Application of Climate Based Daylight Modelling to the Refurbishment of a School Building in Sicily

Abstract

This paper aims at promoting the use of Climate Based Daylight Modelling (CBDM) and related state-of-the-art metrics by discussing a range of design options to improve daylight fruition in rooms with different orientation, shape, function, and furniture of an elementary school that is located in the Mediterranean climate of Agira (Italy). The local climatic conditions, with clear skies for most of the year, require the integration of different shading and re-directing systems with the existing envelope and rooms' layout. Results show that the dynamic modelling is a powerful and 'creative' tool in the designer's hands, which helps to inform about the choice of the most appropriate technological solutions and on their architectural integration. Comparison with mostly used static daylight metrics, such as the average Daylight Factor (aDF) and the Uniformity Ratio (UR), reveals a contrast with what would be suggested if considering these metrics alone, as prescribed by the Italian legislation. These outcomes rebate the need of performing more accurate and dynamic daylight simulations using recorded (i.e., varying) rather than fixed sky conditions to correctly inform the design process.(UDI) metrics [5] for the evaluation of design proposals that were submitted to the Priority Schools Building Programme [6].However, despite the indisputable advances achieved by considering real (i.e., recorded) time series of irradiance/illuminance values from largely available weather datasets, there are some concerns to bear in mind when adopting CBDM.First, the choice of the weather dataset should be based on the purposes of the modelling and the underlying characteristics of the dataset itself (e.g., location, measurement period, statistical techniques being employed for resembling typical or extreme weather conditions). In fact, as demonstrated by Bellia et al. [7], using the IWEC (International Weather for Energy Calculation), Meteonorm, Satel-Light, or TRY weather sources could lead to different results in terms of Annual Light Exposures (i.e., the amount of light falling onto a certain point throughout the year, measured in luxh), and of various dynamic metrics, such as the Daylight Availability (DA, [8]) and the UDI. This happens because usually the TRY datasets show lower values for the global horizontal irradiance than in other sources; however, these outcomes were only proven for a north-oriented room, while different exposures could lead to different results because of sunlight contribution [7].Secondly, there is a lack of consensus around the choice of the metrics and of their thresholds to judge if a space is 'well daylit' or not. The variety of CBDM approaches employed for educational buildings, ranging from traditional illuminance and luminance distribution under fixed sky conditions to novel circadian metrics, has been documented in a recent review paper by Costanzo et al. [9].As an example, in regards to the above-mentioned adoption of the UDI metrics for school buildings design in the UK, Littlefair noted that the...

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