Window shading

Openings tab in model data under External Glazing, Internal Glazing and Roof Glazing headers

 

Window shading can be included to reduce solar gains and increase resistance to heat conduction through windows. To include blinds, transparent insulation or electrochromic glazing check the Window shading checkbox. Then select the window blind component, the position of the shading device relative to the window and the way that the window shading is controlled.

 

Note: Window shading is not included in Heating design calculations

Type

Select the Window blind component type. There are 4 categories of window blinds:

 

Position

The window shading devices can be positioned in one of four ways:

 

 

Note: When selecting the 2-Mid-pane position option you must ensure that there is sufficient gap between the innermost and second pane in the Glazing window gas layer to accommodate the blind Slat width.

Control type

Control data specifies how the shading device is controlled. It determines whether the shading device is “on” or “off.” For blinds and shades, when the  device is “on” it is assumed to cover all of the window except its frame; when the device is “off” it is assumed to cover none of the window (whether “on” or “off” the shading device is assumed to cover none of the wall that the window is on). For switchable glazing, “on” means that the  glazing is in the fully-switched state and “off” means that it is in the unswitched state; for example, for electrochromic glazing, “on” means the glazing is in its darkest state and "off” means it is in its lightest state.

 

The choices for Shading control type are the following. Equivalent EnergyPlus control types are shown in italics. If a setpoint is applicable its units are shown in parentheses.

 

 

The following six control types are used primarily to reduce zone cooling load due to window solar gain.

 

Note: Glare control requires Lighting control to be switched on in the zone.

 

The following two control types can be used to reduce zone cooling load. They are applicable to any Shading type but are most appropriate for interior or exterior blinds, interior or exterior shades with low insulating value, or switchable glazing.

 

 

 

The following three control types can be used to reduce zone heating load during the winter by reducing window conductive heat loss at night and leaving the window unshaded during the day to maximize solar gain. They are applicable to any Shading type but are most appropriate for interior or exterior shades with high insulating value ("movable insulation"). “Night” means the sun is down and “day” means the sun is up.

 

 

 

 

The following two control types can be used to reduce zone heating and cooling load. They are applicable to any Shading type but are most appropriate for translucent interior or exterior shades with high insulating value ("translucent movable insulation").

 

 

 

 

Solar setpoint

The solar setpoint can be defined when one of these shading control types has been selected:

 

 

When the solar radiation (in W/m2 or BTU/h-ft2) is higher than the setpoint entered here and any other required condition are met (control types 9, 10, 17 and 18) and the schedule allows shading operation then the window shading is activated.

Inside air temperature setpoint

The Inside air temperature setpoint can be defined when one of these shading control types has been selected:

 

 

For cooling control types, when the inside air temperature (in °C or °F) is higher than the setpoint entered here and the schedule allows shading operation, the window shading is activated. For heating control types the logic is reversed and shading is activated when the temperature is below this setpoint.

Outside air temperature setpoint

The Outside air temperature setpoint can be defined when one of these shading control types has been selected:

 

 

When the outside air temperature (in °C or °F) is higher than the setpoint entered here and the schedule allows shading operation, the window shading is activated.

Slat Angle Control

Where a Window shading system from the Slatted blinds category is selected, the angle of the slats must be defined using the settings below.

Slat angle control type

The angle of the blind slats can be controlled using 3 options:

 

Slat angle schedule

The schedule defines the angle of the slats for every timestep in the simulation. This setting is only available when the 2-Scheduled slat angle Slat angle control type is set. See Window shading dialog for the definition of Slat angle.

 

Note: the operation of the blinds is controlled independently of the slat angle.

Operation

Operation schedule

For all shading control options apart from Glare and Always on, the shading can only be active when this schedule value is 1. Select the schedule On if the blind is always activated or if the only control is one of the others listed above.

Limitations