Construction Costs

Component cost modelling provides an early design stage estimate of the initial construction capital costs associated with the building and services being modelled. The construction costs input to the EnergyPlus costing calculations are derived from the cost outputs from the Carbon tab of 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 help 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 are calculated by summing individual “line items" through calculations carried out on the Cost and Carbon screen.
2. Project costs are 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. The process is as follows:

1. Ensure that the Detailed HVAC model option is selected which enables the Economics model data tab at building level.
2. Run a Cost calculation on the Cost and Carbon tab.
3. Return to the Edit screen, navigate to the Economics tab and switch on the Include construction costs in simulation inputs checkbox to reveal the Construction cost component selection. The default construction cost option is called "Component cost".
4. Make a copy of the default "Component cost" Construction cost data and select it. It will be called "Copy of Component cost" by default. Working with your own component will allow you to make edits if necessary.
5. Edit the new selected "Copy of Component cost" construction cost component. On the first tab you will find the latest costs calculated on the Cost and Carbon tab, summed for each high level category.
6. Make any changes required on the Adjustments and Reference tabs and press OK to save the costs.
7. Go the Simulation screen and run a simulation.
8. After the simulation is complete, click on the Summary tab, click on the "Table of Contents" link and then on the "Component Cost Economics Summary" link to view the component construction costs.

Corresponding Adjustment and Reference Inputs: