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A window view quality assessment framework

Won Hee Ko, Michael G. Kent, Stefano Schiavon, Brendon Levitt, Giovanni Betti

arXiv:2010.07025v7cs.CY

TL;DR

Window views matter to occupant well-being, but the literature is dispersed and no established framework guides their design. The paper synthesizes standards, certification systems, and research into three view-quality variables and a conceptual index, while identifying research gaps.

  • Problem

    Window-view research is dispersed across disciplines, and there is no comprehensive framework to guide design despite views’ relevance to occupant health and well-being.

    Source: §1 · p. 2, §1.1 · p. 3

  • Method

    A semi-systematic review of daylighting standards, green certification systems, and scientific literature derives content, access, and clarity variables and a conceptual index.

    Source: §1.1 · p. 3, §6.2 · p. 18

  • Results

    The paper presents a framework and View Quality Index that relate content, access, and clarity for evaluating window-view quality.

    Source: §6.2 · pp. 18–19, §8 · p. 26

  • Takeaways & Limitations

    The framework is intended to inform building design and provide a basis for research questions and methods on window views.

    Source: §6.2 · p. 18, §8 · p. 26

    The VQI assumes equal weighting of the three variables and their criteria, while the appropriate relative importance remains an open question.

    Source: §7.4 · p. 25

Abstract

from arXiv · show

The views that windows provide from inside a building affect human health and well-being. Although window view is an important element of architecture, there is no established framework to guide its design. The literature is widely dispersed across different disciplinary fields, and there is a need to coalesce this information into a framework that can be applied into the building design. Based on the literature, we present a framework for what constitutes 'view quality.' At the basis of our framework, we propose three primary variables: View Content (the assessment of visual features seen in the window view), View Access (the measure of how much of the view can be seen through the window from the occupant's position), and View Clarity (the assessment of how clear the view content appears in the window view when seen by an occupant). Each variable was thematically derived from different sources including daylighting standards, green certification systems, and scientific research studies. We describe the most important characteristics of each variable, and from our review of the literature, we propose a conceptual index that can evaluate the quality of a window view. While discussing the index, we summarize design recommendations for integrating these three variables into the building process and identify knowledge gaps for future research.

1. Introduction

Window views connect occupants with the outdoors and are associated in prior research with health, well-being, cognition, satisfaction, stress, and emotion. The paper addresses the lack of a comprehensive design framework by synthesizing fragmented evidence into a proposed view-quality framework.

1. Introduction

  • Window views have been associated with effects on health, well-being, cognitive performance, spatial satisfaction, discomfort, stress, and emotion.The authors note that earlier reviews documented effects of windows, daylight, and views on occupant health and well-being.Source: §1 · p. 2

1.1. Problem identification

  • Existing standards and guidelines address only parts of window-view design, with different systems emphasizing access, visual content, or building orientation.The authors identify the lack of a clear definition and assessment method for view quality as one possible reason for this fragmented guidance.Source: §1.1 · p. 3
  • The literature is dispersed across disciplines, and some existing approaches assess only selected factors or are usable only after construction.A cited study found no strong relationship between current CEN/TC 169 recommendations and observers’ subjective appraisals.Source: §1.1 · p. 3
  • The authors use a semi-systematic review of standards, green certification systems, and scientific literature to derive three categorical variables and a conceptual index.They also offer design recommendations and identify areas for future research.Source: §1.1 · p. 3

2. Window view assessment: Primary variables

The framework organizes window-view quality around content, access, and clarity, derived from literature and considered across successive building-design stages. It presents a View Quality Index and guidance intended to inform design and future assessment.

Design stages

  • The variables correspond to progressively more detailed design stages: site selection, planning, and massing; façade and floorplan design; then façade material selection and control.The paper derives the variables from a review of design standards while considering façade and window design.Source: §2 · p. 3

Primary variables

  • View content is the visual features in the view, access is how much an occupant can see from their position, and clarity is how clearly that content appears through glazing and shades.The framework defines these as the three primary variables affecting view quality.Source: §2 · p. 4

Scope

  • The authors describe defining the three primary variables as a first, and design the framework for spaces such as offices and classrooms rather than spaces not requiring views or where privacy is a problem.The framework is intended for application in most buildings, with museums, theaters, and lavatories given as exceptions.Source: §2 · p. 4

Design application

  • The framework is intended to guide design from early planning through construction and to assess view-quality changes associated with construction, layout changes, and façade or shading changes.The paper links content shifts to new construction, access shifts to floor or furniture layout, and clarity shifts to façade retrofitting, maintenance, or shading-device operation.Source: §2 · p. 4

Review approach

  • The review combines design standards, certification systems, and scientific research, treating the different sources as equally important and including only English-language literature.The sources are introduced by variable and synthesized with empirical evidence from occupant assessments.Source: §2 · p. 4

View Quality Index

  • The proposed View Quality Index (VQI) ranges from 0 to 1.The supplied framework also lists interpretation bands from insufficient to excellent.Source: §2 · p. 6

3. View content: What features?

View content is the set of visual features seen through a window; the section considers how standards and research assess those features, including nature, layered views, distance, and movement.

3. View content: What features?

  • EN 17037 rates view content at minimum, medium, and high levels, while SLL-LG 10 uses insufficient, sufficient, good, and excellent; images may help assess potential views before construction.The image-based method described by Hellinga and Hordijk tallies weighted responses to visual-feature questions into a final view score.Source: §3 · p. 7

3.1. Nature and urban features

  • Nature views are generally preferred, but desirable urban features such as landmarks also matter, and perceptions of urban scenes vary with their age, maintenance, and complexity.Water is associated with higher affect ratings and perceived restoration in both urban and nature views; property-value benefits of nature views are reported mostly for residential buildings.Source: §3.1 · p. 8

3.2. Horizontal stratification

  • Horizontal stratification separates a view into ground, landscape, and sky layers, each offering local environmental information; standards also assess or promote views containing these layers.Fig. 2 illustrates a view classed as high or excellent under EN 17037 or SLL-LG 10 and identifies the three layers.Source: §3.2 · pp. 8–9, Figure 2 · p. 9

3.3. Content distance

  • Distance can contribute to view quality and may relieve eye strain, but its influence is smaller when preferred features such as nature are present; standards specify 6 m or 7.5 m minimums.EN 17037 and SLL-LG 10 specify 6 m, while LEED v4.1 specifies 7.5 m; the distance effect reported for predominantly urban content does not apply as strongly when preferred elements are present.Source: §3.3 · p. 9

3.4. Dynamic features (movement)

  • Dynamic features, including people, traffic, and changing weather or seasons, can be preferred, but no study identified here systematically evaluates them as a design parameter.Their likely influences include moving-object quality and scale, duration and frequency; nearby movement may distract, whereas distant movement may be more preferable, and construction activity was preferred when noise or vibration was not intrusive.Source: §3.4 · pp. 9–10

4. View access: How much?

View access concerns how much of the view an occupant can see from a given location. The section focuses on geometric relationships and viewing-angle recommendations, which vary across standards and research.

4. View access: How much?

  • View access measures how much of a window view an occupant can see from a particular location, with open-plan layouts creating challenges in providing access to everyone.The section focuses mainly on geometric relationships, including the occupant’s distance from and the size of the openings, while noting that standards and literature use different evaluation methods.Source: §4 · p. 10

4.1. View angle of a window

  • EN 17037 and SLL-LG 10 recommend a minimum horizontal view angle of 14°; minimum-angle recommendations vary in whether they use horizontal, vertical, or the smaller angle.Preferred angles may also depend on view features: distant features can make a smaller horizontal angle acceptable, and skyline position can affect preferred window height and frame placement.Source: §4.1 · p. 10, Table 4 · p. 11

4.1.1. View Factor

The review describes view-access assessments based on view angle and content, occupant distance and window size, alternative visual access, and the share of floor area with a view.

4.1.1. View Factor

  • View Factor combines view content and visual angle, rating views from one (lowest) to five (highest), though missing window or furniture dimensions can impede calculation.Using the smaller vertical or horizontal angle may oversimplify the available view area.Source: §4.1.1 · p. 11, Table 5 · p. 11

4.2. Distance from a window and window-to-wall ratio

  • BREEAM varies window-to-wall ratio by workstation distance, from 20% below 8 m to 35% beyond 14 m.Other studies report preferred WWRs ranging from 50% to 80% or 44% to 100%, and visible sky can affect view satisfaction.Source: §4.2 · p. 12

4.3. Alternative view access

  • When window angle is too small or occupants are too far away, certifications also recognize courtyards, atria, green walls, and roof gardens as visual access alternatives.Green Mark and Green Star promote integrating nature onto surfaces such as green walls and roof gardens.Source: §4.3 · p. 12, Figure 3 · p. 12, Table 6 · p. 13

4.4. Spatial assessment of view access

  • Spatial assessments set floor-area targets for views, but most systems do not specify the view angle needed for adequate visual contact.BREEAM requires 95% of floor area to have a view containing landscape, not only sky; DGNB requires all office rooms and at least 80% of break and social rooms to link directly outside.Source: §4.4 · p. 13, Table 7 · p. 13

5. View clarity: How clear?

View clarity concerns how clearly occupants see view content through glazing and shading, and it can vary with window design and changing shade conditions. The review describes how mullions, materials, and shade operation affect clarity.

5. View clarity: How clear?

  • View clarity covers glazing, window design, shading materials, visual acuity, contrast sensitivity, and color perception, and varies more regularly than content or access.Outdoor sunlight can change shading needs to protect occupants from glare and thermal discomfort.Source: §5 · p. 14

5.1. Window design

  • A horizontal mullion can obscure landscape-sky boundaries and distort content, while a vertical mullion may preserve clarity through visual parallax.The described difference is especially prominent in the NUS view when the horizontal mullion blocks the landscape and skyline boundary.Source: §5.1 · p. 15, Figure 4 · p. 15

5.2. Glazing and shading materials

  • Shading systems can block or distort views, while tinted glass can shift outdoor colors and reduce contrast sensitivity and color perception.The review says the effect of view color-naturalness warrants further study.Source: §5.2 · p. 16, Figure 5 · p. 16

5.2.1. View Clarity Index

  • The View Clarity Index predicts fabric-shade clarity from openness factor and visible transmittance, with values from zero for perfectly diffused shading to one for no shading.The index was empirically derived by testing observers' ability to see through 14 shading fabrics.Source: §5.2.1 · pp. 16–17

5.3. Temporal and compositional attributes of view clarity

  • View clarity should account for how long and at what level windows remain clear, as well as the obstruction caused by shading systems.Shade operation changes over time; the review notes that typical occlusion depends on orientation, sky conditions, season, and time of day.Source: §5.3 · p. 17

6. View Quality Framework

The framework organizes window view quality around content, access, and clarity, then relates these variables in a conceptual index for design use. It pairs criteria and design considerations with a scoring approach, while noting areas that need further research.

6.1. Summary

  • The framework identifies content, access, and clarity, with literature-based criteria and design considerations for each variable.Their relative importance reflects consensus across design standards and research, supplemented by an internal review with design practitioners.Source: §6.1 · p. 17, Figure 6 · p. 18

6.2. Introduction to the View Quality Index

  • View quality is modeled as the product of content, access, and clarity; a low score in any one can leave the view unsatisfactory despite high scores in the others.The authors assume equal weighting, although designers may emphasize variables differently for context-specific requirements.Source: §6.2 · pp. 18–19
  • For multiple windows, nearby openings may be treated as one continuous view, but the framework is designed for individual windows and distant separated windows need more research.The authors note uncertainty about whether close windows are perceived as one entity and do not substantiate applying the approach to multiple windows.Source: §6.2 · p. 19

0.5 if % of natural features in the scene ≤ 25 % 0 if no natural feature in the scene

  • Vcontent combines view layers, content distance, dynamic features, and natural features, with distance and dynamic-feature weights applied to landscape and ground layers.The natural-feature weight depends on the share of natural features in the scene; its percentage thresholds require further validation.Source: §6.2 · p. 20, §0.5 · p. 20
  • Vaccess scores the view angle from the occupant’s position against minimum and saturation thresholds, but the literature-based thresholds come from limited experimental settings and need generalization.Scores range from 0 below the minimum angle to 1 at or above the saturation angle.Source: §0.5 · pp. 20–21
  • Vclarity scores view clarity from the occupant’s position, from 0 for a completely blocked window to 1 for a clear, unobstructed window; its minimum and saturation thresholds remain unidentified.The authors call for further research to establish thresholds that achieve sufficient visual contact.Source: §0.5 · p. 21

7. Limitations and research gaps

The review identifies unresolved measurement questions across view content, access, and clarity, as well as the need to extend assessment across spatial and temporal conditions.

7.1. View content

  • View content remains difficult to classify and quantify, and the relationship between individual features and overall appraisal is unresolved.Mixed scenes complicate three-layer criteria, while the whole view may not relate linearly to accumulated attributes.Source: §7.1 · pp. 22–23
  • Perceptual or physical measures could assess a view as a whole, but these approaches are not yet clearly developed.Perceptual qualities include coherence, legibility, complexity, and mystery; physical measures discussed include spatial frequency, fractal patterns, and color contrast.Source: §7.1 · p. 23, Figure 9 · p. 23

7.2. View access

  • View access lacks a reliable unified indicator, and current spatial metrics need clearer criteria for view angles and multiple windows.Research must establish whether multiple views should be aggregated or assessed separately.Source: §7.2 · pp. 24–25
  • View access may depend on viewing direction and visual-field position; observers sometimes benefited more when looking directly at the view.Solid angles, gaze direction, and the view’s location in the visual field are proposed as factors for further study.Source: §7.2 · pp. 24–25, Figure 10 · p. 24

7.3. View clarity

  • View-clarity assessment needs testing across more glazing, shading, and lighting conditions, with design thresholds for clarity and duration.A study found reduced clarity when electrochromic glass lowered sunlight transmission; proposed tests include color-distance, contrast sensitivity, and object recognition.Source: §7.3 · p. 25

7.4. VQI: weightings, the spatial and temporal assessments

  • The index assumes equal weights for content, access, and clarity, while their relative importance and spatial and temporal variation remain open questions.View quality can vary with occupant position, time of day and year, and task or activity.Source: §7.4 · pp. 25–26

8. Conclusion

The paper concludes by presenting a framework and view quality index for evaluating window views. It identifies occupant well-being and further research as relevant to the design agenda.

8. Conclusion

  • The proposed framework and view quality index synthesize building standards, green certification systems, and scientific literature into an approach for evaluating window view quality.The framework covers content, access, and clarity, their limitations and research gaps, and how they can be quantified and related.Source: §8 · p. 26
  • The framework is intended to provide a comprehensive approach for designers and researchers evaluating window view quality.The paper identifies research directions intended to bridge gaps between current research and design.Source: §8 · p. 26
  • Carefully designed window views can enhance building occupants’ physiological and psychological well-being.Source: §8 · p. 26

Appendix A

Appendix A lists green building certifications that include window-view guidance, with entries spanning multiple countries and credit categories.

Appendix A

  • The appendix identifies certifications and organizes them by version, release date, country, and credit.Source: Appendix A · p. 27
  • Listed examples include view-out and visual-comfort credits in certifications from Hong Kong, the United Kingdom, Germany, and China.Source: Appendix A · p. 27
  • The list also includes certifications from countries such as Malaysia, Singapore, New Zealand, South Africa, India, and the United States.Source: Appendix A · p. 27

Appendix B

The appendices provide certification rationales, practitioner feedback context, view-angle thresholds, an unequal-weighting example, and sample content calculations.

Appendix B

  • Several certification rationales link external views with reducing eye strain, refocusing from close work, or breaking indoor monotony.Source: Appendix B · p. 28

Appendix C

  • The framework was presented to approximately 150 architects and building designers for practitioner feedback, not to derive new results.Source: Appendix C · p. 28

Appendix D

Appendix E

  • For unequal VQI weightings, designers can assign coefficients to content, access, and clarity, with their product equal to one.The example assigns 2 to content and 0.71 to each of access and clarity.Source: Appendix E · pp. 28–29

Appendix F

  • Appendix F gives Vcontent calculations for eight window views, with examples using nature and movement weights.Source: Appendix F · pp. 29–30

Appendix G

The research agenda identifies gaps that limit the design-framework utility of existing standards and studies, and prioritizes avenues for future view assessment research.

Appendix G

  • Existing standards and studies often have narrow scopes, limiting their utility for developing a design framework; the agenda assigns priorities to future research.The agenda summarizes key research areas and the urgency of each avenue.Source: Appendix G · p. 31
  • Open questions cover how space function should affect variable weightings, which variables support a space’s needs, and what minimum characteristics and quantitative thresholds define quality views.The agenda also asks how to evaluate dynamic view features and which should be considered based on their magnitude, frequency, or duration.Source: Appendix G · p. 31
  • Further research should determine how much sky, landscape, and ground should appear, whether these layers are equally important, and how people perceive attractive manmade content relative to nature.It also asks whether physical qualities such as spatial frequency can measure visual content and predict occupant responses.Source: Appendix G · p. 31
  • The agenda asks how to assess spaces with multiple windows or fragmented façades, and whether closely neighboring windows can be treated as one entity.This question is assigned high priority.Source: Appendix G · p. 31
  • The agenda asks whether physical window dimensions or solid angle better indicate perceived view quality, and whether viewing distance and direction matter.It also asks how shading and glazing jointly affect view retention, daylight access, glare, overheating, and privacy, including dynamic shading and visual-clarity thresholds.Source: Appendix G · pp. 31–32
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