Glossary

Glossary of common terms used in the xStar software and user guide.

Assembly: Part of a building, inclusive of all materials, labor, and equipment for its construction and installation, that serves a general high-level function, e.g. wall, roof, floor, HVAC system.
Note: An assembly’s properties are normalized by quantity, e.g. $/SF, kgCO2e/SF, and dimension quantities are not used for calculating cost.
Note: Most assemblies are composed of other components, e.g. a wall is composed of a structural element, insulation element, water-resistive barrier element, etc.

Assembly Library: The database containing prebuilt and custom assemblies and components. Custom assemblies & components are automatically saved to a user's assembly library once they are created and any changes to that item will be saved automatically.
Note: Users can remove items from the assembly library when they exit the software or by deleting individual items.

Category (for assembly): A category is in general a grouping of similar objects. As it pertains to assemblies, a category is a group of assemblies that share similar function and shape.
Note: Categories in xStar correspond generally to categories in Revit, e.g. wall, roof, floor, stairs, foundation, furniture, etc.

Component: Part of an assembly.
Note: In general a component must be combined with another component to serve a building.
Example: A sink fixture is a component that requires another component rough-in plumbing that together make a sink assembly.

Design (in xStar): A complete description of a building including its location, orientation, geometry, construction assemblies, and more.
Note: Given a design, everything is known about a building and it can be constructed.

Line Item: Something that impacts the cost and/or carbon of a building’s construction or operation.
Note: A line item can be a physical object (e.g. wall) of a specified size, or a task (e.g. sitework).
Note: Every line item is associated with an assembly. The quantity of the line item multiplied by the cost/carbon of the assembly yields the total cost/carbon of the line item.

Project (in xStar): An xStar session (either currently open in the software, or saved to a computer file) that contains 1 or more designs and/or user-defined assemblies.
Note: One project could contain multiple designs for different buildings.

R-Value (Effective): Total thermal resistance of an entire building assembly including all assembly components.

R-Value (Insulation): Total thermal resistance of only insulation components within an assembly, ignoring thermal bridging effects.

Sitework: Labor and equipment required to prepare a site for a building’s construction.
Note: This is separate from an assembly because sitework is not “part of a building.”

Thermal Envelope: The modeled physical elements that separate the conditioned and unconditioned areas of your building. Typically include exterior walls, windows, exterior doors, floor system, and roof or ceiling system. Users define the thermal envelope of designs using their Revit model and the Thermal Envelope dialog.
Note: The thermal envelope definition is used to calculate the conditioned area and volume which can be viewed in a Design View Card.