Dimensions (Walls)

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

 

You can use settings such as Window to wall %  (WWR) and Window height, Window spacing and Sill height to easily change the amount of glazing and its layout on the walls. The way this data is used for each façade type is described below.

Facade types

There are a number of standard façade types:

 

Window to Wall %

Often referred to as the Window to Wall Ratio (WWR) this setting can be used to change the amount of glazing for all openings at or below the current level in the building hierarchy. For example changing the WWR at building level changes the size of all windows in the model not overridden by other settings lower in the hierarchy.

 

When using the 2-Outer volume Zone geometry and surface areas option (typically one of the "External measurements " convention templates) it is important to understand that the reference surface area used when calculating the window area from the % value supplied is based on the Window to wall ratio method which is accessed from the Constructions tab under the Geometry Areas and Volumesheader.

 

The image below illustrates a wall in a model using the "External measurements" geometry convention template where a window has been created using the 3-Preferred height façade option with a 10% glazing ratio. You can see the black outline showing the available area where the window could possibly be sited. Areas outside this outline to the left and right are taken up by corners with adjacent walls. The % glazing calculation uses the black outline area as the reference area. In an extreme case where 100% glazing is specified the whole of this area would be filled with window, but of course the sides of the surface where there is a corner with an adjacent surface cannot contain a window and so do not take part in the calculation - even though they will form part of the surface used in the simulation.

 

Tip: If you need to ensure that the % window areas used in the simulation exactly match the % you define here then you should consider using the "Simple" Geometry convention template which ensures that 100% of all surfaces are available for containing windows by using zero surface thickness for all surfaces.

Window width

The width of the windows including any frame (in m or ft).

Window height

The height of the windows including any frame (in m or ft).

Window spacing

The spacing between the each window on the façade (in m or ft). The window spacing is the centre to centre spacing between windows, not the gap between windows.

Sill height

This is the height of the base of the window from the base of the block (in m or ft).

Note 1: You can control the configuration of the building façades in greater detail by drawing individual "custom" windows at the surface level or by copying previously drawn windows at building level. In either of these cases glazing, vent and door façade layout model data is ignored.

Note 2: Flat roofs do not have default glazing set up using Roof glazing layout model data. To create openings on a flat roof you should go to the surface level and add them there.

Note 3: When the surface is non-rectangular, even with the 2 façade type options that prioritise Window to wall % (3-Preferred height and 1-Continuous horizontal), the Window to wall % will not be perfectly maintained. For these surfaces, DesignBuilder calculates a rectangle that can accept the windows and starts from one end of the rectangle adding windows using the Window spacing data until no more fit into the rectangle. This results in an approximately correct looking façade but only prioritises Window to wall % in the rectangle, not accounting for the areas outside the bounding rectangle. For relatively large values of Window spacing on non-rectangular surfaces, no glazing may be generated. For example you may find that gable window surfaces have no default windows generated and it is often easiest to draw a window in this case.

Reveal

Reveal surfaces are associated with the setback of the glazing from the outside and/or inside surface of the parent wall. If the depth and solar absorptance of these surfaces are specified, the program will calculate the reflection of beam solar radiation from these surfaces. The program also calculates the shadowing (onto the window) of beam and diffuse solar radiation by outside reveal surfaces.

 

The following fields specify the properties of the window reveal surfaces (reveals occur when the window is not in the same plane as the base surface). From this information and from the geometry of the window and the sun position, the program calculates beam solar radiation absorbed and reflected by the top, bottom, right and left sides of outside and inside window reveal surfaces. In doing this calculation, the shadowing on a reveal surface by other reveal surfaces is determined using the orientation of the reveal surfaces and the sun position.

 

It is assumed that:

 

 

The schematics below show how DesignBuilder reveal data is used to describe real glazing systems.

 

 

Outside reveal depth

The outside reveal depth gives the extent to which the glazing is offset into the wall. As shown in the above diagram it is the distance from the exterior surface of the wall to the glazing outer surface (in m or ft).

Note: The outside reveal depth is used in EnergyPlus, Visualisations and Daylighting calculations.

Note: EnergyPlus models outside reveals through the co-ordinates of the window, which are offset into the zone so the window and the base surface don't lie on the same plane. DesignBuilder provides window co-ordinates to EnergyPlus in this way and there is no specific data item in the IDF data to define it.

Inside reveal depth

The inside reveal depth is the distance (in m or ft) from the innermost surface of the window to the interior wall surface as shown in the diagram above.

Note: Inside reveal depth data is provided to EnergyPlus in the same object as the frame and divider data, so when the Has frame/dividers option is unchecked this data is not provided to EnergyPlus and the equivalent of a 0 inside reveal depth will be simulated.

Inside sill depth

The inside sill depth is the distance (in m or ft) from the innermost surface of the window to the innermost end of the sill as shown in the diagram above.

Note: Inside sill depth data is provided to EnergyPlus in the same object as the frame and divider data, so when the Has frame/dividers option is unchecked this data is not provided to EnergyPlus and the equivalent of a 0 inside sill depth will be simulated.