A metric-driven method for designing daylit interiors that deliver useful illuminance, controlled glare, connection to the outside and circadian benefit — engineered through glazing, geometry and dynamic shading on South African projects.
Most disappointing daylit interiors are not under-glazed — they are under-specified. A brief that asks for 'lots of natural light' produces a space with impressive lux and intolerable glare, blinds permanently down by mid-morning, and none of the daylight the design promised. This masterclass replaces that aspiration with a measurable discipline: define the brief in four numbers, analyse the space on climate-based metrics, predict glare from the occupant's eye, and engineer apertures, glazing and dynamic shading that hold useful illuminance, controlled glare, view and circadian benefit together as the sun moves.
The method is built for South African conditions — brilliant clear skies, high-altitude Highveld light, and the over-lighting that overcast-sky rules of thumb cannot see. Every metric (sDA, ASE, UDI, DGP) is introduced with its exact definition, threshold and the IES LM-83, EN 17037, SANS and WELL framework it belongs to, and every chapter ends in a deliverable. Assembled, the deliverables become a defensible daylighting analysis report that survives client review, green-building submission and value engineering.
Daylight is the only building material that arrives free, changes by the minute, and simultaneously carries heat, glare and biological signal. This opening lecture reframes daylighting from a vague aspiration into a measurable design discipline. We separate the three things 'good daylight' actually means — sufficient quantity (enough light to work by), acceptable quality (no disabling glare, good distribution, connection to view) and circadian value (the right light at the right time) — and show why optimising one in isolation routinely wrecks the others. Using a Cape Town open-plan office where a fully glazed north-west corner delivered impressive lux readings yet drove blinds permanently down by 10am, we trace how a quantity-only brief produced a daylight failure. You leave able to state, in metric terms, what a daylighting brief must specify before a single window is sized: target useful illuminance, glare ceiling, view tier and the role dynamic shading will play in holding all three.
Daylighting design fails most often not from too little glass but from a brief that never defined success in measurable terms, so this course is organised around four quantifiable goals and the metrics that pin each one down. The first goal is sufficient quantity. The legacy metric is the Daylight Factor (DF), the ratio of indoor to unobstructed-outdoor illuminance under a CIE overcast sky, expressed as a percentage; a DF of 2 percent has long been a rule-of-thumb target for general office work. DF is simple and orientation-independent, but that independence is also its fatal weakness: because it assumes a permanently overcast sky it tells you nothing about sun, orientation or the bright clear skies that dominate South African conditions, where overcast assumptions are wildly pessimistic.
The discipline has therefore moved to climate-based daylight modelling (CBDM), which simulates real hourly sky conditions from a Typical Meteorological Year file and reports annual metrics — spatial Daylight Autonomy (sDA), Annual Sun Exposure (ASE), and Useful Daylight Illuminance (UDI) — introduced across Lectures 5 to 8. 45 from imperceptible to intolerable, supplemented by the older Daylight Glare Index (DGI). The third goal is connection: view out, now formalised by EN 17037 into a three-tier quality scale based on horizontal sight angle, view distance and number of view layers. The fourth goal is circadian value — the non-visual effect of light on the human body clock, increasingly specified through metrics such as melanopic equivalent daylight illuminance (melanopic EDI).
The central tension the entire course resolves is that these goals pull against each other: more glazing raises quantity and view but worsens glare and solar load; deep shading kills glare but starves quantity and severs view; a static solution that satisfies the brief at noon fails at 4pm. The resolution is dynamic: glazing tuned for spectral selectivity (high visible transmittance, low solar heat gain), apertures placed for distribution rather than raw area, and automated shading that modulates through the day to hold useful illuminance and cap glare while preserving as much view and circadian signal as possible. The deliverable of this lecture is a daylighting brief template that converts a client's qualitative wish for 'lots of natural light' into four numbers: a target sDA, an ASE ceiling, a UDI band and a DGP limit — the contract every later lecture is measured against.
You cannot control what you cannot measure correctly, and most daylighting confusion comes from mixing up two fundamentally different quantities: illuminance and luminance. This lecture builds the photometric foundation the rest of the course stands on. Illuminance (lux) measures light arriving on a surface — the quantity behind 'is there enough light to work by'. Luminance (cd/m2) measures light leaving a surface toward the eye — the quantity behind 'is this view going to blind me'. We connect these to how the human eye actually responds: adaptation, contrast and the logarithmic perception that makes a bright window against a dim wall so punishing. We work a desk-versus-window comparison showing a 300 lux task surface sitting next to a 6,000 cd/m2 sky patch, and why that 1:20 luminance ratio, not the lux level, is what sends an occupant reaching for the blind. By the end you can read a photometric report and know which number governs which design decision.
Every daylighting metric in this course is built from two base photometric quantities, and conflating them is the single most common technical error in practice. Illuminance is luminous flux per unit area incident on a surface, measured in lux (lumens per square metre). It answers 'how much light is falling here' and governs whether a task is adequately lit: SANS 10114-1 and the SANS 10400 lighting provisions, aligned with international practice, set maintained illuminance targets such as roughly 300 to 500 lux for general office and reading tasks and higher for detailed work. Illuminance is what a horizontal sensor at desk height reads and what daylight-autonomy metrics threshold against (commonly 300 lux).
Luminance, by contrast, is luminous intensity per unit projected area leaving a surface toward the observer, measured in candela per square metre (cd/m2, or nits). It answers 'how bright does this appear to the eye' and is the quantity that governs glare and visual comfort. A clear sky can present 8,000 cd/m2 or more; the sun's disc reaches hundreds of thousands; a well-lit task surface sits around 100 to 300 cd/m2. The eye does not perceive these linearly.
Vision adapts to the average luminance in the field of view, and perceived contrast is roughly logarithmic (the basis of luminance ratios and the older Daylight Glare Index). This is why a 6,000 cd/m2 patch of sky seen past a monitor at 150 cd/m2 — a ratio of 40:1, far beyond the comfortable 1:10 to 1:20 task-to-surround guidance — produces disability and discomfort glare even when desk illuminance is perfectly adequate. The eye constantly readjusts its operating point: looking from a dim interior to a bright window forces a transient adaptation that degrades task visibility for seconds, the everyday experience behind 'I can't see my screen against that window'. Three consequences flow into design.
First, you cannot solve a glare complaint by adding more light; you solve it by reducing the luminance ratio, which usually means taming the brightest source (the sky seen through glazing) with shading or by raising surrounding surface luminance through inter-reflection from light-coloured finishes. Second, illuminance and luminance must be measured and reported separately: a lux meter held flat tells you nothing about the glare an occupant faces, which needs a luminance map (an HDR fisheye image evaluated for DGP) taken from the occupant's eye position and view direction. Third, distribution matters as much as level: 500 lux delivered evenly with low luminance contrast feels better and performs better than 800 lux delivered as a bright pool beside a gloomy core, because the eye must constantly re-adapt across the uneven field. The deliverable is fluency in reading a photometric report: knowing that a lux figure validates task adequacy, a cd/m2 figure and luminance ratio validate comfort, and that dynamic shading is the lever that brings a punishing luminance ratio back into the comfortable band without extinguishing the daylight.
Daylighting strategy is only as good as the sky model behind it, and South Africa's skies are not European skies. This lecture equips you to characterise the daylight resource for any SA site and to choose the right sky assumption for analysis. We work through the three CIE standard skies — overcast, clear and intermediate — and explain why the overcast-sky Daylight Factor that dominates UK guidance is the wrong default for a country where clear and intermediate skies prevail and direct sun is a near-constant design driver. We cover the high illuminance and high luminance of the southern clear sky, the altitude effect that lifts Highveld levels above coastal readings, and where to source the meteorological data (SAURAN, TMY files) that climate-based modelling demands. A Johannesburg-versus-Durban comparison shows how the same window produces very different glare and autonomy outcomes purely because of clearness. By the end you can assemble a defensible daylight basis-of-design for any SA project.
Climate-based daylight modelling lives or dies on the sky description fed into it, and South Africa's sky climate diverges sharply from the overcast-dominated regimes that shaped legacy daylighting guidance. The CIE defines a family of standard skies, of which three matter most. The CIE Overcast Sky is fully cloud-covered with a luminance distribution three times brighter at the zenith than the horizon and, critically, no sun — it is the basis of the classical Daylight Factor. The CIE Clear Sky has a defined gradient with a brilliant circumsolar region and a deep-blue, relatively dim zone opposite the sun; it carries direct beam and is the design driver for glare and overheating.
The Intermediate Sky sits between them. The fundamental South African point is that the overcast assumption, which makes Daylight Factor conservative and orientation-blind in cloudy Northern Europe, is profoundly misleading here: across most of the interior the sky is clear or intermediate for the majority of daylight hours, so an overcast DF calculation simultaneously underestimates available light and ignores the direct-sun glare and solar-gain problems that actually dominate the design. This is the technical reason the course is built on annual climate-based metrics (sDA, ASE, UDI) rather than DF. The magnitude of the resource is large: exterior horizontal illuminance under a clear SA sky regularly exceeds 80,000 to 100,000 lux, and clear-sky luminance routinely exceeds 8,000 cd/m2 with the circumsolar region far higher — numbers that explain why even modest unshaded apertures can produce intolerable interior contrast.
Altitude amplifies this: the thinner atmosphere over the Highveld (Johannesburg at 1,753 m) attenuates less light, lifting both illuminance and the direct-beam component above coastal values at the same latitude and solar position, which is why imported daylighting rules of thumb under-predict both the benefit and the glare risk on interior-plateau sites. Clearness varies regionally: arid interior sites such as Upington and Highveld cities show high clearness indices with crisp, hard daylight and severe potential glare that dynamic shading must manage; humid coastal sites such as Durban have more diffuse, lower-contrast skies where the resource is gentler but more variable. Data sourcing is therefore a competence in itself. Climate-based modelling needs an hourly Typical Meteorological Year file containing global, direct and diffuse irradiance, from which interior illuminance is derived; SAURAN provides ground-measured South African data and is the gold standard for defending numbers in a green-building submission, while Meteonorm and PVGIS supply modelled TMY files convenient for simulation.
You must state which dataset, which sky model and which design conditions you used. The deliverable is a daylight basis-of-design: site latitude and altitude, dominant sky condition, exterior design illuminance and luminance, data source, and the explicit decision to analyse on climate-based annual metrics rather than a single overcast Daylight Factor.
Before you can use the modern annual metrics with confidence, you need to understand the metric they replaced and exactly why it fell short. This lecture dissects the Daylight Factor — its definition, its components, its enduring usefulness and its three fatal blind spots. We compute a DF for a side-lit room by hand, breaking it into the sky component, externally reflected component and internally reflected component, so you understand what the single percentage actually contains. Then we expose why DF misleads on South African projects: it assumes a permanently overcast sky, it ignores orientation entirely, and it says nothing about glare or overheating. We close by mapping each DF weakness onto the climate-based metric that fixes it — sDA for orientation-aware quantity, ASE for direct-sun and glare risk, UDI for the over-lighting DF cannot see. By the end you can use DF appropriately as a quick screen while knowing precisely when it will lie to you.
The Daylight Factor remains the most widely quoted daylighting number, so a specifier must understand both how to compute it and exactly where it breaks, because misuse of DF underlies a great many disappointing South African interiors. DF is defined as the ratio of interior illuminance at a point to the simultaneous unobstructed exterior horizontal illuminance under a CIE overcast sky, expressed as a percentage; DF = Ei/Eo x 100. It decomposes into three additive components. The Sky Component (SC) is the light reaching the point directly from the visible patch of sky through the aperture — the dominant term, governed by window size, position and the solid angle of sky seen.
The Externally Reflected Component (ERC) is light arriving after reflection off external surfaces such as opposite buildings or the ground — usually small but significant in dense urban canyons. The Internally Reflected Component (IRC) is light bouncing off interior surfaces before reaching the point — strongly dependent on surface reflectances, which is why light-coloured ceilings and walls materially lift daylight in the room depth. Average DF can be estimated by the BRE formula DF_avg = (T x A_w x theta) / (A_total x (1 - R^2)), where T is glazing transmittance, A_w window area, theta the visible sky angle, A_total total interior surface area and R the area-weighted mean reflectance — a formula that usefully shows DF rising with glazing transmittance, window area and surface reflectance, and falling with external obstruction. Typical targets evolved as DF 2 percent for general spaces and DF 5 percent for daylight-dominated spaces needing little electric supplement.
So far so useful: DF is fast, needs no weather file and is a legitimate early screen. But three blind spots make it dangerous as a sole metric, especially in South Africa. First, the overcast-sky assumption means DF is computed under the one sky condition SA rarely experiences; it therefore ignores the clear-sky brilliance that drives most local daylighting outcomes and is pessimistic about available light while blind to direct sun. Second, DF is orientation-independent by construction — a north and a south window of equal size return the identical DF, which is absurd in a hemisphere where those facades have utterly different sun exposure — so DF can never inform an orientation strategy.
Third, and most consequential, DF measures only a floor: it tells you whether there is enough light but says nothing about too much. A wall of north glazing can post a wonderful DF and still deliver disabling glare and overheating; DF cannot see the over-lit, high-luminance condition that actually drives occupant complaints and blind deployment. Each failure maps cleanly onto a climate-based successor: orientation-blindness is cured by spatial Daylight Autonomy (sDA), which simulates real annual skies per orientation; the inability to see direct sun is cured by Annual Sun Exposure (ASE), which counts excess-sun hours; and the floor-only nature is cured by Useful Daylight Illuminance (UDI), which bands light into too little, useful and too much. The deliverable is the disciplined use of DF as a concept-stage screen, always accompanied by the knowledge that any orientation, glare or overheating decision must be made on the climate-based metrics that follow.
Spatial Daylight Autonomy is the metric that finally answers, across a real year and real skies, the question DF could only fumble: is enough of this space daylit enough of the time? This lecture defines sDA precisely, works through its thresholds, and shows how to read and challenge an sDA result. We unpack the LM-83 definition — sDA300/50%, the percentage of floor area receiving at least 300 lux for at least 50% of occupied hours — and the IES benchmarks of sDA at or above 75% for 'preferred' and 55% for 'nominally accepted' daylight. We show how sDA is computed on an analysis grid from an annual climate-based simulation, why occupancy schedule and grid spacing matter, and how blind-operation assumptions can quietly inflate or deflate the number. A two-orientation classroom comparison demonstrates sDA exposing a daylight shortfall that a healthy DF had concealed. By the end you can specify, interpret and defend an sDA target on any project.
Spatial Daylight Autonomy is the workhorse quantity metric of modern daylighting, codified by the Illuminating Engineering Society in LM-83, and understanding its exact definition is essential because small assumption changes move the number materially. sDA is built on point Daylight Autonomy (DA), the fraction of occupied hours in a year that a given point receives at least a target illuminance from daylight alone. The standard target is 300 lux, and the standard occupied period is the building's hours of use, conventionally taken as a representative schedule such as 08:00 to 18:00. A point is said to 'pass' if its DA is at least 50 percent — that is, it meets 300 lux for at least half of occupied hours across the year.
sDA is then the spatial extension: the percentage of the analysis-grid points across the floor area that pass. The canonical form is therefore sDA300/50%, read as 'spatial daylight autonomy at 300 lux for 50 percent of the time'. IES and the green-building rating systems that adopt it set two benchmark thresholds: sDA300/50% of 75 percent or higher denotes 'preferred' daylighting (the space is convincingly daylit), while 55 percent or higher denotes 'nominally accepted'. Computing sDA correctly demands several disciplined choices.
6 m, excluding a perimeter offset from walls; too coarse a grid smooths away real variation. The simulation runs the full year of the climate file at hourly or sub-hourly timesteps, accumulating illuminance at every grid point. Crucially, LM-83 specifies that operable blinds be modelled with an active-control assumption: blinds are deployed to block direct sun whenever it would cause excessive sun on the work plane (the same condition that drives ASE), and the daylight autonomy is then assessed with those blinds in their deployed state for the relevant hours. This blind-operation rule is what couples sDA to ASE and is the single most-gamed assumption in practice — an over-optimistic blind model that leaves shades open inflates sDA, while a conservative always-closed model deflates it, so a defensible report must state the control logic explicitly.
The metric's power over DF is that it is genuinely orientation- and climate-aware: a north and a south room of identical geometry return different sDA because the simulation sees their different annual sun, exactly the discrimination DF lacks. Its limitation, which Lecture 7 addresses, is that sDA is still a one-sided 'enough light' measure — it rewards more daylight without penalising the over-lighting and glare that excess daylight brings, which is why sDA must always be read alongside ASE and ideally UDI. In design practice sDA is the metric you optimise through aperture size and placement, glazing visible transmittance and interior reflectances, while watching that the moves which raise it do not push ASE past its ceiling. The deliverable is the ability to set a project sDA target (commonly 55 to 75 percent per the space's ambition and rating goal), read a simulation result, and interrogate its grid, schedule and blind-control assumptions before trusting it.
If sDA tells you whether there is enough daylight, Annual Sun Exposure warns you when there is too much of the wrong kind — direct sun deep in the space, the precursor to glare, overheating and permanently lowered blinds. This lecture defines ASE, explains the LM-83 criterion ASE1000/250h, and shows how it acts as the essential counterweight to sDA. We unpack the definition — the percentage of floor area receiving at least 1,000 lux of direct sunlight for at least 250 occupied hours per year — and the IES guidance that ASE above 10% signals likely visual discomfort, with 7% or below preferred. We show how ASE is computed from direct-sun-only simulation with blinds open, why it is the metric that finally quantifies the glare-and-overheat risk DF and even sDA miss, and how it directly justifies dynamic shading. A west-facade case shows ASE at 28% explaining a space everyone hated despite an excellent sDA. By the end you can use ASE to size and justify a shading strategy.
Annual Sun Exposure is the metric that institutionalised a hard truth daylighting long ignored: more sun is not better, and beyond a threshold it actively harms a space, so ASE is the disciplined counterweight that stops sDA optimisation from running away into a glare-ridden, overheated result. Defined in IES LM-83 alongside sDA, ASE measures the percentage of the analysis-grid area that receives at least 1,000 lux of direct sunlight for at least 250 occupied hours per year — written ASE1000,250h or ASE1000/250h. Three features of the definition are decisive. First, it counts direct sunlight only: the simulation isolates the beam component reaching each grid point, ignoring diffuse and reflected light, because it is direct sun penetrating the space that produces the punishing high-luminance patches and the deep solar penetration behind glare and overheating.
Second, it is assessed with shading devices open (retracted) — ASE deliberately characterises the raw, unmitigated direct-sun risk of the architecture itself, so that the result tells you how hard your dynamic shading will have to work rather than flattering the design by assuming the blinds are already down. Third, the 1,000 lux and 250-hour thresholds together define 'excessive': a point that is hit by strong direct sun for more than 250 occupied hours a year (roughly an hour a day) is flagged as over-exposed. IES benchmarks read ASE the opposite way to sDA — lower is better: ASE1000/250h at or below 10 percent is the accepted ceiling, with 7 percent or below preferred; above 10 percent the space is likely to suffer visual discomfort and occupants will respond by deploying blinds and leaving them down, which then collapses the daylight the sDA promised. This is the crux of why the two metrics are inseparable.
A west or low-north facade can post a superb sDA and a terrible ASE simultaneously: there is plenty of light, but much of it arrives as raw beam sun that no one can tolerate, so the occupants close the blinds, the space goes dark, and the real, in-use daylight autonomy is a fraction of the simulated figure. Reporting sDA without ASE is therefore the modern equivalent of the DF blind spot. ASE's design value is that it directly sizes and justifies the shading strategy: a high ASE is the quantitative trigger for external shading geometry (Lecture 11) and dynamic control (Lecture 12), and the design goal becomes driving ASE under 10 percent while keeping sDA above its target — the two-sided optimisation that defines competent daylighting. ASE also flags overheating risk by proxy, since the same direct-beam penetration that the metric counts is the dominant cooling-load driver, linking daylighting analysis to the SANS 204 energy framework.
Practically, you read ASE and sDA as a pair on the same plan: regions high in both want better dynamic shading and selective glazing; regions high in ASE but low in sDA (deep, badly-distributed sun) want geometric redesign, not just blinds. The deliverable is the ability to interpret an sDA/ASE result jointly, set the ASE ceiling (10 percent, preferably 7), and translate an exceedance directly into a shading and glazing brief.
sDA and ASE each capture one edge of the daylight problem; Useful Daylight Illuminance folds both edges into a single banded picture of how often a space is actually well lit. This lecture defines UDI and its bins, and shows why a metric that explicitly counts over-lighting is so valuable for South African clear-sky conditions. We unpack the standard bands — UDI-fell-short below 100 lux, UDI-supplementary 100 to 300 lux, UDI-autonomous 300 to 3,000 lux, and UDI-exceeded above 3,000 lux (the glare-and-overheat zone) — and how each grid point's annual hours distribute across them. We contrast UDI's two-sided view with sDA's one-sided floor, and show how the UDI-exceeded band is, in effect, a glare early-warning that ties straight back to ASE. A north-facade office comparison shows UDI revealing that a high-sDA space spent a third of its hours over-lit. By the end you can use UDI to balance sufficiency against excess.
Useful Daylight Illuminance, developed by Nabil and Mardaljevic, was the first widely adopted metric to recognise explicitly that daylight has both a lower and an upper bound of usefulness, and it remains the most informative single metric for the bright, clear-sky conditions typical of South Africa where over-lighting is as real a failure as under-lighting. Like Daylight Autonomy, UDI is a climate-based annual metric computed at each analysis-grid point from a full-year simulation against the real sky, but instead of a single pass/fail threshold it sorts every occupied hour's daylight illuminance into bands and reports the percentage of occupied hours falling in each. The standard bands are: UDI 'fell short' (or not-achieved) for illuminance below 100 lux, where daylight is insufficient and electric lighting is required; UDI 'supplementary' for 100 to 300 lux, where daylight contributes but must be topped up; UDI 'autonomous' for 300 to 3,000 lux, the band where daylight alone is sufficient and comfortable, requiring no electric light and unlikely to cause glare or overheating; and UDI 'exceeded' above 3,000 lux, where daylight is so intense it is likely to cause visual discomfort, glare and unwanted solar gain. ) The genius of the banding is that it captures, in one analysis, both halves of the design problem that sDA and ASE address separately: the 'fell short' percentage is the under-lit failure, and the 'exceeded' percentage is the over-lit failure that DF and sDA are structurally blind to.
A space with a high UDI-autonomous percentage and low fell-short and exceeded percentages is genuinely well daylit; a space can post an excellent sDA yet reveal, under UDI, that it spends 30 percent of its hours in the exceeded band — the quantitative signature of a room that is technically 'daylit' but practically intolerable, exactly the clear-sky over-lighting failure South African designers see constantly. UDI-exceeded therefore functions as a glare and overheating early-warning closely allied to ASE: where ASE isolates direct-beam over-exposure with blinds open, UDI-exceeded captures total (beam plus diffuse) over-illumination as actually experienced, making it a fuller picture of when a space tips past comfortable. The two metrics are complementary rather than redundant — ASE for code-style direct-sun screening, UDI for a richer occupant-experience profile. In design, UDI is the metric that most directly rewards the dynamic strategy this course advocates: spectrally selective glazing trims the exceeded band without crushing the autonomous band; well-placed apertures and light-redirecting elements move hours from fell-short into autonomous in the room depth; and automated shading is what keeps hours out of the exceeded band hour by hour.
Because UDI is computed with a given shading assumption, the same blind-control honesty demanded for sDA applies. The deliverable is the ability to read a UDI band chart, set a target (commonly maximising UDI-autonomous while holding UDI-exceeded low), and use the exceeded band as the bridge between quantity analysis and the glare metrics that follow.
Glare is the daylighting failure occupants notice first and forgive last, and it is the reason blinds get pulled down and left down — defeating every daylight gain the analysis promised. This lecture gives you the metrics to predict and control it. We define Daylight Glare Probability (DGP), the perception-validated index that estimates the fraction of occupants who will judge a scene uncomfortable, and the older Daylight Glare Index (DGI) it largely superseded. We work through DGP's thresholds — imperceptible below 0.35, perceptible 0.35 to 0.40, disturbing 0.40 to 0.45, intolerable above 0.45 — and the two things that drive it: the luminance of the glare source and its position in the field of view. We show how DGP is evaluated from an HDR luminance map at the occupant's eye, why view direction is everything, and how shading and glazing each pull DGP down. A trading-desk case shows DGP at 0.46 from an unshaded north sky brought to 0.33 by an automated screen. By the end you can specify a DGP ceiling and design to meet it.
Glare is where daylighting most often fails in occupied reality, and because it is a perceptual phenomenon driven by luminance contrast rather than illuminance level, controlling it requires its own metrics — chief among them Daylight Glare Probability, the current standard for daylit spaces. 45. Its defining strength over earlier indices is that it is dominated by the vertical illuminance at the eye (Ev) — the overall brightness the eye is adapting to — combined with a contrast term summing each glare source's luminance, solid angle and position. 35 for demanding visual tasks.
The two physical levers DGP exposes are luminance and position. Source luminance is the brightness of the glare source — a patch of clear sky at 8,000 cd/m2, the sun's disc, or a brilliantly sunlit external surface seen through the window; reducing it (via shading, lower-transmittance glazing, or fabric that diffuses the beam) is the primary cure. Position is the angular displacement of the source from the line of sight, captured by the Guth position index: a bright window directly in the field of view is far more disabling than the same window at the periphery, which is why occupant orientation and view direction must be part of the analysis — a desk facing a bright window is the classic avoidable glare error. DGP is evaluated not from a lux meter but from a luminance map: a high-dynamic-range fisheye image (real or simulated) taken from the occupant's eye position looking in the actual view direction, processed by software such as Evalglare that identifies glare sources and computes the index.
This is why view direction and seating layout are design variables, not afterthoughts. The older Daylight Glare Index (DGI), derived from the Cornell large-source glare formula, is still encountered and runs on a different scale (roughly 18 'just perceptible' to 28 'just intolerable'); it is useful for legacy comparison but DGP's perceptual validation under daylight has made it the preferred metric, and EN 17037 frames glare protection in DGP terms. Two practical points govern design. First, glare is dynamic: DGP from a given view swings through the day and year as the sun moves, so a single worst-case snapshot is insufficient — best practice evaluates DGP across the year (an enhanced simplified DGP or annual glare metric such as the fraction of occupied hours exceeding a DGP threshold) to size dynamic shading.
Second, because DGP is driven by source luminance and adaptation, the solution is almost always to tame the brightest source while keeping the space generally bright (raising surround luminance through light finishes lifts adaptation and lowers relative contrast), rather than darkening everything. Dynamic shading is the decisive tool: an automated screen or venetian that lowers source luminance precisely when DGP would breach the ceiling, then retracts to restore view and daylight, is what holds glare in band without sacrificing the sDA and UDI the space depends on. The deliverable is the ability to set a DGP ceiling, commission or read an HDR-based glare analysis from the correct eye position and view direction, and translate a DGP exceedance into a glazing and dynamic-shading specification.
Daylight is only half of what a window delivers; the other half is view — the connection to the outside world that affects wellbeing, satisfaction and the perceived quality of a space as much as illuminance does. This lecture formalises view as a designable, gradeable quality rather than a happy accident. We work through the EN 17037 view framework, which grades view out on three quality levels using the horizontal sight angle of the view opening, the outside distance to what is seen, and the number of view layers (sky, landscape, ground) visible. We connect view to the daylighting trade-off at the heart of the course: every shading move that controls glare also risks severing view, so the design challenge is to cap luminance without blinding the occupant to the outside. We show how fabric openness factor, blind type and automation logic preserve view while controlling glare. A hospital-ward case shows how view-tier targets reshaped a shading spec. By the end you can specify and protect a view quality alongside daylight.
View out has moved from a soft amenity to a specifiable performance attribute, formalised most fully by the European daylight standard EN 17037 'Daylight in Buildings', whose framework is increasingly referenced internationally including on South African green-building and wellbeing-oriented projects. EN 17037 addresses four aspects of daylight provision — daylight quantity, view out, exposure to sunlight, and protection from glare — and it is its treatment of view that this lecture targets, because view is the quality most easily destroyed by the very shading that controls glare. The standard grades view out on three quality levels (minimum, medium, high) assessed against three parameters. The first is the horizontal sight angle: the angular width of the view opening seen from inside, with wider openings scoring higher (the standard sets increasing minimum angles for the higher grades).
The second is the outside distance: how far away the nearest viewed object is, since a view to a wall two metres away is poorer than a view to a landscape hundreds of metres off; greater viewing distance scores higher. The third is the number of view layers visible: a complete view comprises a sky layer (upper), a landscape or cityscape layer (middle), and a ground layer (lower), and seeing all three — particularly retaining the landscape layer at eye level — defines the higher grades, while losing the middle layer to a high sill or a lowered blind degrades the view sharply. This layered model is what makes view a precise design target rather than a vague aspiration. The deep design tension the course resolves is that view and glare control are in direct conflict: the bright sky that view depends on is also the dominant glare source, so a crude response (a low-transmittance blind fully deployed) controls glare by abolishing view, trading one EN 17037 failure for another.
The resolution is selectivity in three dimensions. Spectrally selective glazing reduces solar heat and tempers extreme luminance while keeping high visible transmittance, so the view remains bright and natural rather than dim and colour-shifted. Fabric openness factor on roller screens governs the trade directly: a low openness factor (around 1 to 3 percent) gives strong glare and luminance reduction but a more veiled view, while a higher openness (5 to 10 percent) preserves a clearer view at the cost of more transmitted brightness — and openness must be matched to orientation and the luminance of what lies behind the glass, since the same 3 percent fabric reads as near-transparent against a dim courtyard and near-opaque against a brilliant sky. Blind type matters: a venetian can be angled to cut the sky glare source while leaving a horizontal view band open, preserving the landscape layer that a roller blind would cover; a top-down/bottom-up blind can cap the bright upper sky while keeping the eye-level view layer clear.
Above all, automation logic is what reconciles the two goals over time: a control strategy that deploys shading only as far as needed to bring DGP under the ceiling, prioritising retention of the eye-level view layer and retracting the moment the glare threat passes, preserves both view quality and daylight far better than manual operation, which tends toward fully-down-and-forgotten. The deliverable is the ability to set an EN 17037 view tier as a project requirement and to specify glazing, fabric openness, blind type and control logic that protect that tier while meeting the DGP ceiling.
The most significant shift in daylighting thinking this decade is the recognition that light does more than let us see — it sets the human body clock, and the right daylight at the right time is now a measurable design objective. This lecture introduces circadian (non-visual) daylighting and the metrics emerging to specify it. We explain the intrinsically photosensitive retinal ganglion cells and why they respond to bright, blue-rich light by day, and how this differs from the photopic response behind lux. We introduce the melanopic metrics — melanopic equivalent daylight illuminance (melanopic EDI) and the melanopic ratio — and the WELL Building Standard targets that brought them into specification. We connect circadian goals to the rest of the course: daylight is the ideal circadian source, but only if shading and glazing preserve enough morning brightness and spectral quality. A school-classroom case shows morning melanopic EDI driving an east-facing daylight strategy. By the end you can factor circadian value into a daylighting and shading design.
Circadian daylighting represents a genuine paradigm shift: the discovery that the eye contains a non-visual light-sensing system means daylight design now carries a human-health objective measurable in its own units, and the way shading and glazing modulate that signal becomes a design responsibility rather than an afterthought. The biology rests on intrinsically photosensitive retinal ganglion cells (ipRGCs), discovered in 2002, which contain the photopigment melanopsin and are most sensitive to short-wavelength blue light around 480 nm — a spectral sensitivity quite different from the photopic luminous-efficiency curve (peaking at 555 nm) that defines the lumen and the lux. These cells project not to image-forming vision but to the suprachiasmatic nucleus, the brain's master clock, and to centres governing alertness and melatonin suppression. The practical consequence is that bright, blue-rich light in the morning and through the day entrains and reinforces the circadian rhythm — improving alertness, mood, sleep quality and performance — while bright blue light in the evening disrupts it.
Daylight is the ideal circadian stimulus because it is intensely bright (tens of thousands of lux outdoors versus a few hundred from electric light) and naturally blue-rich at the start of the day, and because it follows the correct daily timing for free. This is why a daylighting strategy that delivers strong morning light to occupied spaces has a health value entirely separate from its visual-task value. Quantifying the non-visual effect required new metrics because lux, weighted to photopic vision, systematically under-counts the circadian potency of blue-rich daylight. The CIE standardised alpha-opic quantities, of which the melanopic measure is central; the most usable specification metric is melanopic Equivalent Daylight Illuminance (melanopic EDI, in lux), which expresses the melanopic stimulus of any light source as the equivalent illuminance of a standard daylight (D65) source.
5 or lower — meaning daylight delivers far more circadian punch per visual lux than typical artificial light. The WELL Building Standard brought these into mainstream specification, setting targets such as a minimum melanopic EDI (in the order of 150 to 240 melanopic lux at eye level for part of the day, depending on the option) measured vertically at the eye during daytime occupied hours. The course-wide tension reappears sharply here: the shading and glazing that control glare and heat also attenuate and spectrally shift the very light the circadian system needs. A heavily tinted or low-transmittance glazing can crush morning melanopic EDI; a blind kept fully deployed for glare blocks the circadian dose entirely; a strongly coloured fabric shifts the spectrum away from the blue the ipRGCs want.
The design resolution is, once again, selectivity and dynamism: glazing chosen for high, spectrally neutral visible transmittance preserves the circadian quality of admitted daylight; orientation strategy that brings morning light to occupied zones (an east or north-east emphasis for spaces used early) maximises well-timed dose; and automated shading that admits bright morning light while still controlling later-day glare protects the circadian benefit instead of sacrificing it to a blanket glare response. The deliverable is the ability to incorporate a melanopic EDI target into a daylighting brief and to specify glazing, orientation and shading control that deliver well-timed, spectrally adequate daylight for circadian health alongside the visual and comfort metrics.
Metrics tell you whether a daylighting design works; aperture geometry is how you make it work. This lecture turns the targets of the preceding lectures into built form — the size, shape, position and detailing of openings that deliver daylight deep and even rather than bright and shallow. We work through the toolkit: window head height as the dominant driver of daylight penetration depth (light reaches roughly 1.5 to 2 times the head height into a side-lit room), the role of clerestory and high-level glazing, light shelves that bounce light onto the ceiling and push it deep, the over-rated reality of light tubes, and toplighting strategies — rooflights, monitors and sawtooth — for deep-plan spaces. We connect every device back to the metrics: a light shelf raises room-depth sDA and cuts near-window UDI-exceeded by redistributing rather than adding light. A Karoo gallery case shows toplighting geometry tuned to avoid direct-sun ASE. By the end you can shape apertures to hit daylight targets before any shading is added.
Aperture geometry is the architectural lever that determines daylight distribution, and because distribution — not raw quantity — is what separates a well-daylit space from a bright-but-patchy one, this lecture translates the metric targets into the physical design of openings. 5 to 6 m of room depth. This is why raising the window head, adding clerestory or transom glazing high in the wall, and keeping the upper wall and ceiling light-coloured do far more for room-depth daylight than enlarging glazing at eye level — and why deep-plan spaces cannot be daylit from the perimeter alone. The light shelf is the classic device exploiting this: a horizontal element placed above eye level divides the window into a lower view portion and an upper daylighting portion, its top surface (high-reflectance) bouncing high-angle daylight onto the ceiling and deep into the room while its underside shades the near-window zone from direct sun.
A well-tuned light shelf simultaneously raises room-depth sDA (more light deep in), reduces near-window UDI-exceeded and ASE (it shades the perimeter from high sun), and flattens the illuminance gradient that causes the bright-pool/dim-core discomfort — a redistribution, not an addition, of light, which is exactly why it improves several metrics at once. Its limits must be understood: light shelves work best on equator-facing facades (the north facade in South Africa) where sun is high, and deliver little on east/west low-sun faces. High-level and clerestory glazing bring daylight deep with less glare risk than view-level glazing because the bright sky source is above the normal line of sight, lowering DGP for a given quantity. Toplighting is the decisive strategy for deep-plan and single-storey spaces where side-lighting cannot reach: horizontal rooflights deliver high quantity but, under the brilliant SA clear sky, carry severe ASE and glare risk unless diffused or oriented; roof monitors and sawtooth rooflights solve this by presenting vertical or steeply-pitched glazing facing a controlled direction (classically south-facing in the southern hemisphere to capture diffuse sky while excluding direct beam, or north-facing with shading to admit controlled sun), giving even, glare-controlled toplight — the strategy behind well-daylit galleries, factories and studios.
Light tubes (tubular daylight devices) are useful for small deep cores such as bathrooms and corridors but are routinely over-sold: their delivered illuminance falls off steeply with duct length and bends, and they provide no view, so they supplement rather than replace designed apertures. 5) multiply the internally reflected component and push light deeper; and glazing visible transmittance directly scales delivered illuminance. The crucial discipline is to design aperture geometry to approach the daylight targets first — getting distribution, head height and toplighting right so the space is inherently well-daylit — and only then add the dynamic shading of Lecture 12 to manage the residual glare and over-lighting, rather than relying on shading to rescue a poorly-aperture-designed space. The deliverable is an aperture strategy per space: head heights, clerestory/light-shelf/toplighting selection, reflectance schedule and glazing transmittance, justified against the sDA, ASE and UDI targets.
Every metric in this course points to one conclusion: a static daylighting design cannot satisfy goals that conflict and change by the hour, so the resolution is dynamic shading under intelligent control. This lecture is where the whole method converges. We show why a fixed blind position is always wrong at some time of day — too dark when glare has passed, too bright when sun returns — and how automation holds sDA, ASE, UDI, DGP and circadian dose in band as conditions move. We cover the control toolkit: external versus internal devices, venetians versus rollers, fabric openness, and the control logic — solar-tracking, sensor, DGP-threshold and scheduled strategies, with manual override. We connect shading to glazing as a co-designed pair and to the SANS and WELL frameworks. A Sandton office case shows DGP-driven automation lifting in-use sDA by holding blinds up far longer than occupants ever would. By the end you can specify a dynamic shading and control strategy that delivers the metrics in practice, not just in simulation.
Dynamic shading is the engine that makes metric-driven daylighting achievable in occupied reality, because the goals this course sets — high sDA, low ASE, banded UDI, capped DGP, preserved view and circadian dose — conflict and shift continuously, and only a device that changes through the day can hold them all in band at once. The case for dynamic over static rests on a simple impossibility: any fixed shading position optimised for one moment is wrong at another. A blind set to kill the 3pm west glare leaves the space needlessly dark all morning, collapsing sDA and circadian dose; a blind set for morning brightness admits intolerable afternoon glare, spiking DGP and UDI-exceeded. The single most damaging real-world pattern is the manually-lowered-and-forgotten blind: occupants drop a shade to stop a transient glare event and never raise it, so the space runs dark for the rest of the day and the simulated daylight performance never materialises — the gap between modelled and in-use sDA is overwhelmingly a control-and-behaviour problem, not an architecture problem.
Automated shading closes that gap by raising and lowering precisely as conditions demand and retracting the instant the threat passes, holding blinds up far longer than any occupant would. The device toolkit must be matched to the metric problem. External devices (external venetians, external roller screens, louvres) are thermally superior because they intercept solar radiation outside the glass, controlling ASE-driven overheating as well as glare, and are the strong choice for high-ASE facades — though they demand wind management and an anemometer-driven auto-retract setpoint above a few storeys. Internal devices (roller screens, venetians) are cheaper, easier to maintain and excellent for glare and view control but admit the heat through the glass first, so they pair with solar-control glazing rather than replacing it.
Venetian blinds offer the unique ability to angle slats to block the sky glare source while keeping a horizontal view band open, preserving the EN 17037 eye-level view layer and redirecting light to the ceiling — a daylighting as well as a shading device. Roller screens are selected by fabric openness factor: low openness (1 to 3 percent) for strong glare control where view is secondary, higher openness (5 to 10 percent) where view and daylight are prioritised, always matched to the orientation's luminance. The control logic is where the daylighting intelligence lives. The crudest is scheduled (time-of-day) control, adequate only for predictable facades.
Solar-tracking control deploys shading based on calculated sun position, good for direct-beam (ASE) management. Sensor-based control uses exterior or interior photosensors to respond to actual conditions including cloud. The most sophisticated, and the one this course advocates for demanding spaces, is glare-driven control that estimates DGP (from a facade luminance sensor or a model) and deploys only as far as needed to bring DGP under the ceiling — maximising retained daylight, view and circadian dose for any given glare constraint. All strategies must include accessible manual override with timed auto-return to automatic, because occupant agency improves satisfaction and removing it backfires.
Shading and glazing are co-designed, not sequential: the glazing sets the baseline solar and visible transmittance and the shading modulates around it, so a high-visible-transmittance, low-solar-gain spectrally selective glazing paired with DGP-driven dynamic shading is the combination that simultaneously maximises sDA, UDI-autonomous and circadian dose while holding ASE and DGP in band. This strategy also maps onto the compliance and rating frameworks — SANS 204 energy (automated shading reduces cooling load and lighting energy via daylight harvesting), Green Star SA and WELL daylight/circadian credits — making the dynamic strategy the single intervention that serves comfort, energy and health together. The deliverable is a dynamic shading and control specification: device type and location per facade, fabric openness, control logic with the governing metric (typically DGP ceiling and ASE management), sensor and override provisions, and the glazing it is co-designed with.
A daylighting design is only as good as your ability to assemble it into a coherent, defensible whole and carry it through documentation, compliance and commissioning. This closing lecture binds the course into a deliverable. We assemble the full analysis spine — brief targets, basis-of-design, metric results (sDA, ASE, UDI, DGP), view and circadian provision, aperture and glazing strategy, and the dynamic shading specification — into one report that survives client review, green-building submission and value engineering. We show how to bind every design move to a metric and a standard, so deleting a light shelf or downgrading a blind visibly threatens a target. We map the report onto the compliance landscape: SANS 204 energy, Green Star SA daylight and IEQ credits, EN 17037 and WELL. And we cover commissioning — verifying the automated shading delivers the simulated metrics in use. A mixed-use case shows the report defeating an attempt to value-engineer out the automation. By the end you can produce a daylighting report that holds up under scrutiny.
The final competence of a daylighting specifier is integrative: turning the analyses of the preceding lectures into a single report that defends the design through every downstream pressure — client review, building-control and green-building submission, value engineering, and post-occupancy reality. The report has a standard spine, and each section binds a design decision to a metric and a standard so the logic is auditable and the design is defensible. It opens with the brief targets from Lecture 1 — the agreed sDA, ASE ceiling, UDI bands, DGP ceiling, EN 17037 view tier and melanopic EDI target — stated as the contract against which everything is judged. It then presents the daylight basis-of-design from Lecture 3: site latitude and altitude, sky model, exterior design illuminance and luminance, data source (SAURAN/TMY) and the explicit choice of climate-based annual metrics over Daylight Factor.
The core is the metric results section: the sDA and ASE plan pair read jointly (Lectures 5 to 6), the UDI band profile (Lecture 7), and the DGP analysis from the correct occupant eye positions and view directions across the year (Lecture 8), each compared against its target with a clear pass/fail and, where relevant, the remediation that closes a gap. View provision is reported against the EN 17037 tiers (Lecture 9) and circadian provision against the melanopic EDI target (Lecture 10). The design-response section then documents the aperture and glazing strategy (Lecture 11) and the dynamic shading and control specification (Lecture 12), with every element bound to the metric it serves — a discipline that is the report's defensive armour: when value engineering proposes deleting the light shelf or substituting a cheaper manual blind, the report shows the specific sDA, ASE, UDI or DGP target that move breaks, converting a cost conversation into a compliance-and-comfort conversation. This binding is what makes a daylighting spec survive the same way a structural spec does.
The report then maps onto the compliance and rating landscape. SANS 10400 (and the lighting provisions of SANS 10114) and SANS 204 govern energy and the lighting baseline: automated daylight-responsive shading and daylight harvesting reduce both cooling load and electric-lighting energy, contributing to the SANS 204 energy demand limits and to EDGE's energy threshold. Green Star SA awards Indoor Environment Quality credits for daylight provision (often assessed on DF or sDA) and glare control, and the daylighting report is the evidence base for those credits. EN 17037 provides the view, sunlight and glare-protection framework increasingly cited on premium projects, and the WELL Building Standard provides the circadian and visual-comfort credits (melanopic EDI, glare).
A competent report cites which framework each result serves. The closing discipline is commissioning and verification: the simulated metrics mean nothing if the installed automated shading does not behave as modelled, so the report specifies a commissioning protocol — verifying control setpoints (DGP ceiling, ASE-driven deployment, daylight-harvesting dimming thresholds), confirming manual-override-with-auto-return works, and ideally a post-occupancy measurement of illuminance, luminance (HDR glare) and occupant satisfaction to confirm in-use performance matches the model. This closes the loop between simulation and reality that the manually-lowered-blind problem of Lecture 12 otherwise breaks. The deliverable, and the capstone of the course, is a complete daylighting analysis report: targets, basis-of-design, joint metric results, view and circadian provision, aperture/glazing/shading strategy with every element bound to a metric and standard, compliance mapping, and a commissioning protocol — a document that defends a daylit, glare-controlled, view-rich, circadian-positive design from concept through occupancy.
Three end-to-end calculations applying the metric method to real South African situations. Each runs the chain from sky and geometry through the daylight metrics to a shading and glazing decision.
A 9 m-deep open-plan bay, north-facing, window head at 2.7 m. Will perimeter glazing daylight the full depth, and what does sDA require?
Useful side-lit daylight reaches roughly 1.5 to 2 × window-head height. With a 2.7 m head: 2.0 × 2.7 = 5.4 m of useful depth. The room is 9 m deep, so the back 3.6 m is under-daylit on perimeter glazing alone — the region that will read as UDI fell-short and drag sDA down.
Add a clerestory lifting the effective daylighting head to 3.6 m: penetration ≈ 2.0 × 3.6 = 7.2 m. Add a north light shelf bouncing high sun onto the ceiling and the useful band extends toward the full 9 m, with the ceiling (reflectance 0.85) carrying light deep.
The redistribution lifts deep-zone Daylight Autonomy above the 50% point, pushing sDA300/50% across the bay from a failing ~45% toward the 'preferred' ≥75% benchmark — achieved by moving light, not adding glazing area (which would have worsened glare and ASE).
A desk reads a healthy 450 lux, yet the occupant complains of disabling glare. Diagnose it correctly.
The lux level is fine (300-500 lux target met), so adding light cannot help. The problem is contrast, measured in luminance, not illuminance.
The clear-sky patch behind the monitor sits near 8,000 cd/m²; the monitor face is ~150 cd/m². Ratio = 8,000 / 150 ≈ 53:1, far beyond the comfortable 1:10 to 1:20 task-to-surround guidance. This is what drives the eye's constant re-adaptation and the reach for the blind.
Reduce the brightest source: a 3% openness screen or selective glazing drops the sky patch toward ~1,200 cd/m² (ratio ~8:1), while light interior finishes raise surround luminance and lift adaptation. An HDR-based DGP check confirms the move from intolerable toward imperceptible without darkening the task.
A west-facing studio: sDA300/50% = 80%, ASE1000/250h = 28%, afternoon DGP = 0.46. Excellent on paper, hated in use.
sDA 80% (above 'preferred') says there is ample light. But ASE 28% (ceiling 10%) says much of it is raw direct beam, and DGP 0.46 (> 0.45) is intolerable. Occupants drop the blinds and leave them down, so in-use sDA collapses far below 80%.
Specify spectrally selective glazing (high VLT, low solar gain) plus a DGP-driven external venetian. The control deploys only as far as needed to hold DGP ≤ 0.40, angling slats to cut the sky source while keeping a horizontal view band (EN 17037 landscape layer) open.
ASE falls below the 10% ceiling, peak DGP drops from 0.46 to ~0.33 (imperceptible), and because the automation retracts the moment glare passes, in-use sDA recovers close to the simulated 80% — the two-sided optimisation that defines competent daylighting.
Target audience: South African registered architects (SACAP), interior design professionals (IID), professional engineers (ECSA) and lighting/facade specifiers designing daylit commercial, institutional, healthcare and educational interiors.
Assessment: 10 application-based MCQs (minimum pass mark 70%). The full question bank with worked explanations is provided in the companion Guide.