How Window Frame Design & Materials Impact Thermal Performance

Windows play a crucial role in your home’s energy efficiency, but factors like convection and conduction can impact their performance. Understanding how heat moves through windows and how different materials affect insulation can help you make informed choices about windows for your home. 

This guide breaks down the science behind window convection and conduction, how window frames affect airflow, and what features to look for in energy-efficient designs. 

What Is Window Convection?

Window convection refers to the process where warm air near a window loses heat to the cooler glass surface. This causes the air to sink and create a circulating air current, otherwise called a draft, as the cooler air is pushed away from the window and replaced by warmer air rising to take its place. 

This is the natural movement of air around a window caused by temperature differences. Even if the window is properly sealed, the area near it feels drafty.

What Is Window Conduction?

Window conduction refers to the process of transferring heat from a warmer to a cooler area through the solid materials of a window, such as the glass panes and frame. 

• This causes heat loss or gain through direct contact with the window material itself. 

• It is also one of the primary ways heat is lost through a window. 

How Do Window Frames Influence Convection?

Window frames can significantly influence convection. The wider the barrier of the frames can help lower conduction and create a better-performing system. 

Several other factors influence convection in window frames. Let’s take a closer look!

Cavity Design

When window designers create a window, they often incorporate intentional cavities that provide thermal insulation by limiting convection. 

• The size and shape of these cavities are important, as too much space can allow convection currents to develop, which carries heat from the warmer to the colder side.

• On the other hand, too little space can increase conduction between the surfaces. 

Material Choice

The window frame’s material can affect thermal conductivity and convection. 

• As we’ll see later, low-conductivity materials like wood or plastic provide better insulation and reduce convection. 

• Conversely, metal frames like aluminum are more conductive and require careful design for good thermal performance.

Thermal Breaks

A thermal break is a material with low thermal conductivity that prevents heat from flowing between conductive materials. 

Incorporating thermal breaks in windows can help reduce convection. They also improve energy efficiency in doors, walls, floors, and roofs. 

Multi-Pane Design

Energy-efficient windows usually come in double or triple panes. With proper spacing (around 13 mm), double and triple-pane windows can minimize convection between the panes. 

In addition, manufacturers will add a thin polyester film to divide the air space, further suppressing convection currents.

Edge Seals

Edge seals refer to the sealant applied around the perimeter of a double-glazed window unit, where the glass panes meet the spacer. It creates a barrier to prevent moisture and air from entering the space between panes. 

It helps maintain the window's insulation properties. In addition, improving the U-factors of the frame and glass edge helps manage convection and enhances the overall window performance. 

Frame Thickness

The thickness of the window frame can help provide insulation and reduce convection. As one might expect, a thicker frame provides more insulation and reduces convection. 

However, there is a balance that manufacturers must strike between aesthetics and cost. 

Frame Material and Thermal Conductivity

As mentioned above, the frame material can affect convection and thermal conductivity in windows, which can also impact their energy efficiency. 

Here is a breakdown of the different frame materials and their thermal conductivity. 

• Fiberglass: works as an excellent insulator with low thermal conductivity

• Vinyl (uPVC): as a closed-cell structure, it is a very good insulator with low thermal conductivity

• Wood: as a natural insulator, wood has low thermal conductivity and provides excellent insulation properties 

• Composite: made up of a mixture of materials like wood products and polymers, it offers good thermal performance

• Aluminum with thermal break: aluminum is highly conductive, but adding thermal breaks significantly improves insulation

• Aluminum/Metal: has the highest thermal conductivity, which makes it a poor insulator

To reduce convection, choose windows with low thermal conductivity. These provide better insulation and help prevent heat transfer and drafts. Rather than choosing windows by yourself, consider working with an experienced window installation company, which can help you decide on the best choices for your home. 

Choose Tony’s Lifetime Exteriors for Windows Near St. Cloud, MN

When you need window replacement or any other exterior project completed in the St. Cloud, Minnesota, area, choose Tony’s Lifetime Exteriors. 

We always offer fair and honest pricing for your project, and we’ll help you choose the best and most energy-efficient materials. This can help you save money on energy costs over time and shrink your carbon footprint.

Enjoy the comfort of your home with brand-new windows installed by Tony’s Lifetime Exteriors! Call us at 320-252-9086 or contact us online to request a quote.