November 13, 2024

How to Improve Thermal Performance with Low U-Value Windows

Written by Caitlyn Spracklen

Optimising Thermal Performance with Low U-Value Windows 

As energy efficiency becomes a critical goal in modern architecture, optimising the thermal performance of windows has become essential in building design. Low U-value windows are a key component in this process, offering architects an effective way to significantly reduce heat transfer and improve insulation. With continuous advancements in window technology and materials, understanding and selecting low U-value windows is fundamental for architects seeking to elevate the energy efficiency of their projects. 

The Importance of U-Values in Window Performance 

To maximise insulation, it’s essential to understand U-values and their impact on thermal performance. U-values measure heat transfer through different parts of building materials, with lower values indicating greater insulating capabilities. Specifically, the Uw value represents the overall thermal efficiency of a window, encompassing the glazing (Ug value), frame (Uf value), and spacer (Psi value). For architects aiming to design high-performance buildings, achieving a low Uw value is crucial, and low U-value windows provide the necessary efficiency boost in any building envelope. 

Understanding Heat Loss in Window Assemblies 

Improving a window's thermal performance begins with identifying where heat is most likely to escape. Typically, two-thirds of heat loss occurs through the glazing, with the remainder escaping through the frame and spacer. With low U-value windows, architects can address each of these key points of heat loss. 

As most energy is lost through glazing, the best gains in insulation can be achieved through improving the performance of the glass. 

You can improve the U-value of the glass unit by using; 
 

• Triple Glazing | You can achieve Ug values of 0.4 W/m²K for some specifications 

• High-Performance Coatings | You reduce the Ug-value of even double glazing to 1.0 W/m²K 

Optimising Glazing and Frame Performance for Low U-Value Windows 

When glazing improvements have been maximised, the next step in achieving a low U-value is selecting an optimised frame material. For architects aiming for the best in thermal efficiency, wooden frames are an excellent choice. Timber frames offer natural insulation properties, creating a robust barrier against heat transfer, while maintaining an aesthetic that complements a range of architectural styles. While metal frames are popular, they require plastic thermal breaks to prevent “cold bridging,” which is when heat transfers across uninsulated metal sections. Timber is a natural insulator, therefore there is no need to modify it for better insulation. 
 

Ultra Low U-Value Windows 

For even further insulation, timber framed windows can be created with Passiv house performance. Additional layers of insulation are added to ensure that the ultra-low U value windows achieve the required passiv house performance every time. 
View Our Passiv House window range.

The specific Uw value achievable in a window system depends on the glazing and frame materials selected. Modern double-glazed units with low e-coatings and argon gas fillings typically achieve Uw values between 1.5 W/m²K and 1.2 W/m²K, while triple glazing with a thermally optimised frame can reduce Uw values to 0.8 W/m²K or below. When aiming for values below 0.8 W/m²K, timber frames are particularly advantageous, offering natural insulation properties that, in combination with triple glazing, can reach Uw values from 0.7 to 0.6 W/m²K. For extremely high-performance projects, such as Passivhaus certification, timber frames with additional layers of insulation can achieve Uw values as low as 0.5 W/m²K, making them an ideal choice for architects focused on low U-value windows and superior insulation. 

Get Expert Guidance on Low U-Value Windows 

At Avino, our team of experts is here to help you achieve unmatched thermal performance tailored to your architectural vision. From initial consultation to final specification, we’ll guide you in selecting and integrating the best low U-value window solutions to meet your project’s unique requirements. 

Contact us today to see how Avino can bring your energy-efficient designs to life.