Cost Data

This page gives an overview of the various sources of data used in a building construction cost summary calculation.

 

The capital cost of constructing the building is defined in a number of places in the model:

 

  1. Within the building model on component dialogs:

    1. Construction - cost of constructions
    2. Material - cost of material layers (cost per area or volume),
    3. Glazing - cost of glazing systems (cost per window area)
    4. Window shading devices such as blinds and shades (cost per window area)
    5. Local shading such as overhangs and louvres (cost per window area)
    6. Wind turbines connected to Load centres.
    7. Renewable generation distribution and electrical costs from Load centres.


    and on model data tabs:

     

    1. Constructions - sub-structure, structure and surface finishes.
    2. Lighting - cost of lighting systems (cost per GIFA)
    3. HVAC - cost of HVAC systems (cost per GIFA or capacity)

  2. Building cost summary data on the Building Cost Summary dialog (accessed from Tools menu).

 

This data together with the building geometry allows the construction cost (aka capital expenditure or Capex) of the building to be calculated.

 

A report of the cost can be viewed on the Cost and Carbon screen.

Tip: The Capex totals can also be used as objective or constraints within optimisation or parametric studies.

Note: the default costs for building materials, glazing and other systems provided with DesignBuilder are indicative only and should be replaced with project-specific costs in cases where an accurate cost estimate is required.

1. Super-Structure and Sub-Structure Costs

In general the sub-structure cost is the cost of all works below ground level and super-structure cost is the cost of all works above ground level.

 

Opaque wall, roof, floor and partition fabric costs are calculated using the model geometry, and construction selected for each surface The cost of each surface is calculated from its area and the type of construction used. For an external wall the cost for a surface is calculated from its surface area (minus the area of any windows and other openings) and the cost of the construction per area. The cost of the construction per area is calculated in the way defined on the Cost tab for the construction.

Note: If a construction has more below ground surface area than above ground surface area, then this construction is defined as a below ground construction.

Glazing costs are calculated using the model geometry, the window areas and the glazing selected for each window. The cost of each window is calculated from its area and the type of glazing used. The cost of the glazing per area is defined on the Cost tab for the glazing component.

Note: For costing purposes the Roof/wall transition angle is assumed to be a fixed 70°, which mean if the slope is greater than 70°, then it is defined as a window, otherwise it is defined as a skylight.

Sub-structure costs are calculated as the sum of the Sub-structure settings on the Constructions tab and the construction costs of below-grade surfaces.

2. Building Cost Summary Data

You can access the extra building cost summary data on the Building Cost Summary dialog which is accessed from the Tools menu.