Lighting Analysis
Phân tích chiếu sáng
Calculate natural Daylight Factor, artificial lighting levels, verify QCVN lighting standards, and evaluate lighting electricity consumption.
Common tools
Dialux, Autodesk Insight (daylight)
Value delivered
Supports compliance with QCVN 07-4 (building lighting) and LOTUS/LEED IEQ criteria
Adoption in Vietnam
Rarely formally performed in Vietnam — mainly in green/LOTUS projects.
Level of Information Need (LOIN)
G = Geometry · A = Alphanumeric · D = Documentation (ISO 7817-1:2024 method). A blank cell means this use sets no specific requirement for that discipline/stage.
| Discipline | Concept | Schematic | Developed | Technical | As-built / Operation |
|---|---|---|---|---|---|
| Architecture | — | G2·A1·D0 | G3·A2·D1 | — | — |
| Structure | — | — | — | — | — |
| Mechanical | — | — | — | — | — |
| Electrical | — | G2·A2·D0 | G3·A2·D1 | — | — |
| Plumbing | — | — | — | — | — |
Critical stages: Schematic · Developed
Rationale: ELEC (luminaire placement, photometric data) + ARCH (room geometry, surface finishes, daylight apertures). ELEC needs A2 from ST2 (lamp lumens, photometric IES files). ARCH geometry refines G2→G3 for precise daylight / glare studies at ST3. D1 links illuminance standards (TCVN 7114-1, QCVN).
What it really is
Lighting Analysis uses the BIM model to run quantitative simulation of both daylight and artificial lighting, rather than producing pretty renders for presentation. For daylight, the tool calculates the static Daylight Factor, and for projects needing a seasonal assessment it adds climate-based metrics such as Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE) driven by local weather data. For artificial lighting, the tool simulates illuminance (lux), uniformity and the glare index (UGR) using the actual photometric data (typically IES files) of the fixtures intended for use — not a stock fixture from the software library. Results are then checked against Vietnam's current lighting codes and standards, which sit independently of Decree 217/2026/NĐ-CP. The reliability of the whole analysis hinges on two things that are commonly skipped: real material reflectance values (walls, floor, ceiling, glazing) in place of software defaults, and a context model — neighbouring buildings, trees, terrain — instead of simulating the building as if it stood alone in an open field.
When to use
Worthwhile for projects pursuing green building certification (LOTUS, EDGE, LEED — the lighting-related IEQ credits), works with strict lighting requirements such as hospitals, schools and large offices, and designs with extensive glazing or deep floor plates that need early daylight optimisation. In Vietnam this use is still rarely performed formally outside green-rated projects, so unless the appointing party states it explicitly in the EIR it tends to be skipped.
Prerequisites
- •An architectural model at a Level of Information Need (LOIN per ISO 7817-1:2024) sufficient to simulate: windows, glazed walls, roof, shading elements — depends directly on Design Authoring
- •Real material data: wall/floor/ceiling reflectance, glazing transmittance and reflectance, taken from manufacturer datasheets rather than software defaults
- •A surrounding context model — neighbouring buildings, terrain, trees — whenever the building does not stand alone on open land
- •Lighting performance targets already defined in the EIR/BEP: against Vietnam's lighting codes or a specific green-certification credit (Art. 8(2) assigns this to the contract)
- •An analyst able to configure climate-based simulation (local weather file, calculation times), not just a single static Daylight Factor run
Inputs
Architecture task team · .rvt / IFC
Architect · material manufacturer · .xlsx / .pdf
Survey task team · planning task team · .rvt / .dwg / IFC
Appointing party · .pdf / .docx
Lighting analyst · .epw
MEP contractor · .ies / .pdf
Outputs
Daylight simulation report (Daylight Factor and sDA/ASE where applicable)
.pdf / .xlsx → Appointing party
Accepted when: Simulation uses real materials and context, meets the threshold stated in the EIR/BEP or the applicable green-certification credit
Fixture layout drawing with illuminance, uniformity and UGR calculations
.pdf / .dwg → MEP contractor · appraising authority
Accepted when: Meets the minimum illuminance per TCVN 7114-1:2008 and QCVN 22:2016/BYT for each space type — not average illuminance alone while ignoring UGR
QCVN 09:2017/BXD compliance report (lighting power density, automatic control)
.pdf → Appointing party · competent construction authority
Accepted when: Lighting power density within the permitted limit, with automatic control devices where the code requires them
Model updated with lighting parameters (fixture objects, real materials)
IFC / .rvt → MEP task team
Accepted when: Fixture objects carry sufficient photometric properties for coordination and schedule extraction
General workflow
Prepare the model and assign real materials
Verify the architectural model is detailed enough to simulate, then replace every software-default material with real reflectance and transmittance values from manufacturer datasheets. This is the most commonly skipped step and the largest source of error.
Architect · Lighting analyst · Revit (assign real materials) → Simulation-ready model
Add context and shading to the model
Add neighbouring buildings, terrain and shading trees to the model or a linked model. Simulating the building as if it stood alone when it is actually overshadowed is the most common mistake producing falsely optimistic results.
Architect · Planning task team · Forma (context and sun analysis) → Context model
Simulate daylight
Run a Daylight Factor simulation for the design; for green-certified projects, add a climate-based simulation (sDA/ASE) driven by the local weather file for the main spaces.
Lighting analyst · Autodesk Insight · DIALux → Daylight factor / sDA-ASE report
Lay out and simulate artificial lighting
Place fixture objects with the correct IES photometric data for the intended equipment model, then simulate illuminance, uniformity and the UGR glare index for each space type.
MEP / lighting specialist · Revit (place fixtures, assign IES) · DIALux → Illuminance calculation and fixture layout
Check against codes and standards
Compare simulation results against QCVN 09:2017/BXD (lighting power density), TCVN 7114-1:2008 (illuminance, uniformity, UGR) and QCVN 22:2016/BYT (permissible workplace levels); for green-certified projects, also check the relevant IEQ credit.
Lighting analyst · Autodesk Insight · DIALux (report export) → Code-compliance report
Adjust the design based on results
If targets are not met, adjust the window-to-wall ratio, shading position or fixture layout directly on the architectural model and rerun the simulation — this must happen before the basic design is submitted for approval, not after the facade has been locked.
Architect · Revit → Adjusted design model
Publish the report to the CDE
Store the simulation report, the updated fixture model and the compliance file on the CDE so the appointing party and the MEP team share one source instead of scattered PDFs.
BIM Coordinator · Forma Data Management (CDE) → Published lighting information set
Diagram
↺ Whenever the window-to-wall ratio changes, rerun the simulation — a single early-project result loses its value once the design has moved on
Common pitfalls
The simulation looks good on screen but the real room stays dark, lights stay on all day
Cause: The simulation used software-default materials — assumed wall, floor and glazing reflectance — instead of the actual materials to be built
Fix: Enter the correct reflectance and transmittance from manufacturer datasheets before simulating; do not accept a report built on default materials
The calculated Daylight Factor passes but the real building receives far less light than predicted
Cause: Neighbouring buildings, terrain and trees were left out — the building was simulated as if standing alone on open land
Fix: Include the urban context and neighbouring buildings before simulating, especially for infill projects in an already-built area
Lighting targets are found to fail after the facade and window sizes have already been approved, with no room left to fix them
Cause: Lighting analysis was treated as a formality at the end of design rather than a decision-support tool from the concept stage
Fix: Run the simulation alongside schematic design, repeating it whenever the window-to-wall ratio changes, before the basic design is submitted for approval
Measured illuminance meets the requirement but users still complain of glare and visual discomfort
Cause: Only average illuminance (lux) was checked, ignoring the UGR glare index and uniformity required by TCVN 7114-1:2008
Fix: Check all three criteria in the same review: illuminance, uniformity, UGR — not average lux alone
The simulation report no longer matches the BIM model after a few rounds of design change
Cause: The simulation was rebuilt from scratch in a standalone tool, exported/imported once and then abandoned, with no direct link back to the model
Fix: Prefer a tool that links directly to the BIM model (running inside Revit) or mandate rerunning the simulation each time the model publishes a new version
Measuring effectiveness
Compare simulated illuminance with real measurement at reference points in a space, split into three scenarios: daylight only, artificial light only, and combined
Benchmark: In a study comparing three tools (a BIM-VR system, Radiance, 3ds Max) against real measurement in an experimental office: average error for daylight-only simulation ranged 3.61–11.80% depending on tool (lowest for the Radiance-based tool, highest for 3ds Max), with the largest error reaching 40.92% (3ds Max, daylight) or 37.87% (3ds Max, combined daylight and artificial light). The study cites a 1992 recommendation that the acceptable error threshold is 10% for average illuminance and 20% per measurement point — this is a secondary citation via the paper, not a direct reading of the original recommendation. This is a single office case study, not generalisable to every building type, but it is enough to conclude that the wrong simulation tool can push error well past the acceptable threshold
Spaces passing divided by total spaces simulated, counted at the first review before any adjustment
Benchmark: no independent benchmark — set an internal target
Person-hours from the model reaching simulation-ready LOIN to the issued compliance report
Benchmark: no independent benchmark — set an internal target
Legal basis
There is NO specific requirement for lighting analysis in Decree 217/2026/NĐ-CP — this use falls under Article 8 generally. Art. 8(1)(a) makes BIM mandatory for new-build works Grade II and above; Art. 8(2) assigns scope, content and information requirements to the contract — the basis for bringing lighting targets into the EIR and BEP; at appraisal, BIM data is provided in the open IFC standard or another open format suited to the project's nature; the competent authority may additionally request the native format for cross-checking (Decree 217/2026/NĐ-CP, Art. 8(3)(a) and (b)). The actual lighting performance requirements sit in OTHER instruments, not Decree 217: QCVN 09:2017/BXD (Ministry of Construction) sets lighting power density and automatic-control requirements; TCVN 7114-1:2008 (equivalent to ISO 8995-1) sets illuminance, uniformity and glare limits; QCVN 22:2016/BYT (Ministry of Health) sets permissible workplace lighting levels. The practical consequence: using BIM to simulate and check these lighting codes is a methodological choice, usually made mandatory only when a project pursues green-building certification — the BIM decree itself imposes no specific obligation for this activity.
Sources
Only official sources (legislation, standards) and peer-reviewed academic work are cited. No vendor marketing figures or press sources. Reference only — does not replace legal advice.