Low-E Glass Compared: U Value, SHGC, Light and Price
Low-E Clear, Neutral and Grey all insulate about the same: as a single pane their U value is 3.6 to 3.9 (clear glass 5.4), and as double glazing 1.6 to 1.8 (clear 2.5). The real choice is how much sun and light you want: Low-E Clear is brightest, Low-E Grey blocks the most heat, Low-E Neutral sits in between. Prices below are our online prices for a 1000 × 1000mm piece, delivered.
How to read the numbers
- U value (insulation): lower is better. How much heat passes through the glass. It matters most in winter.
- SHGC (solar heat gain): lower blocks more sun heat. Low for hot west and north windows; higher if you want winter sun to warm the room.
- VLT (visible light): higher is brighter. Low numbers mean a darker tint, more privacy and less glare.
Single glazing: Low-E and energy glass compared
One pane of 6mm glass (single glazing), glass-only figures.
| Glass | U valueinsulation, lower is better | SHGCsolar heat in, lower blocks more heat | Light (VLT)higher is brighter | Price1000 × 1000mm, delivered | In short |
|---|---|---|---|---|---|
| 6mm Clear | 5.4 | 0.84 | 89% | $169 | Standard glass, the baseline |
| Low-E Clear | 3.6 | 0.71 | 83% | $267 | Keeps heat in, still clear and bright. Best value |
| EnergyTech Clear | 3.6 | 0.70 | 81% | $370 | Almost the same as Low-E Clear, Viridian brand |
| Low-E Neutral | 3.9 | 0.54 | 63% | $370 | Insulates nearly as well, cuts more heat and glare, light tint |
| Low-E Grey* | 3.8 | 0.33 | 31% | $394* | Blocks the most sun heat, dark grey |
| EnergyTech Grey | 3.7 | 0.48 | 40% | $415 | Lighter grey, lets in more sun heat than Low-E Grey |
| SolTech Grey | 3.7 | 0.37 | 30% | $496 | Grey with strong heat control |
| 6mm Grey tint | 5.4 | 0.58 | 45% | $239 | Tint only: cuts glare, no extra insulation |
| SuperGrey | 5.8 | 0.36 | 9% | $512 | Very dark, privacy, no extra insulation |
Low-E vs EnergyTech: what is the difference?
Both are the same kind of glass: a hard-coat (pyrolytic) Low-E coating, and they perform almost the same. EnergyTech is the Viridian brand, made in Australia, with certified performance data that energy ratings and building reports can quote. Low-E is imported unbranded Low-E glass: same job, lower price. Need certified data for your builder or energy assessor? Choose EnergyTech. Otherwise Low-E gives the same result for less.Prices: our online price for one 1000 × 1000mm panel, cut edges, not toughened, delivery included. *Low-E Grey is supplied toughened only. Prices change with size, edges and toughening: the calculator gives your exact price. Performance: supplier single glazing data, glass only (whole-window figures depend on the frame).
Double glazing: inner pane options compared
6mm clear toughened + argon gap + 6mm inner pane. Whole glass unit figures.
| Inner pane | U valueinsulation, lower is better | SHGCsolar heat in, lower blocks more heat | Light (VLT)higher is brighter | Price1000 × 1000mm unit, delivered | In short |
|---|---|---|---|---|---|
| Clear | 2.5 | 0.73 | 78% | $394 | Standard double glazing |
| Low-E Clear | 1.6 | 0.63 | 73% | $456 | Warm and bright. Best value |
| EnergyTech Clear | 1.6 | 0.62 | 73% | $524 | Same as Low-E Clear, Viridian brand |
| Dual Eco Plus | 1.4 | 0.55 | 78% | $549 | Better insulation, still very bright |
| Low-E Neutral | 1.8 | 0.45 | 56% | $507 | Balance of light and heat control |
| Low-E Grey | 1.7 | 0.24 | 28% | $485 | Blocks the most solar heat, darker |
| Sunergy Euro Grey | 1.3 | 0.33 | 31% | $505 | Best insulation plus strong heat control |
| Evantage Grey | 1.7 | 0.33 | 29% | $526 | Grey, strong heat control |
| SolTech Grey | 1.6 | 0.28 | 30% | $583 | Grey, strong heat control |
| Grey tint | 2.5 | 0.46 | 39% | $436 | Tint only, no extra insulation |
Low-E vs EnergyTech: what is the difference?
Both are the same kind of glass: a hard-coat (pyrolytic) Low-E coating, and they perform almost the same. EnergyTech is the Viridian brand, made in Australia, with certified performance data that energy ratings and building reports can quote. Low-E is imported unbranded Low-E glass: same job, lower price. Need certified data for your builder or energy assessor? Choose EnergyTech. Otherwise Low-E gives the same result for less.Prices: our online price for one 1000 × 1000mm double glazed unit (6mm toughened + argon + 6mm toughened), delivery included. The calculator gives the price for your size. Performance: supplier data for 6mm toughened / argon / 6mm units. Whole-window figures depend on the frame.
Order Low-E glass cut to size
6mm Low-E Clear6mm Low-E Neutral6mm Low-E GreyDouble glazed units
Low-E glass also comes in 4mm, 5mm, 8mm and 10mm, laminated for safety, and in EnergyTech, SolTech and Sunergy versions: see all Low-E and energy glass.
Common questions
What is the difference between Low-E and EnergyTech glass?
Both are hard-coat (pyrolytic) Low-E glass and perform almost the same: as a single 6mm pane both have a U value of 3.6, and in a 6mm double glazed unit both are 1.6. EnergyTech is Viridian's Australian-made brand with certified performance data for energy ratings and building reports. Low-E is imported unbranded glass that does the same job for less.
Is a lower U value better?
Yes. The U value measures how much heat passes through the glass. Lower means better insulation. A single pane of 6mm clear glass is 5.4 and 6mm Low-E Clear is 3.6. Clear double glazing is 2.5; with a Low-E Clear pane it drops to 1.6, and Sunergy Euro Grey reaches 1.3.
What does SHGC mean?
Solar heat gain coefficient: the share of the sun's heat that comes through the glass. A lower SHGC keeps a room cooler in summer and suits west and big north windows. A higher SHGC lets winter sun warm the room.
Low-E Clear, Neutral or Grey: which should I choose?
All three insulate about the same (single pane U value 3.6 to 3.9). Low-E Clear is the brightest (83% light) and best value, good for south and east windows. Low-E Grey blocks the most solar heat (SHGC 0.33) but is darker (31% light). Low-E Neutral sits in between: 63% light with some heat and glare control.
Does Low-E glass thickness change the insulation?
Hardly. The coating does the insulating: as a single pane, 4mm Low-E Clear is 3.65 and 10mm is 3.6; in double glazing 4mm, 5mm and 6mm all have a U value of 1.6. Choose the thickness for the window size, wind load and safety rules.
Is single Low-E glass worth it, or do I need double glazing?
Single Low-E glass fits most existing frames and loses about a third less heat than clear glass (U value 3.6 against 5.4). Double glazing with a Low-E pane insulates much better (U value 1.6, against 2.5 for clear double glazing), but needs a frame deep enough for the unit.