Comparing daylighting performance assessment of buildings in scale models and test modules

Abstract

Physical models are commonly used to assess daylighting performance of buildings using sky simulators for purpose of research as well as practice. Recent studies have pointed out the general tendency of scale model assessments to overestimate the performance, usually expressed through work plane illuminance and daylight factor profiles, when compared to the real buildings. The cause of the discrepancy between buildings and scale models is due to several sources of experimental errors, such as modelling of building details, mocking-up of surface reflectances and glazing transmittance, as well as photometer features. To analyse the main sources of errors, a comparison of a full scale test module designed for experimentation of daylighting systems and its 1:10 scale model, placed within identical outdoor daylighting conditions, was undertaken. Several physical parameters were studied in order to determine their impact on the daylighting performance assessment. These include the accurate mockingup of surface reflectances, the scale model location, as well as the photometric sensorproperties. The experimental study shows that large discrepancies can occur between the performance figures. They lead, on average, to a relative divergence of + 60 % to + 105 % in favor of the scale model for different points located in the side lit room. Some of these discrepancies were caused by slight differences in surface reflectances and photometer cosine responses. These discrepancies were reduced to a + 30 % to + 35 % relative divergence, by putting in the effort to carefully mock up the geometrical and photometrical features of the test module. This included a sound calibration of photometric sensors, whose cosine-response appeared at the end to be responsible for the remaining relative divergence observed between the daylighting performance figures.

Towards an Analysis of Daylighting Simulation Software

“…However, as studies by Thanachareonkit, Scartezzini and Andersen [3] show, there is a wide divergence between results obtained from a scale model and those observed in a real model.…”

Scale-Model And Simulation-Based Assessments For Design Alternatives Of Daylight Redirecting Systems In A Side-Lighting Educational Room

“…A study focused on discrepancies observed in scale models due to inaccurate internal surface materials. Both higher and lower reflectance values than actual ones were tested in two scale models (Thanachareonkit et al, 2005) . As the actual and model surface materials were mentioned in Section 2.1.2 and Table 1, and there was an emphasis on light redirection, higher reflectance were preferred similarly for internal surfaces as in the previous study.…”

“…Scale models are a means to develop and evaluate variants in architectural design. As a means to access daylighting performance, they require a high degree of accuracy and careful selection of materials to reflect the surfaces properties and geometric precision of the proposed design, as well as a known luminous environment (Bodart et al, 2007;Kesten et al, 2010;Thanachareonkit et al 2005) . The main sources of experimental errors of scale models are due to correspondence of sky conditions and the surrounding buildings (Kesten et al, 2010) .…”

“…Other sources of experimental errors are surface reflectance due to inappropriate materials used in models, and sensors' photometric properties. The use of scale models in the early stage of lighting design process was recommended as a direct approach to daylighting performance of a real building; since scale models mostly and exactly correspond to distribution of daylight in a real room (Bodart et al, 2007;Thanachareonkit et al 2005) . Such features have triggered us for testing and applying procedures of redirecting systems in this study.…”

Comprehensive annual daylight design through a goal-based approach

“…Another attempt to reduce the calculation intensity of glare was developed for DOE-2 in the 1980s. Winkelmann and Selkowitz (1985) used internal illuminances and known building geometry to find glare at given (Ubbelohde, 1998;Cannon-Brookes, 1997;Thanachareonkit et al, 2005), but it still provided an interesting modelling framework from which to build upon, briefly introduced by Kleindienst and Andersen (2009a). The proposed method attempts to improve on the weaknesses of the DGPs while using information from an input model's geometry and materials, without the need for any renderings or non-illuminance simulations.…”