A colourful lighting simulation can make a proposal look convincing before it answers the owner’s questions. The useful question is not which application the designer uses, but whether the report explains your rooms and supports decisions about the actual fittings. Treat the model as a reasoned proposal with stated assumptions. You should be able to connect its results to furniture, activities, products and controls without learning to operate the software yourself.
Ask for a decision, not just a rendering
Tell the designer what remains uncertain: whether a reading corner needs its own light, whether the dining table is adequately covered or whether an alternative ceiling arrangement is worth considering. Ask for a comparison that answers that question using the same room assumptions. A visually attractive image may communicate atmosphere, but it should not replace a clear explanation of why one layout better serves the agreed activity. Keep the decision and the supporting output together in the approval record.
Check what the model actually contains
Compare the model with the latest furniture and ceiling drawings. Look for tall cabinetry, partitions, pendant positions and the selected work surfaces. Ask which items were included and which were simplified. DIALux provides calculation settings that can include or exclude furniture. This makes the assumptions worth discussing rather than treating every image as a complete description of the room. A model based on an early layout should be updated or clearly labelled before it supports a final purchase.
Request readable results for relevant locations
Have the designer identify the surfaces and positions used for evaluation and explain why those locations represent your activities. Ask what target or criterion was selected and who confirmed that it is appropriate for this project. You do not need a page of unexplained values for every corner. A short annotated report connecting the relevant locations with the design intent is more useful. Keep units and legends visible so later comparisons do not confuse different quantities or display scales.
Match every calculation to a product
Ask for an identifiable fitting schedule alongside the calculation. Each model reference should lead to the product data and the version proposed for purchase. If the supplier offers a substitute, have the designer decide whether the comparison needs recalculation. Avoid approving a generic product name while assuming that all products sold under that description will perform alike. Keep a separate list of unresolved selections, because a provisional model is useful only when its provisional assumptions remain visible.
Read scenes as part of the proposal
A room may look satisfactory with every fitting switched on and feel quite different during ordinary evening use. Ask which lighting groups are active in each illustrated scene and what the owner can control. Compare the hospitality, reading and television routines you actually expect to use rather than requesting many decorative scenes. If dimming is proposed, ask the project team to verify the selected components together. The report should help explain the intended experience, while the installation team confirms the practical arrangement.
Agree how the completed room will be reviewed
Before ordering, agree which observations will be checked in the finished room and which require specialist measurement. Record the final drawing revision and retain the calculation report with the approved product schedule. At handover, compare the installed references and lighting groups with that record, then discuss any uncomfortable views under normal use. A simulation is an input to the design process; a clear review plan makes it useful throughout purchasing, installation and final adjustment.
Your practical checklist
- Name the specific decision the calculation should support.
- Check furniture, products, criteria and drawing revision.
- Keep provisional assumptions visible until they are resolved.
Frequently asked questions
Does using a recognised program guarantee a good design?
No. The result also depends on the inputs, the selected products and the designer’s interpretation. Ask how the report answers the needs of your particular rooms.
Should I request the editable model?
Discuss that deliverable in the design agreement. At minimum, obtain readable documentation and the approved schedules. If another specialist may continue the work, agree the required handover format early.
Can a phone photograph validate the calculation?
A photograph can record observations, but it does not replace a specialist assessment or appropriate measurements. Camera settings can alter the appearance, so describe the issue and its viewing position.
Sources and further reading
Sources support the specific facts identified below. Planning examples and checklists are editorial guidance; photographs are illustrative.
- DIALux — Interior lighting calculation — Supports the short factual statement about furniture calculation settings.