Guides
Double vs Triple Glazing in Aluminium Windows
Add a third pane to a window and four things change at once: the insulation goes up, the glass gets heavier, the frame needs more depth, and the hardware carries more load. Whether that trade is worth it depends on the climate, the noise outside and the frame the glass has to sit in. This guide compares double and triple build-ups on insulation, sound, weight and hardware, then shows how the cavity sets the glazing bead on the Adam Alux 95 series.
What the numbers mean
A double-glazed unit holds two panes separated by one sealed cavity. A triple-glazed unit holds three panes separated by two cavities. The shorthand reads left to right, so 5-20A-5 describes a 5 mm pane, a 20 mm air or gas space and a second 5 mm pane. The cavity is the working part: it breaks the direct path heat would take through solid glass, and its width and fill decide how well it does that.
Insulation: what the second cavity adds
Each additional cavity adds another break in the heat path, so a triple unit insulates better than a double unit of the same overall thickness. The gain is real but not linear, and it narrows once the cavity is already wide or filled with a heavier gas. A triple unit also needs more frame depth to hold the extra layer. In a mild climate the second cavity often earns less than its weight and depth suggest.
Sound: why more glass is not automatically quieter
More glass does not automatically mean less noise. Sound travels through a unit in several ways at once, and the cavity width, the thickness of each pane and the seal around the frame all shape the result. A wide cavity with unequal pane thicknesses usually cuts more noise than a triple unit built from thin, equal panes. A sound claim has to name the actual build-up and the frame seal.
Weight, rollers and hinges
Glass is the heaviest single part of a window, and a triple unit adds the weight of a further pane along the whole sash. That weight lands on the hinge set of a casement or the rollers of a slider. A slider carrying triple glass needs rollers that will not flatten, which is why ball-bearing rollers are the sensible default once units get heavy. The Adam Alux 95 series runs ball-bearing rollers as standard at 95 mm depth and a 1.4 mm wall.
Cavity, bead and frame depth
The cavity in the drawing sets the glazing bead, because the bead closes the gap between the glass edge and the frame face. Change the cavity and the bead changes with it, even when the sight-line looks identical. The unit also has to fit the sash depth, so a deeper build-up can force a deeper profile. Standard glazing on the 95 series is 5-20A-5, with single and triple build-ups on request on the same frame.
Choosing between the two
Set the priority first. Where winter heat loss drives the design, a triple unit earns its place. Where noise is the concern, match the build-up to the sound and keep the panes unequal. Where the climate is hot and the worry is solar gain, the glass coating and shading matter more than the extra cavity, a different decision covered in the guide on glazing for hot climates. Weigh depth, sash weight and hardware load, then let the frame follow the build-up.
FAQ
Frequently asked
Is triple glazing always better than double?
No. Each extra cavity improves insulation, but the gain is not linear and it costs frame depth, sash weight and hardware load. In a mild climate the second cavity often earns less than its weight suggests. Match the build-up to the climate and the frame.
Does triple glazing reduce noise more than double glazing?
Not automatically. Sound depends on cavity width, the thickness of each pane and the seal around the frame, and a wide cavity with unequal panes usually cuts more noise than a thin triple unit. A sound claim has to name the build-up and the frame seal.
Can the 95 series take a triple unit?
Yes, on request. The 95 series carries 5-20A-5 insulating glass as standard, with single and triple build-ups on the same frame. Because the cavity sets the glazing bead, the build-up is chosen before the sash is drawn, and the 95 mm depth and 1.4 mm wall are drawn for the standard unit.
What glass is standard on the Adam Alux 95 series?
5-20A-5 insulating glass: a 5 mm pane, a 20 mm cavity and a second 5 mm pane. The series runs ball-bearing rollers as standard, uses EPDM foam gaskets and an open, self-cleaning drainage path, and is drawn at 95 mm depth with a 1.4 mm wall in 6063-T5 aluminium.
Which build-up suits a hot climate?
In a hot climate solar control and shading usually matter more than adding a third pane, so the glass coating and the shading strategy decide the result. The extra weight and depth of a triple unit often buy less than expected. The guide on glazing for hot climates works through that decision.
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Series, glazing and finish come back as one quotation, with the full dimensional pack on PDF and CAD on request.