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What's The Difference Of Window Spacers?

by KE JIAYI 10 May 2023 0 Comments

Windows are essential to any home or building, providing light and ventilation while keeping out the elements. Many components make up a window, including glass, frames, and seals. But one crucial element that often goes overlooked is the window spacer.

In this article, we'll discuss different window spacer types and what makes a perfect window spacer. Also, we will shed some light on a very important topic; warm edge technology or WET. So let's get started!

What’s A Window Spacer?

A crucial component of modern, energy-efficient windows is the window spacer. As a barrier between the glass panes, window spacers are made from low thermal conductivity materials such as silicone foam, butyl rubber, or thermoplastic. This separation helps to reduce heat transfer and increase insulation, making it an essential component for double or triple-pane windows.

There are other benefits as well. The space between the glass panes is filled with an inert gas, usually argon or krypton, further improving the window's insulating properties. Using a window spacer can significantly reduce your energy bills and help create a more sustainable home. Pay attention to the importance of this small but powerful component in your windows!

Warm Edge Technology (WET)

Warm Edge Technology is an innovative solution for minimizing energy loss in double, triple, or quadruple-glazed units. The technology involves modifying the edge structure of these units to transfer less heat or cold compared to standard windows and glazed units.

Typically, standard glazed units use aluminum spacers to keep the glass apart. However, aluminum is highly conductive and leads to significant thermal energy loss. In contrast, warm edge spacers can increase the interior edge temperature by up to 65%, which results in enhanced thermal efficiency and reduced risk of condensation.

Warm edge products can reduce heat loss (or gain) at the exterior edge of windows by up to 94%. By utilizing Warm Edge Technology, you can significantly reduce your energy costs and help to create a more sustainable and eco-friendlier environment.

What Are The Characteristics Of A Perfect Spacer?

The perfect window spacer barely exists. However, if there were any, they must have specific characteristics. Here are some of the attributes of an ideal spacer:

The Seal

The seal between a spacer and multiple glass panes serves the crucial function of reducing water vapor and gas permeability on the edge of the glass. However, with time, most windows leak around 1% of their gas yearly. The longevity of an IGU heavily relies on the seal's integrity.

A primary sealant should maintain low gas and vapor permeability, while a secondary sealant should maintain good adhesion to the glass in the presence of various environmental factors.

Typically, synthetic rubbers like polyisobutylene (PIB) serve as primary sealants. However, their strength decreases as the temperature rises, affecting the glass unit's structural integrity. Hence, in conjunction, secondary sealants such as polyurethane, hot-melt butyl etc., are used.


Adaptability is a crucial feature that any ideal window spacer must possess. It should have the ability to conform to varying climates and temperature fluctuations.

It is because temperature changes can cause the materials within the spacer to expand and contract. If the spacer cannot adapt to such changes, it can result in a broken seal, leading to a loss of energy and infiltration of moisture.

Strength & Durability

The perfect window spacer must have high strength and durability and withstand weight and pressure from wind and other environmental factors.

Additionally, it needs to resist wear and tear, particularly in high-traffic areas. Energy loss and reduced window lifespan can occur without a strong and durable spacer.

Preventing Temperature Transference

The perfect window spacer should prevent temperature transference, keeping the house warm during winter and cool during summer.

The spacer also should have low thermal conductivity to prevent heat transfer and reduce energy loss, resulting in lower energy bills.

Keeping It Dry

Lastly, the perfect window spacer should keep the window dry. Moisture infiltration can cause damage to the window frame and the surrounding walls.

The spacer should be able to prevent moisture from entering the window, even during extreme weather conditions.

Spacer Technology For Different Spacers

There are different types of window spacers available on the market. Here are some examples of various window spacer technologies:

Metal Spacer: Metal spacers are the traditional type of window spacers that have been in use for decades. They are durable and robust and have poor thermal performance. However, metal spacers can cause condensation leading to mold growth and window damage.

Metal and Foam Spacer: Metal and foam spacers have a metal frame with foam insulation. These types of spacers have better thermal performance than pure metal spacers. They are also less prone to condensation and more durable than a pure foam spacer.

Composite and Plastic Spacers: Composite and plastic spacers are made of fiberglass, vinyl, and polycarbonate. They have less thermal conductivity than metal spacers.

Structural Foam Spacers: Foam spacers, including silicone foam and EPDM, present numerous advantages compared to traditional metal spacers when used in IGUs. Their exceptional energy efficiency dramatically reduces heat and cold transfer, resulting in significant energy savings and lower utility bills for homeowners. In addition, their low thermal conductivity makes them less likely to experience sealant displacement.

Thermoplastic Spacers: Made of polyisobutylene, TPSs outshine other spacers with their unique extrusion process. TPS is inserted directly between the glass panes, resulting in a continuous and uniform edge seal that provides exceptional insulation and prevents moisture buildup.

The Width Of A Spacer

The spacer bar is an essential component of double-glazed windows as it maintains a consistent distance between the glass panes, determining the interpane gap's size.

Generally, spacer bars come in a profile width of 4-8 mm, while the most common thicknesses are 12 mm and 14 mm. With a reliable spacer bar, you can enjoy your double-glazed windows' optimal insulation and energy efficiency benefits. 


In conclusion, window spacers play an essential role in windows' energy efficiency and durability. There are two main types of window spacers: metal and non-metallic. Metal spacers are cost-effective but may be less efficient at reducing heat transfer.

Non-metallic spacers, on the other hand, have better thermal performance but are more expensive. Ultimately, the choice of window spacer will depend on individual preferences and the specific needs of each project. Working with a trusted window manufacturer or installer is vital to ensure that the chosen spacer will provide optimal performance and longevity for the windows.


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