What Makes Thermal Performance Challenging in Canada?

Thermal performance is an important consideration when designing and specifying windows in Western Canada, but achieving the right balance between performance, design and project requirements can be challenging.

This article explores:

• What, beyond rating systems, can make thermal performance challenging in North America.
• Why two windows of the same size and configuration can have different U-Values.
• How window design and project requirements can influence thermal performance.

First of all, take a look at the examples below:

This shows how the performance of a window can differ (this can be the case even if they’re the same configuration). The windows above both have exactly the same glass (270/cl), but their U-Values vary due to the type of frame used. The difference can be quite substantial.

What Challenges are We Referring to?

The most significant challenge is balancing design and thermal performance. We’re in an age where building design is a highly creative process. For architects and designers, this is a part of their unique selling proposition. It’s their creativity that makes them sought after. So, to a lot of designers, the aesthetic of the building is just as important as thermal performance. That’s where this particular challenge comes into play.

Thermal requirements for windows are getting ever more stringent – and superior thermal performance in a building usually means smaller openings, less glazing area, or heavier glass packages such as triple glazing

The Cost of a Better U-Value

Because U-Values are often specified to the second decimal place, even a small improvement in U-Value can sometimes require a significant and expensive upgrade to the window system.

Despite seeming fairly insignificant, that last digit can be the difference between higher-performance glass coatings or even double or triple glazing. It’s important to take into account how these small changes can have a big impact on your budget. Do you have flexibility in your project? If so, it's worth consulting with the experts to see if you can make savings while still achieving essentially the same performance.

Published U-Values are based on specific testing or calculation conditions and reference configurations. In a real project, factors such as window size, configuration, framing and mullions can affect the thermal performance of the overall assembly.

For this reason, a published U-Value is a starting point – the right number depends on the specific project.

How to Navigate this Challenge

Prioritize. Sure, sometimes both thermal performance and the envisioned design of a project may be compatible and no changes will be necessary – but with more creative plans, one will likely have to take precedence over the other.

If aesthetics is the most important aspect of the project, then you may look to U-Values between 1.61 and 1.4 W/m²·K (depending on the province and climate zone).

With an energy modeller, the window U-Values can be rather flexible providing performance changes are offset elsewhere. On the other hand, if thermal performance is the top priority, design compromises will be required.

Ultimately, achieving the right thermal performance is about finding the right balance for the project. Window selection involves more than comparing U-Values. Window size, configuration, framing, glazing and the overall building design all need to be considered when determining the most appropriate solution.

Planning a project? Talk to our experts early about balancing design and performance.