FAQ
Commonly asked questions about xStar. Look here first!
General
What is xStar?
xStar is an easy-to-use software that provides real-time estimates of cost, energy use (in development), and carbon emissions (in development) of buildings. It integrates directly with existing architectural design software (i.e. Autodesk® Revit®) as a plugin.
How can I use xStar?
xStar is both a design and sales tool. It provides real-time feedback on a design’s building performance and allows you to easily compare and swap construction assemblies. This helps you answer questions in client meetings or at the design desk like:
Where can we reduce cost/energy/carbon in our design?
How does my building compare to code minimum construction?
What are the benefits of using an alternate wall/roof/floor construction?
How much insulation should I use?
What happens if the cost of lumber increases next year?
and more…
Does xStar work for residential and commercial buildings?
Right now, xStar’s analysis is tuned for residential buildings only. However, users can add their own commercial construction assemblies and data.
What are xStar’s data sources?
See References.
What design software does xStar support?
xStar currently integrates with Autodesk® Revit® 2024, 2025, and 2026.
How do I get access to xStar?
Please email Rick Fenrich at rick@xstarresearch.com.
How do I report issues?
Please email Rick Fenrich at rick@xstarresearch.com with a description of the issue. No issue is too small, whether it is a bug or annoyance. Our software is still in development and we look forward to serving you to make it better!
Editing the Model
When I change the location at the top of the View Assembly dialog or Assembly Library window, what happens?
If a user changes the location displayed in the View Assembly dialog or the Assembly Library, the displayed costs will adjust for the chosen location. This does not adjust the cost multipliers for the design; it only affects the view. To change the location of the design and update the cost multipliers used to calculate results, open the View Design dialog and edit the Address or Latitude & Longitude properties there.
Does my xStar model update when I change my Revit model?
When xStar is initialized, it parses the Revit model and creates an xStar model. However, after that point, the two programs are not actively sharing data back and forth. This means that any edits made in the Revit file after you first open xStar will not be reflected in your xStar designs. If you need to edit the Revit file to include missing elements or adjust geometry, you will need to close and reopen the xStar plugin in order for those changes to be added to the xStar design.
Does my Revit project update when I update my xStar model?
See above for vice versa. Edits made in the xStar file are not reflected in the Revit file and will not update the Revit file at any time, even if you close xStar & reopen.
When I tried to make an alternative design, I copied my original design, then edited an assembly within the new design but the results for my original design changed too. Why did this happen and how do I fix it?
Assemblies in xStar are items in a database and can be assigned to line items in multiple designs simultaneously. When users copy a design, xStar duplicates the design’s line items and their definitions, placing them under a new name. However, the line items reference the same assembly present in the Assembly Library’s database. Therefore, edits directly to an assembly will adjust the original design and any other designs that use this assembly. If the user wants to edit an assembly without affecting other designs where the assembly is used, they need to copy that assembly before editing. Then, within the design they wish to edit, they need to replace the original assembly with the copied and edited assembly.
Cost Analysis
Are overages automatically included in all assembly costing?
No, overages are not automatically included in costs for custom assemblies. Users must manually add an overage percentage to each component they want to include an overage. Prebuilt assemblies typically do include overages.
Energy Analysis
Why does a hand calculated UA not match the Total UA chart?
In xStar, when calculating U-factors for a surface defined with an R-value, air film R-values are added to the surface assembly definition. This means that the U-factor used to calculate the UA values in the Total UA Graph will be slightly different than simply converting the effective R-value a user sees for the corresponding assembly. If a user wants to hand calculate UA values for a line item, they should visit How xStar Calculates UA for more details on air films and calculation method.
Why is the UA metric different from a hand calculated total of UA displayed in the graph?
The UA metric does not include the floor UA displayed in the Total UA graph. Please visit How xStar Calculates UA for more details.
Does xStar’s energy modeling consider the efficiency of HVAC equipment?
Not yet. It is an ideal loads heating and cooling load analysis. The actual energy use of the building will be higher than the metrics displayed in the heating & cooling load data due to the need to supply energy for internal gains (e.g. equipment & appliances) and reduced efficiencies of realistic HVAC systems, etc. See Heating & Cooling Load Analysis for more details.
Comparing Designs
Can I look at xStar designs from two different projects at the same time?
Yes, to view designs from two different xStar projects, use the Import function. Start by opening one of the designs you want to view, then use the Import function found in the File Menu to import designs from the second project. This can be repeated with multiple projects if needed.