Magali Bodart

Global energy savings in offices buildings by the use of daylighting

The objective of the work was to evaluate the impact of lighting energy savings on global energy consumption in office buildings. This evaluation comes from an integrated approach combining the daylighting and the thermal aspects, The study presented here is based on simulation results. Several facade configurations have been modeled, for the four main orientations and three combinations of internal wall reflection coefficients. These simulations were performed by coupling a daylighting simulation tool (ADELINE) and a dynamic thermal simulation software (TRNSYS). These simulations allowed us to determine the main parameters playing a rule on lighting consumption. We learned that daylighting can reduce artificial lighting consumption from 50 to 80%. The global primary energy saving coming not only from the reduction of the lighting consumption but also from the reduction of lighting internal loads could then reach 40%, for a type of glazing usually used in office buildings

Graphical Representation of Climate-Based Daylight Performance to Support Architectural Design

Abstract Many conventional daylighting design tools are limited in that each simulation represents only one time of year and time of day (or a single, theoretical overcast sky condition). Since daylight is so variable – due to the movement of the sun, changing seasons, and diverse weather conditions – one moment is hardly representative of the overall quality of the daylighting design, which is why climate-based, dynamic performance metrics like Daylight Autonomy (DA) and Useful Daylight Illuminance (UDI) are so needed. Going one step further, the annual variation in performance (condensed to a percentage by DA and UDI) is also valuable information, as is the ability to link this data to spatial visualizations and renderings. Trying to realize this combination of analytical needs using existing tools would become an overly time-consuming and tedious process. The challenge is to provide all information necessary to early design stage decision-making in a manageable form, while retaining the continuity of annual data. This paper introduces a climate data simplification method based on a splitting of the year into 56 periods, over which weather conditions are “averaged” and simulated using Perezs ASRCCIE sky model, while information on sun penetration is provided at a greater resolution. The graphical output of the produced data in the form of “Temporal Maps” will be shown to be visually, and even numerically, comparable to reference case maps created using short time step calculations and based on illuminance data generated by Daysim.

A Guide for Building Daylight Scale Models

Abstract Scale models are used frequently to evaluate the daylighting performance of buildings. In order to get accurate results, there are several rules to respect when building these scale models. Some of these rules are universal, while others depend on the measurement and observation devices, the type of sky under which the study is carried out, and the objectives of the study. This paper, based on the authors experience and on a literature review, presents rules to respect when building a mock-up for daylighting studies. These rules are illustrated by project examples that were tested under the Belgian artificial skies (single-patch sky and sun simulator, mirror box and mechanical sun).

Design of a new single patch sky and sun simulator

The design of a new sky simulator and its construction are described in detail. The simulator, comprising 91 tungsten halogen lamps placed in a hexagonal array, is based on the modelling of one patch of the Tregenza sky hemisphere distribution. This concept allows illuminance measurements from one geometric configuration to be used for every sky model. The sun simulator, which is also comprised of halogen lamps placed in a hexagonal array, is also described. Parallax error measurement and validation studies show that the sky presents low errors. The paper includes a review of existing skies and suns.

Review of Factors Influencing Discomfort Glare Perception from Daylight

ABSTRACT Because well-being is becoming a major challenge in construction alongside energy efficiency, there is an increasing need to be able to quantify discomfort in buildings. In the case of discomfort glare, the kind of glare provoking an irritating or distracting effect, no current indices can properly explain the high variability existing between individuals’ discomfort glare perceptions. This is due to the fact that some of the factors influencing discomfort glare perception are still unknown and the mechanism behind the discomfort glare process is not well understood. Therefore, this article aims to review the factors potentially influencing discomfort glare perception from daylight. Every factor having been studied at least once for its potential influence on discomfort glare perception has been listed, described, and analyzed. Furthermore, this study categorizes the influence of these factors on discomfort glare by introducing an influence indicator based on the number of studies having investigated the factor, the sample size of these studies, and the agreement between them. The suggested categories rate a factor influence as “almost certain,” “more likely,” “somewhat likely,” “inconclusive,” “somewhat unlikely,” “less likely,” or “almost certainly null.” Tables summarize the main information about the studies and the influencing factors. As expected, factors almost certainly influencing discomfort glare perception are the luminance of the glare source, adaptation level, contrast effect, and size and position of the glare source. In contrast, factors that almost certainly do not influence discomfort glare perception are the gender and optical correction of the observer. All other factors from the list of 30, such as the attractiveness of the view through the window or the culture of the observer, require additional studies to determine whether or not they influence discomfort glare perception.

Iluminación natural de edificios de oficina

In the search for control of natural lighting and weather inclemency, systems of measurement have been generated based on geographical location, times, and weather conditions. The use of dynamic measurements that consider factors in constant change is applied to evaluate representative typologies of office buildings built in Santiago.

Authors’ response to P Raynham and J Mardaljevic

directly viewed. As far as I am aware, fullhemisphere domes cannot reproduce absolute illumination values. Nor can the illumination effect of the sun be modelled simultaneously with that of the sky, at least not without reducing the absolute illumination from the sky lamps to miniscule levels to maintain the correct relative level with that from the sun lamp. I suspect that most of us would struggle to notice the difference in visual appearance between a model illuminated by a full-hemisphere sky simulator and the same model under an improvised ‘sky’ comprised of some muslin cloth and a few lamps. (Unfortunately, no such comparison has ever been carried out as far as I am aware.) In consequence, I remain sceptical that viewing a model illuminated by a sky simulator dome can offer any meaningful insight. Indeed, the perceived benefits of model viewing under seemingly ‘controlled’ conditions are, I believe, largely illusory, and if it must be done, then it may as well be under a real sky with a real sun. If one shares these views, then the single-patch sky simulator seems to have the upper hand over its more amply endowed full-hemisphere cousins*/at least for quantitative illuminance modelling provided that it can be shown to be reliable. A question however remains: why use physical modelling at all? The single-patch sky simulator reduces the parallax error which is an inherent problem with finite-sized skies. Scale models, however, are subject to construction errors that result in significant divergences between illuminances measured in an actual building and its scale model representation. Cannon-Brookes study showed scale model illuminances to be consistently 200% or more greater than those in the actual building under real sunny sky conditions. In contrast, the Radiance validation under real sky conditions (ie, the BRE-IDMP dataset) showed illuminance predictions to be generally within 20% or less of the measurements. Accordingly, I believe that the case for physical modelling needs to be demonstrated unambiguously: what are the advantages and disadvantages over computer simulation in terms of accuracy, reliability, practicality, and flexibility? Closely related is the deeper issue: what should a daylight evaluation consist of? Should it be qualitative or quantitative, images or numbers, daylight factor or climate-based, or some combination? Daylight evaluation is at a crossroads, and there is disenchantment in many quarters with the standard approaches (eg, daylight factors). Thus the developers of new tools have the opportunity to influence the future of daylight evaluation. I look forward to the author’s comments on this discussion.