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Contextual CTAs

Building a 3D scanning tool for heat loss surveys

Designing a mobile app that compress a days-long on-site process into 30 minutes

Role

Senior Product Designer (founding)

Senior Product Designer (founding)

Status

Shipped to App Store

Scope

iOS room scan app

Timeline

8 weeks

The problem

Room by Room capture

An on-site heat loss calculation depends on complete data. Every wall, window and door facing outside air. There is no partial version of the calculation: if any room is missing, the output is wrong.

The user doing this work is an installer or surveyor standing in someone's house, moving fast going from room to room, on a phone.

approach

"How do we make this faster?"

That was the initial framing. But speed was not the constraint. The constraint was completeness. Every room had to be scanned because the heat loss calculation was only valid if a full floor plan was captured. That meant every design decision had to work within a non-negotiable sequential flow, for a user who was already context-switching between their physical environment and the app, and who had no tolerance for anything that felt like overhead.

solution

A 3D Room scan iOS app

Decision 1: The CTA as status indicator

The primary action button updates at each stage to tell the user exactly where they are and what to do next. Before anything is captured: "Scan room." Once the scan is complete: "Capture heat emitters," with an escape hatch, "No heat emitters to capture," for rooms that do not have any. Once everything is done: "Done with room."

Decision 1: The CTA as status indicator

The primary action button updates at each stage to tell the user exactly where they are and what to do next. Before anything is captured: "Scan room." Once the scan is complete: "Capture heat emitters," with an escape hatch, "No heat emitters to capture," for rooms that do not have any. Once everything is done: "Done with room."

Contextual Call to actions

Decision 2: The confirm scan screen

After every room scan, a confirm screen shows a 3D render of the captured geometry alongside a building elements breakdown: walls, doors, windows, openings, with labeled dimensions. This screen exists to let the user judge scan quality without needing to understand the underlying data model. The render is legible because it maps directly to what they just physically stood in.

Decision 2: The confirm scan screen

After every room scan, a confirm screen shows a 3D render of the captured geometry alongside a building elements breakdown: walls, doors, windows, openings, with labeled dimensions. This screen exists to let the user judge scan quality without needing to understand the underlying data model. The render is legible because it maps directly to what they just physically stood in.

Confirm scan of room

Capture on IOS flowchart

Outcome

The on-site assessment process went from taking days to roughly 30 minutes.

The full user journey shipped to the App Store, from house data entry through room-by-room scanning to web app upload and PDF report generation. What previously took days of back-and-forth was compressed to roughly 30 minutes to an hour on-site.

©2026 anh Thi Lam

GEt in touch

anhthilam1@gmail.com

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