Construction Costs

Component cost modelling provides an early design stage estimate of the initial construction costs associated with the building and HVAC system being modelled. The construction costs input to the EnergyPlus costing calculations are derived from the cost outputs on the Cost and Carbon tab. Initially, the idea of EnergyPlus construction costs is to ensure that cost estimates are consistent with the EnergyPlus model and allow using results calculated during a simulation such as equipment sizes and surface areas.

The DesignBuilder EnergyPlus cost estimating capabilities are intended for early stage estimation and do not cover all the types of analyses included in more detailed cost estimating software.

The usual reason for including component costs in an EnergyPlus simulation will to as part of a larger investment analysis such as life-cycle costing.

Note: The term "component cost" is used almost synonymously with "construction cost" in the DesignBuilder documentation. The "component cost" terminology comes from the EnergyPlus ComponentCost:LineItem, ComponentCost:Adjustments and ComponentCost:Reference data used to include construction costs in the simulation.

To understand how to include cost estimates in EnergyPlus inputs, it may be helpful to first define some terminology and provide an overview of the process used in EnergyPlus. There are three broad steps involved in the EnergyPlus component cost calculations.

1. Construction costs calculated by summing individual “line items".
2. Project costs calculated by adjusting construction costs to account for other factors such as profit or design fees.
3. Finally the current simulation results are compared with equivalent results for a reference case so that marginal alterations can be calculated.

Each of above steps involves using one of the three Component cost data sets described below. These 3 steps are organized by corresponding tabs on the Construction costs dialog:

• Line Item
• Adjustments
• Reference

The results can be included in the Construction Cost Estimate Summary table by checking the Component Cost Economics Summary output option under the Summary Annual Reports header.

Example

The construction cost calculation example below shows the Component Cost Economics Summary output and how this is used as the basis for a comparison with a reference case with adjustment factors applied.

Corresponding Adjustment and Reference Inputs: