Daylight Design for Urban Residential Planning in Poland in Regulations and in A Practice. A Comparison Study of Daylight Conditions Observed in the Four Neighbouring Residential Areas

This paper reports on the partial results of the research aiming to illustrate how an integration of daylight design into an architectural planning process can help designers to create the residential buildings in respect to the environmental issues, solar and illuminance gains, as well as, the residents’ needs and comfort. It describes how changing daylight recommendations affected the design of the block of flats regarding their orientation, the spacing, the forms, and the size of the windows in the four urban residential areas. The results of this study help to determine more precise characterization of daylight indicators useful in architectural planning.


Introduction
Daylight is named as an essential aspect of home [1] and an integrated part of the architectural planning. The design of daylight is crucial in the residential architecture and it influences the residents' visual performance, comfort and health. The perception of daylight variability and contrast contributes to an aesthetic appreciation of the spaces [2]. The quality and quantity of daylight within residential interiors depend on the several internal and external factors (figure 1). A control of daylight within the residential environment can be done in many ways but the major ones are through a control of the build form and through a control of the daylight performance inside the buildings [3]. The questions often asked during the building design process are: how much light is sufficient for humans for the optimal visual, biophysical and psychological performance and how to provide the optimal quantity of a superior quality daylight within the residential environment [4].
The sets of rules that specify the recommended design solutions and the target values of daylight performance through the different daylight indicators are partly explained in the national building and lighting standards. These documents should provide guidelines for the designers to the questions mentioned above. However, the latest Polish building daylight standard PN-71/B-02380 was withdrawn in 2005 [5]. The current Polish daylight recommendations, referring to the sunlight provision, spacing, overshadowing and the window-to-floor area ratio (WFR), included in the national building standards, seems to be very limited (Table 1). To illustrate an impact of the changing daylight recommendations on the design of the residential dwellings, an excerpt from the comparison study of the daylight conditions in the four neighbouring residential areas built in different time periods is presented in this paper.

Daylight in the Polish recommendations
The national documents regulating daylight design in the buildings can be divided into four major categories: daylight and building standards, laws, guidance documents and a various kind of national or regional approved documents [3]. Due to a progress in photometry and the computer aided design tools, the ways and the parameters describing daylight performance keep changing, which is reflected in European daylight recommendations [6]- [9]. The Comité Européen de Normalisation (CEN) Technical Committee: CEN/TC 169/WG 11 is currently working on a revised version of the new European daylight standard EN 17037 Daylight of buildings [7], which contains recommendations for daylight and sunlight provision, target daylight factor values, recommendations for the view, glare protection and procedures of the suggested calculations of the chosen daylight indicators.
The new European standard is awaited in Poland, where it could replace the latest withdrawn building daylight standard PN-71/B-02380 Natural Interior Daylighting Code of Practice [10]. The old regulation detailed the general conditions of daylight distribution, daylight factor (D or DF) calculations and values, daylight coefficients, the glass transmittance and the reflectance values. Apart from the daylight standards, daylight design guidelines were and are mentioned in Polish building regulations. They usually focus on the distances between buildings, an orientation, the WFR and WWR values, and the insolation times. To illustrate the changes in daylight considerations, the review of daylight guidelines derived from historic and current Polish building regulations are presented below ( Table 1).
The analysis of the data presented above show that while the recommendations regarding the orientation and the WFR values have not been changed, the regulations referring to the building spaces and overshadowing have been altered. The recommended distances between buildings are getting smaller which may influence the provision of daylight within the residential spaces.

The provision of daylight within the residential space
The basic daylight consideration in the residential environment include design decisions about a geographical location and orientation, a form of a building, an avoidance of external obstructions, the spacing between buildings, a position and a size of daylight apertures. There are many ways to introduce daylight into a residential building including:  high-performance glazing  daylight-optimized fenestration design,  climate-responsive design of the glass openings  window-to-wall area ratio WWR  skylights  tubular daylight devices  solar shading devices  daylight-responsive electric lighting controls  daylight-optimized interior design  design of shading systems  surface reflectance of the used materials  others. The design of daylight within the residential environment is not only focused on a provision of a right amount of an excellent quality sunlight and skylight to ensure good visual conditions and to reduce the electricity demand, but also on ways how to do it without undesirable effects like glare, veiling reflections and thermal discomfort. It is important to mention, that the daylight availability varies in both: the amount and the spectrum, depending on many factors including a season of the year, a nature of the cloud cover and a predictability of the weather conditions. The control and the appraisal of daylight within interiors is challenging due to the altering daylight conditions and its availability. It may also affect the moods of the occupant of a building. The costs of the daylighting solutions, usage, maintenance can be predicted. However, the non-visual impact of daylight on the residents' wellbeing and health are much more difficult to estimate.

Method
The study of daylight conditions in the four neighbouring residential areas are done in two stages. During the first stage the urban, architectural and physical properties of the building forms significant for the each of the four residential areas are analysed and compared ( Table 3). The comprehensive study of the external, physical parameters like a building orientation, spacing, and a size and position of the windows and rooftops is performed in relation to the daylight recommendations found in building standards (figure 2) along with a photographic documentation, and the sites measurements. During the second stage of the study, the daylight conditions in 0 carefully chosen flats are apprised by a sequence of in-situ measurements, the computer simulations and the direct questionnaires with the residents who occupy them. The daylight performance indicators, which are also included in the daylight recommendation for the Polish building standards, like: insolation time, daylight factor, the WFR, are defined.

Results and discussion
The investigated, neighbouring residential areas were created from 1973 till 2013 in Poznan, Poland ( Table 3). The daylight recommendations considered while the areas had been designed could be obtained from different Polish building standards and the approved documents. For the first stage of this study, only the daylight references found in the building regulations and the PN-71/B-02380 Natural Interior Daylighting Code of Practice [10] were taken into account ( Table 2). The study of the physical characteristic of the buildings and their arrangements in the context of daylight, shows that they were designed accordingly to the daylight recommendations mandatory at the time of their creation. The preferred way for the provision of daylight to all of the investigated buildings were the side and roof windows. In Oswiecenia (C1) and Polanka (C2), cases 1 and 2, there are no apartments with all the widows facing north. The dominant orientation of the windows is NE and SW in C1 and EW in C2. According to the changes in the regulations, the distances between buildings are diminishing. The distances between C1 buildings are approximately 25 m, which is twice the amount of the distance between C2 buildings. The dominant form of the buildings for C1 and C2 are simple perpendicular forms. The Milczanska (C3) and Malta Fountain (C4) block of flats have the compound forms with the inner courtyards. Some of the buildings in C3 and C4 are connected on the ground level. Due to the diminishing distances between buildings, the provision of daylight is the best in C1 and the worst in C4, especially for the one-aspect apartments facing the courtyards. The first observations withdrawn from the physical characteristic comparison were evaluated in the second stage of this study during the insitu measurements inside the 10 selected apartments and during the directed questionnaires. The number of received data is still analysed. However, in relation to the daylight recommendations described in this paper, the values of the widow-floor-ratio parameter are lower in the C2 and C3, although they have not been changed in standards since 1961.
The reviewed standards do not consider key issues for a residential daylit space like: quality of view, protection against glare, brightness uniformity or the non-visual effects of daylight on the residents, which were investigated in the second stage of this study.
The key building parameters affecting daylighting designs and reflected in daylight recommendations in the Polish building standards, do not guarantee good provision of daylight ( Table  2). They do not inform about daylight performance within the rooms. The levels of daylight in residential flats can be severely reduced by neighbouring buildings especially in C4 situation.

Conclusions
The responses to the following questions: how much light is sufficient for the residential rooms and how to provide the optimal quantity of a superior quality daylight within the residential environment, are not found in the daylight recommendations in Polish building standards. The quality and the quantity of daylight and its performance are not addressed in the current daylight regulations.
The preliminary results of the comprehensive analysis of the daylight recommendations and their applications in a context of the investigated buildings and interiors, from the four chosen areas indicate that daylight regulations are fragmentary and focused more on a control of the built form than on an actual performance of daylight. The tendency expressed in the regulation to diminish distances between neighbouring buildings may aggravate a daylight provision to the buildings, an insolation time and a quality of the view, therefore the quality of daylight overall.  The most popular WFR parameter, found in the Polish recommendations, does not indicate anything about a direct obstruction, an orientation or a type of glazing, which all affect daylight provision to the building. Apart from the daylight factor parameter, explained in the PN-71/B-02380 and in use until 2005, none of the others known daylight indicators addressing a quality or a quantity of daylight in the residential buildings, are recalled in Polish standards.
The limitations of the daylight recommendations in the building standards influence the design decisions and a creation process of living spaces. Constantly decreasing distances between the residential buildings and their new compound forms have an impact on daylight conditions which may have consequences for the residents' quality of life.