Marilyne Andersen

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 framework for predicting the non-visual effects of daylight – Part I: photobiology-based model

This paper investigates the formulation of a modelling framework for the non-visual effects of daylight, such as entrainment of the circadian system and maintenance of alertness. The body of empirical data from photobiology studies is now sufficient to start developing preliminary non-visual lighting evaluation methods for lighting design. Eventually, these non-visual effects have the potential to become a relevant quantity to consider when assessing the overall daylighting performance of a space. This paper describes the assumptions and general approach that were developed to propose a modeling framework for occupant exposure to non-visual effects of light, and presents a novel means of visualising the ‘circadian potential’ of a point in space. The proposed approach uses current outcomes of photobiology research to define – at this point static – threshold values for illumination in terms of spectrum, intensity and timing of light at the human eye. These values are then translated into goals for lighting simulation, based on vertical illuminance at the eye, that – ultimately – could become goals for building design. A new climate-based simulation model has been developed to apply these concepts to a residential environment. This will be described in Part 2 of this paper.

Preliminary Method for Prospective Analysis of the Circadian Efficacy of (Day)Light with Applications to Healthcare Architecture

Abstract Recent studies have attempted to link environmental cues, such as lighting, with human performance and health, and initial findings seem to indicate a positive correlation between the two. Light is the major environmental time cue that resets the human circadian pacemaker, an endogenous clock in the hypothalamus that controls the timing of many 24-hour rhythms in physiology and behavior. Insufficient or inappropriate light exposure can disrupt normal circadian rhythms which may result in adverse consequences for human performance, health and safety. This paper addresses the problem of prospective analysis of building architecture for circadian stimulus potential based on the state of the art in photobiology. Three variables were considered in this analysis: lighting intensity, timing, and spectrum. Intensity is a standard design tool frequently used in illuminating engineering. Timing and spectrum are not commonplace considerations, so the analysis that follows proposes tools to quantitatively address these additional requirements. Outcomes of photobiology research were used in this paper to define threshold values for illumination in terms of spectrum, intensity, and timing of light at the human eye, and were translated into goals for simulation – and ultimately for building design. In particular, the climate-based Daylight Autonomy (DA) metric was chosen to simulate the probabilistic and temporal potential of daylight for human health needs. The developed method was applied to study the impact of key architectural decisions on achieving prescribed stimulus of the circadian system in a hospital patient room design; studied variables included orientation, window size, and glazing material. A healthcare setting was specifically chosen with the intent of follow-on research to validate our findings with actual patient outcome data.

Comparison between ray-tracing simulations and bi-directional transmission measurements on prismatic glazing

Evaluation of solar heat gain and daylight distribution through complex window and shading systems requires the determination of the bi-directional transmission distribution function (BTDF). Measurement of BTDF can be time-consuming, and inaccuracies are likely because of physical constraints and experimental adjustments. A general calculation methodology, based on more easily measurable component properties, would be preferable and would allow much more flexibility. In this paper, measurements and calculations are compared for the specific case of prismatic daylight-redirecting panels. Measurements were performed in a photogoniometer equipped with a digital-imaging detection system. A virtual copy of the photogoniometer was then constructed with commercial ray-tracing software. For the first time, an attempt is made to validate detailed bi-directional properties for a complex system by comparing an extensive set of experimental BTDF data with ray-tracing calculations. The results generally agree under a range of input and output angles to a degree adequate for evaluation of glazing systems. An analysis is presented to show that the simultaneously measured diffuse and direct components of light transmitted by the panel are properly represented. Calculations were also performed using a more realistic model of the source and ideal model of the detector. Deviations from the photogoniometer model were small and the results were similar in form. Despite the lack of an absolute measurement standard, the good agreement in results promotes confidence in both the photogoniometer and in the calculation method.

Experimental assessment of bi-directional transmission distribution functions using digital imaging techniques

Many daylighting applications require a precise knowledge of the directional transmission features of advanced fenestration materials. These photometric properties are described by a bi-directional transmission distribution function (BTDF), whose experimental assessment requires an appropriate equipment. A novel bi-directional photogoniometer, based on digital imaging techniques, has been designed and developed for that purpose. The main advantages of this device are the significant reduction of the time required for data measurement and its capability to assess an almost continuous BTDF function. These features can be achieved only through detailed and accurate calibration procedures of the bi-directional photogoniometer, which are described in this paper, together with digital image and data processing. Several experimental results, obtained for different fenestration materials, are used to illustrate the capabilities of this novel equipment.

A generative facade design method based on daylighting performance goals

Successful daylighting design is a complex task which requires the designer to consider numerous design elements and their effects on multiple performance criteria. Facades, in particular, include many variables which may dramatically impact daylighting performance. Genetic algorithms (GAs) are optimization methods which are suitable for searching large solution spaces, such as those presented by design problems. This article presents a GA-based tool which facilitates the exploration of facade designs generated based on illuminance and/or glare objectives. The method allows the user to input an original 3d massing model and performance goals. The overall building form remains the same while facade elements may change. Ten parameters are considered, including materials and geometry of apertures and shading devices. A simple building data model is used to automatically generate a 3d model of each solution. Results from single- and multi-objective case studies are presented to demonstrate a successful goal-driven design exploration process.

Validation of the performance of a new bidirectional video-goniophotometer

An accurate knowledge of the directional optical properties of advanced fenestration materials is necessary for them to be adequately integrated in buildings. These properties are expressed by the Bidirectional Transmission (or Reflection) Distribution Functions (BTDF, BRDF) of such elements, which are measured by specifically designed measuring equipment: an innovative, time-efficient bidirectional goniophotometer, based on digital imaging techniques, was designed and set up for that purpose. In this paper, the in-depth validation used for the bidirectional measurements performed with this apparatus is presented. It is based on different approaches including experimental error estimation, comparisons to analytical or ray-tracing based models and to other measured data, and calculation of the directional-hemispherical transmittance (reflectance) gauged against measurements of the same systems with Ulbricht (integrating) spheres. The high accuracy and reliability of this novel device were confirmed by this detailed investigation, and led to a maximum error for BT(R)DF data of only 10%.

Unified framework to evaluate non-visual spectral effectiveness of light for human health:

The discovery of a novel non-rod, non-cone photoreceptor in the mammalian eye that mediates a range of ‘non-visual’ responses to light has required reexamination of how lighting needs for human health are characterised and evaluated. Existing literature provides useful information about how to quantify non-visual spectral sensitivities to light but the optimal approach is far from decided. As more is learned about the underlying biology, new approaches will continue to be published. What is currently lacking is a flexible framework to describe the non-visual spectral effectiveness of light using a common language. Without a unified description of quantities and units, much of the value of scientific publications can be lost. In this paper, we review the existing approaches by categorising the proposed quantities depending on their application. Based on this review, a unified framework is provided for use in evaluating and reporting the spectral effectiveness of light for human health. The unified framework will provide greater flexibility to model the non-visual responses to light and is adaptable to a wide range of lighting solutions of interest to researchers, designers and developers. A new visualisation tool, the SpeKtro dashboard, is available to explore the unified framework online at spektro.epfl.ch.

Occupants’ behaviour in energy simulation tools: lessons from a field monitoring campaign regarding lighting and shading control

Previous studies have shown that the choice of the behavioural model for the control of lighting and shading devices has important implications in the energy performance assessment of office buildings and directly influences the comparison of design alternatives for control systems as well as for the façades (shading or glazing). Since many behavioural models exist for the same purposes, and in most cases there is no consensus on which ones are more representative of the reality, it is important to perform more real-world observations and draw lessons from them. This study appears in this context and explores the results of a field campaign that continuously monitored occupants’ behaviour regarding manual control of electric lighting and shading devices of eight real-world single offices under normal operation. Detailed measurements and observations were performed over two months in each office with the aim of assessing the level of agreement between existing behavioural models and actual occupants’ behaviour. Findings from this study enabled refining the hypothesis regarding realistic modelling of occupants’ behaviour when considering currently available whole building simulation (BS) software; moreover, needed improvements to increase the reliability of the results in whole BS were identified.

Transmission Illuminance Proxy HDR Imaging: A New Technique to Quantify Luminous Flux

A technique to measure arbitrarily complex luminous fluxes across large areas is presented. The technique is founded on high-dynamic range (HDR) imaging technology and can be achieved using a standard consumer digital camera and everyday materials such as printer-grade white paper. The same approach can also be used to determine the direct and diffuse components of illuminance. The technique has been named transmission illuminance proxy - high dynamic range imaging or TIP-HDRI.