LOW-E Glass vs Standard Glass: Singapore Guide | EZZO.SG

Home › Blog › LOW-E Glass vs Standard Glass Glass Technology LOW-E Glass vs Standard Glass: Which Should Singapore Homeowners Choose? By EZZO.SG 15 January 2025 6 min read Glass Technology Singapore's air-conditioning bill tells a straightforward story: the average four-room HDB flat spends between $150 and $250 per month on electricity, and a substantial share of that goes to cooling rooms that are fighting an incessant, year-round influx of solar heat through the windows. Standard glass, whether clear or lightly tinted, is largely transparent to the long-wave infrared radiation that turns sunlight into trapped heat. LOW-E glass changes that equation fundamentally. It reflects radiant heat back before it enters the room, reducing the thermal load on your air-conditioning system without making your home feel cave-dark. This guide explains precisely what LOW-E glass is, how it differs from standard and tinted glass, which performance metrics matter in Singapore's tropical climate, and how to match the right glass type to your home, budget, and lifestyle. What Makes Glass "Low Emissivity"? Emissivity is a measure of how readily a surface emits thermal radiation. Standard clear glass has an emissivity around 0.84 — meaning it readily absorbs and re-radiates heat. LOW-E glass (Low Emissivity glass) is coated with a microscopically thin metallic layer — typically silver, tin oxide, or a combination — that reduces emissivity to as low as 0.02 to 0.15 on premium double-silver coatings. The mechanism is wavelength-selective: visible light (roughly 380–700 nm) passes through the glass with minimal attenuation, while long-wave infrared radiation — the heat emitted by warm interior surfaces and re-radiated by hot glass — is reflected back by the metallic coating. LOW-E coatings therefore work in both directions: in a tropical climate like Singapore they primarily keep solar-driven heat out ; in cold climates the same coating helps retain indoor warmth. Key Principle LOW-E glass does not block sunlight — it blocks heat. A high-quality LOW-E coating can reject 50–70% of solar heat while allowing 60–75% of visible light to pass through undimmed. You gain a cooler interior without sacrificing the openness and brightness that glazed facades are chosen for. The coating is applied in one of two ways. Hard-coat (pyrolytic) LOW-E is baked into the glass surface during manufacture, making it more durable and easier to handle — but its performance is lower than soft-coat. Soft-coat (sputtered) LOW-E is deposited in a vacuum chamber using magnetron sputtering; it achieves significantly better thermal performance but must be protected inside an insulated glazing unit (IGU) to prevent oxidation. EZZO's IGU configurations — 5mm + 20A + 5mm and 5mm + 27A + 5mm — use soft-coat LOW-E in exactly this protected position, sealed between two panes with an argon or dry-air spacer. LOW-E vs Standard Glass — Key Performance Metrics Three numbers tell most of the story when comparing glass types: the U-value, the Solar Heat Gain Coefficient (SHGC), and the Visible Light Transmittance (VLT). Understanding what each measures — and what you want in Singapore — removes the guesswork from specification. U-Value (Thermal Transmittance) The U-value measures how much heat flows through a material in watts per square metre per degree Kelvin difference (W/m²·K). Lower is better. A single pane of 6mm clear glass has a U-value around 5.8 W/m²·K. Double glazing with an air gap drops that to roughly 2.8 W/m²·K. Add a LOW-E coating and argon fill to that double-glazed unit, and U-values fall to 1.1–1.8 W/m²·K depending on the coating type. While Singapore's indoor-outdoor temperature differential is modest (typically 8–12°C), a lower U-value still reduces conductive heat gain and allows your air-conditioned rooms to maintain setpoint temperature with less compressor work. Solar Heat Gain Coefficient (SHGC) SHGC measures the fraction of incident solar radiation that enters a building as heat — a value from 0 to 1. Lower SHGC means less solar heat entering the room. Standard clear glass has an SHGC around 0.82. Bronze or grey tinted glass lowers this to 0.55–0.65 by absorbing solar energy in the glass itself (though absorbed heat is then re-radiated inward). A single-silver LOW-E coating achieves SHGC of 0.27–0.40; a double-silver formulation can push this below 0.20. In Singapore's near-equatorial location — with solar irradiance commonly exceeding 900 W/m² at midday — even a modest SHGC improvement translates directly into reduced cooling load. Visible Light Transmittance (VLT) VLT is the percentage of visible light that passes through the glass. A VLT of 70% means 70 out of every 100 photons of visible light reach the interior — maintaining natural daylight, views, and the sense of space that open-plan Singapore homes depend on. Standard clear glass sits at around 87–90% VLT. Tinted glass sacrifices VLT (down to 40–65%) to reduce solar gain, but it does so by absorbing energy into the glass body, not by selectively rejecting the infrared spectrum. A high-selectivity double-silver LOW-E coating achieves VLT above 60–72% while keeping SHGC below 0.25 — a dramatically better selectivity ratio than tinting can achieve. Glass Type U-Value (W/m²·K) SHGC VLT (%) Selectivity* Singapore Suitability Standard Clear (single pane) 5.6–5.9 0.82–0.86 87–90% 1.05 Limited Bronze / Grey Tinted (single pane) 5.4–5.8 0.55–0.65 40–65% 0.95–1.00 Moderate Standard Clear IGU (double glazed) 2.6–2.9 0.70–0.76 78–82% 1.08 Good LOW-E Single Silver IGU 1.6–1.9 0.27–0.40 60–72% 1.65–1.90 Excellent LOW-E Double Silver IGU 1.1–1.5 0.17–0.26 62–73% 2.50–3.00 Premium *Selectivity = VLT ÷ SHGC. A higher ratio means more daylight admitted per unit of solar heat gained. Values are representative ranges; exact performance depends on glass thickness, spacer width, and fill gas. The Singapore Context: Why Solar Control Matters Here Singapore sits at 1.35°N, placing it effectively at the equator. The sun passes nearly overhead every day of the year, meaning east and west facades receive intense morning and afternoon radiation at low angles, and even north and south faces are exposed to significant diffuse sky radiation. Unlike temperate climates — where solar gain in winter is an asset — Singapore has no meaningful cool season. Every joule of solar heat that enters a building must be actively removed by air-conditioning. 900+ W/m² peak solar irradiance in Singapore 30–40% of household electricity used for air-conditioning 1.0 W saved per m² of LOW-E glass per degree cooler setpoint 365 days per year of cooling demand (no winter) BCA's Green Mark scheme recognises this reality. Under the Building and Construction Authority's energy efficiency framework, the Envelope Thermal Transfer Value (ETTV) calculation directly rewards lower SHGC glass. Projects targeting Green Mark certification — and increasingly, private residential developments seeking to comply with the revised 2021 code — are specifying LOW-E double-glazed units as standard, not as upgrades. EZZO's insulated glass configurations with LOW-E coatings align directly with these requirements. There is also a comfort argument separate from energy cost. Radiant asymmetry — the uncomfortable feeling of "cold radiation" from a cool glass pane at night, or the enveloping warmth radiating from a sun-heated single pane — is significantly reduced by LOW-E double glazing. Rooms feel more comfortable at higher thermostat setpoints, enabling passive energy savings simply by allowing residents to set their air-conditioning to 25°C rather than 22°C. Types of LOW-E Glass Available Not all LOW-E glass performs identically. The number of silver layers, the position of the coating within the IGU, and the spacer width all determine real-world performance. Single-Silver LOW-E One microscopically thin silver layer, typically applied to surface 3 of the IGU (the inner face of the outer pane, sealed with