Getting started with Vulcan

Vulcan is a browser-based workspace for creating, checking, simulating, and submitting Home Energy Model (HEM) inputs.

It is designed for assessors, consultants, housebuilders, and others who need a faster and more reliable workflow than long-form manual data entry permits.

Users can create or import dwelling geometry, combine it with defaults, validate inputs, and prepare compliance submissions to ECaaS.

Vulcan also supports wider analysis beyond compliance, including multiple zones, local climate, and custom controls, gains, and schedules. This makes it useful for design and scenario modelling, not just compliance.

Vulcan's goal is to make HEM practical, faster, and more useful to work with.

How Vulcan works

Vulcan separates a model into three distinct layers.

1. Geometry file

This is the plot-specific description of the dwelling geometry and any element-level changes made in the drawing interface.

This is saved in a CSV format so it can be reviewed, edited, and integrated with spreadsheet-based workflows where needed.

2. Defaults file

This is a HEM JSON format file that provides the wider assumptions and inputs used to build a complete model: schedules, controls, systems, fabric assumptions, and other required data.

3. Base model

When a geometry file is saved, Vulcan merges the geometry with the defaults file to create a HEM JSON input file.

Calculations and scenarios

That merged HEM input can then be:

• submitted to ECaaS for compliance calculations
• used in local scenario analysis
• combined with alternative parameters such as systems, controls, weather, or fabric changes

This separation is one of the main differences between Vulcan and more monolithic form-based workflows. It helps standardise what should stay consistent across many dwellings, while keeping plot-specific inputs auditable and easy to edit.

First time guide

This is the fastest way to understand the basic Vulcan workflow.

By the end of this guide, you should have created a dwelling model, submitted or prepared your first ECaaS calculation, run a HEM simulation locally, and viewed the results!

Before you start

You will need:

• a modern Chromium or Firefox-based browser
• a local folder that can act as your Vulcan workspace
• dwelling information: floor plan, window dimensions, construction type, and systems. It is recommended to start with your own dwelling so you can easily fill gaps.
• optionally, a SAP worksheet or XML file to compare or validate against.

Vulcan stores most modelling files locally in your chosen workspace, giving you direct access to inputs, outputs, and supporting files. Assessments being prepared for ECaaS submission are also stored in the cloud to support submission and restoration, and given scheme requirements.

While Vulcan supports data restoration for assessments we store, we strongly recommend users secure their device and back-up their workspace to reduce the risk of data loss.

Step 1: Log in and choose a workspace

When you open Vulcan, you will be prompted to select a local folder to be your workspace.

Your workspace is where Vulcan stores geometry files, merged HEM inputs, scenario configs, output files, logs, tariffs, and anything you upload to support modelling (overlays, SAP files).

If you are starting for the first time, install or restore the sample parameter library so the standard example files are available. For more detail, see Setting up Vulcan Software.

Step 2: Create a new dwelling file

Navigate to the Geometry page and create a new model.

Rename it to something distinctive and searchable. Vulcan saves the visual geometry data separately from the wider defaults used to build a complete HEM input.

Step 3: Set global defaults

Open Global Settings from the File menu and confirm the defaults file and model-wide settings.

Typical checks include:

• defaults file - this can be adjusted to fit the thermal properties of the dwelling. An example file is provided as part of the Sample Parameter Library.
• FHS validation - for the main compliance workflow, FHS validation is required. This keeps the model aligned to the fields accepted by the HEM:FHS wrapper.
• heating control type
• airtightness and ventilation settings
• location properties such as wind exposure and altitude
• default assemblies for newly drawn walls, roofs, and ground floors

Room counts such as bedrooms, wet rooms, hot-tapped rooms, and living area should come from Space Labeller once room footprints are labelled. Use Space Labeller for these values in a normal first model.

Step 4: Draw or import the dwelling geometry

Adjust the north offset to make drawing easier. Canvas drawing snaps by default to right angles (and other elements), so adjusting the offset so this is possible will make input creation easier.

You can also add an image overlay (such as a floorplan) and trace over it, or import files from CAD tools such as SketchUp and Revit (in IFC4 format) where appropriate.

Then use the drawing tools to create the dwelling shape and elements.

Most first models only need:

• the envelope: external walls, windows, doors, floors, roofs, and any relevant adjacent walls
• required system inputs: heating source, distribution, hot water, and lighting
• thermal bridging, which can use a simplified zone-level assumption for a first model

If you have drawn closed rooms or spaces, use Space Labeller to assign room types. Space labels help Vulcan set room counts for compliance purposes, as well as the living / rest of dwelling split.

For a first model, focus on getting the core envelope, key systems, and validation right. Additional details (shading, further systems, leaks and individual thermal bridges) can be layered in once the basic workflow is working and you build confidence.

For detailed drawing controls, see the Geometry Section Guide.

Step 5: Review and edit elements

As elements are drawn, they can be selected individually or as a group, edited, and validated.

Use the editor and viewer panels to:

• update elements and their properties, individually or in bulk
• move elements between floors
• review warnings and critical validation issues
• inspect differences against SAP data if SAP inputs have been uploaded

You can switch between 2D mode (better for creating elements) and 3D mode (useful to visualise elevation) to validate your model.

Ventilation and thermal bridge warnings may appear during validation. Review them before preparing a calculation.

Where needed, users can request Vulcan to review their assessment before submission. This is done on the basis of evidence provided (including overlay and SAP files).

Step 6: Save the model

Saving writes the geometry into a CSV file and attempts to create the merged HEM JSON input.

Save status and build status are separate. If the geometry CSV is saved but the merged HEM JSON cannot be created, Vulcan will show a build error to fix. In that case, the drawing itself has still been saved.

After the model has saved, Quick solve can be used for a first preview of headline results where available.

Step 7: Prepare a calculation

Go to the Calculate section of the app. This part of the app is used to create ECaaS submissions.

Create a new submission, and add the input file you created. You can add multiple input files for each submission, and link each input file to multiple plots.

Attach the evidence needed to support the submission. This may include plans, specifications, overlays, SAP files, or element-specific evidence (e.g., airtightness tests, photographs).

Set the purpose of the submission. Users who are not yet Vulcan OCDEA Members can select Training.

For more detail on drafts, evidence, reviews, and ECaaS submission status, see the Calculate Section Guide.

Step 8: Submit to ECaaS

When ready, submit the assessment to ECaaS. ECaaS ('Energy Calculations as a Service') is the official HEM calculation service used for compliance submissions.

Once submitted, Vulcan will show the ECaaS response, submission status, and headline metrics when they become available.

You will not be able to edit an assessment once submitted, but you will be able to create a new submission based on an existing one.

Step 9: Create scenarios

If you want to analyse design changes beyond compliance, use the Scenarios section of the app.

Here you can define simulation configurations that, for example:

• test how variations in fabric, systems, orientation and more impact compliance or performance
• run a Core simulation using FHS assumptions, to get detailed half-hourly data instead of just summary metrics, and better understand compliance results
• test non-compliance scenarios to understand how the dwelling might perform in practice, including alternative loads, control strategies, or local weather conditions

Once you are ready, click Run Simulation. Simulations run on your device, meaning you can run as many as your computer permits. All outputs are stored locally, so are easy to access.

For more detail, see the Scenarios Section Guide.

Step 10: Compare results

Move to the Results section to review the outputs from simulations.

You can visualise metrics from simulation outputs as graphs, or as aggregate metrics. Metrics can be created by combining output columns, aggregation functions, and optional thresholds.

You can use metrics to evaluate, for example:

• the number of hours where unmet demand, or internal temperatures, exceed a threshold
• the consumption or demand for heating or cooling across different parts of the day or year
• the cost of consumption, based on variable tariffs

Tariffs can be added directly to the relevant folder in your workspace, or created using an interface. You can also export graphs and tables as CSV format files.

For more detail, see the Results Section Guide.

Experimental functionality

Some Vulcan features remain experimental and should be used with care.

These currently include:

• SAP generation: Generate a SAP XML from the Scenarios workflow and optionally run it through the netzeroapis SAP engine. Outputs should be checked carefully before use.
• MCP server: Exposes selected Vulcan functions (creating inputs, running simulations, analysing results) to local scripts and AI tools such as Claude or Cursor for workflow automation.
• CAD software imports: Import IFC4 files from CAD tools using different import modes (elements, massing, negative space), with an audit file provided as part of the process.

Experimental features are useful, and we strongly recommend Vulcan users try these out and provide feedback, but they are not yet a substitute for careful checking.

What these public docs do not include

This page is intended as a public introduction and workflow guide.

More detailed reference material, member-specific processes, and other operational documentation remain available within Vulcan for active users.

You will find documentation on the Vulcan API, which can be used by third party software providers to integrate Vulcan's ECaaS submission and quality assurance flow, at https://api.usevulcan.app.

To access Vulcan H3 (HEM-HTC-Harness), an open source workflow to calibrate Home Energy Model simulations with real-world HTC measurements, speak to the Vulcan team.

Access and updates

If you want access to Vulcan, or want to hear about workflow updates, documentation improvements, and HEM-related product developments, register your interest through the website or join the mailing list.