Skylights & Roof Windows

Skylights need to be modelled within a Project for their solar gains, heat-loss & ventilation effects to be modelled.


Skylight Type

The term “Skylight” is used both as a generic term for all Skylight / Roof Window objects, however there are actually three distinct Types of Skylights available for use in Hero.

This property is shown in the Skylight Data-Grid Type column.



Skylight (Standard)

A standard Skylight with a Shaft penetrating a Roofspace Zone.

Only available for use on Ceilings with an Attic Type Assembly.


A Circular Metal Skylight with a Shaft penetrating a Roofspace Zone.

Only available for use on Ceilings with an Attic Type Assembly & as a Circular Shape.

Roof Window

A Roof Window is a Skylight with No Shaft that penetrates a Flat Roof.

Only available for use on Ceilings with a Skillion/Flat Type Assembly


The Skylight Type will change automatically if the Ceiling’s Assembly is changed from a Attic (i.e. Roofspace) Type to a Skillion/Flat Roof Type & Vice-Versa.

E.g: A Roof Window on a Skillion/Flat Ceiling Assembly will get changed to a Skylight Type if the Ceiling’s Assembly is changed to an Attic Roof Assembly



All Skylight Types except for Roof Windows are modelled with a Shaft. This Shaft has attributes mostly changed within the Skylight Data-Grid, including Shaft Length, Reflectivity, Insulation & a Bottom Diffuser.

Each of these Shaft attributes are modelled within the Chenath Simulation.


Skylight Shape

Skylights uniquely have two possible Shapes: Polygon & Circular. The shape is determined by the initial Skylight Drawing Sub-Mode and can be changed after Skylight creation by changing the value in the Shape Column of the Skylight Data-Grid.




Skylights are created using the Skylight & Hole Drawing Mode


Skylights are shown on the Visual View & Skylight Data-Grid and can be selected as per normal objects.

You can also use the Visual View’s Select Parent context-menu action for a Skylight (or it’s 🖱 Double Left-Click mouse shortcut). In this case, the action selects the parent Ceiling of the Skylight.


Skylights can be Deleted as per normal model objects using the Delete keyboard shortcut, or 🖱 Right-Click Context-menu action ⌨ Delete or via the Data-Grid’s Delete button.

Points can be deleted off a Polygon Skylight’s shape by 🖱 Right-Clicking the Point and selecting Delete Point.

Moving Skylights

Skylights can be moved in the Visual View by selecting them and then 🖱 Dragging them into their position.

For Polygon Skylights: You can 🖱 Drag the Points of a Polygon Skylight to move that Point and extend or shrink the length.

For Circular Skylights: You can 🖱 Drag the Radius Point of the Skylight to increase the Radius of the circular Skylight.

Skylights cannot be moved outside the bounds of the Zone

You can move a Skylight or a Skylight Point in a straight up or down direction by holding   ⌨ Shift.

Adding Points

Points can be added to a Polygon Skylight by 🖱 Right-clicking the Skylight near it’s edge and selecting the Add Point Context Menu action.





Edited Within


The Name of the Skylight

Name Column


The Type of Skylight (Skylight, Roof Window or Tubular).

Available options depend on Ceiling Assembly Type (see Type section above for more details)

Type Column


Change the Shape of the Skylight between Polygon or Circular

Shape Column


The Specification of the Skylight as per the Selected Skylight List from the Skylight Library and filtered for Type within the Data-Grid.

Various Specifications are available that changed the Glass & Frame of the Skylight.

Specification Column


The Pitch or Incline of the Skylight on the Roof (in degrees) with 0 being Horizontal / Flat and 90 degrees being Vertical

Pitch Column


The Direction the Face of the Skylight is facing (it’s normal face direction). Ignored if Pitch is 0 degrees.

Orientation Column


The Pitched Area of the Skylight (in m2)

Not editable

Openable Percentage

Roof Windows only

The Percentage of the Roof Window’s Area that is Openable for Ventilation

Openable % Column

Internal Shade Device

Roof Windows only

The Internal Shade device for the Skylight as specified & noted on the Plans, and it’s effective R-Value, Solar Transmittance (ST) & Solar Absorptance (SA)

Internal Shading Column

External Shade Device

The External Shade device for the Skylight as specified & noted on the Plans, and it’s effective Shading Coefficient (SC)

External Shading Column

Shaft Sub-Properties

Shaft Length

Skylight & Tubular Types only

The Length of the Skylight Shaft through the Roofspace (in mm), from Centre of External Face of Skylight to Internal Face of Skylight

Shaft Length Column

Shaft Reflectivity

Skylight & Tubular Types only

The Reflectivity (%) of the Internal Surface of the Skylight Shaft

Shaft Refl % Column

Shaft Insulated

Skylight & Tubular Types only

Whether the Walls of the Skylight Shaft are insulated or not (simulated default is R2.0)

Shaft Insulated Column

Shaft Diffuser

Skylight & Tubular Types only

Whether the Bottom of the Skylight Shaft is fitted with a Diffuser Cover or not, or is open directly into the Zone.

Shaft Diffuser Column


Modelling Roof Windows in Attic Ceilings

Given the restrictions in Chenath on adding a Roof Window to a Roofspace/Attic Ceiling, to model a Roof Window in such a circumstance requires splitting the Ceiling such as to create a Ceiling that can be set as a Flat roof type, which will therefore accept a Roof Window within it.

Note however that all the shaft walls will need to be modelled as Roofspace adjacent floating walls to accurately describe the skylight shaft walls.


Skylight Library

The Skylight Library holds the complete library of all Skylight & Roof Window Specifications available for NatHERS Simulation. The Selected Skylight list within the Library is what is presented to Users within the Skylight Data-Grid’s Specification column (as well as filtering by Skylight Type).

Further Information: Skylight Library


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