Bright environments: Daylight in Sustainable Building Design

Friday 25 Aug 2023, 08:30 → 18:00 Europe/Zurich

ETH Zurich. Building HIB, Hönggerberg

Arno Schlueter (ETH Zurich, Architecture and Building Systems), Lars Oliver Grobe, Hubert Klumpner (ETH Zürich, Chair of Architecture and Urban Design), Michael Walczak (ETH Zurich Chair of Architecture and Urban Design)

The Bright environments: Daylight in Sustainable Building Design Conference offers a multi-disciplinary platform to discuss aspects of daylight in buildings such as its impacts on the health, well-being, productivity, and overall satisfaction of building occupants with a particular focus on human-centered approaches.

Researchers as well as practitioners from all involved disciplines are invited to the conference taking place at 25th August at the Institute of Technology in Architecture on the Hönggerberg Campus of ETH Zurich. Attendence is free.

08:30 Coffee break

Conference organisers: Registration

Conference organisers: Opening and welcome

1 Conference opening

Speaker: Prof. Arno Schlüter (ETH Zurich, Architecture and Building Systems)

Invited speakers:: Input lectures

2 The time for the light and the time for the darkness

Speaker: Dr Lenka Maierová (Czech Technical University in Prague)

3 From moon to sun – experimental design processes

Speaker: Mr Alexander Rotsch (Arup)

4 Challenges while measuring and assessing comfort and health impacts from light

Speaker: Dr J. Alstan Jakubiec (University of Toronto)

5 Questions and answers

10:30 Coffee break

Presentations: Subjective response to daylight

6 Mixed effect of time of day and correlated colour temperature on discomfort glare

Daylight supports multiple visual and non-visual needs. With occupants spending significant portions of day indoors, lack of daylight can lead to circadian disruption and other adverse effects. Even for buildings with external views, blinds tend to be closed at first instances of glare and often not reopened. Additionally, the use of electric light during daylit hours has energy implications. Towards maximising daylight benefits, glare responses need to be better characterised. Yet, although models for glare prediction exist, they do not address the within- and between-subject variances deriving from personal and contextual factors. These variances need to be better framed toward enhancing glare tolerance.
Previous studies have established that source spectrum influences glare perception, with higher estimates of discomfort glare evoked by shorter wavelengths. Time of day (ToD) has also been found to influence glare evaluation, with increasing tolerance reported as the day progresses. Yet, no research has yet been done on the potential mixed effects of spectrum and time of day on glare assessments. To meet this gap, a laboratory experiment was designed, using a category-rating approach and tunable (intensity and CCT) LED luminaires. The setup, located in an artificially-lit semi-hexagonal chamber, included a dimmable light source subtending 0.009sr at the eye, and a background luminance of 65 cd/m2. A fixation-point was placed with a 15° vertical displacement below the glare source. With a sample size of 36 participants, the experimental procedure was organised across four IES-GI thresholds – corresponding to glare source luminance of 1627, 3860, 9150 and 21700 cd/m2 - three ToDs - Morning (09:00), Midday (13:00), and Afternoon (17:00) - and two CCTs - 2600K (warm) and 6200K (cool).
Demographic data, subjective chronotype, and perceived photosensitivity were collected prior to the first session. At each session, personal factors including perceived fatigue, caffeine ingestion, sleep quality, mood, and prior light exposure were also collected from test participants. At the start of the procedure, the subject was invited to place their head on a chinrest, and then they were blindfolded for one minute. Meanwhile, the scene was set to one of the two CCTs, and the source luminance was adjusted to one of the four IES-GI thresholds. The subject was then asked to stare at the fixation point for 30 seconds, following which they were asked to mark their glare sensation vote (GSV) and level of discomfort due to glare on two Visual Analogue Scales (VAS). The subject was then blindfolded again, while the scene was toggled to next state. The procedure was repeated for the remaining settings of CCTs and IES-GI values, across three ToDs.
The data collection was concluded in May, and the data is currently being analysed. The responses on the VAS will be converted to percentage sensation score (PSS). For each CCT/ToD/GSV group, an initial analysis of variance (ANOVA) will be conducted to detect any differences in PSS across independent variables. Since the PSS data for each GI are nested across ToDs and CCTs, the data will be analysed via mixed-effect multilevel modelling.

Speaker: Dr Marshal Maskarenj (UCLouvain Belgium)

7 Integrative lighting in educational building: Results from simulations and field measuring campaigns in classrooms

The awareness about the non-visual effects of lighting plays an important role in all building types, both residential and non-residential, and a new term, ‘integrative light’, was introduced within the CIE to combine the photopic and melanopic effects on the health and comfort of the occupants of indoor spaces. Integrative lighting is particularly crucial in educational buildings, as it strongly affects the learning process along with physiological growing of young pupils in lower education levels. Regarding the Italian context, the educational building sector has become particularly strategic in terms of architecture interventions over the last decade, through increasing funds for optimizing the building energy performance, as well as the comfort and health conditions for teachers and students.
In this frame, results from a study carried out for classrooms of different educational buildings (from middle schools to universities) are presented. The analyzed classrooms presented different architectural characteristics (in terms of orientation, size, window area, color of internal surfaces, obstructing setting with different geometry and color) and types of lighting systems (fluorescent and LEDs).
The study relied on a combination of two approaches: (i) on the one hand, simulations were run, with the objective of analyzing the dynamic variation of photopic and melanopic quantities during the course of a year; (ii) on the other hand, field measurements were taken using calibrated instruments for the purpose, such as the spectro-photometer BTS256-EF manufactured by Gigahertz, with the objective of verifying visual and non-visual conditions in real spaces and to collect data to calibrate the simulation models. Simulations and measures were repeated for different lighting conditions: electric light only, daylight only (in the presence of a clear sky and of an overcast sky), and a combination of both. Different times of the day were chosen to take measurements, in the afternoon and in the morning, so as to account for the different spectral distribution of daylight. The simulation tool ALFA-for-Rhino was used for the purpose, by implementing the spectral reflectance properties of the materials used in the classroom, measured through the Minolta CM600d contact spectro-photometer.
The research was conducted with two main objectives: (i) on the one hand, to assess the influence on integrative lighting (photopic and circadian illuminances) played by architectural and photometric features of the classrooms (orientation, WWR, surface colors, obstruction; lighting systems); (ii) on the other hand, to verify if the circadian values (m-EDI) calculated or measured in the classrooms could meet the reference values that have been prescribed in recent literature, for instance in the WELL protocol or within the second expert symposium organized by the CIE in Manchester.
The method adopted for the study the results that were obtained are described in detail and critically discussed.

Speaker: Valerio Lo Verso

8 Discomfort glare from daylight: Influence of transmitted color and the eye's macular pigment

Designing architectural façades that allow sufficient daylight to create visually comfortable and pleasant environments is a challenging aspect of building design as it requires to account for visual comfort and discomfort glare risks, and understand the factors that influence them. Amongst the key factors that contribute to one’s perception of discomfort glare, we find the quality and quantity of daylight transmitted through the façade on the one hand, and the characteristics of the human eye and its synergistic functioning with the brain on the other hand. In the last two decades, several prediction models have been developed to quantify discomfort glare by considering almost exclusively the photometric properties and spatial distribution of incoming light. Although these empirical models have been derived to best match the user perception of glare, they fail to account for the significant inter-individual variability that exists in glare perception and are furthermore limited in their applicability in certain visual environments.
Focusing on the factors not considered in these models so far, we conducted user studies investigating the influence of the color of (day)light and the human eye morphology, as these seemed, based on the available literature, to be two particularly promising factors in terms of their potential impact on discomfort glare perception. More specifically, we examined the influence of i) the color of a small-sized, intense glare source (visible sun) resulting from the use of saturated-colored glazing (red, green, blue, and grey) and ii) the macular pigment density in the retina. By means of three psychophysical experiments conducted in office-like test rooms along with ocular examinations of the participants, we determined the influence of these factors on discomfort glare from daylight for young and healthy individuals. Each experiment followed a similar protocol of exposing every participant to four daylight glare scenarios and recording their responses to questionnaires. The four daylight scenarios differed only in the color and transmittance of the glazing through which the sun was visible as the main glare source.
Results do indicate that the color of daylight can have a strong influence on human perception of glare. The sunlight filtered through the four types of colored glazing of the same transmittance indeed caused different levels of perceived discomfort glare amongst the participants. More precisely, participants experienced statistically higher levels of glare under the red and blue glazing than the grey or green glazing. As far as eye morphology was concerned, while macular pigment density in the retina did not seem to have an influence on sensitivity to glare under color-neutral conditions, it did have a significant effect under saturated blue glazing for the sampled population: participants with higher pigment densities indeed experienced lower levels of discomfort glare under daylight filtered through the blue glazing used. To advance our understanding of discomfort glare and extend the applicability of the discomfort glare prediction models to colored daylit scenarios, these findings can provide useful insights on building design strategies for achieving better visual comfort.

Speaker: Sneha Jain (EPFL)

9 Office building typologies and circadian potential

Circadian rhythms are internal manifestations of the solar day that allow adaptations to environmental temporal changes. Mood disorders are often associated with disrupted circadian clock-controlled responses, while disruption of circadian rhythms is correlated with jet lag, night-shift work, or exposure to artificial light at night. Modern lifestyles patterns lead to a disruption in the circadian rhythm, resulting in several diseases. Circadian disruption is one of the factors raised, alongside smoking, diet, fatigue, and sleep quality, increased body mass index and obesity. The lack of enough daylight during the day and the exposure to electric light at night has disconnected people from the environment, eliciting psychological problems. The objective of this research is to analyze the circadian potential of three building models according to WELL Certification, compare their performance, and draw design guidelines about circadian rhythm and users’ well-being for office buildings. Adaptive Lighting for Alertness (ALFA) tool was used to calculate the Equivalent Melanopic Lux for WELL Certification criteria in the scenarios. The results indicate that shallow office plans could benefit users, providing them with a regular circadian rhythm which improves sleep quality, reduces stress, and prevents serious diseases.

Speaker: Erika Ciconelli de Figueiredo (Mackenzie Presbyterian University)

10 Questions & Answers

Lab tours

11 ZCBS Lab tour A (12:00 to 12:30)

Speakers: Illias Hilschier (ETH Zurich, Architecture and Building Systems), Valeria Piccioni (ETH Zurich, Architecture and Building Systems)

12 ZCBS Lab tour B (12:30 to 13:00)

Speakers: Mr Bharath Seshadri (ETH Zurich, Architecture and Building Systems), Illias Hilschier (ETH Zurich, Architecture and Building Systems)

12:00 Lunch break

Presentations: Assessing daylight and cross-domain effects

13 Novel measurement concepts for a visual and thermal characterization of semi-transparent façade systems

With the increasing number of hot days in the cooling season, a correct use of semi-transparent façade systems to face healthy requirements and ensure comfortable indoor situations is of enormous importance. Thus, a well-planned façade system must fulfill the essential tasks of summer overheat protection through intelligent shading as well as visual requirements such as daylight utilization and glare protection. To be able to characterize and optimize complex façade systems based on these requirements, beside simulations supplementing measurement methods are needed that allow both: a static evaluation of the components in terms of normative characteristic values and KPIs as well as dynamic evaluations to monitor the transient behavior of a façade system during operation.
Within the 5-year EU research project MEZeroE, at the Unit for Energy Efficient Buildings at the University of Innsbruck a "Pilot Measurement and Verification Line" (PM&VL) is established and tested together with industrial partners, which aims to evaluate semi-transparent envelope products from a thermal and visual point of view and to provide product data for manufacturers, engineers and planners. In the sense of an open innovation process, a virtual marketplace will be established together with other research partners within the framework of the research project, where living labs will be installed in addition to other pilot lines with different focal points.
The presentation will give an overview of the project and the novel simulation- and measurement concepts being developed. A focus will be made on the presentation of a novel goniophotometer measurement concept as well as on a newly developed in-situ measurement concept for the acquisition of transient g-values for complex glazing’s under installed conditions. As a concluding result, measurement-assisted methods for a visual and thermal characterization of semi-transparent façade systems will be proposed.

Speaker: Dr Martin Hauer (University of Innsbruck, Unit for Energy Efficient Buildings)

14 IndiLight Module: A control system for combined operation of façade and artificial lighting systems to optimize human comfort and overall building energy consumption

Optimizing the thermal and lighting conditions in office rooms for each worker individually tends to be an expensive task in terms of both planning and operation. An workplace-individual lighting module (IndiLight module – ILM) facilitating this task has been developed and will be introduced in this work and compared to state of the art façade control strategies. To minimize the installation effort, the quantification of the lighting situation at each working place is performed by simulation, based on measured values from only outdoor sensors. For keeping the planning effort low, model data of the standard planning phase is used in the process of setting up the control module, which can therefore be easily integrated into a BIM workflow. To keep the indoor lighting and thermal condition close to optimal, the module is executed in defined intervals (e.g., every 15 min). Since the module is planned to run on embedded hardware of the building control system, performing a full daylight simulation in every time step is not affordable. To overcome this problem, the major part of the daylight simulation is done in a pre-calculation step, comprising the generation of the matrices for the radiance three phase method. During operation, the module has only to perform the multiplication of those matrices in every time step to retrieve the daylight illuminance on each working desk, which is further used to calculate the artificial lighting demand, and the luminance values observed from each working position to estimate the individual glare situation. For the thermal situation, the solar heat gain coefficient is taken as an input in a thermal model, based on the (outdated) standard EN 13790. In the optimization routine first some of the possible façade states are excluded due to glare issues or potential overheating risk and for all remaining states a target function is calculates, which depends on the estimated heating or cooling and artificial lighting energy demand and on the degree of façade opening. The façade state with the best target function value is then chosen. In this work the ILM is applied to office rooms in a thermal and in a lighting simulation environment. In the annual dynamic building simulation in TRNSYS, the heating, cooling and artificial lighting energy demand is calculated. The daylight glare situation is verified by calculation of the daylight glare probability for each working place throughout the year applying the raytraverse simulation workflow. The same process is also applied to state of the art reference control strategies and the results are compared. The main benefit of this study is to investigate the influence of façade control algorithms on the thermal and lighting comfort for office workers and on the total building energy demand.

Speaker: Daniel Plörer (Universität Innsbruck)

15 Analysis and control of cross-domain effects of inhomogeneous pattern on switchable membrane constructions

The Collaborative Research Centre 1244 at the University of Stuttgart interdisciplinary investigates adaptive building skins and structures to reduce resource consumption in building construction as well as energy consumption in building operation and increase occupant comfort.

Switchable membrane cushion constructions are the focus of the investigation, as they provide a considerable reduction in the installed mass and great design flexibility. They consist of multiple layers of highly recyclable plastic, whereby the pattern of the outer membrane is complementary to the second membrane. By adapting the distance between the layers, the heat, sound, light and radiation transmission can be adjusted, which in turn affects the acoustic, visual and thermal comfort in the room. Therefore, a multidisciplinary investigation is required, especially to develop optimal control strategies. Although switchable membrane constructions have been used for some time (cf. Festo Technology Center 2001), there is a lack of cross-domain models describing the complex interactions due to the individual printing patterns, layer distances, solar angles and are available within the equation-based modelling environment Modelica. In this study, we investigate a plane-parallel layered structure with a striped pattern as a first step. In order to investigate the influence of different control scenarios, the comfort states to be investigated must be dynamically available. Subsequently, control concepts can attempt to simultaneously fulfil the partially conflicting goals of energy efficiency as well as thermal and optical comfort (daylight availability, uniformity and glare).

For this purpose, suitable domain-specific interface variables and coupling models are first elaborated. Each interface variable is then pre-calculated for all previously defined discrete façade states. For the metrics of the daylight domain, the 3-phase-method is applied using RADIANCE. For the interface variables of the thermal domain, RADIANCE-genBSDF and WINDOW-Klems matrix layer methods are used. Then, the interface value is interpolated to the continuous controller output within the Modelica model. Through this, thermal- or optical-centered control schemes are compared with mixed control schemes.

Speaker: Simon Weber

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16 Questions & Answers

14:00 Coffee break

Presentations: Planning with daylight

17 Kaleidoscope pragmatism: enhancing indoor daylight access and visual comfort in dense urban environments

This presentation focuses on a case study of an existing building in central Athens, which is undergoing transformation into a new office space. The work embodies a collaborative effort between Transsolar and DECA Architecture, with an ambitious goal to address the challenge of daylight access and visual comfort in established urban structures.

The city center of Athens, with its densely populated, high-rise structures often struggles with natural light accessibility. Most buildings, up to 10 stories high, face very narrow, canyon-like streets, significantly reducing daylight access and views. The typical building floorplate is 27 meters deep, a dimension conducive to open-plan work environments. However, with the building facades significantly apart, the depth of these floor plates restricts the penetration of natural light to their centers.

Our solution to this issue involves the introduction of a new concept, integrating both passive and active means to enhance natural light penetration. A primary feature is the inclusion of a lightwell in the center of the floor plate. A dual-axis heliostat—a mirror equipped with a mechanical bracket—is placed at the top of this lightwell. This mirror tracks the sun, reflecting its light into the lightwell and thereby allowing sunlight to illuminate the building's inner portions throughout the day.

Complementing the heliostat, the architects have innovatively designed a scaled kaleidoscope within the new lightwell. This optical instrument, consisting of highly reflective triangular mirrors and diffusers, creates multiple reflections, effectively channeling daylight further into the inner part of the building.

Our methodology revolves around a unified, step-by-step approach, initially involving testing and optimization through computer simulation. We use daylight simulation tools like Radiance, ClimateStudio, and Ladybug Honeybee, which facilitate rapid assessment of potentials, geometry optimization, and target definition for finish properties. Following this, we measure the finishes for both a 1:20 scale model and the actual 1:1 mockup using lux and candela meters. This rigorous procedure ensures alignment of surface properties and meaningful comparisons between simulations, model measurements, and the actual building.

The combined effort of incorporating the heliostat, kaleidoscope, and a set of other design strategies, has proved successful in enhancing daylight access, autonomy, and visual comfort on the building's typical floors.
This presentation, targeted at daylight professionals and practitioners in Architecture and Engineering, hopes to contribute to the broader discourse on daylight access, visual comfort, and architectural design, particularly within the constraints of existing building stock.
Currently renovation works are ongoing and the building will open in early 2024.

Speaker: Alberto Bruno (Transsolar Energietechnik GmbH)

18 Daylight is the best teacher.

The problem is that daylight is often only integrated into architecture in individual aspects and not in its full bandwidth. As a result, it cannot develop many of its qualities.
We have to acknowledge, that daylight is a holistic entity, inseparably interwoven in all aspects of life.
I present a structured entity of different approaches to natural light in architecture and urban planning. Natural light includes day- and nightlight.
A holistic view on natural light is the base for a good lighting design, including all sciences.
The range of topics is on Nature, Evolution, Perception, Culture, Sustainability, Health, Darkness, Dynamic, Composition, Atmosphere and Magic.
In this talk we focus on the three following topics: Nature, Composition, Darkness.
Nature - Natural Light
Nature represents the variety of natural light. We have a small toolbox of physical laws, that lead to a richness of various phenomena.
We have one light source (the sun), a diffuse filter (the atmosphere) and we observe the effects of reflection, refraction, absorption, direct light.
Composition – It’s all in the mix
From daylight, we understand that inspiring environments evolve through the combination of these different atmospheres. They have specific effects on humans. We learn this from medicine, psychology and biology.
Darkness – Daylight in Transition
The dynamic of natural light includes bright and dark environments. Especially, the transition phase between day and night is deeply rooted in cultural narratives and shared identity. Working globally, we observe that the duration of sunset in different regions of the world has an impact on the preference of people for warm or cold colour temperatures in artificial lighting.

Understanding these links between diciplines teaches us to strengthen the exchange between scientists and designers, such as architects, lighting designers and artists.

Speaker: Ulrike Brandi (Ulrike Brandi Licht GmbH)

19 Shaping daylight: The Komorebi effect via the Radiance mist material in renovation architecture

This presentation revolves around the renovation of an old farm in Marvao, Portugal, transformed into a residential complex. This case study signifies a collaborative effort between Transsolar and DECA Architecture, aiming to simulate the Komorebi effect—a Japanese term denoting the interplay of sunlight streaming through the leaves of trees—within the redesigned space.

Our methodology fosters a unified approach, converging the architects' vision and clients' desires with a rigorous daylight and visual comfort analysis. The ultimate goal is to create a space harmoniously integrating nature and architectural design, vividly echoing the Komorebi effect. This approach enables optimal spatial configuration, yielding uniform daylight distribution, minimal glare, and the successful replication of the Komorebi effect, all while upholding the project's overarching sustainability concept.

A distinguishing aspect of our approach is the application of the Radiance Mist material in simulations. This medium enables light particles to scatter, visually representing the Komorebi effect and simulating the appearance of light beams traversing a medium like fog or mist, a task typically requiring the construction of scale mock-ups and fog machines.

Despite the Radiance Mist material being well-documented in "Rendering with Radiance" and other sources, its application in daylight simulations remains a complex process, one often limited to Radiance experts. We present a simplified application pathway within an actual project using Radiance through Solemma's Climate Studio (CS), a state-of-the-art environmental performance analysis software.

CS streamlines the radiance rendering process, enhancing efficiency, and swiftly allowing for the creation of stunning visual representations. Our findings highlight the advantages of using Solemma's Climate Studio in conjunction with Rhinoceros 3D for accurate light divergence evaluation.

This presentation is targeted at daylight professionals proficient in Radiance, Rhino 3D, and Grasshopper, and extends to students, researchers, and practitioners in Architecture, Climate Engineering, and Building Physics. It aspires to contribute to the broader discourse on daylight utilization, its impact on energy demand, visual comfort, and the complex integration of daylight within sustainable building design.

Speaker: Daniel Lago Leal (Transsolar)

20 How daylight design effects architecture and human well-being

The presentation examines the effect of daylight control systems on the interior user by means of completed projects. Time-lapse videos will be shown of how the sun models the illumination of the interior over the course of a day, taking into account the position of the sun.
In order to make these optical, design effects comprehensible, the mirror optics of the light control systems and the type of glare-free light guidance within different façade zones are also discussed. The principle of bifocal blinds is explained, which have an outward focus to protect against overheating and an inward focus for better room illumination. Furthermore, systems are explained that direct the zenith light into the interior depth in the skylight area of a window and serve to save artificial lighting.
The light guidance of the mirror optics is explained by means of ray tracings as well as interior photos. The visual appearance of the systems and the façade design will be discussed on the basis of completed projects with external, internal or integrated systems in insulating glass.
Furthermore, daylight redirection technology will be evaluated from an urban climatic point of view with regard to its ability to prevent the heating up of the streets and inner-city spaces by reflecting the sun back into the sky.
As far as time permits, the health effects of improved daylight illumination are also discussed and explained on the basis of medical studies in a school as well as under the aspect of the length of stay depending on the compass direction of patient rooms in hospitals.

Speaker: Dr Helmut Köster (Köster Lichtplanung)

21 Questions & Answers

Invited speakers:: Keynote

22 Light, clocks & behavior in the open ocean

Speaker: Dr Sören Häfker (Alfred-Wegener-Institute Helmholtz-Centre for Polar and Marine Research)

23 Questions & Answers

Conference organisers: Outlook and conference closing

24 Conference closing - Daylight in sustainable urban design

Speaker: Prof. Hubert Klumpner (ETH Zürich, Chair of Architecture and Urban Design)

17:00 Apero

Lab tours

25 ZCBS Lab tour C (17:00 to 17:30)

Speakers: Dr Illias Hilschier (ETH Zurich, Architecture and Building Systems), Ms Valeria Piccioni (ETH Zurich, Architecture and Building Systems)