What the highveld sun actually does to a house in a suburb this old, this small and this shaded — elevation by elevation, with the trade-offs written down rather than glossed over.
Forest Town was first surveyed in 1908, on land then called Sachsenwald — the timber estate that supplied the mines, and the reason these streets sit under old trees.[1][2] The whole suburb is 0.64 km², squeezed between Jan Smuts Avenue and Oxford Road with the Johannesburg Zoo forming one entire boundary, and at roughly 1,700 people per square kilometre it is denser than Saxonwold or Houghton next door.[1]
The houses are old enough to still have their original openings. Deep reveals, timber frames, proportions an off-the-shelf blind will not flatter. Not a survey of every street — just what a suburb laid out in 1908 tends to look like, and what we find when we measure.
The canopy is already doing half the shading, unevenly. Deciduous trees shade a north window in January and let the sun through in July, so two rooms on one elevation can need different answers depending on what grows outside them.
The stands are small. The neighbour's window is genuinely close on most streets, so privacy and light control are one decision rather than two. The exception is the Zoo boundary, where one side has no neighbouring house and the brief narrows to heat and glare.
Forest Town sits at about 26 degrees south, 1,753 m above sea level.[3] At Pretoria's latitude, fifty kilometres north, the sun stands 87.7° above the horizon at noon on 21 December and only 40.84° at noon on 20 June.[4] Forest Town's own figures land within half a degree of those, and that 47-degree swing splits the year in two.
In summer the noon sun is almost straight overhead, so a north window with any eave above it largely shades itself at midday. In winter it has the sun at 40° and due north, driving light and warmth deep into the room — which, with June nights around 4 °C, you want.[5]
The problem is the afternoon. On 21 December the sun sets on a bearing of 243°, about 27 degrees south of due west.[4] From three o'clock it is low, coming from the west and south-west, arriving nearly horizontally. An overhang cannot block a horizontal ray, and the Pretoria simulations say it plainly: western afternoons run far hotter than mornings.[4] So the west side of a house here needs something at the glass or outside it, not above it.
Same house, four different problems. Work out which wall a room sits on first.
North is where the sun lives all winter: high enough mid-summer that an eave does most of the work, then at 40° and pouring in by June.[4]
Living rooms and studies here do best with a venetian — bounce high summer light off the ceiling, open flat in winter. A blockout roller is a blunt instrument on this wall: up or down, and you lose the winter warmth you were entitled to.
Low, near-horizontal afternoon sun from about three o'clock, arriving from 27° south of west at midsummer.[4]
If a west room is unbearable at four, it is because the glass itself is heating and radiating inwards. Interior blinds fix the glare at once and the heat only partly — once the sun is through the pane the energy is inside, and a closed blind absorbs it.
The same geometry mirrored, but into a house that cooled overnight. Bedrooms get woken early in December; kitchens take an hour of hard glare and then it is over — so, usually, a blockout in the bedroom and something you can see through in the kitchen.
Almost no direct sun for most of the year, so these rooms hold the steadiest light in the house — and are the coldest in winter.[5]
Shading is rarely the problem here. Heat loss through old single glazing usually is, and so is privacy from a close neighbour.
Tell us which rooms are the problem and we'll send you this same handbook with your elevations noted against it — which windows we'd treat first, and what we'd be weighing up on each one.
It is an email, not a visit. Nobody phones you about it.
Each is right somewhere and wrong somewhere else.
The canopy gives dappled, moving light, so the useful control is angle, not coverage: a venetian throws high summer sun onto the ceiling and opens flat in June. Timber also sits against an old timber reveal in a way aluminium does not.
Heavier and dearer than aluminium, and a very wide window has to be split across one headrail. Above a bath or sink, choose aluminium: timber and steam age badly together.
One flat sheet of open-weave fabric on a tube. It cuts the glare and a useful share of the solar gain while leaving the garden visible — no more curtains closed at four o'clock.
It reverses after dark: lights on, and you are the one on display. On a close stand we would pair it with a blockout on the same window rather than pretend one fabric does both.
A flat sheet, no folds, sitting inside an old reveal without fighting the frame's proportions. Against a December sunrise on an east bedroom window, the most effective thing there is.
Binary — down is dark, up is everything — so the wrong tool for a north living room. Without side channels, light always finds the edge of the reveal.
Sheer bands and solid bands sliding past each other, so you hold privacy from a neighbour three metres away and keep usable daylight — often the honest answer on the smaller stands here.
More mechanism than a plain roller, so more to go wrong across ten years, and never fully blockout. Not for a bedroom you want properly dark.
The cells hold a layer of still air against the glass — the cheapest thermal improvement you can make to an old single-glazed window without touching the window. No permit, no builder, no change to the facade.
A soft product, so not for a busy kitchen — and not a heat-rejection answer on a hot west window. The gain sits on the winter side of the ledger.
Aluminium slats in side guides, outside the glass, tilting the sun away before it reaches the pane. On a hard west elevation we would specify these over an interior blockout roller: stopping the heat outside the glass keeps a room cooler than absorbing it inside, where the pane still warms and radiates. You keep a view through the slats.
It changes the facade from the street, which in a suburb this old is a conversation to have first — see below. And it is exterior, in a hail belt,[6][7] so a motorised version should retract on a wind signal.
Rigid aluminium slats rolling down from a headbox outside the building, covering the whole opening — heat and glare handled outside the glass, with a real drop in road noise.
Shading, not security. These are made for sun, heat and glare control. They are not security-rated shutters — a different product, which we can quote on request.
The most visible exterior change here, and the headbox has to live somewhere — on an old facade a design decision, not a measurement.
Turns a baking paved patio back into a usable room, then folds away for the winter sun. Where the garden is the extra room, often better value than anything you could do to a window.
Storms roll through most summer afternoons[5] and Gauteng sits in the higher hail zone,[6][7] so we would specify a wind sensor and a cassette that closes over the fabric.
Also on the list below: aluminium venetians where timber would not last, zip screens to hold a stoep against wind, motorisation for windows an old house puts out of reach, and skylight and shaped blinds for gable glass.
Forest Town was surveyed in 1908,[1] so a great many houses here are over sixty years old — which matters more than owners realise. Section 34(1) of the National Heritage Resources Act 25 of 1999 says no person may alter or demolish any structure, or part of one, older than 60 years without a permit from the relevant provincial heritage resources authority.[8] The Act defines "alter" broadly: any action affecting the structure, appearance or physical properties of a place.[8] Age alone triggers it — the house need not be declared or listed.[9] In Gauteng the authority is PHRA-G.[10]
We fit blinds; we are not heritage consultants. On the measure we will say plainly which options touch the outside of the building, so you can take that question to the right person.
Renovating? SANS 10400-XA:2021 requires a fenestration calculation once glazing exceeds 20% of floor area — it was 15% in the previous edition — and no longer treats west, north and east glass differently for solar heat gain.[11] Ask your architect early how your shading is being counted.
Everything above is what we know about Forest Town. What we can't know is your house — and five things decide the specification.
Depth decides whether a blind fits inside the opening at all, and old openings are rarely square. A 12 mm difference top to bottom is normal, and it changes how the blind is made.
Plaster over brick, plaster over stone, or a later stud addition. The existing fixings decide what can hang there — and for exterior products, whether the job is possible.
We take a compass reading at the window: twenty degrees changes the recommendation between west and south-west. Then we look out of it, because the tree doing half your shading differs at every window — and half of it falls off in winter.
For anything motorised, the route from a power point to the head of the window is the real constraint — a walk-around with a torch in an older house, not a guess over the phone.
Awnings and zip screens live or die on this. A sheltered courtyard and an open west corner need different products and sensors — obvious in two minutes on site.
A consultant comes to the house with fabric and slat samples, measures every window properly, and leaves you with a written quote per window. It costs nothing and commits you to nothing. If you'd rather have a rough number first, the ballpark tool underneath the form does that instead.
Anything you ticked while reading is already carried into the form — you don't have to type it again.
Not ready for a visit or a number? Tell us which rooms are the problem and we'll email you this handbook with your own elevations noted against it. Nothing is booked, nobody phones.
Every climate, geography and legal claim above traces to one of these. Where we've reasoned rather than cited, we've said so in the text.
Two honest caveats. The solar figures in source 4 are calculated for Pretoria at 25.7° south; Forest Town sits at roughly 26.2° south, so its own angles differ by well under a degree — we've quoted the published Pretoria numbers rather than invent our own. And we could not retrieve the full text of source 6, only its published abstract, so we've used it to support the hail and storm-timing points rather than to carry them alone.
Free in-home measure, a written quote per window, and one of our expert consultants on the phone before anything is fitted.