A rigorous, climate-data-driven method for analysing building facades and engineering external solar shading that controls heat gain, glare and overheating across South African orientations.
Most overheating disputes on South African buildings trace back to a facade that was never analysed orientation by orientation. This masterclass replaces guesswork with a repeatable, climate-data-driven method: read the sun-path, derive the shadow angles, characterise the glazing, quantify the gain, and engineer a device that intercepts the beam before it reaches the glass. Every chapter ends in a deliverable, and the deliverables assemble into a build-ready facade analysis report and shading specification.
Worked examples are drawn from real South African orientations and conditions — Highveld altitude irradiance, low-altitude west sun, mixed-mode comfort — and every quantitative method is reconciled against the SANS 10400-XA and SANS 204 compliance framework that governs approval. The southern-hemisphere geometry is treated as primary throughout: the north facade is the high-sun, easily-shaded face, and the west facade is the hardest problem in the building.
Before any blind, louvre or fin is specified, the facade must be understood as a dynamic thermal filter that mediates between the South African sky and the occupied space behind it. This opening lecture establishes the mental model the entire masterclass depends on: every square metre of glass is a two-way valve admitting daylight and solar heat while leaking conditioned air, and the specifier's job is to tune that valve orientation by orientation. We define the four control variables you will manipulate throughout the course — orientation, solar geometry, glazing performance and shading device geometry — and show how they interact rather than act in isolation. Using a Sandton commercial tower as the worked anchor, we trace how a single uncontrolled west facade drove a 31% chiller oversizing penalty, and how a structured analysis would have caught it at concept stage. You leave this lecture able to state, in engineering terms, exactly what problem a shading strategy is solving on each face of a building.
A facade behaves as a coupled radiative-convective-conductive system, and treating it as a single 'wall with windows' is the root cause of most overheating disputes on South African projects. Begin by decomposing the facade into its heat-flow paths. Solar (short-wave) radiation strikes the glazing and is split into three fractions: a reflected fraction, an absorbed fraction (which re-radiates inward as long-wave heat), and a directly transmitted fraction. The Solar Heat Gain Coefficient (SHGC, also called the g-value) is the single number that captures the total admitted fraction — directly transmitted plus the inward-flowing portion of what the glass absorbs.
35 before any external shading is added. The second path is conductive, governed by the U-value (W/m2K), which controls fabric heat flow driven by the indoor-outdoor temperature difference. The third is air infiltration. Crucially, on a sunny Johannesburg day at 1753m altitude, direct beam irradiance on a normal surface can exceed 950 W/m2 because the thinner atmosphere attenuates less radiation — higher than many European design assumptions, which is why imported facade rules of thumb routinely under-shade SA buildings.
Now layer orientation onto this. The sun's position is described by two angles: solar altitude (vertical angle above the horizon) and solar azimuth (horizontal angle from true north). In the southern hemisphere the sun tracks across the northern sky, so the NORTH facade is the high-sun, easily-shaded face, while EAST and WEST faces receive low-altitude morning and afternoon beams that are geometrically hard to block and deliver the highest instantaneous gains. The south face receives only diffuse and, in summer, brief early/late direct sun.
This inversion of the northern-hemisphere intuition is the most common error junior specifiers import. The analysis method that follows in this course is therefore strictly per-orientation: you will compute the relevant sun angles for each face, characterise the glazing's SHGC and U-value, and only then engineer a shading device whose geometry intercepts the beam before it reaches the glass. 15 will outperform an internal blind of nominally identical fabric because the internal blind has already let the radiation through the glass, where 85% of the absorbed energy is trapped indoors. We close the deep-dive by formalising the workflow as a five-stage pipeline — Climate & Site, Orientation Audit, Solar Geometry, Glazing & Load, Device Engineering — that maps onto the remaining lectures, and by establishing the SANS 10400-XA and SANS 204 compliance envelope within which every decision must sit.
Shading design is only as good as the climate data feeding it. This lecture equips you to source, read and apply the right meteorological inputs for South African sites, moving past generic 'sunny country' assumptions to the genuinely different design conditions of the six SANS climatic zones. We work through dry-bulb temperature design days, global horizontal and direct normal irradiance, and the altitude effect that makes Highveld irradiance materially higher than coastal readings at the same latitude. You will learn where to obtain TMY (Typical Meteorological Year) files, how SAURAN and PVGIS data differ, and how to convert horizontal irradiance to the vertical and tilted values that actually strike a facade. A Cape Town versus Polokwane comparison shows how identical glazing demands different shading depths purely because of latitude and clearness index. By the end you can assemble a defensible climate basis-of-design page for any SA project.
Robust facade analysis starts with the correct radiation dataset, and South Africa's spread of latitude (roughly 22 degrees S at Musina to 34 degrees S at Cape Agulhas) plus its altitude range makes a single national assumption indefensible. SANS 10400-XA divides the country into six climatic zones (Cold Interior, Temperate Interior, Hot Interior, Temperate Coastal, Sub-tropical Coastal, Arid Interior), each with characteristic heating and cooling demands; your shading depth, fabric openness and glazing target must be set against the zone, not a national average. The core radiation quantities are Global Horizontal Irradiance (GHI), Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DHI), related by GHI = DNI x cos(zenith) + DHI. For shading work the value you ultimately need is irradiance on a vertical plane of a given azimuth, obtained by transposing GHI/DNI/DHI onto the facade using the solar incidence angle and a diffuse/ground-reflected model (isotropic or Perez).
65 with very high DNI, meaning crisp, hard shadows and severe beam gain that external shading handles efficiently; humid coastal sites such as Durban have lower kt with proportionally more diffuse radiation, so even a perfectly geometric shading device cannot block the diffuse component and you must lean more on glazing SHGC and fabric openness factor. Altitude compounds this: at 1753m, Johannesburg's air mass is lower, so clear-sky DNI peaks near 950-1000 W/m2 versus roughly 850-900 W/m2 at sea level for the same solar position — a 10-15% beam uplift that directly scales peak solar gain Q = A x SHGC x I(beam+diffuse). Data sources matter for accuracy and for defending your numbers in a green-building submission: SAURAN provides ground-measured minute data from a national station network and is the gold standard for SA-specific work; PVGIS and Meteonorm provide modelled TMY files convenient for energy simulation; NASA POWER is coarse but globally available. 4% summer dry-bulb for cooling) you used.
Temperature data drives the conductive and overheating side: you need the summer design dry-bulb and the diurnal swing, because a high swing (typical of arid interior zones) opens the door to night-purge ventilation strategies that change how aggressively you must shade. The practical deliverable of this lecture is a one-page climate basis-of-design listing zone, latitude, altitude, summer/winter design dry-bulb, peak DNI and the per-facade peak vertical irradiance — the numbers that every subsequent calculation in the course consumes.
This is the geometric heart of the course. You will learn to read and construct a sun-path diagram for any South African latitude and to extract, for any date and hour, the two angles that govern shading: solar altitude and solar azimuth. We derive the angles from declination and hour angle, then show how to plot the analemma and the solstice/equinox arcs on a stereographic chart centred on your site. Working at Pretoria's latitude, we locate the worst-case summer afternoon sun on the west facade and read its altitude and azimuth directly off the chart. You will also learn to overlay obstruction masks — neighbouring buildings, deep reveals — so that the chart tells you when a facade is already self-shaded. By the end you can produce the sun-path basis that every shadow-angle and device-depth calculation in the following lectures depends upon.
The sun's apparent position at any instant is fully defined by solar altitude (elevation above the horizon) and solar azimuth (compass bearing of the sun, measured here from true north). 45 degrees at the June solstice in the southern-hemisphere convention), and the hour angle (H = 15 degrees x (solar time - 12), so H is negative in the morning and positive after solar noon). Altitude is found from sin(altitude) = sin(phi)sin(delta) + cos(phi)cos(delta)cos(H), and azimuth from the companion relation cos(azimuth) = (sin(delta) - sin(altitude)sin(phi)) / (cos(altitude)cos(phi)), with quadrant corrected by the sign of H. Two southern-hemisphere subtleties trip people up.
First, declination sign convention: in summer (December) the sun is south of the celestial equator relative to the northern hemisphere but the geometry yields high midday altitudes for SA sites and a sun that rises south of east and sets south of west. 5 degrees — almost directly overhead — which is precisely why a modest horizontal overhang completely shades a north window in summer yet a near-vertical fin is needed for east/west. The stereographic sun-path chart projects this hemisphere of sky onto a circle: concentric rings are altitude (horizon at the rim, zenith at the centre), radial lines are azimuth, and the curved arcs are the sun's daily track for representative dates (solstices and equinox). Hour lines crossing those arcs let you read altitude and azimuth for any date/time pair at a glance.
The power of the chart is twofold. For device design, you locate the design sun position — typically the moment of peak vertical irradiance on the facade in question, which for a west facade is mid-to-late summer afternoon at a low altitude of perhaps 15-30 degrees and an azimuth swung well past due west — and read the angles straight off. For obstruction analysis, you overlay an obstruction mask: survey the angular height and bearing of every surrounding object (adjacent tower, mountain, deep balcony above) and shade the corresponding region of the chart; wherever the sun's track passes behind the mask the facade is already shaded and needs no device for that period. This prevents the common waste of specifying shading for hours when an adjacent building already blocks the sun.
We also distinguish solar time from clock time: South Africa uses SAST (UTC+2) referenced to 30 degrees E, so a site at, say, 28 degrees E runs roughly 8 minutes behind the standard meridian, and the equation of time adds a seasonal correction of up to +/-16 minutes. For shading geometry these corrections rarely change the device but they matter when you present hour-by-hour shadow studies to a client. The deliverable is an annotated site sun-path chart with the design sun positions for each facade marked — the single reference sheet feeding Lectures 4 through 8.
Sun angles describe where the sun is; shadow angles describe what a device must do. This lecture introduces the two angles that translate solar geometry directly into device geometry: the Horizontal Shadow Angle (HSA) and the Vertical Shadow Angle (VSA). You will learn to compute VSA for horizontal overhangs and HSA for vertical fins from the solar altitude and the wall-solar azimuth, and to use the shadow-angle protractor overlaid on a sun-path chart to design a device that shades a window across a chosen period. We size a north-facade overhang for a Bloemfontein office so it fully shades at the summer solstice noon yet admits winter sun, demonstrating the seasonal selectivity that good shading exploits. By the end you can convert any required shading period into the precise overhang depth or fin spacing that delivers it.
The shadow-angle method is the bridge between astronomy and construction detail, and mastering it is what separates a specifier who guesses overhang depths from one who engineers them. Two angles do all the work. The Vertical Shadow Angle (VSA), sometimes called the profile angle, is the angle of the sun's projection onto a vertical plane perpendicular to the window — it governs horizontal devices (overhangs, light shelves, horizontal louvre blades). It relates to solar altitude (alt) and the wall-solar azimuth (gamma, the horizontal angle between the sun's azimuth and the facade's outward normal) by tan(VSA) = tan(alt) / cos(gamma).
The Horizontal Shadow Angle (HSA) is simply the wall-solar azimuth itself, HSA = solar azimuth - wall azimuth, and it governs vertical devices (fins, vertical louvres). When the sun is directly in front of the facade gamma is zero and VSA equals the solar altitude; as the sun swings to the side, gamma grows, cos(gamma) shrinks, and VSA rises above the altitude — meaning a horizontal device 'sees' a steeper effective sun and shades more easily, while simultaneously the growing HSA is what a fin must catch. This is the geometric reason horizontal overhangs suit the high-sun north facade and vertical fins suit the low-sun, wide-azimuth east and west facades. To design a horizontal overhang you fix the target: for example, full shading of the glass at the December-solstice design hour.
You read the VSA at that moment, then the required projection depth P for a window of height h below the overhang is P = h / tan(VSA). 22m of winter sun penetrate, delivering exactly the seasonal selectivity passive design seeks. e. d = s / tan(HSA).
The shadow-angle protractor — a transparent overlay matching the sun-path chart's scale — lets you do all of this graphically: you mark the arc of sun positions for the period you want shaded, and the protractor reads off the single VSA and HSA pair that just covers that arc, which you then convert to depth. Two engineering cautions. First, full geometric cut-off blocks beam radiation only; diffuse sky radiation still reaches the glass, so even a perfect overhang leaves a residual diffuse SHGC that you account for in the load calc (Lecture 7). 7h), which is precisely why you switch to fins, egg-crate grids, or operable fabric systems for those faces.
The deliverable is a shadow-angle worksheet per facade: design hour, VSA, HSA, resulting device depth and the residual diffuse fraction carried forward.
With sun-path and shadow-angle tools in hand, this lecture systematises the per-orientation strategy that defines competent SA facade design. We walk each cardinal face — and the awkward intermediates — and prescribe the device family that suits its solar geometry: horizontal overhangs and louvres for the north, light management rather than heat rejection for the south, and the genuinely difficult east/west problem that demands vertical, operable or high-performance-glazing solutions. We critique a real Durban mixed-use scheme where a glazed west elevation was 'shaded' with shallow horizontal fins that did nothing, and redesign it. You will leave with an orientation decision matrix that pairs each facade with a primary and fallback shading family, the foundation of a coherent whole-building strategy.
Orientation is the highest-leverage decision in facade analysis because it sets the solar geometry every device must answer, and in the southern hemisphere the rules invert from the European textbooks most SA professionals trained on. Take each face in turn. The NORTH facade receives the sun at high altitude through the middle of the day across all seasons, with the sun close to the facade normal (small wall-solar azimuth) around solar noon. High altitude means high VSA, so horizontal devices are extremely efficient: a shallow overhang or a few horizontal louvre blades fully shade summer sun while the much lower winter sun slips underneath, giving free seasonal selectivity.
North is the orientation you actively want your principal glazing to face in SA. The SOUTH facade is the inverse: for most of the year it receives only diffuse skylight, with brief, low, sharply-angled direct sun in early morning and late afternoon around the summer solstice. The design problem here is not heat rejection but glare control and even daylight; heavy shading wastes a high-quality, low-glare daylight source. The right move is light-diffusing or operable internal/mid-pane treatments and, for the short summer flanking sun, a small vertical return fin at the window edges.
The EAST and WEST facades are the hard problem and the source of most overheating litigation. The morning (east) and afternoon (west) sun is at low altitude and a very wide azimuth from the facade normal, so VSA is small and a horizontal overhang would need a projection several times the window height to achieve cut-off — geometrically and structurally absurd. The west is worst because peak solar coincides with the afternoon peak in ambient air temperature and with the building's accumulated daily heat, driving the highest instantaneous cooling loads of any facade. 25) combined with internal high-reflectance screens.
The Durban case study illustrates the classic failure: a fully glazed west elevation was 'treated' with 150mm horizontal fins. 57) = 32 degrees, so each 150mm fin shaded just 150 x tan(32) = 94mm of glass below it — token shading that left over 80% of the glass in full beam and produced afternoon indoor temperatures above 32 degrees C. 27 glazing, cutting peak west gain by roughly 70%. The deliverable is an orientation decision matrix: for each facade list the design sun position, the geometric verdict (horizontal/vertical/egg-crate/glazing-led), a primary device family and a fallback, and the residual SHGC target.
This matrix governs the whole-building shading strategy and prevents the single most expensive facade error in SA practice — applying a north-facade solution to a west facade.
Shading devices and glazing are two halves of one system, and this lecture gives you fluency in the glazing half. We define the three numbers on every glazing datasheet that matter for facade analysis — Solar Heat Gain Coefficient (SHGC/g-value), U-value, and Visible Light Transmittance (VLT) — and the Light-to-Solar-Gain ratio (LSG) that captures the spectral selectivity you want. You will learn how low-emissivity and solar-control coatings, tints and double/triple glazing shift these numbers, and how the combined shading coefficient of glass-plus-device is computed. A worked comparison of three IGU specifications for a Cape Town curtain wall shows how the right coating can do part of the shading job and reduce device depth. By the end you can read a glazing schedule critically and specify glass that complements, not duplicates, your shading.
Glazing is the other half of the solar valve, and a specifier who cannot interrogate a glazing datasheet will either over-build shading or leave gains uncontrolled. Three performance numbers dominate. The Solar Heat Gain Coefficient (SHGC, identical in meaning to the European g-value) is the fraction of incident solar energy admitted: directly transmitted plus the inward-flowing share of absorbed energy, on a 0-1 scale. The U-value (W/m2K) is the conductive/convective heat-transfer rate per unit area per degree of indoor-outdoor temperature difference; it dominates winter heat loss and night-time gain/loss but is secondary to SHGC for summer solar control.
Visible Light Transmittance (VLT) is the fraction of visible light admitted, governing daylight and view. 25) signals a spectrally selective product that admits daylight while rejecting near-infrared heat — exactly what you want, because roughly half the sun's energy is invisible near-infrared that contributes heat but no useful light. 07 — poor selectivity. 4 — admitting two-thirds of daylight while rejecting three-quarters of solar heat.
Coatings and build-up drive these shifts: low-emissivity (low-e) coatings suppress long-wave radiative transfer to cut U-value; solar-control coatings (often pyrolytic or sputtered silver layers) reflect near-infrared to cut SHGC; body tints absorb energy but re-radiate part of it inward and can run hot, so they are inferior to reflective coatings for the same SHGC; a second pane and an argon-filled cavity cut U-value further. The system metric you ultimately design to is the combined shading coefficient or, more rigorously, the combined SHGC of glass plus device. 30; for a perforated screen F is near its openness factor). For internal devices the interaction is weaker and less favourable because the device sits inside the glass, so the manufacturer-tested combined value must be used rather than a simple multiplication.
2) controls heat AND preserves daylight, allowing the external fins to be shallower (because the glass already rejects much of the diffuse and off-angle gain) and reducing both cooling and lighting energy. The lesson: glazing and shading are co-designed. Spend SHGC budget on the glass where view and daylight are priorities (south, view-critical north), and on the device where you need operability and architectural depth. Always cross-check that VLT does not fall so low that daylight harvesting fails the SANS 204 intent, and verify the U-value supports the SANS 10400-XA fabric requirement for your climatic zone.
The deliverable is a glazing-and-device pairing table per facade carrying combined SHGC, VLT and U-value into the load calculation.
Analysis must end in numbers a mechanical engineer can use. This lecture shows you how to convert your orientation, sun-path, shadow-angle and glazing work into a quantified solar gain and its contribution to peak cooling load. We build the solar gain equation step by step — area, combined SHGC, beam and diffuse irradiance, and shading fraction — and aggregate across facades to a building peak. Working a Gauteng open-plan floor, we compute the west-facade peak gain with and without external shading and show the kW of chiller capacity the shading saves. You will also learn to express results as W/m2 of facade and as a fraction of total cooling load so designers and clients can see shading's value. By the end you can produce a defensible solar-load summary that drives both HVAC sizing and the business case for shading.
The purpose of all the preceding geometry and glazing analysis is to land on defensible heat-gain numbers, because shading that cannot be quantified cannot be justified to a cost-cutting client or sized into an HVAC system. The instantaneous solar heat gain through a glazed element is Q_solar = A x SHGC_combined x I_total, where A is the glazed area (m2), SHGC_combined is the glass-plus-device coefficient from Lecture 6, and I_total (W/m2) is the irradiance on the facade plane at the design instant, split into beam and diffuse: I_total = I_beam x (1 - f_shade) + I_diffuse x (1 - f_diffuse_block). The critical refinement is that a shading device blocks beam and diffuse differently. During its design shaded period an external overhang or fin removes essentially all the beam (f_shade approaching 1) but only the portion of the diffuse sky it physically subtends — often only 20-40% — so the diffuse term dominates the residual gain and must never be dropped.
The full conductive companion term is Q_cond = A x U x (T_out - T_in), added for the fabric, and for a peak-cooling design instant you sum solar plus conduction plus internal gains (people, lighting, equipment) plus infiltration to reach the space load. 70, design west afternoon irradiance I_beam 620 W/m2 and I_diffuse 180 W/m2 on the vertical plane (Highveld, high DNI, low altitude so beam strikes the vertical face strongly). 2 kW from one facade at one instant — a number that alone explains the chiller oversizing in the Lecture 1 anchor. 28 and add external vertical fins giving full beam cut-off at the design hour (f_shade = 1) while blocking 30% of diffuse.
2 kW. 2 kW — a 94% reduction at the design instant, equivalent to roughly 18-19 kW of chiller capacity once diversity and the rest of the building are accounted for, at typical SA installed-cooling costs a six-figure-rand capital saving plus the recurring energy benefit. 2 kW / 120 m2 = 560 W/m2 unshaded versus 35 W/m2 shaded) for facade-to-facade comparison and benchmarking; and as a percentage of the floor's total cooling load to make the business case visible to the client. Two rigour points.
First, the design instant for each facade differs — east peaks mid-morning, west mid-to-late afternoon, north near noon — so the building peak is NOT the sum of individual facade peaks but the worst coincident combination, which an hourly profile or simulation resolves; hand calculation uses the dominant facade plus diversified contributions from the others. Second, for code and green-building submissions these hand calculations seed and sanity-check a dynamic simulation (Lecture 11) rather than replace it. The deliverable is a per-facade and whole-building solar-load summary: area, combined SHGC, design irradiance, shaded and unshaded Q, W/m2, and the kW and rand saving attributable to the shading strategy.
Cooling load is the engineer's metric; overheating, comfort and glare are the occupant's — and they are what generate complaints and disputes. This lecture connects facade performance to human criteria: adaptive thermal comfort, overheating risk metrics, mean radiant temperature near glazing, and glare indices. You will learn why a person seated beside a sunlit window feels hot even when the air is cool (radiant asymmetry), and how to set and test against overheating thresholds. We diagnose a Pretoria boardroom where occupants near the west glazing abandoned the room each afternoon despite the air-conditioning running, and show how the shading fix resolved both the thermal and glare complaint. We also distinguish static fixed-threshold overheating limits from the adaptive comfort band that rises with outdoor temperature, which matters for South Africa's warm, mixed-mode buildings. By the end you can specify shading against occupant-comfort criteria expressed as operative temperature, degree-hours of overheating and a glare target, not just kW of cooling load.
Facades fail in the minds of occupants long before they fail an energy model, so a rigorous analysis must close the loop on human comfort and glare. Thermal comfort is not air temperature alone; it is governed by six factors — air temperature, mean radiant temperature (MRT), air velocity, humidity, metabolic rate and clothing. Near glazing the decisive and most-neglected factor is MRT. A person seated 1m from a sunlit single-glazed window experiences direct beam radiation on their skin plus a hot inner glass surface radiating long-wave heat at them; the operative temperature, roughly the average of air and MRT, can sit 4-8 degrees C above the air temperature the thermostat reads.
This is radiant asymmetry: one side of the body faces a hot surface while the air is nominally cool, producing the universal complaint 'the aircon is on but I'm roasting by the window'. External shading attacks this directly by keeping the inner glass surface cool — it never lets the beam reach the glass — whereas an internal blind absorbs the transmitted beam and itself becomes a hot radiating surface close to the occupant, improving glare but only marginally improving radiant comfort. Overheating risk is assessed with criteria rather than a single number. The static approach sets a fixed operative-temperature threshold (commonly 25-28 degrees C for offices) and limits the hours exceeded.
The adaptive approach (from the comfort research underpinning standards such as ASHRAE 55 and EN 16798, applicable to naturally ventilated and mixed-mode SA buildings) sets a comfort band that rises with the running mean outdoor temperature, recognising that people in warmer climates accept and prefer warmer indoors; SA's climate and widespread mixed-mode operation make the adaptive model especially relevant. Useful overheating metrics include the percentage of occupied hours above the threshold and degree-hours of exceedance (sum of (T_op - T_limit) over occupied hours), the latter capturing severity, not just frequency. Glare is the second occupant criterion and is independent of heat: it is driven by luminance contrast, quantified by Daylight Glare Probability (DGP) or the simpler Daylight Glare Index. Direct sun in the field of view, or a very bright window against a dim interior, produces disabling glare that drives occupants to close blinds permanently — which then defeats daylighting and forces lights on, wrecking the SANS 204 energy case.
The shading device must therefore manage luminance, not just heat: operable systems, perforated screens with controlled openness, and light-redirecting elements (light shelves bouncing daylight to the ceiling while blocking low direct sun) resolve glare while preserving daylight. The Pretoria boardroom case ties it together: occupants near a fully-glazed west wall abandoned the afternoon despite a running chiller. Measurement showed air at 23 degrees C but inner glass surface at 41 degrees C and beam sun on the table, giving an operative temperature near 30 degrees C and severe glare on screens. The internal blinds in place reduced glare slightly but, sitting inside the glass, radiated heat and were always drawn, killing daylight.
28 glazing from earlier — dropped inner glass surface temperature to 26 degrees C, operative temperature to 24 degrees C, eliminated beam glare while preserving a view and useful daylight, and the room returned to full afternoon use. g. DGP below the 'perceptible' threshold), and prefer external devices precisely because they control MRT and glare simultaneously. The deliverable is an occupant-criteria checklist per occupied facade zone: target operative temperature, allowable overheating hours/degree-hours, glare target, and the device feature that delivers each.
Every SA facade decision sits inside a regulatory and rating framework, and a specifier who cannot map shading to clauses cannot get a project approved or credited. This lecture decodes the compliance landscape: SANS 10400-XA as the mandatory energy-usage regulation, SANS 204 as the energy-efficiency design standard it references, and the voluntary rating tools — Green Star SA and EDGE — that reward good shading. You will learn which clauses fenestration and shading must satisfy, how the prescriptive, rational-design and reference-building routes work, and how documented shading lowers the effective SHGC credited in the SANS 204 fenestration calculation so an otherwise non-compliant facade passes. We map a completed Cape Town office's shading package to specific compliance outcomes and to Green Star SA energy credits and the EDGE 20% energy-reduction threshold. By the end you can position any shading strategy correctly within SA's mandatory and voluntary frameworks and keep the calculation trail auditable for a building-control official or rating assessor.
Compliance is where facade analysis meets the law and the rating economy, and the structure is layered. SANS 10400-XA ('Energy usage in buildings') is the mandatory part of the National Building Regulations governing energy use; it is the document a building must satisfy to be approved and occupied. It offers compliance routes: the prescriptive/deemed-to-satisfy route with fixed maximum fenestration areas, minimum glazing performance and orientation rules; the rational-design route where a competent person demonstrates compliance by calculation; and the reference-building (performance) route where the designed building's energy use must not exceed that of a notional reference building meeting the deemed-to-satisfy provisions. SANS 10400-XA references SANS 204 ('Energy efficiency in buildings') for the technical detail, including the fenestration provisions: SANS 204 limits the conductance and solar heat gain admitted through the fenestration of each facade as a function of climatic zone and the percentage of floor area that is glazed, expressed through a fenestration energy calculation that combines glazing area, SHGC and orientation.
This is exactly where shading earns its keep: an external shading device reduces the effective SHGC used in the fenestration calculation (using the standard's shading multipliers or a calculated combined SHGC), so a facade that would fail on glazing alone passes once compliant shading is credited. The specifier must therefore document the device geometry and its shading effect to claim that reduction — geometry that the shadow-angle work in Lecture 4 produced. SANS 204 also drives the daylight and artificial-lighting provisions, which is why over-darkening glazing or shading (Lecture 6/8) can win a heat battle but lose the energy war by forcing lights on. On the voluntary side, Green Star SA (GBCSA) awards credits under energy and indoor-environment-quality categories where effective shading reduces modelled energy and improves thermal comfort and glare control; the points are earned through the same dynamic energy model and comfort analysis the course has built toward.
EDGE (the IFC's certification) sets percentage-reduction targets (commonly 20% each for energy, water and embodied materials) against a base case, and external shading plus solar-control glazing is one of the most cost-effective energy measures for hitting the EDGE energy threshold in SA's high-irradiance climate — its software explicitly models window-to-wall ratio, glazing SHGC/U and shading. 30) brought the calculated fenestration energy within limit via the rational route, simultaneously contributing to a Green Star energy credit and clearing the EDGE 20% energy reduction. The professional point: shading is not decoration to be value-engineered out; in SA's framework it is frequently the line item that makes the fenestration legal and the rating achievable. Two practice cautions.
First, keep the shading documentation auditable — sun-path basis, shadow angles, device geometry, combined SHGC — because the building-control official or the GBCSA/EDGE assessor can require the calculation. Second, verify which edition of SANS 10400-XA and SANS 204 applies to the project's approval date, as the fenestration provisions and zone definitions are revised. The deliverable is a compliance map: for each facade, the route taken, the SANS 204 fenestration figures with and without shading, and the specific Green Star/EDGE credits the shading supports.
Geometry tells you what shape a device must be; engineering tells you how to build it, operate it and keep it working. This lecture surveys the device families and their selection logic: fixed overhangs, fins, louvres and egg-crates; operable external venetians, roller screens and folding shutters; and motorised, sensor-driven systems integrated with the building management system. We weigh fixed versus dynamic on cost, maintenance, performance and architecture, and address fabric openness factor, wind loading, and the cleaning and durability realities of SA conditions. A Johannesburg facade that switched from fixed fins to motorised external venetians illustrates the performance-versus-capital trade-off. By the end you can select and broadly specify the right device type, not just its geometry.
A geometrically perfect device that cannot survive SA wind, dust and sun, or that the client cannot afford or maintain, is a failed specification — so device engineering weighs performance against buildability, cost, maintenance and control. Start with the fixed family. Fixed horizontal overhangs and louvres suit the north (high-sun, single design geometry); fixed vertical fins and egg-crate (combined horizontal+vertical) grids suit east/west where both altitude and azimuth vary widely. Fixed devices are cheapest over life (no motors, minimal maintenance) and architecturally clean, but they are a single-geometry compromise: sized for the worst case they over-shade at other times, cutting useful winter sun and daylight, and they cannot respond to sky condition or glare.
The operable family — external venetian blinds, roller/zip screens, folding/sliding shutters, projecting awnings — trades capital and maintenance for the ability to track the sun, retract under overcast skies to recover daylight, and stow in high wind. External venetians are the performance benchmark for east/west because tilting blades give near-total beam control at any sun position while admitting diffuse light when retracted; their weakness is wind vulnerability and cost. The motorised/automated tier adds actuators, sensors (rooftop irradiance, facade-mounted sun sensors, internal glare/lux sensors) and control logic, typically integrated with the BMS so blinds track the sun, retract above a wind-speed setpoint, and respond to occupancy and glare — delivering the best simultaneous energy, comfort and daylight performance at the highest capital and the introduction of a maintenance/IT dependency. Several engineering parameters decide success regardless of family.
Fabric openness factor (the percentage of open weave in a screen fabric, typically 1-10%) sets the trade-off between view/daylight and heat/glare rejection: a 3% openness gives strong glare control with a residual view, while 10% preserves view but admits more solar and diffuse; openness factor feeds directly into the device transmission F in the Lecture 7 load calc. Wind loading governs structure and operability: external devices are exposed to the full facade wind pressure (which rises with building height and the SA regional wind speed per SANS 10160-3), so fixed fins need engineered fixings and operable systems need an anemometer-driven auto-retract setpoint to avoid storm damage — a non-negotiable on Highveld and coastal high-rise. Durability and maintenance in SA conditions are decisive: intense UV degrades polymers and fabrics (specify UV-stabilised, colour-fast materials and check warranties), Highveld dust and coastal salt foul mechanisms and soil fabrics (design for cleaning access and corrosion resistance — marine-grade finishes on the coast), and any motorised system needs accessible, serviceable actuators because a stuck external blind on a tower is an expensive cherry-picker call-out. The Johannesburg case quantifies the trade-off: a tower west facade originally specified with fixed vertical fins achieved compliant peak-gain control but over-shaded mornings and shoulder seasons, measurably increasing artificial-lighting energy and drawing tenant complaints about the 'caged' view.
5x but recovered daylight (cutting lighting energy), improved the glare and view experience, and, tracking the sun, slightly improved peak-gain control; the payback came through lighting energy plus tenant retention rather than cooling alone. The selection logic to carry away: default to fixed for north and budget-constrained projects; specify operable or motorised for east/west, view-critical, or high-grade commercial facades where daylight recovery and glare control justify the capital; always pin down openness factor, wind/auto-retract strategy, and a maintenance/cleaning access plan as part of the spec. The deliverable is a device specification sheet per facade: family, geometry (from Lectures 4-5), openness factor, operation/control, wind strategy, materials/finish for SA exposure, and a maintenance access note.
Hand calculations size the problem and sanity-check the answer; dynamic simulation proves it across the whole year and underpins compliance and rating submissions. This lecture demystifies thermal and daylight simulation: what an hourly energy model does, the inputs it consumes from your facade analysis, and how to read and trust its outputs. You will learn the role of weather files, the difference between thermal and daylight (radiance-based) simulation, and how to set up parametric runs that test shading depths and fabric openness. We compare a hand-calculated west peak against a simulated annual profile for a Durban tower and reconcile the two, treating the comparison as a deliberate error-catching discipline rather than a formality. You will also see why daylight metrics must be read alongside cooling energy so a device that controls heat does not quietly kill the daylight the SANS 204 lighting case depends on. By the end you can brief, commission and critically interpret a facade simulation rather than treat it as a black box.
Dynamic simulation is where the static analysis of the previous lectures becomes an annual, hour-by-hour verification, and the specifier's job is not to run the model but to brief it, feed it correct inputs, and interrogate its outputs critically. A whole-building or zonal thermal simulation (EnergyPlus and its front-ends such as DesignBuilder, IES-VE, or TAS) solves heat balances for every zone at every hour of a Typical Meteorological Year, capturing the dynamics hand calculation cannot: thermal mass storing and releasing heat (a heavy concrete floor lags and flattens the cooling peak), the time-shift between peak solar and peak load, the non-coincidence of facade peaks (east mid-morning, west mid-afternoon) that means the building peak is less than the sum of facade peaks, and the interaction of shading with ventilation and internal gains over the year. The inputs the model consumes are precisely the deliverables this course has produced: the weather file (Lecture 2), the geometry and orientation (Lecture 5), per-element glazing SHGC/U/VLT (Lecture 6), the shading device geometry or a scheduled shading transmission (Lectures 4 and 10), and internal gain and occupancy schedules. Garbage in, garbage out applies with force: an SA model run on a default European or wrong-zone weather file will mis-predict because of the altitude/irradiance effects from Lecture 2, and a shading device entered as a flat SHGC multiplier rather than its true geometry will mis-time the shaded hours.
Daylight simulation is a separate physics: radiance-based tools (Radiance, ClimateStudio, DIVA, Honeybee) compute illuminance and luminance across the year to produce climate-based daylight metrics — spatial Daylight Autonomy (sDA, the fraction of area meeting a lux target for a set fraction of occupied hours) and Annual Sunlight Exposure (ASE, the fraction of area receiving excessive direct sun, a glare/overheating proxy) — plus point-in-time Daylight Glare Probability for the worst sun positions. These daylight outputs are what let you prove that a shading device controls heat and glare WITHOUT killing the daylight that the SANS 204 lighting-energy case depends on; a device that drives ASE to zero but also collapses sDA is a failure the thermal model alone would not reveal. Parametric studies are the real power: rather than guess a fin depth, you sweep depth, spacing, openness factor and glazing SHGC across runs and read the trade-off surface — annual cooling energy, peak load, lighting energy, sDA, ASE and overheating hours all at once — selecting the option that satisfies all criteria at least cost. The reconciliation discipline is essential for trust: take the Durban tower west facade, hand-calculate the design-instant peak gain as in Lecture 7, then locate the same hour in the simulated annual profile and confirm the model's instantaneous gain agrees within a sensible tolerance (differences are expected and explicable — the model includes thermal mass lag, exact transposed irradiance, and ground reflectance the hand calc simplified).
If hand calc and model diverge wildly, one of them is wrong, and resolving that disagreement is how you catch input errors before they reach a compliance submission. Outputs to demand and read critically: annual and peak cooling/heating energy (kWh/m2/yr and kW), the load duration and peak-day profiles, per-facade gain breakdowns, sDA/ASE/DGP for daylight, and overheating hours/degree-hours against the comfort criteria from Lecture 8. Always check the model's assumptions list — infiltration rate, internal gains, HVAC setpoints, schedule — because these swing results more than the shading often does, and a vendor model with optimistic assumptions can flatter a weak facade. The professional posture: simulation underpins the rational-design and reference-building compliance routes (Lecture 9) and the Green Star/EDGE energy credits, so the specifier must be able to defend its inputs and reconcile them to first-principles hand calculations.
The deliverable is a simulation brief and a results-interpretation note: weather file and zone, modelled glazing and shading inputs, the parametric matrix tested, the chosen option with its annual energy, peak load, daylight and overheating results, and the hand-calc reconciliation.
Analysis only creates value when it is communicated in a form the design team can build from. This closing methodology lecture assembles everything into the two deliverables that carry your work into construction: the facade analysis report and the shading specification. You will learn the report structure that a SACAP architect, an ECSA mechanical engineer and a building-control official can each use, and how to write a shading specification that survives value engineering by tying every device to a quantified outcome and a compliance clause. We dissect a complete C18-format facade report for an SA commercial project, showing how the per-facade analysis, the compliance map and a value-engineering-proof specification fit into one package. You will learn to write a spec for three readers at once — architect, mechanical engineer and building-control official — with every device traceable back to a climate input, a sun angle, a shadow angle and a glazing datasheet. By the end you can package facade analysis into defensible, build-ready documentation — the capstone skill of the course.
The masterclass ends where real projects live: in documentation that a multidisciplinary team and a building-control official act on. Two deliverables carry the analysis forward. The facade analysis report is the reasoned narrative; the shading specification is the buildable instruction. The report should follow a structure that each reader can navigate to their own clause.
Open with an executive summary stating the headline outcomes — peak gain reduction, compliance route and result, energy/comfort/glare verdict — because decision-makers read only that. Then the climate basis of design (Lecture 2): zone, latitude, altitude, design dry-bulb, peak DNI, per-facade vertical irradiance, dataset cited. Then the solar geometry basis (Lecture 3): the site sun-path chart with design sun positions and any obstruction mask. Then, per facade, the analysis chain: orientation verdict (Lecture 5), shadow-angle worksheet and device geometry (Lecture 4), glazing-and-device pairing with combined SHGC (Lecture 6), quantified shaded/unshaded gain (Lecture 7), occupant-criteria outcomes (Lecture 8), and the compliance contribution (Lecture 9), with the dynamic-simulation verification (Lecture 11) consolidated as an appendix.
This per-facade spine is exactly the worked sequence the course taught, which is why a specifier who has done the analysis can assemble the report almost mechanically. The shading specification is the document most exposed to value engineering, and writing it to survive that pressure is a discrete skill. The failure mode is a spec that describes a device ('150mm aluminium fins at 600 centres') without tying it to a consequence; a quantity surveyor under cost pressure deletes it because nothing in the document says what breaks if it goes. 30 is the value credited in the SANS 204 fenestration calculation; without it the west facade fails the fenestration energy limit and the building cannot be approved'), and (c) a comfort/occupant consequence ('without it, operative temperature at the west glazing reaches ~30 degrees C with disabling glare, per the comfort analysis').
When deletion visibly threatens approval, comfort and a six-figure HVAC cost, value engineering redirects rather than deletes. The specification must also carry the buildable detail from Lecture 10: device family and geometry, fabric openness factor, materials and finish suited to SA UV/dust/salt exposure, wind/auto-retract strategy referencing the wind load basis, control and BMS integration for operable systems, and maintenance and cleaning access. Reference the relevant standards explicitly — SANS 10400-XA and SANS 204 for energy, SANS 10160-3 for wind actions, and any product standards — so the building-control official and the contractor can verify compliance. Write for three readers at once: the SACAP architect needs the geometry and the architectural intent; the ECSA mechanical engineer needs the W/m2 and kW to size plant and the assurance that the load schedule assumes the shading is present; the building-control official needs the compliance route, the clause references and the auditable calculation trail.
The capstone professional habit is traceability: every number in the spec should be traceable back through the report to a climate input, a sun angle, a shadow angle and a glazing datasheet, so that when challenged — by a cost engineer, an assessor, or in a dispute — you can defend the entire chain. We dissect a complete commercial-project report built to this structure, showing how the per-facade analysis, the compliance map and the survive-VE specification fit together into a single defensible package. The deliverable, and the deliverable of the whole masterclass, is exactly this: a facade analysis report plus shading specification that is rigorous, climate-correct for South Africa, compliant, and build-ready.
Three end-to-end calculations showing the method applied to real South African orientations. Each runs the full chain: climate input, sun angle, shadow angle, glazing, gain, and device geometry.
A 1.8m-tall north window. Goal: full shade at summer-solstice noon, admit winter sun.
Latitude ~29°S. Summer-solstice noon altitude ≈ 90 − 29 + 23.45 = 84.5°. The sun sits close to the facade normal at noon (wall-solar azimuth ≈ 0°), so VSA ≈ altitude ≈ 80° at the design instant accounting for a small azimuth offset.
P = h / tan(VSA) = 1.8 / tan(80°) = 1.8 / 5.67 = 0.32 m. A modest 320 mm overhang fully shades the glass at peak summer.
Winter-solstice noon altitude ≈ 90 − 29 − 23.45 = 37.5°, VSA ≈ 35°. Winter sun penetration = P × tan(35°) = 0.32 × 0.70 = 0.22 m below the head — free passive solar gain in winter, exactly the seasonal selectivity sought.
120 m² of west glazing. Compare unshaded clear DGU against an engineered glazing-plus-fin package.
Highveld west afternoon, low altitude, high DNI: vertical-plane irradiance ≈ 800 W/m² (620 beam + 180 diffuse).
Clear DGU, SHGC 0.70: Q = A × SHGC × I = 120 × 0.70 × 800 = 67.2 kW at the design instant from one facade.
Switch to spectrally selective DGU (SHGC 0.28) and add external vertical fins giving full beam cut-off (f_shade = 1) while blocking 30% of diffuse. Beam term collapses to 0; diffuse residual = 0.28 × 180 × (1−0.30) = 35.3 W/m². Q = 120 × 35.3 = 4.2 kW.
Peak west gain falls from 67.2 kW to 4.2 kW — a 94% reduction, roughly 18–19 kW of avoided chiller capacity after diversity. Expressed per facade area: 560 W/m² unshaded vs 35 W/m² shaded.
A glazed west elevation 'shaded' with token 150 mm horizontal fins. Diagnose and redesign.
Design afternoon sun: altitude ~20°, wall-solar azimuth ~55°. VSA = tan⁻¹(tan20° / cos55°) = tan⁻¹(0.36 / 0.57) = 32°. Each 150 mm horizontal fin shaded only 150 × tan(32°) = 94 mm of glass — over 80% of the glass stayed in full beam, driving indoor temperatures above 32°C.
HSA at the design hour ≈ 53°. For full cut-off at 600 mm spacing: d = s / tan(HSA) = 600 / tan(53°) = 600 / 1.327 = 452 mm projection.
Combine 450 mm external vertical fins with SHGC 0.27 glazing. Peak west gain cut by ~70% versus the failed scheme, and inner-surface and operative temperatures returned to the comfort band.
Target audience: South African registered architects (SACAP), professional engineers (ECSA), interior design professionals (IID) and facade/shading specifiers undertaking commercial and institutional building work.
Assessment: 10 application-based MCQs (minimum pass mark 70%). Full question bank with worked explanations is provided in the companion Guide.