glass coatings

Low-emissivity (Low-E) glass has become standard in modern construction — especially across Texas, Oklahoma, Louisiana, New Mexico, Arkansas, Missouri, and Kansas, where heat control and energy efficiency are critical. For glazing contractors, glass fabricators, and window manufacturers, correctly identifying the type and placement of Low-E coatings is essential for both performance and compliance.

Whether you’re fabricating insulated glass units (IGUs) or installing storefront systems, understanding how to spot and verify Low-E coatings will help you avoid installation errors, warranty issues, and costly rework.

This guide breaks down how to identify Low-E glass layers in production and confirm that the right coating is in the right place — every time.

1. What Low-E Glass Actually Does

Low-E (low-emissivity) glass has a microscopically thin coating — usually made of metal oxide — applied to one or more glass surfaces. Its purpose is simple: reflect infrared and ultraviolet light while allowing visible light to pass through.

This reduces solar heat gain in the summer and keeps heat inside during the winter, creating more energy-efficient buildings without sacrificing clarity or natural light.

For hot-weather states, this means less HVAC load, lower energy bills, and improved comfort in homes and commercial spaces.

2. Understanding Coating Placement: Which Surface Matters

Each pane of glass in an IGU has four numbered surfaces:

  1. Surface 1: Exterior-facing (the outermost side of the first pane)
  2. Surface 2: Inside of the outer pane (facing the air gap)
  3. Surface 3: Inside of the inner pane (facing the air gap)
  4. Surface 4: Interior-facing (the innermost side of the second pane)

Low-E coatings can be applied to different surfaces depending on climate and performance goals:

  • Warm climates (like Texas and Oklahoma): Coating typically on Surface 2 to reflect solar heat outward.
  • Cold climates: Coating often on Surface 3 to reflect indoor heat back inside.

In high-performance units, double Low-E coatings may be used — one on each side of the airspace — to balance solar control and insulation.

3. Types of Low-E Coatings

There are two main types of Low-E coatings, and identifying which you’re working with is crucial during production.

a. Hard Coat (Pyrolytic Low-E)
  • Applied during glass manufacturing at high temperatures.
  • Fused permanently to the glass surface.
  • More durable and scratch-resistant.
  • Slightly higher visible light reflection (slight tint or haze).
  • Often used in single glazing or exterior applications.
b. Soft Coat (Sputter-Coated Low-E)
  • Applied in a vacuum chamber after the glass is formed.
  • Provides superior performance for energy efficiency.
  • Must be sealed inside an insulated unit (not exposed to air).
  • More delicate and prone to scratching if mishandled.

Most commercial projects today use soft-coat Low-E glass for better solar control, but it’s essential to verify this before sealing units or installing panels.

4. Visual Identification: The Quick Glare Test

The simplest way to check for Low-E coatings in production is with a glare test:

  1. Hold the glass at an angle under bright, indirect light.
  2. Look for a subtle color shift — usually a light green, blue, or purple hue — when compared to clear glass.
  3. Rotate slightly; the coated side will often show a faint mirror-like reflection.

This test helps confirm that a coating exists, but not which surface it’s on. For that, you’ll need a more precise method.

5. Using a Flame Test to Identify Coated Surfaces

One of the oldest and most reliable techniques is the flame reflection test:

  1. Hold a small flame (like a lighter or pen torch) about an inch from the glass.
  2. Look at the reflection of the flame in the glass.
  3. Each pane will show four flame reflections — one for each surface.

If one of the reflections appears a different color (usually slightly pink or purple), that’s your coated surface.

  • If the altered reflection is the second from the outside, the Low-E coating is on Surface 2.
  • If it’s the third, it’s on Surface 3.

This simple test is fast, safe, and effective in most factory or field environments.

6. Using a Low-E Detector (Recommended for Production Lines)

For higher accuracy, especially in fabrication or assembly environments, use a Low-E coating detector — a handheld device that identifies coated surfaces instantly.

These devices use infrared light to measure emissivity and determine:

  • Whether a coating is present.
  • Which surface it’s on.
  • Whether it’s single or double coated.

Sky Building Materials recommends this method for any large-scale glass production or IGU assembly line, where visual tests aren’t practical for every unit.

7. Recognizing Coating Orientation Errors

Installing or sealing glass with the Low-E side facing the wrong direction is one of the most common fabrication mistakes — and it can ruin performance.

If the coating faces outward when it should face inward:

  • The coating oxidizes faster and loses performance.
  • The glass may appear hazy or uneven.
  • Building energy efficiency drops significantly.

If the coating faces inward when it should face outward:

  • Solar heat gain increases dramatically in hot climates.
  • Interior comfort and HVAC performance suffer.

Always double-check surface orientation before sealing units or installing panels — it’s much cheaper to fix on the floor than after installation.

8. Common Quality Control Mistakes in Fabrication

Even experienced fabricators make errors when handling Low-E glass. The most frequent issues include:

  • Scratching coatings due to improper handling or dirty gloves.
  • Incorrect storage — stacking coated surfaces together without separators.
  • Using ammonia-based cleaners, which can damage coatings.
  • Failing to verify coating type before production, leading to incorrect IGU configurations.

To prevent these, establish a consistent inspection process for every shipment and assembly stage.

Sky Building Materials provides contractors and fabricators with product specifications and handling best practices tailored to each coating type we supply.

9. Combining Low-E with Other Performance Glass Types

Many modern buildings use multi-functional glass systems — combining Low-E coatings with tints, laminates, or reflective coatings.

Examples include:

  • Low-E + Tinted: Reduces glare and heat for southern exposures.
  • Low-E + Laminated: Adds safety, sound insulation, and UV protection.
  • Low-E + Reflective: Provides both privacy and energy efficiency for commercial façades.

When fabricating or installing these combinations, always confirm that the Low-E layer is sealed correctly within the unit and oriented as designed for its performance purpose.

10. Tools and Techniques for Accurate Identification

For consistent results in a production or jobsite setting, equip your team with:

  • Low-E coating detectors (handheld or bench-top).
  • Surface numbering charts for reference during IGU assembly.
  • Lighting stations with neutral-color LED for reflection checks.
  • Inspection logs for tracking verification by shift or production batch.

Establishing a simple quality-control process can eliminate almost all Low-E orientation errors — and protects your bottom line.

11. The Importance of Regional Knowledge

In hot-weather regions like Texas, Oklahoma, and Louisiana, the right Low-E placement can make a measurable difference in comfort and cooling costs.

Sky Building Materials works closely with architects, contractors, and fabricators to specify climate-appropriate coatings that perform in high-solar-load conditions. We help ensure every glass unit shipped meets regional performance standards and fits within local energy codes.

12. Why Correct Identification Protects Your Reputation

A single mistake with coating direction or type can compromise energy ratings, trigger callbacks, or void warranties. Contractors and glass producers who verify every unit demonstrate professionalism and earn trust quickly with architects and builders.

When you can confidently confirm your glass specs on-site — coating, surface, and type — you separate yourself from competitors still guessing.

Conclusion: Clarity Comes from Precision

Low-E glass is one of the smartest technologies in modern glazing — but only if it’s handled correctly. Knowing how to identify coatings, confirm placement, and use the right testing tools ensures every project delivers on performance and efficiency.

At Sky Building Materials, we supply glazing contractors, window fabricators, and general contractors with Low-E, tinted, laminated, and insulated glass units designed for the heat and humidity of the southern U.S. — backed by technical support that helps you get every detail right.

Visit Sky Building Materials in Dallas at 10835 Shady Trail, Dallas, Texas 75220 (972) 807-9616 or in Houston at 4600 S Pinemont Drive, Houston, TX 77041 (346) 200-5046.

For technical specs, coating data, or bulk ordering support, visit the Sky Building Materials Contact Page or connect with us on the Sky Building Materials Facebook Page.