Heat loss is one of the highest-risk numbers in a renewable job because it affects design, emitter sizing, system confidence and customer expectation. A heat loss survey company should show how the calculation was built and provide the room data behind the final total.
Inputs that should be visible
The report should show the basic evidence trail for each room: dimensions, room use, exposed walls, floor and roof context, window and door areas, likely construction, and ventilation assumptions. Without that, the calculation is hard to trust or review.
The main Vertex service route is here: heat loss survey.
Assumptions that should be separated
Measured data and assumed data should not be mixed together without explanation. If wall construction, insulation level, floor type, or glazing performance is assumed, that should be visible in the report.
- Show which dimensions were measured or taken from plans.
- State fabric assumptions clearly.
- Flag weak or missing evidence.
- Keep room-by-room output reviewable.
Desktop versus measured route
A desktop heat loss calculation can be right when the evidence is strong. A measured heat loss survey is usually better when plans are missing, room dimensions are unclear, or the installer needs more confidence before quoting.
Use the heat loss calculations guide for the broader calculation context and the provider checklist when comparing survey companies.
What the output should help you decide
The report should show whether the design route is credible and where emitter sizing may be tight. It should identify assumptions that still need customer confirmation and make the next step clear: quote, design or further evidence gathering.
For booking and guide pricing, use the guide price builder.