, monumental arts, town-planning or landscape design;

(iii) bear a unique or at least exceptional testimony to a cultural tradition or to a civilization which is living or which has disappeared;

(iv) be an outstanding example of a type of building, architectural or technological ensemble or landscape which illustrates (a) significant stage(s) in human history” [10].

2.2. Outdoor Lighting Techniques

The wide variety of lighting equipment on the market greatly facilitates experimentation to produce interesting results. Nonetheless, there are common lighting techniques that have emerged in recent years, and their synthesis is due to the collaboration of lighting designers and manufacturers of luminaires and associated equipment who try to organize luminaires in groups and deliver specific results on a case-by-case basis. These techniques have been collected by the author and are presented below.

Wall washing (Figure 1a) is an ideal technique when uniform illumination of a flat surface is desired. The luminaires in this case are placed at a distance from the surface, usually 30–40 cm, to allow the space to “spread” the light evenly. Grazing (Figure 1b) is a similar type of lighting to that of wall washing; the difference here is simply that the luminaires are placed much closer to the building (almost in contact) so that the light can bring out the texture of the surface, creating shadows on the relief obstacles it encounters. Care needs to be taken in this way, as if there is no barrier above the surface (e.g., a projection, cornice, etc.) to stop the path of light, it vertically increases the levels of light pollution. Floodlighting (Figure 1c) is the technique used in cases where it is desirable to uniformly illuminate the entire volume of a building or a large part of it (e.g., a dome). In order to achieve diffusion lighting, the luminaires need to be placed at a distance from the object and at different positions from each other so that their beam covers the whole object but also minimizes shadows. Down lighting (Figure 1d) is the technique that is mainly used when vertical elements need to be illuminated. Its effect is interesting when carried out mainly with narrow beam luminaires, as it describes the verticality of the elements. It should be noted that it ‘shortens’ the elements and that the positioning of the luminaires may cause dazzling effects to observers or an unnecessary glare in the area in front of the view (e.g., sidewalk). Up lighting (Figure 1e), similarly to the previous way, can emphasize the verticality of the elements. It is used considerably more than down lighting for two main reasons: its effect gives emphasis and grandeur to the features of the building, while its installation reduces glare to the observer.

The use of accent lighting (Figure 1f) is chosen in cases where a morphological element, for example on a facade, needs to be particularly emphasized (e.g., a statue) and to stand out in terms of intensity from the rest of the lighting. Usually, for best results, it is achieved by lighting from a distance at different positions, to achieve the three-dimensional volume and with low-beam luminaires. The mirroring effect (Figure 1g) is not exactly an illumination technique in the sense of the others presented but relies more on a collaboration of some factors to make its effect successful. Clearly, the building being illuminated must be adjacent to a calm liquid element, it must be possible to observe the building from a point where the liquid element is in the middle, and finally, the illumination of the building must be divided into different levels covering the entire elevation so that the observer can see the reflection of the entire facade. Silhouetting (Figure 1h) is the outline of an element that can be shown directly, with illumination from the front or indirectly with illumination from behind. The most common effect of contour lighting is when, for example, the interior of a portico is illuminated, and the illumination is interrupted by the silhouette of the columns that define the portico. Also, silhouetting lighting is considered when, in a facade with multiple openings (e.g., windows), the luminaires accentuate the inner contour of the openings. Spotlighting (Figure 1i) is a technique that is not so much used on building facades as on horizontal surfaces to create repetition, e.g., a pathway. It is very similar to accent lighting, but the essential difference is that the effect is produced by a luminaire and the size and shape of its diffusion is part of the design.

The above lighting techniques help designers to choose the effect they want to achieve. There is no rule that defines which of them is the most appropriate, as each building, and especially heritage buildings, is unique and needs to be approached individually by the designer. Moreover, the above-mentioned techniques can be combined, offering interesting results as long as their choice can be visually documented. As far as intensities are concerned, a slight variation in illuminance between the object and background with a 2:1 ratio is common. For a more noticeable difference, the variation can be as high as 5:1. When it is desired to give emphasis, bordering on dramatic contrast, this differentiation can go up to 15:1. When the different intensities need to be more than two, they are perceived, creating an ideal effect when their difference is a constant ratio (e.g., 1:3:9:27) [34]. The relationship also between diffused and focused lighting must be clear so that the observer can perceive the differentiation. The intensity of the illumination in a view will largely result from the ambient lighting, which will determine it. When individual decorative elements are illuminated, the whole form of the building needs to be perceived by illuminating it evenly at a lower intensity.

2.3. Basic Categories of Lighting Heritage Building Facades

The lighting of the building at night does not need to copy the effect of natural light during the day. It can promote the building by emphasizing its most important features and, as far as possible, without the presence of natural light, to convey its original character. If, for example, the structure is circular, then its circularity may be emphasized. If the building is tall, its height can be emphasized, and so on. If the building is the only one in its surroundings, it may be possible to highlight it more gently and effectively in a more conventional way, such as with uniform general lighting (volume lighting). If the building is located within an urban environment and somehow “competes” with other buildings, then lighting design needs a different approach [35].

This section presents some basic categories to consider for the lighting to promote historic buildings, so that the lighting effect highlights the historical significance and architectural value of the building. These categories, organized and established by the author, were based on the most common characteristics and the structure of historical buildings (symmetry, repeated structural and decorative elements on the facades, different vertical layers, etc.), so that a designer can find solutions according to the task he is called upon to carry out. It is common in cases of historic buildings that the lighting follows certain guidelines depending on the design of the building. These have to do with the horizontal or vertical character of the decorative elements of the facade, the emphasis of some individual decorative elements or the multiple openings of the facade, and the enhancement of the overall volume by varying the lighting on the different surfaces of the building. In Figure 2, the categories are shown above the 3D-modelled building “Monnaie de Paris”.

Uniform volume lighting is considered the most conventional category of illumination but is not considered undesirable (Figure 2a). When the techniques for illuminating the whole volume are used in the right way, the result can appear, visually, to be quite satisfactory. Usually, to properly achieve the illumination of the facade, multiple points are selected at a distance from it (e.g., on poles across the street or on adjacent buildings) and spotlights with a wide angle of diffusion are placed to cover the entire surface. The different positions of the luminaires work together to eliminate a very strong shadow. In this situation, the positions also determine which small shadows are needed so that the effect emphasizes all three dimensions of the facade. A critical point to be considered by lighting designers is the wide angle of diffusion, which must direct light exclusively to the facade to avoid unnecessary consumption and increased levels of light pollution. Of course, there is also the possibility of placing multiple linear luminaires on the facades, which have the same characteristics to achieve a uniform effect. The display of different layers (Figure 2b) is mainly proposed on facades with a large projection or recessed surfaces, and this is the main difference with the lighting of a uniform volume. This basic principle is similar to that of the uniform volume simply differentiated in intensities and/or color temperature, so that the diversity of lighting on each surface is clearly indicated. The emphasis on vertical elements (Figure 2c) is a category most found in historic buildings. This highlighting can be achieved either with spotlights or linear luminaires (if the width is sufficient), and the way of lighting is achieved from top to bottom or bottom to top.

The promotion of horizontal elements (Figure 2d) is proposed mainly on facades that include entablatures and cornices that divide the height of the building into parts (e.g., base, body, coronation). Where facades are long, this category highlights this size. The best way to achieve this is by placing narrow-beam linear luminaires on the ground when the ground-to-linear element distance is short, and no other elements are interposed in between. In the same way, the lighting can be achieved by placing the luminaires at the top of the cornice that is at a lower height to illuminate the next cornice that is higher up. The same technique can be used to illuminate a parapet or an attic on the coronation of a facade. The lighting of openings can highlight facades in which there are several openings that are repeated (Figure 2e). Particularly, in buildings that do not have enough decorative elements, this is a category of intervention that stands out. The important feature here, in terms of equipment, is that the luminaires should have a quite narrow beam, so that the lighting remains within the inner contour of the window while not becoming an intrusion that enters the interior. Mainly, this basic principle is achieved using small spotlights which are placed in the lower part of the opening, on either side of the sills. In cases where the building does not accommodate a user during the evening or night hours (e.g., a public building), the same effect can be achieved by placing a single spotlight in the center of the landing which creates a 180° light frame. The emphasis of decorative elements is recommended in cases where individual elements such as statues, masks, medals, garlands, etc., are found on the facades (Figure 2f). This intervention can create a dramatic effect in the result when the surface of the facade is not illuminated, while grandeur results when the entire surface of the facade is gently illuminated. When elements are not contained within another element or set of other elements (e.g., a statue in a niche) and stand alone, the best way to illuminate them, empirically, is from a distance with small beam spotlights.

3. Architectural Lighting Simulations

3.1. Methodology

Having analyzed the main parameters needed to achieve a methodology, the implementation of the methodology begins, which is developed in eight (8) steps until the results are obtained. The proposed methodology is based on the common procedure of a lighting study in terms of the steps it proposes, but its development processes, experimentation, findings, and verification or not of the hitherto commonly accepted factors, constituting its own autonomy. The steps of the methodology are as follows in Figure 3:

3.1.1. Selection of the Building

A historic building is initially selected, which will be studied, and its typology features are examined, together with its historical significance and location within the surrounding environment. Since the methodology starts to deal with the lighting of the individual decorative and morphological elements, it allows for a wide selection of a structure. This research focused on the neoclassicism period, as it covers a wider range of chronological time, since most of the elements of neoclassicism originated from the classical architecture of ancient Greece and ancient Rome, but also, this architectural style spread to more countries worldwide compared to the previous ones created by specific political, economic, and cultural shifts in a country [36]. However, the evolution of the database can be extended to other periods in the future, as its logic is not influenced by the diversity of the structure and characteristics of each period, as long as the object is of historical significance.

3.1.2. Modelling of the Building

The building is digitally modelled in 3D. The material that a designer needs for the digital design of the facade of a historic building is the accurate capture of the volume, its surface, and the detail of each element. This can be achieved by detailed measurement either manually or with the assistance of equipment (Gps, drones, photogrammetry, etc.), depending on the difficulty in capturing the facade. In this research, the 3D modelling needed to be performed in several buildings. After collecting the material related to the information of each building (drawings, dimensions, etc.), 3Ds max software was chosen as the tool for the modelling and the simulations. The Level Of Detail or Level Of Development (LOD) of the BIM methodology, which is deemed necessary to obtain valid results, is set at LOD500 according to the Level Of Development (LOD) specification, as this is the level that relates to existing buildings and the information that can be directly extracted from the field, as described in the above framework [37].

3.1.3. Materials

It is essential that all materials are recorded and that their accurate representation in the simulation software is rendered with the highest detail. In the recording of materials, it should be taken into serious consideration whether a lighting design will be proposed in the existing situation or in the future renovation of the facade. This is something that significantly varies the results, because an existing surface that has a very low reflectivity due to environmental pollution or some problematic coatings (e.g., graffiti, posters, etc.) is very far from the outcome of its renovation. The most important process is the accurate reproduction of the colors, which should be performed after it has been determined what the actual color is in each material, e.g., on a facade, because time and environmental conditions alter the original color. In the process, the production of textures is decisive for the outcome, as the glossiness, transparency, type, and characteristics of the relief need to be rendered in great detail.

An example of the importance of materials in relation to lighting is shown in Figure 4. In the interior space of the portico of the 3D-designed building, linear wide-beam luminaires have been placed in the inner part of the portico, above each colonnade, which are aimed towards the interior facade. In these luminaires, the color temperature (3000 K, 4000 K, 5000 K, 6000 K) is varied in each simulation, along with the different reflectivity of the material. On the exterior surface, similar luminaires have been placed at the base of the columns to consistently show the color temperature at 3000 K in each simulation and act as a guide to each differentiation. For the same reason, the reflectivity of the pilasters located laterally on the inner surface remains constant at 70% in each simulation as a benchmark. The results show the simultaneous presence of both factors in each simulation without overshadowing each other. This shows that in cases of a building with low reflectivity values of its surface material, the light can give its own character regardless of its color temperature.

3.1.4. Morphological Elements and Simulation Areas

Each facade shall be divided into regions according to the morphological and decorative elements that compose it to analyze them individually and to examine their dynamics in the facade as a whole. In some cases, the area may consist of a single element. The analysis of the facades of this architectural period is framed by various principles common to other architectural styles as well (Figure 5). The principle of classifying elements in rhythmic order when the elements are uniform and create by their presence a unity that has a beginning and an end. The principle of subordination is observed when a unit in a unity has a greater dynamic and dominates. Finally, the principle of the triadic unity is shown diagrammatically by the base, body, and coronation [38].

An example of the division and analysis of facades reflects the present research, where 150 neoclassical buildings were studied and a total of 70 different elements were identified on the facades of the buildings, which were analyzed and classified in alphabetical order according to their type (Figure 6). It was also found that there is a rich terminology for naming the elements that vary according to the way or location of their placement on the facades. Thus, some elements are therefore counted differently depending on their position [28].

3.1.5. Luminance Contrast

At this point, and just before choosing the artificial lighting, the wider environment around the building needs to be studied. Ambient lighting is a catalyst in its presence and needs to be considered in the study, as, if it consists of high intensities (e.g., the building is located on a commercial street in a large city), it can easily lead the study to incorrect results. So, there is the need to verify the lighting conditions and adjust the contrast between the lights.

3.1.6. Lighting Fixtures

The selection of different luminaires is made, depending on the characteristics of each element (e.g., its position in the facade, size, etc.) to be placed in the simulation area, and on some specific lighting criteria related to technological and aesthetic factors. The factors include the following:

• Their technology covers basic safety requirements concerning the placement of the equipment outdoors such as having high IP and IK indexes (Ingress protection and impact resistance) and energy such as having high luminous efficacy (l m/W). The high color rendering index (CRI) of the source is needed to accurately reveal the colors of various elements. The ability of a luminaire to render the color as faithfully as possible on a material is due to the color rendering of the lamp.
• The dimensions of the luminaire should be chosen so that they are not (as far as possible) visible in the view. Their weight, but also the weight of their peripheral equipment (cables, bases, etc.), should be as light as possible in order to not stress the building in places such as plaster frames and also to not require many and large perforations in the facade for their mounting. Being part of a family of luminaires is also important, so that there is a choice of multiple common luminaires with different beams or a luminous flux.

3.1.7. Position Selection

The positions in the simulation areas (if there are two or more elements and a luminaire is appropriate to cover the lighting effect of more than one element) or individually in a particular element, where the luminaires selected in the previous step will be placed, are defined. Another parameter of the study is the position and aiming of the luminaires. Depending on each element being studied, an attempt is made to identify the appropriate positions, which, on a theoretical level, could highlight this element. An element is studied in isolation, but it is considered that it is part of a facade, so that unnecessary diffusion outside the element is not avoided. Light pollution is a reason that goes beyond the notion of the historicity and architectural value of a building, as it should be taken for granted that we are not interested in a satisfactory lighting effect to highlight a historic building if there is unnecessary diffusion in the surroundings. In cases where luminaires are illuminating downward, the levels of glare should be taken into account.

3.1.8. Simulations

The last step and the most important one, as it is from this point that the results will be produced, concerns the simulations. Each simulation is also a visual result, a photorealistic image. In each image, the result of the illumination of the selected luminaires at the selected positions is obtained. Combining more types of luminaires in different positions helps at this point to study the visual results and draw conclusions. As already mentioned before, 3Ds max software was chosen as the tool for modelling and simulations. For the final rendering of the lighting in each photorealistic image, each morphological element and each luminaire had been previously simulated in Relux and Dialux software in order to verify the characteristics of each luminaire and the quality of the IES files used. This was crucial for the research, as it aims to provide a precise simulation of the luminaires and elements investigated, rather than a simple lighting hypothesis.

3.2. Simulation Results

In accordance with the above methodology, in the process of the research conducted by Balafoutis and Zerefos [39], a great number of more than five hundred simulated images were rendered, whose characteristics varied according to the factors analyzed. From this research, a database of images was created with information from which interesting conclusions can be drawn from their evaluation (Figure 7 and Figure 8). The evaluation of the results was multifaceted and addressed several topics, such as the aesthetic evaluation of the final visual outcome, lighting performance considerations in terms of technical parameters (e.g., intensity, uniformity, etc.), and light pollution levels produced by each proposed lighting scenario. An important issue in this research are the emotions evoked by the different lighting scenarios on historic features on each observer;therefore, lighting experts were asked to accompany and evaluate the results, as presented below.

4. Results

4.1. Evaluation of the Results

The implementation of a lighting study in a historic building or, more generally, in a heritage site, is not completed by the activation of the luminaires but by the activation of the observers’ emotions. So, nowadays there is a need to consider issues related to lighting studies of historic buildings, which can be grouped into “functional factors” and “emotional factors”. Functional factors are related to the quality, technology, and functional characteristics of the lighting equipment. Emotional factors are those that influence users’ evaluation and can be the most difficult to ascertain.

A survey was created for this reason, and its aim is to analyze the different perspectives of the experts, to see whether they converge in any specific direction, but also to compare them in order to examine the relationship between them. The survey was conducted in online form and was accessible from the survey website (http://lhb.eap.gr/) (accessed on 19 July 2019). Several lighting experts were invited by email. The majority of the invitations were sent to members of the International Association of Lighting Designers (IALD). There were 99 evaluators who responded to the questionnaire from 19 different countries around the world. Most of them declared lighting design as their main professional specialty. The survey started with the presentation of some results in image format, from two to four per step. In total, it was completed in eight steps. Once the expert has reviewed the images, he or she is asked to evaluate them on the basis of the visual effect of the lighting, i.e., without giving any further information or technical characteristics. The evaluation consists of a Likert-type rating scale with Close Ended Questions on various topics, e.g., aesthetic impact, lighting intensity, light pollution, etc. One of the many basic topics concerns the emotions generated by the type of lighting scenario of each image (tension, tranquility, awe, boredom, sadness, happiness, neutrality). The analysis plan is to correlate the questions; for example, if an image is rated positively in terms of its aesthetic effect, it is then compared with the evaluation of the light pollution question to determine whether or not the levels are considered low. The analysis of the data obtained from the survey is currently being examined in a research project currently in progress at the Lighting Design Laboratory of the School of Applied Arts and Sustainable Design of the Hellenic Open University.

What emerges from the evaluations is the verification that lighting intensity, depending on its amount, alters emotions. It is found that low light intensities cause boredom in 30–38% of respondents (Figure 9a,b), while very low intensities shoot up to 59% (Figure 9c). In the images where the experts rated the intensities as moderate, the feeling of tranquility is most frequently chosen at 37–40% (Figure 10a,b). As the intensity of the lighting increases according to the evaluators, the feeling of tension increases as well, starting at 40% and reaching 61% (Figure 10c and Figure 11a–c).

Other than the above cases, the responses on the emotions in the remaining images were moderated by the selection of all emotions given to the evaluators. The highest proportion (18%) of the emotion of happiness was selected in lighting that emphasized one element more than the other (Figure 10a), creating a calmness in the whole (37%). The emotion of awe was often found in lighting vertical elements (e.g., column, pilaster) from bottom to top (Figure 12a–c). Finally, a particular finding is that two spots illuminating from the base of a column upwards evoke awe (Figure 12c), perhaps because they highlight the third dimension in the column and the capital, whereas one spot on the same column evokes boredom (Figure 6c), where the effect seems a little flatter.

4.2. Combination of the Results on the Entire Facade

Subsequently, an attempt was made to combine, in each view, the emotions that emerged from the evaluations. The main preferences of the evaluators were collected so that a synthesis of these results could be made, and it was found that the emotions that stood out were those of awe, boredom, tension, and tranquility. Figure 13 shows the morphological elements from which the results were synthesized on the whole facade. The coding of the elements (A, B, C, D) whose results are combined was performed to present the features in each simulation in the following tables (Table 1, Table 2, Table 3 and Table 4).

For the lighting of the base, since the evaluation did not reveal any noticeable effect, a linear luminaire (Flood Angle 32°, 3000 Κ, 2163 lm) was used, and the position of the luminaires, as shown in Figure 14, was considered a neutral effect by the experts and common in the market. For the illumination of the coronation, the same luminaire was used as the base, so that in the result there is a uniformity at the two boundaries of the facade (top and bottom), to focus the observation on the piano Nobile and to show the variation of the illumination from image to image.

The following figures (Figure 15, Figure 16, Figure 17 and Figure 18), shows visually the effect of the synthesis of the emotions on the entire facade.

Figure 15. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of awe (Balafoutis, 2021).

Figure 15. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of awe (Balafoutis, 2021).

Table 1. Luminaires of Figure 15.

Element	Luminaire
A (Window with balustraded balconette)	A3—Flood Spot (38°)—3000 K—2600 lm
B (Ionic column)	C2—Spot—3000 K—3780 lm
C (Door with pointed pediment)	A2—Narrow Spot (12°)—3000 K—2450 lm
D (Window with shouldered surround)	A6—Flood Spot (34°)—3000 K—850 lm

Table 1. Luminaires of Figure 15.

Element	Luminaire
A (Window with balustraded balconette)	A3—Flood Spot (38°)—3000 K—2600 lm
B (Ionic column)	C2—Spot—3000 K—3780 lm
C (Door with pointed pediment)	A2—Narrow Spot (12°)—3000 K—2450 lm
D (Window with shouldered surround)	A6—Flood Spot (34°)—3000 K—850 lm

Figure 16. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of boredom (Balafoutis, 2021).

Figure 16. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of boredom (Balafoutis, 2021).

Table 2. Luminaires of Figure 16.

Element	Luminaire
A (Window with balustraded balconette)	A1—Light Blade Spot (Laser)—390 lm
B (Ionic column)	A2—Narrow Spot (12°)—3000 K—2450 lm
C (Door with pointed pediment)	C4—Wide Flood—3780 lm
D (Window with shouldered surround)	A1—Light Blade Spot (Laser)—390 lm

Table 2. Luminaires of Figure 16.

Element	Luminaire
A (Window with balustraded balconette)	A1—Light Blade Spot (Laser)—390 lm
B (Ionic column)	A2—Narrow Spot (12°)—3000 K—2450 lm
C (Door with pointed pediment)	C4—Wide Flood—3780 lm
D (Window with shouldered surround)	A1—Light Blade Spot (Laser)—390 lm

Figure 17. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of tension (Balafoutis, 2021).

Figure 17. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of tension (Balafoutis, 2021).

Table 3. Luminaires of Figure 17.

Element	Luminaire
A (Window with balustraded balconette)	A3—Flood Spot (38°)—3000 K—2600 lm
B (Ionic column)	C1—Narrow Spot—3000 K—1470 lm
C (Door with pointed pediment)	C2—Spot—3000 K—3780 lm
D (Window with shouldered surround)	C1—Narrow Spot—3000 K—1470 lm

Table 3. Luminaires of Figure 17.

Element	Luminaire
A (Window with balustraded balconette)	A3—Flood Spot (38°)—3000 K—2600 lm
B (Ionic column)	C1—Narrow Spot—3000 K—1470 lm
C (Door with pointed pediment)	C2—Spot—3000 K—3780 lm
D (Window with shouldered surround)	C1—Narrow Spot—3000 K—1470 lm

Figure 18. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of tranquility (Balafoutis, 2021).

Figure 18. Simulation of the entire facade and synthesis of lighting scenarios with the most positive evaluations of the emotion of tranquility (Balafoutis, 2021).

Table 4. Luminaires of Figure 18.

Element	Luminaire
A (Window with balustraded balconette)	B1—Spot Angle (8°)—3000 K—541 lm
B (Ionic column)	C2—Spot—3000 K—3780 lm
C (Door with pointed pediment)	C4—Wide Flood—3780 lm
D (Window with shouldered surround)	A6—Flood Spot (34o)—3000 K—850 lm

Table 4. Luminaires of Figure 18.

Element	Luminaire
A (Window with balustraded balconette)	B1—Spot Angle (8°)—3000 K—541 lm
B (Ionic column)	C2—Spot—3000 K—3780 lm
C (Door with pointed pediment)	C4—Wide Flood—3780 lm
D (Window with shouldered surround)	A6—Flood Spot (34o)—3000 K—850 lm

In the case of awe (Figure 15), the division of tonality into levels with emphasis on certain elements, such as the cornices, was noted, and this may have led the evaluators to select this emotion. Boredom was possibly chosen because of the low brightness of the elements and consequently of the whole face (Figure 16).

In the tension example (Figure 17), the strong variations in the concentration of light in the elements may be the main reason for the selection of this emotion. Finally, tranquility in the latter case is quite similar to that of awe, with the only difference being the greater visual uniformity of Figure 18, which is probably what caused the emotion of tranquility.

5. Discussion and Conclusions

In recent years, the exterior lighting of buildings and monuments of cultural heritage has become a topic of discussion, in which there is a need to explore directions that can create a framework for thoroughly considering the lighting techniques that are supposed to highlight an architectural heritage object. Does emphasis by lighting on structures of such architectural typology need to have specific boundaries that define it and differentiate it from other forms of illumination such as artistic lighting? It also raises further concerns regarding the possible proper methods and context within which such illumination can be achieved and who can define these methods. Highlighting is concerned with the most ideal presentation of the subject matter on display, i.e., the most ideal presentation of the architectural value and historical significance, as in the case of this research, of a historic building.

The aim of this research is to create a methodology for the lighting of buildings and monuments of cultural heritage. This methodology proposes and studies the parameters that need to be considered. Parameters that have aesthetic, technical, and environmental characteristics underline that the lighting of a historic building cannot be implemented as an artistic approach of an individual and clearly not as a technical solution of a composition of luminaires on a facade with the main criterion of sufficient illumination. Instead, it explores, in a step by step way, each element found on the facades of historic buildings and selects possible positions of equipment and luminaires that are then presented through simulated images to experts in the field of lighting to evaluate the result. The experts come from various disciplines such as architecture, electrical engineering, physics, arts, etc., and this creates a plurality of opinions, which is evident in the results of the evaluations.

The current part of the research presented here focuses on a case study derived from the database of the methodology and concerns the emotional impact of the visual effect of different lighting scenarios. What is immediately evident is what we now consider obvious: lighting evokes emotions. The results of the methodology evaluated according to the question “What emotion does this effect cause you?” show the potential that lighting has nowadays to cover many emotions with its diversity. Of course, negative emotions are not considered eligible in the methodology, but they can certainly be considered as a good guide to avoid unsatisfactory results in a lighting study. Therefore, it may be that the methodology created considers a multitude of scientific and technical factors that have been simply mentioned in this article, such as energy, environment, light pollution, equipment technology, lighting performance, protection of the monument, its proper promotion, etc., but it is certainly human emotion that dynamically determines the outcome, and for this reason, it needs to be respected.

However, the goal of this methodology is to further enrich the database and complete a framework with verified results through which researchers can consult, gain ideas, and synthesize lighting scenarios for heritage buildings. This proposal can form the basis and assist with the output material for the future setting of standards in the field of lighting for the illumination of historic buildings, as historic buildings have been holistically studied, either as a whole, or in terms of the individual morphological elements of cultural heritage, and their relationship with lighting. These standards will guide designers to verified results with which to highlight the values of the subject matter, without the subject matter being the background for an unrelated lighting study.