Today’s session focuses on performing building load calculations in accordance with ASHRAE Standard 183 using OpenStudio. This workflow assumes that OpenStudio has already been installed, along with the associated SketchUp interface, which typically installs automatically and does not require a separate setup. The process begins by creating a new OpenStudio Model (OSM) using the wizard. The OSM file is the native file format for OpenStudio models. For this example, an office building template is selected using the ASHRAE 90.1–2010 construction set, which ensures that envelope components such as walls, windows, doors, and roofs comply with ASHRAE 2010 requirements. The model is configured for Climate Zone 2A, with space types, construction sets, and building defaults applied. After creating the model, initial preferences are configured to improve model stability and usability. The auto-save interval is set, commonly to 15 minutes, to minimize data loss in case of software crashes during complex modeling. The unit system is then set to IP (inch-pound) for projects using U.S. customary units. Next, the project Geo-Location is added through the Model Info window; in this example, the location is set to Madera, Washington, United States, allowing the model to reference appropriate climate data. The OpenGL setting for maximum texture size is also enabled to improve the visibility of imported images such as floor plans, with the understanding that system performance may vary depending on hardware capability. The workflow then addresses space type requirements beyond the base office template. While the office construction set covers most spaces, a laboratory space is required for this project. To accommodate this, the Space Type and Construction Set Wizard is used to import additional space types from a hospital template, which includes laboratory definitions. Only space types are imported during this step; no construction sets are added, and building defaults are not changed. This approach preserves the original office construction set for envelope elements while allowing specialized internal space classifications. Geometric modeling begins in SketchUp by establishing accurate scale. A scaling line is drawn using a known real-world dimension of 58 feet 8 inches. The project floor plan image is then imported, placed at the origin, and scaled to match the scaling line. At this stage, it is essential to save the model using the OpenStudio Save button rather than the standard SketchUp save command, as only the OpenStudio save updates the OSM file correctly. The floor plan is then traced using SketchUp drawing tools, with frequent use of hide and unhide functions to prevent the image from obscuring newly drawn geometry. As tracing continues, reference points and aligned edges are used to ensure accurate room boundaries and proper connectivity between spaces. When drawing errors occur, surfaces and edges are corrected by selecting and deleting the geometry and redrawing it as needed. This process continues until all spaces, including office areas, laboratory rooms, and storage or garage areas, are fully defined in two-dimensional space. Once tracing is complete, the floor plan image is hidden, all line elements are selected, and the “Create Spaces from Diagram” function is used to convert the traced geometry into OpenStudio spaces, completing the initial geometric setup for load calculations and further energy modeling. After tracing the floor plan, the “Create Spaces from Diagram” button is used to generate the building geometry. At this stage, OpenStudio prompts for basic parameters such as floor height and number of floors. In this example, a nine-foot ceiling height and a single floor are selected, after which the software automatically creates the building spaces. Once the spaces are generated, each space can be edited individually by double-clicking into it. This allows the user to modify heights, add plenums, and insert architectural elements such as windows and doors. It is critical to double-click the target space before adding windows or doors; otherwise, these elements will not associate with the space and will remain unattached in the model. Windows and doors are added using SketchUp drawing tools, with specific conventions that OpenStudio recognizes. Windows are drawn detached from edges, while doors must start from the bottom edge of a wall so OpenStudio correctly identifies them as doors. Approximate dimensions are generally sufficient for load calculations, as minor dimensional differences have minimal impact on results. Repetitive elements such as windows can be efficiently duplicated using copy and paste, ensuring the entire component—including edges and surfaces—is selected. This process continues until all required windows, doors, and garage doors are placed throughout the model. Once openings are complete, space geometry must be refined to support accurate heat transfer calculations. A roof is added by creating a new space, which serves as an attic. This attic space is drawn by tracing the footprint of the building and then extruding it vertically to form the roof geometry. Alignment tools and axis snapping are used to maintain symmetry. Because roof geometry can be difficult to select when overlapping other spaces, temporarily hiding other elements can help during editing. After the roof geometry is finalized, the model is prepared for surface interaction calculations. The next critical step is intersecting and matching space geometry. First, the “Intersect Space Geometry” function is applied to the entire model. This operation projects wall boundaries from lower spaces onto adjacent surfaces, such as attic floors or ceilings, ensuring OpenStudio can distinguish between interior and exterior heat transfer surfaces. Following this, the “Surface Matching” tool is used to match the entire model. Before matching, boundary conditions can be reviewed using “Render by Boundary Condition,” which color-codes surfaces to show whether they are exterior, interior, sun-exposed, or wind-exposed. After surface matching, interior ceilings, floors, and walls are correctly identified, enabling accurate thermal calculations. With geometry finalized, space attributes are assigned using the “Set Attributes for Selected Spaces” tool. Each space is named according to the floor plan and assigned an appropriate space type, such as office, laboratory, corridor, restroom, garage, or attic storage. Construction sets and building stories remain unchanged at this stage. Once space assignments are verified in the OpenStudio Inspector, thermal zones are added using the “Add New Thermal Zone for Spaces with No Thermal Zone” script. Thermal zones are then renamed automatically based on space names, making them easier to identify. Finally, spaces can be grouped and combined into shared thermal zones as needed using the same attributes dialog, allowing multiple spaces—such as offices and adjacent corridors—to be served by a single thermal zone. After combining the hallway and office into a single thermal zone, the original hallway thermal zone becomes unused and is removed to keep the model clean. At this stage, unused thermal zones are deleted, and window shading options are addressed. OpenStudio provides a script to add overhangs by projection factor, which can be applied by first selecting the windows and then running the script through the User Scripts menu. Although default overhangs can be added quickly, this example instead demonstrates custom shading by creating a new shading surface group. A simple perimeter overhang is modeled around the building footprint, offset by two feet, to represent an overhanging roof. The model is saved as a new version to preserve progress before continuing. Next, the model is rotated to align with true north so that solar exposure is calculated correctly. The geo-location may need to be cleared and reinserted to restore orientation references. Using the rotate tool, the entire model is rotated by 60 degrees based on site conditions. Once aligned, additional shading objects such as adjacent buildings or trees can be created using new shading surface groups. These surrounding objects are important for capturing morning and afternoon solar shading effects. To visualize shading behavior, the Shadows tool is used, allowing inspection of shadow patterns by date and time. Unnecessary shading surfaces can be deleted to reduce EnergyPlus calculation time. With geometry and shading complete, the model is cleaned up by purging unused objects through the OpenStudio Inspector. This removes unused space types, schedules, and templates imported earlier, such as unused hospital schedules. The building is then named and saved as a new version. At this point, the SketchUp portion of modeling is complete, and the workflow transitions into the OpenStudio application using the Launch OpenStudio button. Inside OpenStudio, unit preferences are confirmed (IP or SI as required), and the appropriate weather (.epw) and design day (.ddy) files are selected. Design day files are particularly important for load calculations, as they determine peak heating and cooling conditions. Schedules are then configured, beginning with a simple on/off exhaust fan schedule. This schedule is assigned to the restroom exhaust fan within the Thermal Zones tab. Thermostat schedules are added next by applying standardized heating and cooling setpoint schedules—such as small office schedules—to all thermal zones. Cooling and heating sizing parameters are reviewed, with supply air temperatures adjusted (e.g., 55°F for cooling and 90°F for heating) and air distribution effectiveness set according to ASHRAE ventilation guidance. These parameters are applied consistently across zones, and the model is saved before simulation. Finally, reporting measures are added from the Building Component Library (BCL), including the OpenStudio Results measure. The simulation is run, and results are reviewed through the generated HTML reports. Ideal Air Loads are enabled to calculate worst-case peak loads for each zone, providing conservative sizing values. For whole-building equipment sizing, zone equipment such as PTACs can be added instead, and simulations rerun to generate equipment selection outputs. Results can be exported as PDF or HTML, and EnergyPlus reports may also be reviewed for more detailed diagnostics. If IP-unit EnergyPlus output is required, the “Set Output Table to IP Units” reporting measure is applied and the simulation rerun. This concludes the workflow for performing load calculations using SketchUp and OpenStudio.