The benefits of double glazing come down to one simple idea: two panes of glass with a sealed layer of air between them let far less heat, cold and noise through than a single pane. This guide explains the seven benefits that matter in South African homes and businesses, how our 24.76 mm double-glazed unit is built, what it costs on popular window and door sizes, and when it is worth paying for.
See the prices by size for double glazed windows and double glazed sliding doors.
Double glazing is one of several upgrades covered in our guide to premium aluminium windows and doors, alongside heavier frames, slimline sliders and folding doors.
In this guide
The benefits of double glazing, one by one
Every Coetz™ window and door comes with 6.38 mm clear laminated safety glass as standard. Double glazing replaces that single pane with a sealed unit, and these are the benefits of double glazing you notice once it is in.
1. A warmer house in winter
Highveld nights are cold and a single pane loses heat fast. The sealed air gap in a double-glazed unit slows that heat flow, and can roughly halve the heat lost through the glass compared with a single pane, so rooms hold their warmth for longer.
2. Cooler rooms in summer
The same gap slows heat coming in through north- and west-facing glass. Pair it with shading, an overhang or good window placement and rooms stay more comfortable on hot afternoons.
3. Less condensation
Condensation forms when warm, moist air meets cold glass. With double glazing the inner pane stays closer to room temperature, so far less water runs down the glass on winter mornings. Ventilation still matters – see aluminium window condensation.
4. Quieter rooms
Two panes and an air gap block more traffic and neighbourhood noise than one, and in our unit both panes are laminated, which damps sound further. It is not soundproofing, but on a busy road the difference is clear. Read more on laminated glass and noise.
5. Safety glass on both sides
Many double-glazed units use ordinary float glass. Ours uses 6.38 mm clear laminated safety glass for both panes, so the glass holds together if it breaks, inside and out. See safety glass vs float glass.
6. Less fading of floors and furniture
The interlayer in laminated glass blocks most of the sun’s ultraviolet light, the main cause of faded curtains, floors and furniture, and with two laminated panes that protection is doubled.
7. Help with the energy rules
New buildings and extensions have to meet the energy-efficiency part of the building regulations, SANS 10400-XA, published by the SABS. Double glazing can help a design meet the glazing requirements; your architect or a competent person confirms what a specific project needs. See our Glazing Compliance Centre.
How our 24.76 mm double-glazed unit is built
The unit is 24.76 mm thick: a 6.38 mm clear laminated pane, a 12 mm sealed cavity and a second 6.38 mm clear laminated pane, sealed at the edges, and that build is behind most of the benefits of double glazing above. For the benefits of double glazing on windows, it is available on top hung, side hung and fixed windows with the 30.5 mm Standard frame, and top hung windows also come in our Casement 34 frame, double glazed as standard. On doors it is available on hinged, pivot, stable, folding and sliding doors – not on Patio sliding doors, louvre or clad designs, or automatic doors.
What double glazing costs
To get the benefits of double glazing, it costs R1 952.50 per m² extra, worked out on the catalogue size (width × height), excluding VAT, the same in every colour; 30.5 mm windows add a small charge for the deeper glazing bead. Some examples:
- Top hung window 1 200 × 1 200 mm, 30.5 mm Standard frame: +R2 970.30
- Pivot door 1 200 × 2 100 mm: +R4 920.30
- Hinged door 900 × 2 100 mm: +R3 690.23
- Premier sliding door 3 000 × 2 100 mm: +R12 300.75
A top hung window 1 200 × 1 200 mm in the Casement 34 frame costs R6 750 excluding VAT, double glazing included, so the benefits of double glazing come built in. Choose double glazing in the Glass option on any aluminium window (30.5 mm Standard frame) or aluminium door page or in the online estimator, or pick the Casement 34 frame on a top hung window.
When is double glazing worth it?
The benefits of double glazing are biggest in bedrooms and living areas you heat or cool, on cold south-facing walls, on hot west-facing walls, and on houses next to busy roads. For a garage, a store room or a small bathroom window, 6.38 mm laminated glass is usually enough. Whatever you choose, ask your installer for a glazing certificate on new work.
Benefits of double glazing: frequently asked questions
Is double glazing worth it in South Africa?
In most homes, yes, for rooms you heat or cool and for walls that get strong sun or cold. It costs R1 952.50 per m² extra, so it pays most where comfort and energy use matter.
Does double glazing reduce noise?
Yes. Two laminated panes with a 12 mm air gap block more noise than a single pane, though no window is fully soundproof.
Does double glazing stop condensation?
It greatly reduces condensation on the inside because the inner pane stays warmer, but ventilation still matters.
Can I get double-glazed windows?
Yes. Top hung, side hung and fixed windows with the 30.5 mm Standard frame can be double glazed online, and top hung windows also come in our Casement 34 frame, double glazed as standard, so you get the same benefits of double glazing on windows.
Is double-glazed glass safety glass?
Ours is. Both panes are 6.38 mm clear laminated safety glass, so the unit holds together if it breaks.
Coetz™, Unit 2, 84 Ridge Road, Laser Park, Johannesburg. Call 010 412 0062, WhatsApp 076 613 4418 or use our contact page.
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