Windows U-value for Passive Houses consists of more factors than what we typically see in Australia. Apart from frame and glass components that are typically part of the U-value, there are few more values that are considered in the calculation: spacer thermal bridge and frame installation value based on the installation details and frame location in the wall. These two factors can play a significant role in the Passive House as they can be the condensation factor that will mean a failure of the concept.
Here are our details for the values of our items:
Our uPVC windows and doors have a frame U-value of around 1.2 on average (varies for each particular profile setup and combination).
(photo single double triple)
The glass U-value range we recommend based on climate data and requirements is:
Double glazed with Light Bridge – 1.36
Triple glazed with Light Bridge – 0.9
Triple glazed with 2 Light Bridge panes – 0.7
Obviously, warm edge spacer is available for all the glass combinations above with any of the frames.
Since this is a critical point for success a lot of architects and designers are often confused as to how to pick the compliant product. A lot still believe it is a guessing game and anything is possible 🙂
However, this is not true!
Windows and doors that we sell have tests that were completed with leakage values. Every time you refer to us a project that will be Passive House we will ask for the TFA and volume values to determine how much air leakage windows and doors are allowed to have.
Windows and doors can’t have a leakage of complete 0 – it is impossible. Some of the tests neglect the results by saying that leakage is too low to specify. However, it is never a zero. So in order to identify the potential loss the best way is to calculate it and multiply by safety factor. This will help to determine whether some extras will be needed such as concealed hinges, allowing some sliding door styles and french doors etc. Because even things like having inward and outward opening windows in the same area can change the blower door test results.
Passive House is not only about certification. It is designed to last for a long time, so have to do the windows and doors. The biggest test for success in Passive House is condensation. If that has occurred it means either components are incorrectly used or design went wrong. There are usually two points of condensation and thermal bridging in windows and doors that have to be looked at and eliminated:
Glass edge spacer – use of warm edge spacer is critical for passive house as it does not only improves the U-value, but most importantly removes condensation problem on the glass.
Installation detail – avoiding any metal brackets, sections and installing the window in the correct section of the wall area – these are all important factors for thermal bridging and condensation avoidance.