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  • windows

Are Double Glazed Aluminium
Windows Worth It in Cape Town?

  • CGAW TEAM
  • 6 MIN READ
  • UPDATED JULY 2026

If you’ve priced electricity in the last two years, you’ve probably wondered whether your windows are quietly costing you money. In Cape Town, where summer sun pours through every north-facing pane and winter southeasters find every gap in an old frame, windows do more heavy lifting than most homeowners realise.

So the question we get asked most often at CGAW: is double glazing actually worth it here, or is it overkill for a coastal climate that doesn’t see snow?

What double glazing actually does

A double glazed window uses two panes of glass with a sealed air or gas-filled gap between them, set inside an aluminium frame. That gap acts as an insulating barrier — slowing down how fast heat moves through the glass.

In practical terms: a standard single glazed aluminium window has a U-value of around 5.6. A double glazed equivalent drops to roughly 2.8 — meaning it lets through about half as much unwanted heat transfer. The lower the U-value, the better the insulation.

Why this matters more in Cape Town than people think

Cape Town’s climate is mild compared to, say, Johannesburg or the Eastern Cape highlands, which leads some homeowners to assume double glazing is unnecessary here. In practice, three local factors make it worthwhile:

  • Coastal wind-loading. Properties near the Atlantic seaboard, Tableview, or the West Coast deal with strong, near-constant wind. Double glazed units add rigidity and reduce draughts that single glazing simply can’t match.
  • Big temperature swings between seasons. A Cape Town summer day can swing from a cool morning to a 30°C afternoon. Double glazing buffers your interior against that swing, reducing how hard your aircon has to work.
  • Noise. If you’re anywhere near a busy road, an airport flight path, or close-set suburban housing, the extra pane cuts noise transmission noticeably — often by 30–44 decibels depending on the glass specification.

What it costs

As a rough guide for Cape Town in 2026: a standard 900mm x 900mm double glazed aluminium sliding window typically costs more than its single glazed equivalent, with most homeowners seeing aluminium-framed double glazing priced from roughly R2,500 to R5,000 per square metre installed, depending on glass type, hardware, and frame finish (powder coated vs anodised). It’s a real upfront investment — but one that tends to pay for itself over time through lower heating and cooling costs, plus the added benefit of noise reduction and improved security from the extra pane.

Is it right for every room?

Not necessarily. We typically recommend prioritising double glazing where it earns its keep fastest:

  1. North and west-facing rooms that take the brunt of the afternoon sun.
  2. Bedrooms facing busy roads where noise reduction matters as much as temperature.
  3. Open-plan living areas with large sliding or stacking doors, where glass surface area is highest.

For a south-facing guest bathroom window, the case is weaker — standard single glazing may be perfectly adequate.

Not sure if double glazing makes sense for your home? We’ll walk you through where it’ll actually save money — and where it won’t.

get a free assessment

The CGAW view

We don’t believe in upselling double glazing across an entire home if it doesn’t make sense for the budget or the brief. What we do is walk every client through where it will actually save money and improve comfort, and where standard glazing does the job just as well. As an AAAMSA and SAGGA accredited installer, every recommendation we make is based on what’s appropriate for your specific Cape Town property — not a one-size-fits-all quote.

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