Daylight Modelling Research Articles

96/04285 A theoretical investigation of the best heat demand for public baths

In Malaysia, no long-term daylight data are measured. It was only recently that the need to measure the availability of daylight became urgent when the importance of daylighting in buildings was rediscovered. The hourly daylight availability has been simulated for the Malaysian sky using daylight modelling techniques based on empirical and measured solar irradiation and cloud cover data. This paper presents the techniques involved in producing exterior illuminance data. These data were then compared with measured illuminance at Shah Alam and Bangi, Malaysia. The global illuminance levels are generally high, with values exceeding 80,000 lux at noon during the months when solar irradiation is highest. Even during the months when the ground receives less solar irradiation, the peak illuminance can reach 60,000 lux. Applications and uses of such data are in daylighting design, both for visual and thermal comfort, task illuminance and energy-conscious design of buildings. Recommendations are made at the end of the paper on the various climatic data that are required to be measured for overall daylighting design applications.

95/04067 R502/R22 — substitute refrigerant R507 in industrial cooling

Currently, there is no methodical procedure for selecting solar-optical properties of roller shades, which affect the energy and indoor environmental performance of perimeter building zones. This paper presents a new systematic methodology for identifying the range of shading properties (openness factor and visible transmittance) that can significantly reduce the risk of glare. A model that calculates angular beam–beam and beam–diffuse shading optical properties using minimum inputs is used within a hybrid ray-tracing and radiosity daylighting model, validated with full-scale experiments. The temporal variation of beam and total vertical illuminance is used to define the annual visual discomfort frequency and establish a process for selecting the range of acceptable shading properties for each set of external parameters (location, orientation, glazing visible transmittance, and buffer zone). The combined impact of visible transmittance and openness factor on discomfort frequency and daylight metrics is non-linear and complex. Recommendations for openness factors and visible transmittance values are made for different scenarios. Selecting the upper limits of suggested ranges can provide more daylight into the space and reduce the probability of high contrast. These guidelines may be used for selection of shading products, followed by considerations about energy savings and provision of outside view.

Luminous efficacy: Evaluation of models for the United Kingdom

Daylight values are frequently required in building design and yet daylight records are unavailable for most sites in Europe. This paper presents several different approaches used for the prediction of global, diffuse and direct luminous efficacies. A much simpler luminous efficacy model is also proposed. The analysis is divided into the sections which describe luminous efficacy of direct, global and diffuse irradiance. The focus of this work is the evaluation of various models against measured data from Edinburgh. In addition, a brief description of the most common atmospheric parameters incorporated in daylight models is presented. The need for these design tools is unquestionable as the models provide the relationship between a commonly measured quantity (solar radiation) and illuminance.

Artificial sky for use with large-scale architectural daylight models

The Research Institute for Building Physics (NIISF) has developed a unique installation - a successfully functioning large 'Artificial sky'. The paper gives a detailed description of its structural features and facilities.

Daylighting with windows, skylights, and clerestories

This paper examines the impact of several fenestration options on building space heating, cooling, and lighting loads. The use of skylights, windows, and clerestories is evaluated for a single floor commercial building, using the NBSLD-2 building energy analysis computer program, which possesses a fully integrated daylight model (DALITE). The evaluation focuses on: 1. (a) the impact of daylighting on heating and cooling energy and equipment sizing; 2. (b) the potential reduction in electric lighting energy requirements through daylight utilization; 3. (c) the relative daylighting and thermal performance of skylights, clerestories, and windows; and 4. (d) the effect of building orientation on fenestration optimization and selection. The NBSLD-2 computer procedure performs a dynamic simulation of hour-by-hour building thermal performance and energy requirements for a one-year period. The thermal and daylighting characteristics of each fenestration aperture are modeled to enable evaluation of the trade-offs associated with the use of each fenestration type. The results are correlated in the form of design guidelines to enable the preliminary design decisions to be made regarding fenestration location, type, configuration, and size. The energy calculations are presented as functions of fenestration characteristics, so that the potential energy advantages can be estimated for different fenestration designs.

Glazing energy performance and design optimization with daylighting

This study systematically explores the influence of glazing systems on component loads and annual energy use in prototypical office buildings. The DOE-2.1B building energy simulation program, which contains an integrated daylighting model, is used to determine fenestration energy performance in diverse climates. The sensitivity of total energy use to orientation, window area, glazing properties (U-value, shading coefficient, visible transmittance), window management strategy, installed lighting power, and lighting control strategy are all described. We examine the conditions under which daylighting reduces net anual energy use as well as those conditions under which energy use may increase. Combinations of wall and fenestration properties that minimize net energy requirements as a function of climate and orientation are described.