If you have ever pressed your palm against a single-pane window on a sunny Singapore afternoon, you already understand the problem. The glass is almost too hot to touch, your air-conditioner runs non-stop, and every passing bus or MRT train finds its way straight into your living room. For the vast majority of homes built before the mid-2010s, a single sheet of glass — 6 mm at most — stands between you and the full force of the equatorial sun. An insulated glass unit, or IGU, changes that equation entirely, and understanding how it works is the first step to making a genuinely informed decision about your doors, windows or skylights.
What Exactly Is an Insulated Glass Unit?
An insulated glass unit is a pre-manufactured assembly of two or more panes of glass separated by a hermetically sealed gap. The gap — typically filled with argon or another inert gas — acts as a thermal and acoustic barrier between the exterior environment and your interior space. Unlike a single pane, which conducts heat directly from one face to the other, an IGU interrupts that conduction path at multiple points.
The term "double glazing" is often used interchangeably with IGU in everyday speech, and in most residential applications the two terms describe the same thing: a two-pane assembly. Triple glazing — three panes with two sealed cavities — exists but is comparatively rare in Singapore, where acoustic performance and solar heat gain are the primary concerns rather than sub-zero winter cold.
Key concept: An IGU is not simply two panes of glass placed next to each other. The sealed cavity, the spacer bar chemistry, and the choice of gas fill all work together as an engineered system. Replacing just one element — say, the glass — without considering the others leaves significant performance on the table.
The Anatomy of an IGU — Layer by Layer
A standard double-glazed IGU consists of four principal components. Each plays a distinct role, and the overall performance of the unit is only as good as its weakest element.
Cross-section of a 5mm + 20A + 5mm IGU — the standard EZZO.SG configuration. The LOW-E coating sits on Surface ② (inner face of the outer pane), protected inside the sealed cavity.
Outer Pane
The outer pane is the first line of defence against the exterior environment. In Singapore — where afternoon sun angles are steep and UV intensity is high year-round — this pane is almost always tempered safety glass. Tempering involves heating the glass to approximately 620 °C and then rapidly cooling it, creating a pre-stressed surface layer. Should tempered glass break, it shatters into small, blunt fragments rather than dangerous shards — meeting the safety requirements for high-rise glazing under Singapore Building and Construction Authority (BCA) guidelines.
The outer pane is also the ideal location for a LOW-E coating, positioned on its inward-facing surface (Surface ② in glazing notation). Here it is shielded from direct environmental contact while still intercepting incoming solar radiation before it enters the cavity.
Spacer Bar
Running along the perimeter of the unit, the spacer bar performs two jobs simultaneously: it holds the two panes apart at a precise, consistent distance, and it contains the desiccant material that absorbs any residual moisture inside the sealed cavity. Conventional spacer bars are hollow aluminium — effective at holding geometry, but also an excellent thermal conductor. A traditional aluminium spacer creates a thermal bridge at the edge of every unit, allowing warmth to flow between panes precisely where the sealed cavity ends. Modern warm-edge spacers, made from materials such as stainless steel, foam or composite polymer, significantly reduce this edge conduction and are increasingly standard on premium IGUs.
Gas Fill
The cavity is filled with an inert gas — typically argon — rather than air. Argon is denser than air and has a lower thermal conductivity (approximately 0.016 W/m·K versus air's 0.024 W/m·K), which means convective heat transfer across the cavity is meaningfully reduced. The gas is sealed into the unit at the factory under controlled conditions, ensuring consistent fill levels and no contamination.
Inner Pane
The inner pane — facing your interior — is typically the same tempered specification as the outer pane for safety compliance, though the glass type may vary. A clear inner pane allows maximum visible light transmission; a tinted inner pane can further reduce solar gain without heavy reflective coatings on the exterior.
Why the Spacer Bar and Gas Fill Matter
These two components are the ones most commonly glossed over in product brochures, yet they are largely responsible for the real-world performance difference between an average IGU and an excellent one.
Heat moves through a window via three mechanisms: conduction (through the glass and frame), convection (currents within the gas cavity), and radiation (electromagnetic energy re-emitted from warm surfaces). A LOW-E coating addresses radiation. The gas fill addresses convection. The spacer bar addresses edge conduction. An IGU that optimises all three mechanisms will consistently outperform one that neglects any of them.
Why argon over air? Argon gas has roughly 34% lower thermal conductivity than air. In practice, an argon-filled IGU can reduce the U-value (heat flow rate) of the assembly by 10–15% compared to an identical air-filled unit. Over Singapore's year-round cooling season, that difference translates directly into measurable energy savings — and a quieter, more stable interior temperature.
The cavity width also matters. A gap under 10 mm does not provide enough space to suppress convective currents effectively. A gap beyond around 20–24 mm for argon allows large convective cells to form, which actually increases heat transfer rather than reducing it. The sweet spot for argon-filled IGUs sits between 12 mm and 20 mm — which is precisely the range EZZO.SG's standard 20 mm cavity (the "20A" in 5mm+20A+5mm notation) is designed to exploit. The wider 27 mm option pushes slightly beyond this sweet spot in the interest of acoustic mass, a deliberate trade-off that makes sense for high-noise environments.
IGU Glass Specifications: What the Numbers Mean
When you see a glazing specification written as 5mm+20A+5mm or 5mm+27A+5mm, you are reading a shorthand description of the unit's cross-section from exterior to interior. Each segment is explicit:
- 5mm — Thickness of the outer glass pane. In all EZZO.SG products, this is tempered safety glass.
- 20A or 27A — Width of the sealed cavity in millimetres, where "A" denotes argon gas fill.
- 5mm — Thickness of the inner glass pane, also tempered in EZZO.SG configurations.
The overall unit thickness is therefore 30 mm for the standard configuration (5 + 20 + 5), or 37 mm for the wider-cavity option (5 + 27 + 5).
| Property | 5mm + 20A + 5mm | 5mm + 27A + 5mm |
|---|---|---|
| Total unit thickness | 30 mm | 37 mm |
| Cavity width | 20 mm | 27 mm |
| Gas fill | Argon (standard) | Argon (standard) |
| Typical U-value with LOW-E | ~1.5–1.8 W/m²K | ~1.3–1.6 W/m²K |
| Acoustic performance (Rw, est.) | 30–33 dB | 33–36 dB |
| Glass type options | Clear / LOW-E / Tinted / Smart / Coated | Clear / LOW-E / Tinted / Smart / Coated |
| Best suited for | Standard residential, offices, north-facing | High-traffic roads, MRT proximity, west-facing |
LOW-E coating explained. LOW-E (Low Emissivity) glass has a microscopically thin metallic oxide coating — often silver-based — applied to one surface of the unit. This coating reflects long-wave infrared radiation (heat) back toward its source. In Singapore's climate, the coating is positioned on Surface ② (the inner face of the outer pane) to reflect solar heat back outside before it enters the cavity, while still allowing the majority of visible light to pass through. The result: a glass that stays cooler, keeps your space cooler, and reduces air-conditioning load — without making your home look like a mirror from the outside.
How IGUs Perform in Singapore's Climate
Singapore sits just 1.3° north of the equator. The sun reaches near-zenith at noon and the city receives intense solar radiation year-round, with no winter reprieve. Relative humidity rarely drops below 70%, and ambient temperatures consistently sit between 25 °C and 34 °C. This creates a specific set of demands on building glazing that differ substantially from temperate European or North American climates where most IGU research originated.
Thermal performance
In Singapore, the primary concern is keeping solar heat out — not keeping warmth in. The relevant metric shifts from U-value alone to Solar Heat Gain Coefficient (SHGC) and Total Solar Transmittance (g-value). A LOW-E IGU with an appropriate solar control coating can achieve an SHGC of 0.25–0.35, compared to 0.85–0.87 for a standard single pane. In practical terms, this means roughly 60–70% less solar heat entering your home through each window — a difference your air-conditioner will reflect immediately in reduced run time and lower electricity bills.
Singapore's Green Mark scheme, administered by the BCA, uses the Envelope Thermal Transfer Value (ETTV) as a key compliance metric for non-residential buildings. Glazing with high SHGC values directly inflates ETTV scores; LOW-E IGUs are one of the most effective tools for meeting ETTV targets. While private residential projects operate under different frameworks, the same physics applies — homeowners who invest in LOW-E IGUs commonly report monthly electricity savings of 15–25% on air-conditioning, depending on window-to-wall ratio and orientation.
Acoustic performance
Urban noise is an underappreciated quality-of-life issue across Singapore's dense residential landscape. HDB estates along major arterials, condominiums adjacent to expressways, and landed properties near the Circle Line or Thomson-East Coast MRT lines all face significant noise intrusion. A single 6 mm pane offers a weighted sound reduction index (Rw) of roughly 27–29 dB — enough to muffle sound somewhat, but not enough to create a genuinely quiet interior.
An IGU changes this dramatically. The gas gap mechanically decouples the two panes, so sound energy must convert to vibration, cross the gas cavity as a pressure wave, and reconvert to vibration on the inner pane — losing energy at each step. A 5mm+20A+5mm argon-filled unit typically achieves an Rw of 30–33 dB; the wider 5mm+27A+5mm configuration reaches 33–36 dB. Combined with laminated glass options (where a PVB interlayer further damps resonance), acoustic performance can reach 38–42 dB Rw — enough to render most road traffic inaudible at night.
Humidity and condensation
Singapore's humidity creates a secondary problem: surface condensation. When warm, humid indoor air contacts a cold glass surface — typically one chilled by air-conditioning — condensation forms. This is not just aesthetically unpleasant; chronic condensation promotes mould growth on frames and sills, degrades silicone seals, and can cause long-term structural damage to timber reveals. The inner pane of an IGU stays significantly warmer than a single-pane equivalent because it is insulated from the cold exterior and isolated from direct air-conditioning blast by the sealed cavity. In correctly installed IGUs, condensation on interior glass surfaces is largely eliminated.
IGUs in Aluminium Frames: Why the Frame Matters Too
Even a high-specification IGU will underperform if it is installed in a thermally inefficient frame. Glass and frame are a system; one cannot be optimised in isolation from the other.
Standard aluminium profiles conduct heat almost as readily as a solid metal rod — which is precisely what they are. The 6063-series aluminium alloy used in most window extrusions has a thermal conductivity of approximately 160–200 W/m·K. For comparison, argon gas conducts heat at 0.016 W/m·K. When a thermally unbroken aluminium frame surrounds an otherwise well-performing IGU, the frame itself becomes the dominant heat path through the entire assembly.
The solution is a thermal break: a continuous barrier of low-conductivity material inserted into the aluminium profile, physically separating the exterior aluminium from the interior aluminium. EZZO.SG profiles use a PA66 Nylon (Polyamide 66) thermal break, which has a thermal conductivity of approximately 0.25 W/m·K — roughly 640 times lower than the surrounding aluminium. The thermal break also serves as the structural connection between the outer and inner profile halves, so the frame retains its mechanical integrity while substantially reducing the conductive heat path through the assembly.
| Material | Thermal Conductivity | Role in EZZO Frame |
|---|---|---|
| 6063-T5 Aluminium alloy | ~160–200 W/m·K | Structural frame outer + inner shells |
| PA66 Nylon thermal break | ~0.25 W/m·K | Continuous thermal barrier between shells |
| Argon gas (cavity) | ~0.016 W/m·K | Thermal + acoustic insulating medium in IGU |
| Air | ~0.024 W/m·K | Baseline for comparison |
The alloy specification itself also matters. EZZO.SG profiles use 6063-T5 aluminium, which offers good extrudability (allowing finer, more complex profile geometries), reliable surface-finish quality, and strong corrosion resistance — particularly relevant in Singapore's coastal and permanently humid environment, where salt air and constant moisture accelerate galvanic corrosion in lower-grade alloys.
Choosing the Right IGU for Your Project
Not every opening in every home requires the same specification. Understanding your priorities — and the particular constraints of each façade — allows you to allocate budget effectively, rather than over-specifying everywhere or under-specifying where it matters most.
- West-facing windows and skylights receive the most direct afternoon sun in Singapore and benefit most from LOW-E coatings combined with the wider 27 mm cavity. This pairing delivers the greatest reduction in solar heat gain for the worst-case orientations.
- High-rise units above the 20th floor face stronger winds that accelerate convective heat transfer across the external glass surface. Wider cavities and argon fill are particularly valuable at elevation where wind-washing effect is pronounced.
- Units adjacent to major roads or MRT lines should prioritise acoustic performance. A 5mm+27A+5mm configuration with laminated glass on the outer pane can reach Rw values in the high 30s — a meaningful improvement for sleep quality and daytime concentration.
- Skylights present the most demanding thermal case: direct overhead sun, no shading from overhangs, and heat that rises and accumulates beneath the glazing. Argon-filled LOW-E IGUs are non-negotiable for roof glazing in Singapore. Single-pane skylights are effectively solar collectors pointed directly at the interior.
- Smart glass IGUs — electrochromic or PDLC — suit applications where variable transparency is required, such as bathroom partitions, boardroom screens, or privacy windows. The IGU structural principles remain identical; the switching layer is laminated into one of the glass panes.
- North-facing openings with limited direct sun can tolerate clear glass IGUs (without LOW-E coating) if budget is constrained, prioritising visible light transmission and saving the LOW-E premium for the more thermally demanding orientations.
Practical note on frame rebate depth: IGUs are thicker than single panes. A 5mm+20A+5mm unit is 30 mm thick; the wider 5mm+27A+5mm is 37 mm. Your aluminium profiles must have a glazing rebate deep enough to accept the chosen unit. EZZO.SG profiles are designed and extruded to match our specific IGU thicknesses — but if you are considering retrofitting IGUs into existing frames, a site measurement is essential before ordering glass.
EZZO.SG IGU Options
At EZZO.SG, our standard insulated glass offering is built around two core configurations — both using tempered safety glass and argon gas fill as standard — with five glass type options available across both cavity sizes.
Argon-filled · Tempered safety glass
Argon-filled · Solar control coating
Argon-filled · Grey / bronze / green
PDLC or electrochromic switching
Reflective or anti-reflective finish
All EZZO.SG IGUs are installed within PA66 Nylon thermal-break aluminium frames using 6063-T5 alloy profiles, ensuring that the performance of the glass unit is matched — not undermined — by the surrounding frame. Perimeter sealing uses marine-grade neutral-cure silicone rated for Singapore's high-humidity, high-UV environment. All external hardware is stainless steel as standard.
To discuss the right IGU specification for your project, or to receive a detailed quotation, contact the EZZO.SG team at admin@ezzogenics.com or visit us at Bartley Biz Centre, Blk 15 Kaki Bukit Rd 4, #01-44, Singapore 417808. You can also reach our technical director David directly at david@ezzogenics.com.