# Windows

A window is a part of the building envelope that allows for light penetration and can significantly impact heat loss and gain. 

## Specify a Window

Glazing is defined at each aspect where a glazing system occurs and can either be the entire width of the aspect selected or be placed within the boundaries of the aspect.

**As Default** - Selecting a glazing system as a design enables quick specification of a glazing system by adopting the default wall specification for the project. 

**From Template** - Selecting a glazing system from a template enables quick access to supplier specifications.

**From Design** - Selecting a glazing system from a design enables quick access to a glazing system you have created and saved in your Project. Once selected, all associated glazing must be updated within the design, saved, and then reselected.

**As Concept** - Selecting a floor system as a concept enables quick specification of a glazing system from baseline (low performance), moderate (typical performance) or enhanced (high performance). Once selected, all associated glazing can be updated. 

Add Glazing by selecting a Zone and then the aspect to be determined as glazed. Left-click 'Select Glazing', and you will be presented with various options to nominate the glazing performance. These included 'From Template, 'From Design', As Concept' and 'As Default'.  Hit ' As Concept' and the select the indicative  'Concept Fabric'. This can be changed later. Next, select the 'System U-value or System R-value', region dependent, the System SHGC and VLT and hit 'Save and Close'.

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## Set Glazing Dimensions

After the glazing specifications have been set, the dimensions of the glazing system need to be assumed. To do so, navigate to 'Window Placement'  to see an elevation view of the Aspect selected. You can then place the window either as a 'Repeating' window (the entire width of the aspect drawn) or as a 'Single' window (any width and location of the aspect). 'Repeating' allows for copying of windows from one aspect to another, which is recommended in most cases. Glazing dimensions can be resized by either clicking the 'Resize' button, where 'Height and 'Resize From' options can be assumed or it can be dragged to size in the elevation view by selecting the nodes.

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## Add Glazing Openability

Applicable to H1 Energy Efficiency or airflow networks only, each window can be adjusted to allow a fraction of the window area to be openable for natural ventilation. The conditions for when the window will be open are set under '[Ventilation](/user-guide/2d-building/building/spaces/set-ventilation.md)' setting in 'Spaces' and are connected to the Occupancy profile of the building.

For those unfamiliar with Glazing Openability, the following % can be used for each window type.

| **Type**                                 | **Openable (half fixed, half openable)** | **Openable (full)** |
| ---------------------------------------- | ---------------------------------------- | ------------------- |
| Awning                                   | 45%                                      | 90%                 |
| Casement / tilt’n’turn                   | 45%                                      | 90%                 |
| Double-hung                              | 22%                                      | 44%                 |
| Louvre                                   | 45%                                      | 90%                 |
| Sliding                                  | 45%                                      | 90%                 |
| Hinged door                              | 0%                                       | 0%                  |
| All window types with safety restrictors | 10%                                      | 10                  |

Add Glazing Openability by selecting the aspect with glazing in the drawing space. Then select 'Add Openability' and set the desired fraction of the window area to be 'Openable' for natural ventilation.&#x20;

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## Add Clerestory Glazing

Clerestory Glazing or any other type of glazing can be applied to a Roof for energy and daylight modelling. See [Add Roof Windows](/user-guide/2d-building/building/levels/roof-geometry/add-roof-windows.md) for more information.&#x20;


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