Solar-control glass guide
Same sun. Two very different rooms.
Choosing between Low-E vs reflective glass can look like a choice of colour. In reality, it is a choice between two ways of handling the sun. One keeps the heat out and lets the daylight in. The other mostly changes how your building looks.
Blocks light to block heat
Most of the daylight bounces away along with the heat.
Filters heat, keeps light
Visible light passes through, while the coating turns most of the invisible heat away.
The physics / 01
Sunlight Is Three Things, Not One
To understand the difference, start with the sun itself. First of all, sunlight reaches your facade as three kinds of energy. A few percent is ultraviolet. A little under half is visible light, the part we see. The rest, roughly half, is invisible near-infrared, which we feel as heat.
- Clear glass
- Reflective glass
- Solar-control Low-E
Bars show the approximate share of each band that passes through. These are illustrative values; actual figures vary by product.
This is the key insight. Because so much solar heat is invisible, a glass does not need to block light to block heat. Reflective glass cuts all three bands together. By contrast, Low-E glass is spectrally selective. It lets the visible band through and pushes back the infrared one.
Two technologies / 02
How Each Glass Handles the Sun
Reflective Glass: A Metallic Mirror
Reflective glass carries a thin metal-oxide coating. As a result, it bounces a large share of sunlight straight back outside. Seen from the street, the glass therefore looks like a mirror, often in silver, blue, green or bronze. However, the coating cannot tell light from heat. So it blocks both, and rooms behind it get noticeably darker.
Low-E Glass: A Selective Filter
Low-E stands for low emissivity. The glass carries microscopic layers of silver and metal oxides, far thinner than a human hair. Together, these layers reflect infrared heat while passing visible light. Moreover, they reduce the heat the glass itself radiates into the room. That is why Low-E glazing keeps interiors cooler and brighter at the same time.
Why the Climate Matters
Not every Low-E is the same, though. In cold countries, for instance, some Low-E glass deliberately lets solar heat in. For Tamil Nadu, you need solar-control Low-E, which keeps solar heat out. Always check that the product is meant for hot climates before you specify it.
See the difference / 03
Low-E vs Reflective Glass: How Your Facade Will Look
Appearance is where reflective glass made its name. Drag the handle to compare the same office elevation in both glass types on a bright afternoon.
Meanwhile, modern architecture has moved towards transparent, honest facades. Many design teams now prefer the clear look of Low-E for curtain wall glazing. After all, it shows activity inside and feels more welcoming.
The night-time surprise / 04
Reflective Glass Only Works While the Sun Is Up
Many owners pick reflective glass for privacy. However, the one-way mirror effect depends on light levels. Flip the switch to see what happens after sunset.
Reflective
Mirror outside, so passers-by can’t see in. Inside, rooms are dim.
The interior is on full display. Meanwhile, staff see only their own reflections.
Low-E
Clear outside with soft reflections. Inside, rooms are bright with daylight.
The interior is visible, just like reflective glass. Use blinds or frit where privacy matters.
In other words, at night both glasses behave the same way. So daytime privacy is the only real privacy advantage reflective glass offers. If you need privacy around the clock, blinds, frits or switchable glass do the job better than a mirror coating.
Spec lab / 05
Compare the Numbers That Matter
Looks aside, however, performance lives on the datasheet. Pick a glass type below to see its typical values. Notice how reflective glass lowers heat gain mostly by lowering daylight.
Typical illustrative values for 6 mm single glass or a 6-12-6 DGU. Always confirm with the manufacturer’s datasheet.
Datasheet decoder / 06
How to Read a Glass Datasheet
Every glass product comes with a performance sheet. At first, it can look like a wall of numbers. In practice, five lines tell you almost everything.
| 1Visible light transmission | 60% |
| 2Solar heat gain coefficient | 0.28 |
| 3Light-to-solar-gain ratio | 2.14 |
| 4Visible reflectance (outside) | 12% |
| 5U-value (W/m²K) | 1.7 |
| UV transmission | < 10% |
- 1VLT: how bright the room will beThe share of daylight that passes through. Below about 30%, most rooms feel dim.
- 2SHGC: how much solar heat gets inAlso called the solar factor or g-value. Lower means a cooler room and a lighter AC load.
- 3LSG: the efficiency scoreVLT divided by SHGC. It shows how well a glass separates light from heat.
- 4Reflectance: how mirror-like it looksHigh values mean a shiny facade and more glare for neighbours.
- 5U-value: how well it insulatesLower is better. Double glazing cuts this sharply compared with a single pane.
One number to compare / 07
The Efficiency Score Reflective Glass Can’t Win
If you remember one metric, make it LSG. It measures how much daylight you get for each unit of solar heat you let in. Here is the formula.
- Clear float (single)1.07
- Reflective (single)0.56
- Reflective DGU0.69
- Solar-control Low-E DGU2.14
A common industry benchmark treats glass with an LSG of 1.25 or more as spectrally selective. Notably, reflective glass usually scores well below 1, because it sacrifices light to stop heat. Solar-control Low-E, on the other hand, often reaches 1.8 to 2 or more.
Quick recommendation
Three photos. One clear glass choice.
Not sure which glass suits your building? Send us three quick photos on WhatsApp, and our glazing team will suggest a direction for your facade.
- The full elevation you plan to glaze
- The view from inside, at midday
- Your current glass, up close
Head to head / 08
The Seven-Round Scorecard
To keep things fair, we scored both options on what owners and architects actually ask about. Reflective glass does win two rounds. Still, the final score is clear.
Put simply, reflective glass wins on daytime privacy and initial price. Low-E wins on everything you live with every day: comfort, daylight, views and energy use.
Looks and performance / 09
You Don’t Have to Trade Looks for Performance
Some clients still love the colour or sheen of reflective glass. Fortunately, that look no longer forces you to give up comfort. Today, Low-E comes in several finishes, so the facade can look the way the architect wants while the coating handles the heat.
Clear Low-E
Maximum daylight and a transparent look. It is ideal for offices, showrooms and classrooms.
Tinted Low-E
Adds a soft colour, such as green, blue, grey or bronze. In addition, the tint gives a little extra glare control.
Reflective Low-E
Gives a gentle sheen and some daytime privacy. Even so, it keeps far more light than plain reflective glass.
Low-E laminated
Combines heat control with safety and sound insulation. It is great for busy roads and overhead glazing.
In short, the decision is no longer “pretty or efficient”. Instead, start with a solar-control Low-E base, then choose the tint, sheen or laminate that suits the design. That way, you get the appearance you want and the performance you need.
Orientation guide / 10
Match the Glass to Each Face of the Building
After all, each elevation gets a different sun. So the smartest projects tune the glass by orientation. Tap a direction on the compass.
This matters even more in Tamil Nadu, where the sun is strong almost all year. For example, a west-facing showroom in Chennai can overheat badly by late afternoon. Our team plans glazing works in Chennai around exactly these patterns.
Find your fit / 11
Which Glass Suits Your Project? Find Out in Three Taps
Answer three quick questions. We’ll then point you to a sensible starting point for your project.
What matters most in the rooms behind the glass?
Is the space air-conditioned for most of the day?
How long will you own or occupy the building?
Avoid these / 12
Four Specification Mistakes We See Often
AVOIDJudging glass by its colour
A darker or shinier glass is not automatically cooler. Instead, compare the SHGC on the datasheet.
AVOIDUsing cold-climate Low-E
Some Low-E products actually let solar heat in. So confirm that you are buying a solar-control product for a hot climate.
AVOIDIgnoring the night view
Teams often approve reflective glass on a sunny site visit. However, the night-time look can surprise everyone later.
AVOIDForgetting the neighbours
Highly reflective facades can throw glare onto roads and nearby buildings. Therefore, check outdoor reflectance early in design.
Inside a Low-E unit / 13
Where the Low-E Coating Actually Sits
High-performance Low-E coatings are delicate. That is why they usually live inside a sealed double-glazed unit, protected from weather and cleaning.
- 1Outer paneFaces the weather and takes the cleaning.
- 2Low-E coating on surface 2Turns away heat before it reaches the air gap, and stays protected.
- ∞Sealed air or argon gapSlows heat conduction, which brings the U-value down.
- 4Inner pane and edge sealKeeps moisture out, so the unit performs for years.
How AYSH Gets Low-E Right
See it before you specify
Hold the Glass Up to Your Own Sky
Datasheets tell half the story. So we bring real Low-E and reflective samples to your site. Then you compare them against your own light and surroundings.
- Free site visit with glass samples
- Orientation-wise glass recommendation
- Drawings, BOQ and a clear budget proposal
Questions / FAQ
Low-E and Reflective Glass: Your Questions Answered
Is Low-E glass better than reflective glass for hot climates?
For most buildings, yes. Solar-control Low-E glass blocks a similar or larger share of solar heat while letting in far more daylight. As a result, rooms stay cooler without turning dim. Reflective glass still has a place where daytime privacy or a mirror look is the main goal.
Does reflective glass give privacy at night?
No. Reflective glass works like a one-way mirror only when the outside is brighter than the inside. After dark, interior lights reverse the effect, so passers-by can see in while occupants see their own reflections.
Can Low-E glass be used as a single pane?
Yes, hard-coat Low-E works as a single pane. However, suppliers usually place high-performance soft-coat Low-E inside a double-glazed unit. The unit protects the coating and adds insulation. For Indian facades, a Low-E DGU is the most common choice.
What do VLT and SHGC mean on a glass datasheet?
VLT is the share of visible light that passes through the glass. SHGC, also called solar factor, is the share of solar heat that enters the room. In hot climates, look for a low SHGC with a VLT that still keeps rooms bright.
Will Low-E glass make my building look different?
Only slightly. Most solar-control Low-E glass looks clear or softly tinted from outside, with low reflectance. So your facade keeps a transparent, modern look. If you want some colour or sheen, tinted or lightly reflective Low-E options are also available.