Glass types and low-E coatings: A Comparative Guide

When it comes to glass, it's not just about transparency.

Different types of glass, such as clear, mid-iron, and low-iron, offer distinct visual properties that can significantly impact the overall aesthetic and functionality of your project. Adding low-E coatings will effect the u-value, Solar Heat Gain Coefficient and Visible light Transmittance as well as the color, reflectivity and tint.

The majority of residential projects use clear glass which is perfectly acceptable and functional for most applications. When increased optical clarity is desired, mid-ron and low-iron glass options provide a higher level of clarity.

Clear Glass: The most common type of glass used in windows and doors. Contains a moderate amount of iron oxide, which gives it a slight greenish tint, especially noticeable in thicker sheets. Suitable for general-purpose applications where cost-effectiveness is a priority. However, its greenish tint may be noticeable in larger or thicker installations.

Mid-Iron Glass: A step up in clarity from clear glass, mid-iron glass has a reduced iron content, resulting in a clearer and more neutral appearance. It is ideal for applications where a higher level of clarity is desired making it ideal for applications where a more modern look is desired.

Low-Iron Glass: Also known as extra-clear, ultra-clear, as well as manufacturer’s brand names- Starphire , Optiwhite and Diamant. Low-iron glass has a minimal amount of iron oxide, making it virtually colorless. It offers exceptional clarity and light transmission, making it perfect for high-end applications. It provides the highest level of clarity and light transmission, making it perfect for applications where the glass itself is a focal point. It's often used in high-end architectural projects, display cases, and museum exhibits.

Low iron glass has greater optical clarity than standard clear glass.

Image courtesy of AGNORA.

The thicker the glass the more the color or tint of the glass becomes apparent.

Low iron glass is not affected by the thickness of the glass as much as clear glass. Image courtesy of AGNORA.

Factoring in low-E coatings

Low-E coatings are thin, virtually invisible metalic layers applied to glass to improve its energy efficiency. While these coatings are designed to be transparent, they can subtly affect the way glass appears, particularly in terms of color and reflection. Low-E coatings can introduce a slight color shift to the glass, often a subtle blue or green hue. This is because the coating reflects certain wavelengths of light more than others.

The color shift is usually minimal and often imperceptible, especially in smaller window panes. However, in larger glass installations, such as curtain walls or large windows, the cumulative effect of the color shift might become more noticeable.

When choosing the type of glass for your project, consider the following factors:

• Desired level of clarity: If you need the highest level of transparency, low-iron glass is the best choice.

• Aesthetics: The color and clarity of the glass can significantly impact the overall look of your project.

• Budget: Low-iron glass is more expensive than clear or mid-iron glass.

• Thermal requirements: If you live in an environment with extreme cold, heat and/or sunlight, one or more low-E coatings can help create a more comfortable living environment and a more thermally efficient dwelling.

We have an extensive library of glass samples from Guardian, St Gobain, Pilkington, and Vitro with clear to low iron glass, and various types of low-E coatings available for review.

We will work with you to select the correct glass makeup for your project.