How Heatworx builds a room model

A heat loss calculation starts with a model of the room: its shape, its surfaces, what those surfaces are made of, and where heat escapes. This page explains how Heatworx turns a room scan or manual capture into that model — what is measured, what is inferred, and what you can change.

Heatworx helps produce and review a structured heat loss estimate. It does not replace professional judgement, manufacturer requirements, regulatory obligations, or a full heating system design where one is required.

What happens when you scan or manually capture a room

Heatworx offers two ways to capture a room.

LiDAR room scanning

On devices with a LiDAR sensor, Heatworx uses Apple's RoomPlan framework. You walk slowly around the room with your phone or tablet, and the sensor builds a three-dimensional model of the space. The scan captures wall positions, floor area, ceiling height, and the approximate location and size of windows and doors.

The scan takes roughly 30 to 60 seconds for a typical domestic room. It works best in rooms with clear wall surfaces and reasonable lighting. Complex geometry — alcoves, bay windows, vaulted ceilings — may need manual adjustment afterwards.

Manual room capture

If your device does not have LiDAR, or if you prefer to work from measurements or a floor plan, you can draw the room shape manually. You enter wall lengths and room height, and Heatworx builds the room model from those dimensions.

Manual capture also supports non-rectangular shapes — L-shapes, U-shapes, and other common domestic room layouts. You add windows and doors to each wall after drawing the outline.

Both methods produce the same kind of room model: a set of surfaces with dimensions, each of which can be assigned a construction type and U-value.

How Heatworx creates walls, floors, ceilings, windows and doors

Once the room geometry is captured, Heatworx derives the individual surfaces that make up the room envelope.

Walls

Each wall segment becomes a surface with a measured length and height. The wall area is calculated from those dimensions, minus any window or door openings. Each wall can be classified as external (facing outside), internal (shared with another heated room), or adjacent to an unheated space.

Floors and ceilings

The floor area is derived from the room footprint — the polygon formed by the wall layout. The ceiling area is typically the same as the floor area. Heatworx supports vaulted and sloped ceilings. The user can set the ceiling profile for each room, and the app adjusts surface areas and room volume accordingly.

Windows and doors

Windows and doors are placed on walls either from the LiDAR scan detection or by manual entry. Each opening has a width, height, and construction type — for example, single-glazed, double-glazed, or solid timber door. The opening area is subtracted from the parent wall area so that fabric heat loss is calculated correctly for both the glazed and opaque portions.

What geometry is measured vs inferred

Not everything in a room model comes directly from a tape measure or a LiDAR sensor. It is worth being clear about which inputs are measured and which are estimated.

Measured from the scan or manual entry

• Room dimensions — wall lengths, room height
• Room volume — calculated from floor area and height
• Floor and ceiling areas — derived from the room footprint
• Window and door positions and sizes — from scan detection or manual placement

Inferred or estimated

• Wall thickness — Heatworx uses a reasonable estimate based on construction type rather than measuring wall depth directly
• Construction type — the scan cannot see inside a wall; construction type is selected by the user or defaulted from the property age
• U-values — derived from the selected construction type, not measured in place
• What is on the other side of a surface — whether a wall faces outside, faces another heated room, or faces an unheated space is partly detected (for adjacent scanned rooms) and partly set by the user

The distinction matters. The geometry of a room can be captured with reasonable accuracy from a scan or careful measurement. But the thermal properties of each surface — what the wall is made of, how much insulation it has, how airtight the construction is — are assumptions that depend on the user's knowledge of the building.

How adjacent rooms and shared surfaces are handled

Where rooms share a wall, Heatworx is designed to identify the adjacency so that the temperature difference across internal partitions reflects whether the neighbouring space is heated, unheated, or belongs to another property. A shared wall between two heated rooms loses very little heat, because both sides are at similar temperatures. The temperature difference across that surface is small, so the fabric heat loss contribution is small.

This matters for accuracy. If every wall were treated as an external wall, the heat loss for internal rooms would be significantly overstated. Heatworx adjusts the temperature difference used in the fabric heat loss formula based on the conditions on the other side of each surface:

• External wall — full temperature difference between inside and outside design temperature
• Wall shared with a heated room — reduced temperature difference (often close to zero if both rooms are at the same setpoint)
• Wall adjacent to an unheated space — intermediate temperature difference, because the unheated space is warmer than outside but cooler than a heated room

The same logic applies to floors and ceilings. A first-floor bedroom above a heated living room loses very little heat through the floor. The same bedroom above an unheated garage loses considerably more.

What the user can edit after capture

The room scan or manual capture is a starting point, not a locked result. After capture, you can edit:

• Wall lengths and room height — correct any measurement the scan got wrong
• Surface areas — override calculated areas if needed
• Window and door dimensions — adjust sizes, add or remove openings
• Construction types — select the wall type, floor type, glazing type and roof/ceiling type for each surface
• U-values — accept the value derived from the construction type, or enter a known U-value directly
• Room type and internal design temperature — change the room's purpose (living room, bedroom, bathroom) which affects the target temperature
• Ventilation inputs — record evidence of draughts, vents, suspended floors, flues and mechanical ventilation
• What is on the other side — mark surfaces as external, internal, or adjacent to an unheated space

This editability is deliberate. A scanned room model captures the shape, but the thermal assumptions behind each surface depend on what you know about the building. Heatworx is designed to let you review and adjust those assumptions rather than hiding them.

What Heatworx does not capture automatically

It is important to be clear about what the room scan does not tell you.

Construction type and insulation level

The LiDAR sensor sees the surface of a wall, not what is inside it. It cannot distinguish a solid brick wall from a cavity wall with insulation. That information must come from the user — from visual inspection, building records, or professional knowledge.

Airtightness evidence

The scan does not measure how airtight the room is. Ventilation heat loss depends on factors like draughty windows, unsealed floors, open flues and background vents. Heatworx asks you to record this evidence through survey selections, which then feed into the ventilation heat loss estimate.

Heating schedule and setback

How the heating system is used — when it runs, what temperature it targets, how long the building is unheated overnight — affects the reheat allowance in the calculation. This is a user input, not something captured by a room scan.

External conditions

The design outside temperature comes from the property's location, using data from 28 UK weather zones with a GPS-derived altitude correction. This is looked up automatically based on the survey location, but it is not measured by the room scan itself.

How this appears in Heatworx

In Heatworx, the room model is the foundation of the entire survey. Each room you scan or draw becomes a structured set of surfaces, each with its own area, construction type, U-value and boundary condition.

The app presents this as an editable room view where you can see every surface, its assumed construction, and its contribution to the room's heat loss. You can drill into any surface to change its type, override its U-value, or adjust its dimensions.

All data is stored locally on your device using an offline-first architecture. You do not need an internet connection to capture rooms, edit assumptions, or run calculations. The survey syncs when connectivity is available, but the core workflow works entirely offline.

This approach — measured geometry combined with transparent, editable assumptions — is aligned with recognised UK domestic heating design guidance. The room model is not a black box. It is a structured starting point that you can inspect, question and refine.

Frequently asked questions

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