Applicability of Window-to-Wall Ratio (WWR %)

The Window-to-Wall Ratio (WWR) % is a fundamental parameter in DesignBuilder, used to control the proportion of glazing on building façades. Its behavior changes significantly when custom windows are introduced. This article explains how WWR % operates in DesignBuilder, especially in the context of parametric tools analysis, and clarifies its interaction with custom windows.

How WWR % Functions in DesignBuilder

• Default Façade Mechanism:

WWR % automatically sizes and places windows on building façades based on the specified ratio. This setting can be applied at building, block, zone, and surface levels.

• Parametric Tools:

WWR % is commonly used as a variable in parametric studies to evaluate the impact of different glazing ratios on building performance.

Impact of Using Custom Windows

• Override of Default Mechanism:

When you manually draw or size windows (custom windows) on a surface, the automatic façade mechanism—including WWR %, window width, height, and spacing—is disabled for that surface.

• WWR % Not Applicable:

For surfaces with custom windows, changes to the WWR % setting will not affect those windows. Only the manually defined windows are considered in calculations.

• Restoring WWR % Control:

To re-enable WWR % control, use the “Clear data to default” option. This removes custom windows and reinstates the automatic façade mechanism.

Practical Implications for Parametric Calculations

• If your parametric study relies on varying WWR %:

- WWR % will only affect surfaces without custom windows.

- Custom windows remain fixed in size and position, regardless of WWR % changes during parametric runs.

• To ensure WWR % is applied throughout your model:
  

         - Avoid drawing custom windows, or clear them before running your parametric analysis.

         - Use the default façade settings to allow WWR % to control window area and placement.