How can multi-parameter filtering in Grasshopper reveal microclimate risks using the infrared.city connector?

This blogpost shows a fast, reproducible workflow to intersect thermal comfort and wind speed maps, highlight comfort-critical microzones, and support evidence-based design choices — directly inside Grasshopper using the infrared.city connector

You can download the ready-to-use Grasshopper file filling the form and start exploring alongside the blogpost.

• Starting a project: If you’re unfamiliar with the basics, check out the Running Your First Simulation Guide which walks through the setup and launch of environmental simulations step by step.

• Using the Grasshopper plugin: To get comfortable with the connector workflow, see Getting started with Connectors: infrared.city in Grasshopper where the process of linking simulations directly in Grasshopper is introduced.

What you will get

• An interactive thresholding setup to filter thermal comfort index together with wind fields
• A binary mask of “heat-trapped zones” or “cold-wind-exposed zones” that updates live as you slide thresholds
• Quick area statistics to quantify how much of the site falls into user-defined risk bands
• Export-ready visuals and a repeatable method you can adapt to different climates

Step-by-step workflow

1) Log in and list your projects

Open the tools panel and click Login. Hit Refresh to pull your Active Projects List so Grasshopper can sync with your infrared.city workspace. This binds the session to your account and retrieves your existing projects and configured analyses.

2) Load the target project

Use the Projects dropdown to pick the project you want to analyze, then pass it into Load Project. This brings project metadata and current analysis settings into the canvas so you can run, update, and fetch results without leaving Grasshopper.

3-4) Connect your building geometry

After loading a project, the connector automatically places two new components in your Grasshopper canvas:

• Buildings – includes the editable geometries currently saved in your project
• Analyses – lists the analysis configurations already set up in infrared.city

Because Grasshopper works through an explicit dependency chain, these components are separate from the Load Project block. This ensures you can adjust or replace elements without creating conflicts.

Plug the Buildings output into the Mesh input of the cluster to generate multiple instances of your geometries.

5) Update the project with the analyses you need

Feed the project and geometries into Update Project and ensure two analyses are present:

• Thermal Comfort Index
• Wind Speed

You can add or configure these analyses directly in the infrared.city web app before syncing the project, or within Grasshopper using the dedicated analysis components for greater flexibility.

If you want to include a new geometry, such as your own design, you can merge it with the existing context. To do this, first triangulate the geometry and connect it to the Geometry input of the Update Project component. This ensures the model updates correctly and the new design is included in all subsequent simulations.

6) Run the simulations

Trigger Simulate to compute or refresh results. The connector automatically sends the simulation request to your infrared.city workspace and syncs the results back into Grasshopper once they’re complete. If you already ran them, this step will simply refetch the latest versions

7) Wire the results into the filtering blocks

Connect the outputs of the simulate component to the to the two “Results” components — one for thermal comfort index, one for wind. Each result carries the raster grid, metadata, color map, and KPI fields.

8) Set your thresholds and filter

Use the two sliders to define what risk means for your context

The workflow creates a Boolean field for each condition and then intersects them to isolate heat-trapped zones — hot and under-ventilated at once. Reverse or swap comparisons to find cold-wind-exposed areas for winter comfort studies

9) Read the numbers and visualize

The definition reports quick area shares for each mask and builds a clean red overlay for the intersected risk zones. Sliding the thresholds updates both the overlay and the percentages instantly. Use this for sensitivity checks and to align assumptions with project stakeholders.

Example threshold sets to try

• Very hot-humid day → UTCI > 38 °C and Wind < 1.5 m/s to expose dangerous stagnant zones
• Transitional season→ UTCI > 26 °C and Wind < 2.5 m/s to identify moderate heat traps
• Winter discomfort → UTCI < 0 °C and Wind > 5 m/s to find windy corners and canyon effects

Why this helps

• Sensitivity made explicit — small threshold changes can swing the “risk” area. Seeing it live supports transparent decision-making.
• Context-aware — swap thresholds to reflect local comfort policies or seasonality. For tropical sites, emphasize heat-plus-stagnation. For temperate winters, emphasize wind-chill exceedances.
• Design-ready — the mask guides where to place shade, trees, canopies, wind corridors, porosity, or material changes to break up problematic zones fast.

Tips for robust results

• For reporting, store several snapshots at key threshold pairs to document the sensitivity range
• Pair with scenario variants to compare how a design move reduces the flagged area

What’s next

• Explore different analyses individually — for example, switch the filtering inputs to visualize Thermal Comfort Statistics, Pedestrian Wind Comfort, or Solar Radiation results separately
• Combine insights from multiple simulations to prioritize mitigation actions, such as identifying where shading, vegetation, or ventilation corridors would have the highest impact
• Convert area masks into design targets — e.g., reduce heat-trapped coverage from 40% to 20% by adding trees and permeable passages