External Venetian Blinds

Why outside the glass changes the maths

An indoor blind manages heat that has already got into the room. An external venetian intercepts most of it before it ever crosses the glass — the difference is dramatic on a hard west or north elevation. In a valley that holds its heat later into the evening than a coastal site, that head start matters more than it would somewhere with a daily sea breeze doing some of the work for free.

What's actually involved

• Wide aluminium slats (60–90mm class) running in guided side rails or cables, tilting and raising like a standard venetian, mounted outside the window
• Effectively always motorised, with a wind sensor for automatic retract — an exposed external system has to protect itself, and this valley's mountain-funnelled gusts make that non-negotiable rather than a nice-to-have
• Powder-coated finishes engineered for weather and farm-dust exposure
• Needs facade fixing points and ideally some design-stage planning; retrofit is possible on most suitable elevations, but the earlier we're involved on a new build the cleaner the result

Honest limitations

This is a premium spend and a visible change to the facade — not a product to add quietly after the fact if the look of the house matters to you. It's not a DIY or budget item, and it needs a proper wind-rated motor and sensor to earn its keep here. We'll say plainly at the measure if a window is better served by an indoor sunscreen roller instead.

Where they earn their keep across the valley

New wine-estate builds around Groot Drakenstein and the open, less-sheltered farmhouses of Simonsvlei are the two places we fit these most — both run wide glass toward the vines with little natural shading from trees or neighbouring buildings, which is exactly the situation external venetians are built for.

The rand figure, valley-wide

External shading costs more than anything else we fit, and a figure serves you better than an adjective. As a rate for a square metre fitted and working: R3,000 to R4,500 in a manual configuration, R4,500 to R6,500 motorised with a wind sensor. Out on a valley elevation it is nearly always the second rate, because a blind that cannot take itself in ahead of a gust becomes a repair bill.

Guide rails, a headbox and a facade assessment are required whatever the size of the glass, so small openings carry a minimum. Use the rates to see whether the idea belongs in the budget at all; the elevation is assessed and each opening priced on paper after the free measure.