Model Geometry Example

This section documents the way the DesignBuilder model geometry you define is used in the calculations and visualisations. The description is based on the Model Geometry Example.dsb example building shown below. The file Model Geometry Example.dsb is supplied with DesignBuilder. The model consists of 4 blocks, each block containing a single zone, except the Ground floor block which is divided into equal sized North and South zones.

and Visualisation view:

See the Visualisation Limitations section for information on some minor differences in the rendered images and the model used in the calculations.

The model consists of:

1 x 10m x 10m Ground floor block partitioned into equal size North and South zones using partition of thickness 0.05m.

1 x 10m x 10m First floor block stacked on ground block.

1 x 10m x 5m Block with flat roof and external floor connects with the First floor block on the North side.

1 x 10m x 10m Roof block with 45° roof slope drawn in the vertical plane and extruded horizontally, i.e. it is not defined as a Pitched roof block form. The Roof block is stacked on top of the First floor block.

Above are external block dimensions.

Block wall thickness = 0.2m for all blocks.

30% Glazing ratio for all blocks, all glazing uses default facades (i.e. no windows or doors have been drawn).

Model uses default Zone volume calculation options - Internal floor constructions not subtracted from zone volume, External floor constructions not subtracted from zone volume and Ground floor construction is below ground and is not subtracted from zone volume.

When exported to 3-D DXF using the Whole model with details option and dimensioned the model looks like this:

The same model in 3-D view looks like this:

The ceiling / floor surface between First floor block - Zone 1 and Roof block - Zone 1 has area 9.6m x (9.6 - 2 x 0.2 / sin 45°) where the 0.2 / sin 45° term is the Roof block wall thickness (0.2m) adjusted to account for the roof slope (45°) as shown in the diagram below.

The dimension data for the zones, surfaces and openings used in the calculations can be seen in the Navigator and can also be obtained by exporting a csv report file.

The general principles used in DesignBuilder are:

Internal zone surface areas are used in calculations and these are derived from block outer dimensions accounting for block wall thickness.
Full block height is used when calculating wall areas
Zone volume is calculated accurately even for very complex shaped zones but for a simple 'shoebox' model the zone volume is simply zone floor area x block height.
If one of the Zone volume calculation options is not selected then the volume of appropriate floor constructions is subtracted from the basic zone volumes. The volume of the floor construction is the Thickness of the construction x the surface area.

The tables below list the most important geometric data and show how each item is calculated. Note that surfaces with glazing have area of glazing subtracted. The areas below are consistent with EnergyPlus and SBEM calculations.

Zone Ground floor block - North		Calculation Note
Floor area (m2)	46.08	4.8m x 9.6m
Volume (m3)	138.24	46.08m2 x 3m (subtract volume of ground floor if Ground floor construction is below ground and is not subtracted from zone zolume model option set)

Surface	Area (m2)	Area Calculation Note	Adjacency (Orientation / adjacent zone)
Ground floor	46.08	4.8m x 9.6m	Ground
Ceiling	46.08	4.8m x 9.6m	First floor block - Zone 1
Wall Outside	10.08	4.8m x 3m - glazing area on surface (2.88m x 1.5m)	90
Glazing Outside	4.32	2.88m x 1.5m	90
Wall Outside	20.16	9.6m x 3m - glazing area on surface (5.76m x 1.5m)	0
Glazing Outside	8.64	5.76m x 1.5m	0
Wall Outside	10.08	4.8m x 3m - glazing area on surface (2.88m x 1.5m)	270
Glazing Outside	4.32	2.88m x 1.5m	270
Partition	28.8	9.6m x 3m	Ground floor block - South

Zone Ground floor block - South		Calculation Note
Floor area (m2)	46.08	4.8m x 9.6m
Volume (m3)	138.24	46.08m2 x 3m (subtract volume of ground floor if Ground floor construction is below ground and is not subtracted from zone volume model option set)

Surface	Area (m2)	Area Calculation Note	Adjacency (Orientation / adjacent zone)
Ground floor	46.08	4.8m x 9.6m	Ground
Ceiling	46.08	4.8m x 9.6m	First floor block - Zone 1
Wall Outside	10.08	4.8m x 3m - glazing area on surface (2.88m x 1.5m)	90
Glazing Outside	4.32	2.88m x 1.5m	90
Wall Outside	20.16	9.6m x 3m - glazing area on surface (5.76m x 1.5m)	180
Glazing Outside	8.64	5.76m x 1.5m	180
Wall Outside	10.08	4.8m x 3m - glazing area on surface (2.88m x 1.5m)	270
Glazing Outside	4.32	2.88m x 1.5m	270
Partition	28.8	9.6m x 3m	Ground floor block - North

First floor block - Zone 1		Calculation Note
Floor area (m2)	92.16	9.6m x 9.6m
Volume (m3)	276.48	92.16m2 x 3m (subtract volume of ground floor if Ground floor construction is below ground and is not subtracted from zone volume model option set)

Surface	Area (m2)	Area Calculation Note	Adjacency (Orientation / adjacent zone)
Floor	46.08	4.8m x 9.6m	Ground floor block - North
Floor	46.08	4.8m x 9.6m	Ground floor block - South
Ceiling	90.569	9.434m x 9.6m (9.434m = 10 - 2 x 0.2 / sin 45°)	Roof block - Zone 1
Wall Outside	20.16	9.6m x 3m - glazing area on surface (5.76m x 1.5m)	90
Glazing Outside	8.64	5.76m x 1.5m	90
Wall Outside	20.16	9.6m x 3m - glazing area on surface (5.76m x 1.5m)	180
Glazing Outside	8.64	5.76m x 1.5m	180
Wall Outside	10.08	9.6m x 3m - glazing area on surface (5.76m x 1.5m)	270
Glazing Outside	8.64	5.76m x 1.5m	270
Wall (with hole)	0.201	Necessary surround for interblock partition	0
Interblock partition	28.649	Interblock partition 9.6m x 3m - wall (with hole) (0.201m2)	Block with flat roof and external floor - Zone 1

Block with flat roof and external floor - Zone 1		Calculation Note
Floor area (m2)	44.16	4.6m x 9.6m
Volume (m3)	132.48	44.16m2 x 3m (subtract volume of external floor if Internal and external floor construction is below ground and is not subtracted from zone volume model option set)

Surface	Area (m2)	Area Calculation Note	Adjacency (Orientation / adjacent zone)
Floor	44.16	4.6m x 9.6m	Outside
Flat roof	44.16	4.6m x 9.6m	Outside
Wall Outside	9.66	4.6m x 3m - glazing area on surface (2.76m x 1.5m)	90
Glazing Outside	4.14	2.76m x 1.5m	90
Wall Outside	20.16	9.6m x 3m - glazing area on surface (5.76m x 1.5m)	0
Glazing Outside	8.64	5.76m x 1.5m	0
Wall Outside	9.66	4.6m x 3m - glazing area on surface (2.76m x 1.5m)	270
Glazing Outside	4.14	2.76m x 1.5m	270
Wall (with hole)	0.201	Necessary surround for interblock partition	180
Interblock partition	28.649	Interblock partition 9.6m x 3m - wall (with hole) (0.201m2)	First floor block - Zone 1

Roof block - Zone 1		Calculation Note
Floor area (m2)	90.569	9.434m x 9.6m (9.434m = 10 - 2 x 0.2 / sin 45°)
Volume (m3)	213.615	90.569m2 x (5m - 0.2 / cos 45°) x 0.5

Surface	Area (m2)	Area Calculation Note	Adjacency (Orientation / adjacent zone)
Floor	90.569	9.434m x 9.6m (9.434m = 10 - 2 x 0.2 / sin 45°)	First floor block - Zone 1
Wall Outside	15.576	9.434m x (5m - 0.2 / cos 45°) x 0.5 - glazing area (6.676)	90
Glazing Outside	6.676	4.45m x 1.5m	90
Wall Outside	15.576	9.434m x (5m - 0.2 / cos 45°) x 0.5 - glazing area (6.676)	270
Glazing Outside	6.676	4.45m x 1.5m	270
Roof (slope 45° )	64.042	6.671m x 9.6m, 6.671 is the internal eaves to apex length = (5 - 0.2 / cos 45) / sin 45	90
Roof (slope 45° )	64.042	6.671m x 9.6m, 6.671 is the internal eaves to apex length = (5 - 0.2 / cos 45) / sin 45	270

Other related information

Block and Zone Dimensions is an introductory section explaining how to enter blocks and the relationship with zones.
Also see Constructions for how to edit the construction configuration.
See Combined Constructions for information on the meaning of the Construction Model data.