ThermaSim — Insulation & Transient Thermal Simulator

Simulate room and pipe temperatures with editable insulation, heat input, ambient conditions, timelines, material comparisons and JSON/CSV exports.

What this tool does

ThermaSim is a browser-based preliminary thermal simulator for spaces, houses, workshops, pipes, ducts and cylinders. It uses a lumped-capacitance model to show how entered geometry, insulation, ambient conditions, heat input and thermal mass affect temperature over time.

When to use this tool

Use ThermaSim when you need an early insulation, room warm-up, pipe heat-loss or heat-trace comparison before verifying material data, safety requirements and final design conditions.

Who this is for

• Building and mechanical designers comparing early insulation and heat-input scenarios
• Energy, HVAC and process students learning transient heat-transfer concepts
• Homeowners, facility teams and maintenance planners exploring room or freeze-protection assumptions before professional review

How to use this tool

1. Choose a starting template such as a single room, bungalow, workshop, hot-water pipe, freeze-protection pipe, chilled-water pipe, process pipe or heated-air duct.
2. Select the space or piping mode and adjust geometry, floors, window area, air changes, pipe dimensions, insulation thickness, material and thermal properties.
3. Set starting, target and ambient temperatures, HVAC or trace mode, heat-input power, internal gains, humidity, emissivity and thermostat hysteresis as applicable.
4. Click Start simulation or use Play, then inspect the live thermal view, temperature timeline, insulation comparison and report tabs.
5. Use the step and reset controls to examine the transient response, save the project in this browser, open a JSON project, or export JSON and timeline CSV files.

Inputs

Space inputs include width, depth, height, floors, window area and U-value, air changes, insulation material and thicknesses, thermal mass, starting and desired temperatures, ambient temperature, HVAC mode and power, internal gains and hysteresis. Piping inputs include pipe length, outside diameter, wall thickness, fluid or medium, insulation material and thickness, temperatures, humidity, emissivity, heat-trace power and trace mode.

Outputs

Outputs include current and settling temperatures, time to target, heat transfer, thermal time constant, energy, temperature-field visualization, timeline curves, material heat-transfer comparisons and report tables. Pipe studies also show heat loss per metre, total loss, outer surface temperature, dew point, trace output and required trace power at the target.

Example use cases

• Compare insulation materials at the same room or pipe geometry and thickness.
• Explore how HVAC power, internal gains, ambient temperature and thermal mass affect room warm-up or cool-down.
• Screen hot-water, chilled-water or freeze-protection pipe assumptions and compare heat-trace requirements.

Limitations and responsible use

This is a preliminary lumped-capacitance model, not a code-compliance calculation, certified energy model, detailed building simulation, pipe-design approval or manufacturer selection tool. Results depend on entered assumptions and do not model multidimensional thermal bridges, moisture migration, phase change, stratification, solar schedules, pipe supports, valves, insulation aging or manufacturer heat-trace derating.

Validate final designs against applicable codes, verified material data, project-specific weather and operating conditions, ventilation requirements, condensation control, fire and electrical requirements, and manufacturer installation instructions. A qualified building-services or mechanical professional should review any safety-critical, freeze-protection, process or occupied-space application.

ThermaSim stores projects in browser local storage and can export JSON for portability. Browser storage may be cleared, so export a project file when a durable copy is needed. Simulation history is kept in the current session and is exported through the timeline CSV action.

Frequently asked questions