# A Novel Approach for the Definition of an Integrated Visual Quality Index for Residential Buildings
## 3 Methods
### Quantitative Parameters  
Several parameters are responsible for the perception of visual comfort. The first step for the definition of the VQI therefore involves the proper choice of the parameters being taken into account. The building function strongly influences the process: in dwellings, it is important to create a pleasant and relaxing environment, while productivity may be of secondary importance. Another crucial issue is the flexibility of the lighting environment: the same space may be used for very different tasks and every inhabitant should be able to adapt the space to his/her needs or preferences.  
The IESNA lighting handbook [27] detects a number of design issues that are determinant for the design of indoor environments. They regard for instance daylighting, the type and position of the artificial sources of light, and the surface characteristics; according to the use of the building, they more or less affect comfort. As an example, for residence--an ordinary task--the \"very important issues\" are illuminance, source/task/eye geometry, direct and reflected glare, and color appearance. According to [PERSON] et al. [22], whose study regards visual quality in residential buildings in Hong Kong, satisfaction with daylighting is the most important factor in determining the level of luminous comfort, and in particular there is a direct correlation between solar access and user satisfaction. Among other parameters, the most important are the perception of uniformity and the avoidance of glare. In residential environments people may be more tolerant of glare than in office settings, where glare may impede the task performance. Finally, color temperature is gaining interest in literature and its influence on mood, cognitive performance, and satisfaction has been deeply investigated in the last years [44]. In particular, it is interesting to consider how color temperature influences melatonin production and therefore human alertness and response [45]. It is important to recall that all visual stimuli affect human comfort following three different routes: the visual system, the circadian timing system, and mood and motivation [46]. Therefore, every parameter involves a physiological response from the viewer but affects also his/her psychology in a relation that has not been completely explained yet. An interesting study in this field was conducted by [PERSON] et al. [47] who tried to measure the two components independently using both questionnaires for user satisfaction and a wearable biometric device for physiological responses (heart rate and skin conductance). Research of this kind is beyond the scope of this paper and the effect of each parameter on visual comfort will be considered in its entirety.  
Based on the bibliographic research previously presented and on the opinion of a panel of experts interviewed within the CASA project, the aspects of visual quality which were taken into account for the proposed index are the following:  
1. Daylight access;
2. Glare probability from daylighting;
3. Illuminance level from electric lighting;
4. Glare probability from electric lighting;
5. Color appearance of electric lighting.  
During the design phase, these aspects help to properly tackle the design of orientation, shape, and position of windows (a-b), the lighting system (c-d), shading devices (b) and lighting bodies (d-e). Uniformity of illuminance was not considered because it is not an absolute value when task performance is not predominant [48]. In residential buildings, inhabitants tend to appreciate different patterns of light and shadows.