Decision-Making with Sefaira RTA

The Master Class Series is a bi-weekly interactive webinar session discussing topics related to performance-based design with Sefaira. The following post recaps our first two sessions; and summaries of the third and fourth sessions, Building Science 101 and Sefaira + LEED, are available on our blog.

We dedicated our first two Master Classes to decision-making using Sefaira’s Real Time Analysis plug-in for SketchUp and Revit. During the sessions, we reviewed the basic inputs and outputs of the plug-in, and worked through analyses in real time. Current customers can view a recording of each of these sessions by logging into the Knowledge Base and following this link: Master Class Series.

Achieving Performance Step by Step

Every design decision you make has some effect on the building’s performance. Given that you will make thousands of decisions before project completion, it is critical that you understand the impact of each. Previously, you may have relied on experience or rules of thumb to estimate or guess at an impact. With Sefaira, now you can analyze design decisions rather than make assumptions, and quantify impacts quickly. This approach, guided by the following steps, enables you to build your building’s performance incrementally:

    1. Start with a specific question: You are essentially running small experiments as you design. “What will happen if…” and “Is my expectation correct…” etc. If you start with a specific question, the analysis is more manageable, than if you tried to deliver high-performance all at once.
    2. Be an efficient modeler. You don’t have to model everything to answer a specific question. Often, building a quick study model off to the side–of a representative floor, or a typical condition, for example–is a fast and easy way to inform the refinement of your design.
    3. Work to gain insight, not to replicate the final built condition. Use analysis to compare options and refine your overall strategy rather than to assess final performance.

Real Time Analysis Plug-in

If you’ve used Sefaira’s Real Time Analysis tool, you are likely familiar with the basic inputs and outputs associated with its performance analysis. If, however, you’re new to Sefaira or maybe just want a refresher, here is a brief summary of what you’ll see from the plug-in.

Basic Inputs

There are four main inputs you’ll need to provide Sefaira in order to analyze performance:

  1. Modeled Geometry – Your SketchUp or Revit model. It provides a basis for the calculation engine to calculate area and volume.
  2. Occupancy Type – The building’s function (an office, a residence, etc.), which provides typical use schedules which inform energy use.
  3. Location – The building’s address. It enables Sefaira to gather the appropriate weather file which in turn informs daylighting and energy use.
  4. Building Properties – The specific elements of your building (e.g. insulation values, glazing performance, appliance efficiencies, etc.). You can adjust each property manually, or select pre-populated values based on common baselines, like ASHRAE and Part L.

Basic Outputs

There are four main outputs that provide the data you need to assess your building’s performance. The fifth item describes how this data is generated:

  1. Energy Use (EUI) – EUI values help compare against values for similar use types. Sefaira compares against the EUI benchmarks set by the 2030 challenge (US median of building type of CBECS and 60% reduction)
  2. Energy Segments – Shows you where you are using the most energy. This provides insight into design: For example, you might be able to reduce a high cooling load by limiting solar gain.
  3. Glare – “Glare” is defined as 1000 lux for 250 or more occupied hours, per the LEEDv4 Annual Sunlight Exposure metric. Sefaira expresses Glare as a percentage of your building’s floor area.
  4. Well Lit “Well lit” refers to adequate daylighting, measured at the height of a desk. “Adequate daylighting” is 300 lux for at least 50% of the annual occupied hours per the LEEDv4 Spatial Daylight Autonomy metric. Sefaira expresses Well Lit areas the percent of your floor area.
  5. Under the hood – The Real Time Analysis Plug-in calculates energy use using Sefaira’s Fulcrum engine which is based on ASHRAE’s radiant time series method of calculation. Daylighting is calculated with Radiance (providing backwards ray-tracing), and DAYSIM (layering climate data onto the analysis).

SketchUp & Revit

The preceding inputs and outputs are the same for both the SketchUp and Revit environment. However, because each modeling platform is unique, there are some operational specifics to be aware of.

Entity Information

You may have noticed that the “Basic Inputs” did not include specifying the general entity types of your model (e.g. wall, floor, roof, window, etc.). That’s not listed, because Sefaira does it for you! Through the course of your analyses, however, you may very well wish to verify that Sefaira has interpreted the model as you intended.

In SketchUp, you can accomplish this by clicking “Show Entity Types.” Doing so will paint the surfaces of your model with an indication of what Sefaira is analyzing:

Hide Entity Types Sefaira

In Revit, you can verify Sefaira’s interpretation by clicking “Generate Sefaira Views” and examining views of the whole building as well as specific entity types:

Sefaira Views Revit

Ignore from Analysis & Tag as Shading

Given Sefaira’s interpretation of your model, you may want to adjust or override it. For example, you may have contextual buildings that shade your building, but should not be analyzed for energy use themselves. Or, perhaps there are entourage elements–like a trash enclosure, or scale figures–that have no impact on performance and should simply be ignored. You can accomplish both adjustments as follows.

In SketchUp, to ignore elements, simply select them, and set their entity type to “Ignore”

Entity Type Ignore
In Revit, select the elements, and toggle the “Ignore for Sefaira” radio button in the properties section:

Revit Ignore for Sefaira


To conclude each session, we asked attendees to provide questions that we could analyze in real time. Here are a few of the items we addressed:


  • Comparing massing options for a campus of buildings within the same model.
  • Preparing daylighting analysis to consider interior partitions and skylights.
  • Examining the impact of a brise-soleil on energy performance.


  • Comparing design options within Revit.
  • Analyzing daylighting with respect to various plan layouts.
  • Interpreting heating and cooling gains and losses to inform adjustments to the building envelope properties.


After reviewing the plug-in’s interface, the basic inputs and outputs associated with analysis, and the nature of questions to ask, we reiterated the overarching concept of decision-making with Sefaira for SketchUp and Revit: Build your building’s performance with a series of small decisions. Start with a specific question, be an efficient modeler, and work to gain insight, not to replicate the final built condition. This incremental approach ensures progress towards your ultimate goal of optimizing the building’s performance.