Trial / Demo
Geometry is one of the foundations of any building performance simulation. It defines how heat moves through a space, how sunlight enters a building, and how HVAC loads are calculated. If the geometry isn’t modeled correctly, every calculation that follows — energy use, daylighting, thermal comfort — will be flawed.
Despite this, geometry is often not modeled correctly. Many engineers and architects focus on defining HVAC system performance, defining envelope performance, daylight levels & lighting design, and extracting loads & energy results without ensuring that the physical form of the building is modeled correctly. This can lead to misleading results and, in some cases, costly design decisions based on inaccurate data.
Every energy model is only as good as its inputs, and geometry is one of the most critical. Wall areas, window-to-wall ratios, shading devices, and adjacent buildings all influence how much heat is gained or lost from the design building. An incorrect floor area, for example, could mean drastically over- or underestimating energy use intensity (EUI), leading to incorrect evaluation of performance and overly-optimistic metrics.
A building’s orientation and shading elements can have a huge impact on cooling loads. Overhangs, adjacent structures, and even PV panels can cast shadows that alter solar heat gain. If these aren’t modeled accurately, cooling loads might be overestimated (leading to oversized HVAC equipment) or underestimated (causing comfort issues and higher operational costs). It is important to use a tool that has the capability to capture nuanced geometry characteristics that affect results.
Thermal zoning determines how spaces are grouped together for heating and cooling calculations. If zones are not defined properly, a simulation might assume uniform conditions where they don’t exist, leading to incorrect HVAC system sizing. For example, perimeter zones with large glazing areas experience significantly different loads than core zones, and treating them the same can lead to inefficient system design. The Virtual Environment is equipped with effective thermal zoning tools to enable the model to accurately align with the HVAC thermal zoning strategy and design.
Many building codes and energy standards, including ASHRAE 90.1 and NECB, rely on performance-based modeling. If the geometry doesn’t accurately reflect the real-world building, compliance results may not be accepted. Worse, a project could fail to meet energy targets due to incorrect assumptions about building massing and envelope characteristics. The Virtual Environment is equipped with automated reporting for loads & compliance (among others). This makes it very easy to gather the relevant metrics to quickly and correctly evaluate the current modeled performance.
Start with a Clear Reference – Whether working from architectural drawings, BIM models, or imported data, ensure that the base geometry aligns with the project’s actual design.
Check for Errors Early – Run a visual inspection of the model before simulations begin. Look for incorrect room heights, or zoning issues.
Consider the Surroundings – Nearby buildings, topography, and shading elements can all impact performance. If the site context isn’t included, the results won’t fully capture real-world conditions.
Use the Right Import Methods – If bringing in BIM or CAD files, understand the limitations of different file formats (e.g., gbXML vs. DXF) and clean up unnecessary details before importing.
Validate Against Renderings – Compare the model geometry against any additional references such as renderings/images.
TIP: The Virtual Environment comes with an Open Street Map link (type OSM in command line). Set your project location and import the surrounding buildings and topography automatically.
No matter how sophisticated an energy model is, bad geometry leads to bad results. Taking the time to get it right ensures that simulations provide useful insights, leading to better design decisions, optimized building performance, and successful project outcomes.
For more information how IESVE software can lead to improved model geometry, have a look at our training options or reach out to chris.flood@iesve.com.
