Exploring daylight in two different hemispheres: Sweden and Uruguay: a comparative study of daylight as a formgiver and its impact on visual comfort

Daylight’s critical significance for both the built and natural domains underscores its potential to enhance energy efficiency and environmental sustainability in architecture. This study presents a careful exploration, using a tailored case study, to reveal diverse strategies for leveraging daylight’s inherent attributes as a building material. Integrated climate adaptation serves as the bedrock of architectural projects, fostering regenerative development as well as liveable and sustainable spaces. This research delves into daylight’s complexities, positioning it as a primary input in early architectural stages. Through comprehensive analysis in Uruguay and Sweden, this study highlights the interplay of daylight’s effects. An experimental cabin serves as a focal case study, bolstered by Climate Studio software, yielding a thorough daylight analysis across these locations. The synthesis of academic and practical approaches underscores daylight’s pivotal role in shaping sustainable built environments.


Introduction
Access to daylight is vital in any dwelling (Mark Rea, 2014), yet effectively integrating it into new projects presents challenges.Prioritizing natural lighting design from the outset is crucial for a regenerative built environment.Designers face the responsibility of crafting spaces aligned with sustainability goals.This thesis explores strategies to master natural lighting design, emphasizing that daylight quantity and quality should not be afterthoughts, as they profoundly impact the built environment's quality.By designing an experimental cabin and using Climate Studio, daylight analysis is conducted in Uruguay and Sweden, showcasing how academic methods enhance design practice.Examining daylight in different latitudes reveals unique qualities and enriches the understanding of its role in sustainable design.As stated by Reinhart (2014) "designers must hence understand how much solar radiation is available at different sites throughout the world"

Daylight at different scales
The multifaceted nature of daylight, as emphasized by Peter Tregenza (2014), holds intrinsic qualities of changeability and dynamism.Its significance transcends mere illumination, deeply impacting life and well-being for individuals in terms of both health and emotional satisfaction.
At planetary scale, daylight's interplay with Earth's rotation and orbit results in predictable variations throughout the seasons and the daily 24-hour cycle.However, the unpredictable element of weather adds complexity that designers must address when harnessing daylight's potential.

Methodology
The methodology unfolds across four distinct phases (Fig. 1), each contributing to a comprehensive exploration of daylight's impact.First, a dwelling is meticulously designed as a case study.This deliberate choice is driven by the desire to anchor the daylight analysis within a well-structured, square plan footprint.The role of voids within this confined space becomes paramount.Achieving a harmonious equilibrium between window dimensions and potential energy concerns, while addressing visual comfort, constitutes the study's primary objective.
The second phase involves subjecting the case study to scrutiny in four orientations at each location, achieved through a 90-degree rotation of the floor plan.This experimentation introduces varying sun exposure on each facade.Additionally, alterations to interior materials are implemented to gauge their influence on illuminance levels.
Moving on to the third phase, the case study, modeled in Revit and transferred to Rhino, undergoes analysis through the Climate-Studio plugin (v1.9.8389.21977).Employing 30 sensors on the lower floor and 36 on the upper floor, this software affords dynamic daylight metrics such as Daylight Autonomy (DA), Useful Daylight Illuminance (UDI), Annual Sunlight Exposure (ASE), and Spatial Daylight Autonomy (sDA).The analysis encompasses calculations under CIE standard clear sky at 9:00 am, 12:00 pm, and 15:00 pm during equinoxes and solstices for both locations, with Sweden's solstices extended to 6:00 am and 18:00 pm.Further calculations involving CIE standard overcast sky are performed at 12:00 pm.
The final stage involves evaluating visual comfort conditions across the spatial realm.Insights garnered from this assessment inform potential modifications to building orientation and materials, aimed at optimizing performance.

Limitations and Considerations
This study acknowledges four main limitations.Firstly, it addresses climate conditions exclusively, omitting the influence of social, cultural, and physical contexts which significantly shape the built environment in practical scenarios.Secondly, the analysis excludes trees and neighboring structures due to their potential to introduce complex lighting scenarios that could distort the results.The immediate environment's contribution is approximated with grass (R.vis=15.70%) in both locations.Thirdly, while the study focuses on wood-based systems, a thermal analysis with different building systems -other than IOP Publishing doi:10.1088/1755-1315/1320/1/0120263 wood-should be carried out in order to have a more complete picture of what should be the optimal design adapted to each climate.Lastly, quantitative assessment should be complemented with qualitative methods such as the one proposed by Liljefors (1999), for deeper insights into daylight quality.Such analysis would require an in-depth qualitative study of actual living experiences that fall out the scope and extension of this thesis.

Case study design
The case study serves as an experimental project, offering a flexible platform to assess daylight dynamics.With this objective in mind, project decisions were strategically crafted to facilitate experimentation, featuring a compact 4m by 4m square plan floor (Fig. 2).The rotation of such a building, aimed at exploring its impact across various orientations, ensures clearer outcomes compared to a larger and more intricate layout.
Designed as a one-person cabin, the program is intentionally open-ended, embracing an undefined purpose.This design allows for the examination of annual glare probability, particularly if the cabin were employed as a workspace.
The cabin's sectional composition draws inspiration from contemporary architectural projects such as the Living Spaces pavillion in Copenhagen (Velux, 2023) and Tham & Videgård's Vertical Village II in Gothenburg (Videgård, 2018), which offer intriguing spatial possibilities (Fig. 3).Simultaneously, an exploration of asymmetry is introduced, fostering a play of light that enhances the ambient atmosphere.
Rooted in sustainability, a wooden structural system emerges as an apt choice for this endeavor, built in grey sawn wood façades with natural aesthetic and demanding minimal maintenance.Both Sweden and Uruguay, as timber-producing nations, extensively employ this system.Employing locally-sourced materials stands as a crucial step towards carbon neutrality by minimizing material transportation.Within the cabin's interior, material variations are orchestrated to assess their reflective attributes and their impact on lighting conditions.The windows design adheres to specific principles: firstly, each façade boasts distinct glazing areas (Fig. 4), cultivating diverse lighting scenarios to enrich the analysis.Secondly, windows are strategically positioned to establish a connection with the external environment, while others artfully frame exterior views, integrating external elements within the cabin's interior (Martin, 2017).

Case study review
As mentioned before two main actions will be applied to the case study: rotating the building and changing the interior materials.
All facades have been numbered from 1 to 4, starting from the access facade as 1.In order to change the orientation, the plan has been rotated clockwise, following the same sense that Climate studio uses to rotate the building (Fig. 5) The materials used for the purpose of this research were taken from Climate Studio library and are specified in material packs in Fig. 6.The selection criteria consisted of starting with materials with high reflectance properties, as is the case of white plaster walls with a R.vis=89.9%, and then start testing different options according to the resulting analysis.Also, the glazing was modified by adjusting its reflective properties.

Results and discussion
The initial phase of analysis involved the utilization of Dynamic Daylight Metrics (DDM) within Climate Studio.For this assessment, the materials chosen corresponded to option 1, characterized by an average reflectance of 51%.Additionally, façade 2, encompassing a glazing area of 3.2m², was oriented towards the East in both studied locations.
Surprisingly, the findings unveiled an unexpected outcome: despite registering a relatively high glare probability (sDG) (53.2% for Uruguay and 60.8% for Sweden), the Useful Daylight Illuminance (UDIa) metric failed to exceed 52%.This underscored the need for alterations in either the chosen materials, the orientation, or possibly both, to yield an improved performance.
Aligned with the research methodology, a two-fold series of modifications ensued.Firstly, an adjustment in the cabin's orientation was implemented, followed by an alteration of materials deployed within the cabin's interior space.

Point-in-time analysis
Therefore, an analysis of point-in-time illuminance levels was carried out in Climate Studio for each location.Four orientations were tested by rotating the floorplan clockwise, combined with three different types of materials (option 1-3).These measurements were taken during summer solstice, since it presented the more critical situation according with the preliminary results.
After analyzing the data, we chose two materials, one for each location (Table 1), based on their lower reflectance properties to avoid excessive illuminance beyond 3000 lux.The aim was to strike a balance between the desired illuminance range of 100-3000 lux and maintaining glare below 40%.This selection aligns with Marie-Claude Dubois' (2019) research on optimal lighting activation (100-300 lux), LEED v4's suggested range (300-3000 lux), and Tregenza's task-related recommendations for different lighting levels.
The main reason for the aforementioned criteria is avoiding heat gaining.Furthermore, the use of the cabin is broad, and being a working place is also a possibility, so glare probability should be reduced to lower values than 40%, as mentioned before.

Material & orientation
As anticipated, both locations required different materials to achieve the desired range of illuminance levels.A potential solution for Uruguay could involve the use of treated pine wood (option 2).In the case of Sweden, employing wood panel walls (option 3) along with Clear-Solarban 90 glazing (option 4) could prove effective.
While material selection also took orientation into account, our exploration delved deeper into this aspect.Once the chosen materials were established, Climate Studio was employed to compute the Useful Daylight Illuminance (UDIa), a pivotal metric for evaluating the optimal orientation for each location with the designated materials (Table 2).
The UDIa analysis yielded intriguing results.For Sweden, the most effective configuration involved positioning the cabin with façade 4 facing the North.This arrangement meant that the façade with the largest glazed area (3.2m²) would be oriented towards the South.Similarly, in Uruguay, an analogous conclusion was drawn, suggesting a North-facing façade 4 and positioning the larger glazed area of façade 2 towards the South.These findings are of particular interest as they challenge a simplistic 7 design approach that might have suggested orienting the cabin with its largest glazed area to the north, aligning with the analysed solar path, in the case of Uruguay.

Daylight metrics with chosen materials and orientation
With the materials and orientation choices firmly established, the subsequent phase entailed conducting fresh measurements within Climate Studio.This encompassed both point-in-time evaluations of illuminance and the computation of daylight metrics to pinpoint critical scenarios.The outcomes of these analyses unveiled that, despite the adjustments made to achieve the desired levels of visual comfort, certain values still exceeded the intended range.This discrepancy was notably pronounced during Uruguay and Swedish's summer solstice, as well as both equinoxes at 12:00 pm. in Sweden (Table 3-4).These findings underscore the necessity for further refinements in the design.Another crucial facet that merits close attention is the spatial distribution of light.This element serves as a potent design instrument capable of elevating a space from uniform monotony to one enriched with contrasts.The significance of achieving perceptual uniformity in evaluating daylight quality has been stressed by Dubois (2019).
Addressing uniformity emerges as another facet of consideration from these calculations (Table 5).A closer scrutiny of the point-in-time analysis and the correlation between average and minimum illuminance reveals that uniformity occasionally deviates from the recommended range for workspace (0.4-0.8).Upon meticulous examination of the results of point-in-time illuminance in Uruguay, it becomes apparent that 58% of calculations fall below 0.4, with 42% falling within the recommended 0.4-0.8range.In Sweden, 64% of calculations fall below 0.4, while 36% lie within the suggested range.It is essential to note that these guidelines are relevant to workspaces.In the context of residential spaces, the focus lies in maintaining uniformity below 0.8, as exceeding this threshold could result in an overly monotonous ambiance.

Impact of material variation
To delve into the ramifications of altering the reflective attributes of the interior materials within the cabin, we embarked on calculating the average illuminance for each orientation and material.In the case of Uruguay, the disparities between the highest average (7935 lux -option 1) and the lowest (5279 lux -option 2) amount to 2656 lux.Similarly, in Sweden, a comparable variance of 2479 lux emerged, with the peak average being 4984 lux (option 1) and the nadir at 2505 lux (option 2).These figures underscore the tangible influence of material selection on the overall illuminance levels.While the anticipation of this impact was rational, what captures our interest is the extent to which illuminance levels fluctuate (fig.7).
Distinct differences, albeit consistent with the inherent variations between the two countries, become most apparent during the equinoxes.A plausible explanation for this phenomenon may lie in the shared characteristic of both locations wherein the facade with the most expansive glazed area faces south.
Despite endeavors to optimize daylight performance through material and orientation adjustments, the comprehensive results indicate a need for design reassessment.While the outcomes remain within acceptable bounds, the pursuit of preventing illuminance levels surpassing 3000 lux appears to inadvertently lead to significant reductions in levels at specific points or impacts on light dispersion.
These revelations, though insightful, could potentially be confined by the absence of comprehensive thermal analysis employing diverse building materials.To gain a comprehensive panorama of the ideal design for each locale, further investigations are imperative to validate thermal conditions across distinct climates.

Conclusions
The aim of the present research was to analyse daylight and utilize it as an input at the early stages of architectural projects.By considering two different latitudes and a wide range of information, the study highlighted the complexity and importance of assessing daylight.Thus, combining academic methods with practical design can offer a more comprehensive approach to architectural projects.
The relevance of analysing daylight with a simulator is clearly supported by the final findings, since it provided interesting data regarding the effect of using certain materials and on the cabin's orientation.The metrics provided by Climate Studio can help to evaluate the overall daylighting within a space at the very outset of the project.
However, this quantitative approach using digital tools must be complemented with qualitative information to consider subjective aspects, as discussed in the limitations.The same applies to thermal analysis with different building materials, which is crucial for evaluating final project decisions.
Nonetheless, the utilization of this digital method has been positive, resulting in a highly recommended methodology for professional practice.Familiarity with these calculations equips architects with tools to meet user needs and promote buildings with responsible energy use.Lars Courage's perspective, as shared in a conversation with Marilyne Andersen (The Daylight Award, 2023), advocates for a distinctive approach to architectural design, encouraging architects to begin their design process by considering the external environment and strategically incorporating natural light where needed, as opposed to simply adding openings to an enclosed structure.This approach emphasizes a deep comprehension of daylight and its integration into the design process.This viewpoint serves as the driving force behind the motivation for this research.Understanding the differences between both hemispheres and utilizing digital tools to verify and modify designs are assets in this regard.
Daylight is an essential element for both the built and natural environment.A careful design that acknowledges daylight performance can improve energy efficiency, wellbeing and environment protection.

Fig. 6 -
Fig.6 -Groups of materials used in the analysis Fig.5 -Floor plan rotation for the analysis

Fig. 7 -
Fig.7-Scheme depicting the optimal scenarios in Uruguay and Sweden.Data sourced from Climate Studio and Dr. Andrew Marsh's blog.

Table 1 -
Point in time calculation during summer solstice in Uruguay and Sweden

Table 2 -
Dynamic Daylight metrics with the chosen orientation (facade 4 facing north for both locations).Regarding materials, option 2 was chosen for Uruguay and option 4 for Sweden.Information from Climate Studio.

Table 3 -
Point in time in Sweden using materials option 4. Facade 4 is facing North (facade 2 with biggest glazing area is facing south).Data from Climate Studio.

Table 4 -
Point in time in Uruguay using materials option 2. Facade 4 is facing North (facade 2 with biggest glazing area is facing south) Data from Climate Studio.