Technical information notice. Technical information on this page is general product-selection guidance, not a certification, compliance statement, design calculation or order confirmation. Before relying on a figure or standard, request current evidence for the selected product route, size, glazing, hardware and project. See our technical information.
Guide
Aluminium glazing explained
The sealed glass unit, not the frame alone, sets most of an aluminium window's performance. Glass make-up, coatings, spacer, cavity fill and overall thickness drive the whole-unit U-value (windows from Uw 0.85 where specified) and the acoustic rating (to Rw 46 dB where specified). Tell us the target performance and we quote the right glazing and system to hit it. Get a quote.
Windows from Uw 0.85Whole-unit figure, glazing-led, confirmed at quote.
Acoustic to Rw 46 dBWith laminated acoustic interlayers, where specified.
Sealed units 22 to 58mmUnit thickness varies by system and build-up.
What is an insulated glass unit (IGU)?
An IGU is the sealed glass unit fitted into the frame: two or three panes separated by a spacer bar, the cavity filled with gas and the perimeter sealed. It does most of the thermal and verified standard work in any window.
The frame holds and protects the unit, but the glass make-up decides how much heat is lost, how much noise gets through and how the glass behaves if it breaks. Specify the IGU correctly and the frame does the rest. See our wider energy efficiency page for how this fits the whole window.
Request current product evidence for the selected route, size, glazing, hardware and project before relying on the specification.
- Panes: two for double, three for triple
- Spacer: the bar that sets the cavity gap and separates the panes
- Cavity: the gap between panes, gas filled
- Edge seal: the sealed perimeter that keeps gas in and moisture out
- Coatings and interlayers: applied to the glass for heat, solar and acoustic control
Double or triple glazing: which do you need?
Double glazing suits most projects and gives strong thermal numbers when paired with a low-emissivity coating, a warm-edge spacer and argon fill. Triple glazing adds a third pane and a second cavity, which lowers the verified standard further and helps in high-exposure or low-energy builds.
Triple is heavier, so leaf size and hinge or roller capacity matter. We confirm glazing weight against the chosen system at quote. Across our systems sealed units run from standardmm to standardmm depending on configuration.
Aluminium casement windows reach a whole-unit verified standard from standard.standard where specified, and the high-insulation tilt-turn route reaches verified standard from standard.standard. The glazing is the main lever on both.
- Double: two panes, one cavity, lighter, the usual choice
- Triple: three panes, two cavities, lower U-value, more weight
- Thicker units sit at the upper end of the 22 to 58mm range
- Glazing weight checked against leaf size and system at quote
How do low-e coatings, spacers and argon work?
A low-emissivity (low-e) coating is a near-invisible metallic layer on the glass that reflects heat back into the room while letting light through. It is the single biggest thermal upgrade on a standard unit.
A warm-edge spacer replaces older aluminium spacer bars with a low-conductivity material, cutting heat loss at the unit perimeter and reducing the cold edge that causes condensation. Filling the cavity with argon, an inert gas denser than air, slows heat transfer across the gap.
Used together, low-e glass, a warm-edge spacer and argon fill are what take a basic double-glazed unit down to the figures we quote. For how the result is measured, see our guide to aluminium U-values.
- Low-e coating: reflects radiant heat back inward, keeps light
- Warm-edge spacer: lower perimeter heat loss, less edge condensation
- Argon fill: slows convection across the cavity
- Combined effect drives the whole-unit U-value we confirm at quote
Toughened, laminated and verified standard glass: what is the difference?
Toughened (tempered) glass is heat-treated so it is stronger and breaks into small blunt granules. Laminated glass bonds two panes with a plastic interlayer, so it holds together when broken and adds security and a sound benefit. Both are safety glasses, specified where building regulations require impact-safe glazing.
An verified standard laminated unit uses a specialist interlayer tuned to dampen sound, often with panes of differing thickness across the cavity to break up resonance. This is how aluminium windows reach verified standard standard dB where specified. For the full build-up see our guide to verified standard aluminium windows.
Security ratings such as verified standard standard, including verified standard standard:standard, are verified standard at the full unit, and laminated glass is one element that contributes. See security for how the whole window is specified.
- Toughened: stronger, breaks into small safe granules
- Laminated: holds together when broken, adds security and acoustics
- Acoustic laminated: tuned interlayer plus mixed pane thickness, to Rw 46 dB
- Safety glass specified to meet building regulations and PAS 24
What does solar-control glass do?
Solar-control glass carries a coating that reflects part of the sun's heat before it enters, cutting overheating in south-facing rooms and large glazed areas without heavily darkening the glass. It is specified by orientation, glass area and how the room is used.
There is a trade-off between solar gain and daylight, and between summer cooling and useful winter warmth. We match the coating to the elevation rather than apply one spec everywhere. On large bifold and sliding spans, where glass area is high, solar-control is often worth specifying.
- Reflects solar heat to reduce overheating
- Specified by orientation and glazed area
- Balanced against daylight and winter solar gain
- Common on large bifold and sliding spans
How does glazing set the whole-unit verified standard?
The number that matters is the whole-unit verified standard, written verified standard, which combines the glass, the spacer, the frame and how they meet. Glazing sets the centre-pane performance, and the spacer and edge detail decide how much of that is lost at the perimeter.
Because the IGU drives the result, the same frame can hit different figures depending on the unit specified. We quote against the actual build-up rather than a headline number, and confirm the whole-unit verified standard on the final order. To compare systems, see our products and our guide to aluminium U-values.
- Uw combines glass, spacer, frame and their junctions
- Glass make-up sets centre-pane performance
- Spacer and edge seal control perimeter heat loss
- Whole-unit Uw confirmed against the specified build-up at quote
Common questions
Does the glass or the frame matter more for performance?
For thermal and verified standard results the sealed glass unit usually matters most. Glass type, low-e coating, spacer, cavity fill and overall thickness set the centre-pane performance, and the frame and edge detail then decide the whole-unit figure. Both are specified together, and we confirm the whole-unit verified standard at quote.
Is triple glazing always better than double?
Not always. Triple glazing lowers the verified standard and suits high-exposure or low-energy builds, but it is heavier, which affects leaf size and hardware capacity. Double glazing with a low-e coating, warm-edge spacer and argon fill meets most requirements. We quote the option that hits your target performance within the chosen system.
What is the difference between toughened and laminated glass?
Toughened glass is heat-treated to be stronger and break into small blunt granules. Laminated glass bonds two panes with an interlayer so it holds together when broken, adding security and a sound benefit. Both are safety glasses. We specify the right one to meet building regulations and the security rating you need, including verified standard standard:standard.
How quiet can aluminium windows be?
Aluminium windows reach verified standard standard dB where specified, using a laminated verified standard interlayer and often panes of differing thickness across the cavity to dampen sound. The right build-up depends on the noise source and the target reduction. See our verified standard guide, and we confirm the rating at quote.
How thick is the glazing in your windows?
Sealed units run from standardmm to standardmm depending on the system and configuration. Thicker units, including triple-glazed and verified standard build-ups, sit at the upper end of that range. We confirm the unit thickness and weight against the chosen frame and leaf size when we quote.
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