Interaction between qualitative and quantitative approaches in the teaching of architectural design

In order to improve the understanding of daylighting by students in architecture, we seek a better integration between scientific and architectural languages and we try to strengthen the links between quantitative (knowledge on daylighting as a physical phenomenon expressed in mathematical terms) and qualitative (knowledge on daylighting as a modifier of luminous ambiance expressed in a descriptive way using natural language).

This will help students to reach a better control of the phenomenon, to build their own criteria and to apply them in the sketch phase of architectural design. It may also be a basis for a aiding-system for the design in the sketch phase. We used fuzzy set methods and multivalued logics to model the building and its environment and to structure knowledge taking architect’s preferences into account.

Measurements and qualification of luminous ambience in daylighting

This paper is centered on the relationship between intuitive and quantitative approaches for the understanding of luminous ambience in order to formalize criteria for the classification of luminous ambiences.
We measured luminance and illuminance levels on glazed and opaque surfaces in interior spaces and built a synthetic scheme of these levels. We then analyzed and compared these measures and their interpretation to impressions felt by several subjects in the spaces, or to intentions expressed by the architect during the design of the project when available.
This comparison has proved itself very meaningful and shows that many relations between the intuitive approach and quantitative measured data may be established. The second part of the work deals with the definition of criteria to classify ambiences. They allowed us to prepare a computer tool, based on neural nets which will be used to help architects store and browse through a large number of images.

A comparative analysis of luminous ambience designed for equivalent functions

The first part of this work focused on the elicitation of links between qualitative and quantitative approaches for luminous ambience in daylighting. We measured luminance and illuminance levels on glazed and opaque surfaces in interior spaces. We analysed and compared these measures and interpretations to impressions felt by subjects in the spaces, or to intentions expressed by the architect during the design of the project when available. This comparison has proved itself very meaningful and shows that many relations between the intuitive approach and quantitative measured data may be established.
In the second part, we performed a comparative analysis between qualitative and quantitative data for luminous ambience designed for equivalent functions. It helped us better define the meaning of the qualitative terms used by subjects. It also helped us enrich the quantitative point of view through the definition of new notions such as the rhythm of repetition of contrast levels or the size of surfaces having a particular level of luminance. This work can also be used to enrich the language on luminous ambience and be of great help on the classification of luminous ambience. We use this comparative approach in teaching, in our school of architecture.
Beyond quantitative data, our method allows to perform an analysis closer to architects’ needs and expressed in his language. This link between qualitative and quantitative allows to fill the gap between scientific technique and architectural design. It may be included in RADIANCE, to provide results related to architects’ intentions.

Comfortable and/or pleasant ambience: conflicting issues?

We present here a theoretical study about the relationships between comfortable and pleasant ambiences. The notion of comfort is not sufficient for the study and design of ambience. Ambience is defined here as the way the environment affects a subject. Subjects are naturally affected by a global ambience. However, for the analysis, we distinguish between luminous, aesthetic, thermal, acoustic…ambience.
Comfort definitions exclude the notion of tension and psycho-physiological disturbance on subjects, whatever its level may be. The question of pleasant ambience is naturally not fully answered. However, one way to define a pleasant ambience especially includes the notion of tension on subjects affected by an ambience. The case of the house on the cascade by F L Wright perfectly illustrates this point. This house is situated on a waterfall whose acoustic level is above all norms. Therefore this house is not comfortable. However, it is widely recognised and taught as a reference for its pleasant ambience, especially for the contribution of the acoustic ambience. In this case, the comfortable and pleasant sides of ambience are conflicting.
As modern technologies are improving, artificial lighting and ventilation, for example, can lead to perfectly comfortable ambience. However, it is widely recognised that natural lighting and passive ventilation are more pleasant.
We develop this discussion on the basis of the results of a study on qualifications of luminous ambience and on other theoretical and technical works. We believe that this investigation is nowadays important because the technological sides of ambience are improving: comfortable ambience may be designed, but are they pleasant? We think that a very global view on ambience is now needed.

Dimensions of personality in the responses to luminous ambiences

In this multidisciplinary work, we propose a practical framework to study the variability of subjective responses to identical luminous ambiences (atmosphere). We focus on the influence of personality dimensions.
Architects build spaces for which they define functional characteristics and an esthetical concept, while considering the quality of ambiences. The success of a building depends on the subjective perceptions and the behavioural responses of users regarding these functionalities and ambiences. In most works on ambiences, the user is generally considered as an “average user” (mister anybody). The importance and variability of the subjective character of responses has often been mentioned. However, we still do not have effective indicators on the relationship between personalities and the sensations of comfort and pleasure in a luminous ambience.
The purpose of this work is therefore to study the relationship between the perceptivo-cognitive handling of luminance and chromaticities and the way social spaces are occupied and used depending on their luminous ambience.
We study the behaviour of subjects in a laboratory and on sites (in rest areas). At the same time, we study the luminous ambiences in these areas.

We obtain indicators on subjects:
1) by measuring perceptive sensitivity to luminous stimuli (ERP method, in laboratory) with an electroencephalogram on 48 people in order to detect high and low level sensation seekers according to their sensations of pleasure
2) by observing the behaviour of the same subjects in rest areas and by discussing with them with a questionnaire.
We obtain indicators on existing luminous ambiences (with natural light and artificial light to complement it) in rest areas by measuring luminance, illuminance and chromaticities on opaque and transparent envelopes in these areas.
We then greatly modify luminous ambiences in these areas (by partially covering windows and by modifying artificial light). We then repeat the observations with the same kind of subjects.

Luminous ambience, quantitative/qualitative data and subjective response

This paper presents several years of research in luminous ambience in daylighting. It began with works on the relationship between intuitive and quantitative approaches for the understanding of luminous ambience. We collected quantitative data from measurements of illuminance levels on glazed and opaque surfaces in interior spaces.
From these measures we could build an interpretation related to the luminous ambience. They were compared to what was expressed by interviewed subjects in these spaces or to intentions expressed by the architect during the design when available.
At the end of this work, a first issue was: how could we explain that comfort and pleasantness of an ambience may often be conflicting? We investigated this question and showed that comfort is not sufficient to express the quality of a luminous ambience and that some degree of “discomfort” may be needed by individuals to feel an ambience as pleasant.
Confronted to the variety of answers given by people about luminous ambience, we tried to understand how subjective responses to a luminous ambience relate to the dimensions of personality. As this particular point of view seemed to have seldom been investigated, we decided to start a project specifically focused on this subject. The purpose of this paper is therefore to sum up this line of research, from quantitative measurements to dimensions of personality.

Measurement and interpretation of luminous ambience

This paper presents part of a multidisciplinary work with three teams: two laboratories of psychology and a laboratory of lighting/architecture. We concentrate here, within the project, on activities on luminous ambience and focus on the lighting/architecture part. The problem we studied was:
How is it possible to concisely express the variety of luminous ambience qualities on the basis of a large number of light measurements? More precisely, in order to analyse the quantitative data collected from measurements, we intend to define interpretation models. The result of these interpretation models should be easily usable for further analysis and understandable by architects. Architects do not manipulate expressions such as luminance levels. In order to express their intentions for a luminous ambience, they use qualitative and descriptive expressions.
On the basis on these interpretations, how can we change the existing concept of artificial lighting for a space in order to lessen energy costs, to keep a good performance of lighting and to improve the comfort and pleasantness of users? More precisely, comfort and pleasantness are closely linked to contrasts thresholds, gradual ranges of luminance and chromaticities on the interior envelope. Artificial lighting is used by the general public and designers not only to reach a sufficient level of lighting on work surfaces, but also to increase or decrease contrasts and gradual ranges of luminance and modify the colour of the light on the interior envelope in order to reach a comfortable and pleasant ambience. In that respect, we can say that the expenditure in electric energy is also due to the fraction of artificial lighting used to create comfort and pleasantness of ambience.
To address these two questions, we have studied existing luminous ambience in two sites in Paris. The spaces under study were rest areas. We defined the method for light measurement on the opaque and glazed interior envelope (with luminancechroma and luxchroma meters) in mixed lighting (both natural and artificial). We interpret the measurements in terms adapted to architects. We defined the concepts for different luminous ambiences and built these modified ambiences in the sites themselves.

Simulation of Luminaires in Radiance: Verification Method

In the process of architectural design architects can use different software tools for modelling and simulation. These programs allow them to simulate imaginary buildings, and verify their intentions, preferences and respect of norms, in order to bring the resulting ambience closer to architects intentions. On the other hand, programs follow strictly defined geometrical and physical laws, which give quantitative accuracy to the project.
For modelling and simulation in architecture there is a great number of different computer programs available on the market, such as AutoCAD, 3DStudio Max, PovRay, Radiance, etc. All these programs offer similar possibilities for modeling of geometrical primitives, but their capability to simulate luminous ambiance of the building is different. Definition of luminous ambiance is rather complex, and it involves description of artificial (luminaires) and natural (sun, sky) light sources, building position and environment, and materials used for building interior and exterior. Lighting design programs are software tools for calculation and visualization of luminous ambiance.
Due to the complex nature of light, all lighting design programs, in the process of light modelling, involve some simplifying assumptions, which lead to some amount of calculation inaccuracy.
The aim of this paper is to propose a method for evaluation of the error introduced by computer simulation of luminaires. The method compares luminaire simulation results from Radiance2 software against results obtained from lighting calculation methods proposed by “Illuminating Engineering Society of North America” – IESNA.

Will it really be soft and calm, my luminous ambience?

The intake and distribution of natural light in interior spaces are imagined early in architectural design: placement of openings, orientations and inclinations, depth of spaces, etc. are defined during the first sketches. However, existing design aid tools are ill adapted to this early phase where the building is not completely defined.
In order to help overcome these difficulties, we propose to use the models of buildings in design. They are placed under an artificial or natural sky. Inside images are displayed via micro-cameras on a computer screen. The software computes correspondence between points of the image and luminance levels in the actual models. Knowing luminance in every point of the interior envelope, the software we are developing, analyses the luminous ambience on the image.
The main contribution of this work lies within ambience analysis on images, expressed in qualitative and quantitative terms. For example, the result of the analysis of a field of vision is “calm and clear ambience” or “tense and rather dark”, etc. Definitions of such qualitative terms, based on previous works, are shown to users along with related quantitative and reference data.
These methods help the use of natural light, hence of renewable energy. It allows good use of the natural luminous flux: to have enough but not too much (avoiding visual discomfort and overheat). It also allows architects to follow the aesthetic evolutions of the ambiences they imagined.

Interpretation models and their application for luminous ambience

Quantitative information from measurements or simulations of interior luminous ambiences yields a large quantity of data. These data may be very useful to analyse the performance and comfort of a luminous ambience in design or rehabilitation and promote a controlled use of daylighting instead of artificial light. However it is necessary to interpret these data with terms accessible to architects.
The purpose of our work was both theoretical and applied: we improved data collection and interpretation methods of quantitative data on luminous ambience. We then applied these methods to design a modified luminous ambience in an existing space.
We had the opportunity to work in the cafeteria of the “Galeries du Grand Palais” in Paris.
We improved the measurement method for luminance and chromaticities on the interior opaque and glazed envelope of spaces in natural and mixed lighting (both natural and artificial). We interpreted these measures (a large number of quantitative data) in qualitative terms. On the basis on these analyses, we followed the inverse path: we expressed the concepts for modified luminous ambiences, then built these ambiences. We could verify with measurements the correspondences between our qualitative intentions and measured quantitative data.
This work gave interesting insights for the definition of criteria for the analysis of luminous ambience.

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