Potential Energy Savings (PES) Chart

Detail information on Potential Energy Savings Chart.

For design teams working to reduce a building's energy use, the Potential Energy Savings chart is a tool to focus their limited time on only the features of a building's design, construction, and systems that can save the most energy. (This chart is currently in beta).

The data in the chart comes from 37 separate energy simulation runs that are run simultaneously in the cloud. Each simulation varies a combination of 9 building features, including things like roof and wall insulation, glazing properties, lighting controls, and infiltration. These simulations are meant to test extreme values seen in new and existing buildings and help design teams get a high level understanding of how sensitive the building's energy performance is to each parameter (See Potential Energy Savings Chart Validation for details on validation study).

How to read the chart

1. Building Features Analyzed. Each bar in the chart represents a building feature that is being analyzed to determine how important it is to the building's energy performance. A range of design options are tested for each building feature.

2. Current model baseline. The center vertical line at 0 represents the energy performance of your building model, as submitted to GBS.

3. Savings/Losses potential. Features with the highest potential to save energy are at the top of the list. The size of the bar to the right of the centerline is the potential savings percentage, based on the current model. The size of the bar to the left of the centerline is the potential losses percentage.

4. Sensitivity. The overall size of the bar is how sensitive the energy analyses are to this building feature. If this bar is large, changing this feature can have big impacts to energy use. The size of the bar is also driven by how much the value of this feature is varied within the alternative runs. The runs are chosen to represent extremes.

How to Use the Potential Energy Savings chart

Energy analysis is most valuable when used early and often enough in a project to take advantage of opportunities to make choices that will reduce a building’s energy use. Architecture and engineering teams need to work together to scope and prioritize energy efficiency measures. This chart is meant to make that process easier and can be generated easily from any Revit model (or other gbXML authoring tool).

The chart is designed to enable these easy takeaways:

• Large bars are important building features affecting energy use (more sensitive). Smaller bars are less important to energy use (less sensitive).

• Bars that extend further to the right of the baseline have higher potential for energy savings and bars that extend further to the left have higher potential for energy losses.

Use this data to help focus your design team on the building features that have the biggest impact on energy performance.

• Focus on the largest opportunities to improve on the baseline by investigating the features at the top of the list that have large bars on the right of the vertical line. Remember that there may be aspects of the design that are important to your building's energy use that are not simulated and represented on the chart.

• Take care to avoid reducing energy performance by making sure you don't backslide on building features that have large bars on the left of the vertical line.

• Know where you can be flexible. Building features where modifications will have little effect on energy performance have small bars on both the left and right side of the vertical line.

• For an existing building, the chart results can help prioritize your time during the building audit. Building features that have a big impact should get more of your attention during an audit and subsequent efficiency studies.

Example of Interpreting the Potential Energy Savings chart

The chart below was generated from this Revit model of an office building and simulated near Shanghai. The bottom of the U-shape is facing south.

Takeaways from this chart:

• The most sensitive building features for energy use are the Window Glass, Plug Loads, and Infiltration. Given the alternatives tested, these three features each have the potential to impact energy use by about 35%. Other parameters that are important, with about a 10-15% potential impact to energy use, are Roof Insulation, Lighting Efficiency, and Wall Insulation.

• The most room for energy improvement is changing the window glass, based on the current building model (~ 20% improvement). The current building model has clear double pane glazing with a U-value (SI) of 3.16 (0.56 English), SHGC of 0.69, and VLT of 0.78.

• More efficient lights are the next biggest area for improvement over the baseline, and can improve energy performance by about 8%.

• Because changes in infiltration and plug loads make a big difference to energy use, and because these values can vary widely in reality, work to check the assumptions in your model. If the building is sealed poorly, infiltration could cause over 30% worse energy performance than the model submitted.

• The roof and wall insulation specified are relatively good. There is only a small energy savings potential here, but it’s important to avoid backsliding.

• You can expect about a 3% improvement in overall energy efficiency from Daylight Controls. You can see this impact in the “Daylight Controls – DC” alternative, and also in the window glass and skylight glass alternatives that include daylight controls (DC). Daylight controls are bundled with skylight and window glass to determine if you get more benefit from daylight controls if you use different glass.

Accessing the Potential Energy Savings Chart in Revit, Vasari, and GBS

The Potential Energy Savings chart is created automatically whenever you initiate an analysis run in Autodesk Revit, Vasari or Green Building Studio. Follow instructions for submitting runs here:

• Energy Analysis for Autodesk Revit

• Energy Analysis for Vasari

• Sending Your Model to Green Building Studio Outside of Revit.

The Potential Energy Savings chart is available through the Revit and Vasari Results and Compare windows, as well as the Green Building Studio web interface.

1. Alternative Runs for Each Model Submitted. Each time a model is sent to Green Building Studio, the 37 additional alternative runs are created and nested under that base run.

2. Run Status. If any runs fail, the Potential Energy Savings chart will not generate. You can either resubmit the base run or remove all the runs of the same parameter of the failed run to view the PES with the successful parameters.

3. If you navigate away from the page and return, or access this page after a Revit-initiated run has finished, these status bars will be replaced by the EUI and energy cost data for each run.

4. Potential Energy Savings Chart Icon. When the alternate runs are complete, the Potential Energy Savings icon will appear in the far right column of the Run List table within GBS.

5. Simulation Run List. If there are multiple baseline simulations within a project, they and their alternative runs will likely be displayed on different pages by default. To see the other run sets, choose to show more runs per page. Click "-" next to the Alternate Runs label to collapse the list.