What Is Building Environmental Simulation? CFD Wind, Sunlight and Daylighting, Thermal Comfort and Energy Modeling Explained
What Is Building Environmental Simulation?
Building environmental simulation (also called building performance simulation, BPS) uses computer models to recreate a building and its site according to the laws of physics, then applies hour-by-hour weather data for the full year at that location to predict how wind, sunlight, daylight, heat and energy use will behave, so the design team can compare options and quantify results before construction. Common analyses include CFD wind, sun and shadow studies, daylighting and glare, indoor and outdoor thermal comfort, and annual energy modeling. GreenJump's "Human Factors & Cyber Sense (CyberSense)" approach turns simulation results into people-centered design evidence: the question a simulation answers is not whether a building looks good, but whether the people in it will be too hot, too exposed to the sun, dazzled by too much light or buffeted by too much wind, and how much energy it will take.
Building Environmental Simulation at a Glance
| English term | Building Performance Simulation（BPS） |
|---|---|
| Core method | Computer model + hour-by-hour weather data for the full year, used to compare design options |
| Main analyses | CFD wind and ventilation, sun and shadow, daylighting and glare, indoor and outdoor thermal comfort, annual energy modeling |
| International process standard | ASHRAE 209-2024（Building Performance Simulation Process） |
| Certification applications | LEED v5 energy and daylight credits, WELL v2 thermal comfort and daylight, design optimization for EEWH and BERS |
| Best timing | Planning and massing studies; the earlier, the cheaper |
What Types of Building Environmental Simulation Are There, and What Question Does Each Answer?
Will the massing, building spacing, podiums and arcades create corner wind acceleration, downwash or stagnant hot spots? Are plazas and entrances comfortable enough to linger in?
Are openings in the right places and large enough? Does cross-ventilation pass through the areas where people actually stay? During which hours can the air conditioning stay off?
Where do shadows fall at the winter and summer solstices? How much will neighboring buildings and rooftop PV be shaded? How deep do the sunshades need to be?
Can the windows, floor-plate depth and glazing specifications let most spaces use less electric lighting during the day? At what times will seats near windows suffer glare?
Will perimeter zones by the windows overheat in summer? Can people comfortably spend afternoons in plazas and on walkways? How much can planting, shade and wind corridors lower the perceived temperature?
Taking the envelope, shading, air conditioning and lighting controls together, how much electricity will the building use in a year? Which option is the most cost-effective? Can it meet certification thresholds?
Common Metrics and References
| Simulation type | Common metrics | Common references |
|---|---|---|
| Pedestrian wind | Wind speed exceedance probability, comfort classes (sitting, standing, walking) | Lawson criteria, NEN 8100; CFD practice follows AIJ and COST 732 guidelines |
| Daylighting | sDA (spatial daylight autonomy), ASE (annual sunlight exposure), daylight factor (DF) | IES LM-83-23、EN 17037 |
| Glare | DGP (daylight glare probability); UGR for electric lighting | EN 17037、LEED v5 |
| Indoor thermal comfort | PMV/PPD, operative temperature, mean radiant temperature (MRT) | ASHRAE 55-2023、ISO 7730:2025 |
| Outdoor thermal comfort | UTCI、PET、MRT | UTCI model of the International Society of Biometeorology |
| Energy modeling | Annual energy use, EUI (annual electricity use per square meter), peak load | ASHRAE 90.1 Appendix G (LEED), ASHRAE 140 (software validation) |
How Is Human Factors & Cyber Sense Different from Conventional Simulation?
Thermal comfort is about more than air temperature. ASHRAE 55 and ISO 7730 use PMV/PPD to assess how people feel by combining air temperature, mean radiant temperature, air speed, humidity, clothing and activity level; Taipei City's "Development Site Perceived Temperature Cooling Program" likewise defines "perceived temperature" as the combined effect of air temperature, humidity, wind speed and radiation on the human body.
Human Factors & Cyber Sense (CyberSense) is GreenJump's design philosophy for the building environment, centered on people's comfort, health and experience of a space: the same sunlight is an asset over a laundry-drying area but a burden over a rest area where people stay for long stretches in the afternoon. So we first clarify how a space will be used, then use simulation to compare strategies such as setbacks, openings, shading, planting and materials, and present the results as CyberSense 3D interactive displays that can be rotated and switched between scenarios in a web browser, so owners and architects can understand them together.
International trend : the intent of the "Occupant Experience" credit in LEED v5 is to move from "neutral spaces" toward people-centered design that occupants can adjust and choose, covering the thermal environment, daylight, glare and views.
When Is Simulation Most Cost-Effective?
During planning and schematic design, while the massing can still change. At this stage, adjusting building spacing, openings or shading costs almost nothing; discover strong winds, glare or overheating only after construction, and the only fixes are added equipment and added screening. ASHRAE 209-2024 also places the first round of simulation in the massing study stage.
| Design stage | Suitable simulations | Typical deliverables |
|---|---|---|
| Planning/massing studies | Pedestrian wind CFD, sun and shadow, solar radiation, simplified massing energy modeling | Wind comfort classification maps, winter and summer solstice shadow maps, roof solar radiation maps, option comparison tables |
| Schematic design | Annual daylighting (sDA/ASE), glare, parametric analysis of envelope and shading, outdoor thermal comfort, natural ventilation | Daylight floor plans, glare-hour maps, heat stress maps, envelope and shading recommendations |
| Detailed design | Hour-by-hour annual energy modeling, indoor thermal comfort, indoor CFD (HVAC airflow, smoke exhaust, data centers) | Energy modeling reports, PMV distribution maps, airflow and temperature sections, certification documentation |
| Construction and changes | Model updates to reflect design changes | Impact statements for changes |
| Operations | Model calibration with utility bills and metered data, scenario modeling for energy-saving improvements | Calibration reports, payback period analysis for energy-saving measures |
Do LEED, WELL and EEWH Require Simulation?
| System | Role of simulation |
|---|---|
| LEED v5 | The energy prerequisite can follow the ASHRAE 90.1 prescriptive path, so simulation is not strictly required; but to score high on "Enhanced Energy Efficiency," whole-building annual energy modeling (Appendix G, 90.1-2019 with addendum cr, or 90.1-2022) is practically the main path. Daylight credits must calculate sDA and ASE according to IES LM-83-23. |
| WELL v2 | The thermal comfort precondition can be assessed in advance with simulation and then verified by measurement or occupant surveys; daylight simulation earns optimization points. IWBI is rolling out the next version, One WELL. |
| EEWH green building label | Calculated with formulas from the ABRI manual; applicants are not required to run annual dynamic simulations. Simulation is used to optimize the design for daily energy saving, indoor environment, and outdoor shading and ventilation. |
| BERS building energy rating | Calculated with the dynamic zoning EUI formulas and equipment specifications in the ABRI manual; before submission, simulation can compare envelope, shading and air-conditioning options to find the combination that achieves Grade 1 or Grade 1+. |
Note: EEWH and BERS use the calculation methods in the manuals of the Ministry of the Interior's Architecture and Building Research Institute (ABRI), not ASHRAE 90.1 Appendix G; LEED v5 also no longer uses the old threshold of "at least 10% energy savings over the baseline." Further reading: " What Is LEED Certification?", " What Is WELL Certification?", " What Is the BERS Building Energy Rating?".
Do Taiwan's Regulations Require Wind or Energy Simulation?
Taipei City's urban design review checklist requires a wind environment impact assessment for buildings taller than 60 meters, without specifying CFD or wind tunnel testing. New Taipei City's urban design review principles address the issue through principles such as staggered massing, wind corridors and maximum widths for continuous facades.
The Ministry of the Interior's "Wind-Resistant Design Specifications for Buildings" recommend wind tunnel testing for buildings taller than 100 meters or with significant wind effects.
The "Taipei City Net-Zero Emissions Management Autonomous Ordinance" requires public and new buildings to undergo energy consumption assessments using local climate data from 2030 onward; the "Taipei City Regulations on Building Energy Consumption Control" require new buildings to achieve BERS Grade 1, and buildings legally required to obtain the EEWH green building label to achieve Grade 1+.
From July 1, 2026, all new public buildings must achieve BERS Grade 1 or Grade 1+, so energy performance targets must be secured at the design stage.
The "Standards for Installing Solar Photovoltaic Power Generation Equipment on Buildings" take effect on August 1, 2026: new projects with a building area of 1,000 m² or more must install PV, and projects claiming exemption due to insufficient sunlight must obtain a power generation simulation assessment report issued by a designated assessment body.
The statutory PV generation assessment report must be issued by a designated body; a design consultant's sunlight simulation can estimate rooftop yield and shading at the planning stage, but it is not a substitute for the statutory report.
CFD Wind Simulation or Wind Tunnel Testing: Which Should You Choose?
In early design, CFD can quickly compare multiple massing options, shows the complete three-dimensional flow field, and is inexpensive to revise. In practice, the computational domain, mesh and boundary conditions are checked against international guidelines such as AIJ and COST 732.
Measurements are taken on a scale model in a physical wind tunnel. This is the traditional method for structural wind loads and wind environment assessment of supertall buildings, and the Ministry of the Interior's wind-resistant design specifications recommend it for buildings over 100 meters.
The two are complementary. The City of London's 2019 wind microclimate guidelines require taller buildings to use both CFD and wind tunnel testing. Our practical recommendation: use CFD to screen options during planning and schematic design, then use a wind tunnel to verify the final design for supertall buildings or when the review process requires it.
How Accurate Is Simulation?
Simulation is a tool for "comparing options": relative comparisons (how much better option A is than option B) are usually more reliable than absolute values. Credibility depends on three things:
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Validated software
For example, energy modeling software is tested according to ASHRAE 140-2023, which added an empirical validation test suite in an April 2026 update.
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Modeling that follows best practice
For example, pedestrian wind studies follow AIJ or COST 732 guidelines and check the computational domain and mesh independence.
-
Reasonable input assumptions
These include local weather data, occupancy schedules and equipment efficiency. Energy modeling predicts standard usage scenarios; actual energy use is also affected by how the building is operated, and once it is in operation the model can be calibrated with utility bills.
Building Environmental Simulation FAQ
What is building environmental simulation? Is it the same as building performance simulation?
They are two names for the same thing. It uses computer models combined with hour-by-hour weather data for the full year to predict how a building and its site will perform in terms of wind, sunlight, daylight, heat and energy use, so options can be compared before construction. Internationally, ASHRAE 209-2024 calls it Building Performance Simulation (BPS).
What is Human Factors & Cyber Sense (CyberSense)?
Human Factors & Cyber Sense is GreenJump's design philosophy for the building environment, centered on people's comfort, health and experience of a space. It uses simulation to analyze the wind environment, sunlight, daylighting, thermal comfort and energy, turns the results into quantifiable design evidence, and presents them through CyberSense 3D interactive displays.
What is CFD, and what can wind simulation reveal?
CFD (computational fluid dynamics) uses numerical methods to solve the equations of airflow. Pedestrian wind simulation calculates multiple wind directions combined with long-term local wind statistics, and applies criteria such as Lawson or NEN 8100 to determine whether each location is suitable for sitting, walking, or is uncomfortable, identifying corner wind acceleration, downwash and stagnant hot spots.
When is simulation most cost-effective?
During planning and schematic design, while the massing can still be adjusted. At this stage, adjusting building spacing, openings or shading costs almost nothing; discover strong winds, glare or overheating only in detailed design or after construction, and the only fixes are added equipment or added screening.
Do LEED, WELL and EEWH require simulation?
The LEED v5 energy prerequisite can follow a prescriptive path, but to score high on the energy efficiency credit, annual energy modeling is practically the main path, and daylight credits must also be simulated according to IES LM-83-23. WELL v2 thermal comfort can be assessed in advance with simulation. EEWH and BERS are calculated with the ABRI manuals, and simulation is used for design optimization.
Do Taiwan's regulations require wind or energy simulation?
Taipei City's urban design review checklist requires a wind environment impact assessment for buildings taller than 60 meters; from 2030, new buildings in Taipei City must undergo energy consumption assessments using local climate data. Nationwide, new public buildings must achieve BERS Grade 1 or Grade 1+ from July 2026, and projects claiming exemption from rooftop PV due to insufficient sunlight must submit a power generation simulation assessment report.
What is the difference between CFD and wind tunnel testing?
CFD is suited to quickly comparing multiple massing options in early design and seeing the complete flow field; a wind tunnel takes physical measurements on a scale model and is the traditional method for supertall wind environments and structural wind loads. The two are complementary: a common approach is to screen options with CFD first, then verify the final design in a wind tunnel.
How accurate is simulation?
Simulation is best suited to comparing options, and relative differences are more reliable than absolute values. Credibility depends on whether the software has been validated (e.g., ASHRAE 140), whether the modeling follows best practice (e.g., AIJ and COST 732 guidelines), and whether inputs such as weather data and occupancy schedules are reasonable; once the building is in operation, the model can be calibrated with actual utility bills.
How long does simulation take, and how much does it cost?
It depends on the analyses required, the size of the site and building, the complexity of the model, the number of options compared and the format of the deliverables. The process includes data collection, modeling, simulation, interpretation of results and design recommendations. Clarifying the design questions to be answered first lets the work focus on the analyses that are truly useful. Fees are quoted per project.
Need Help with Building Environmental Simulation?
GreenJump's CyberSense team provides CFD wind, sunlight and daylighting, thermal comfort and energy modeling, and works with our LEED, WELL and EEWH certification teams to turn simulation results into design recommendations.
