Sunlight study for a permit: from SketchUp to an auditable PDF

Why sunlight studies are separate work for architects

A sunlight study for the environmental permit is a quantitative document: a table of sun hours per measurement point, a test against the TNO standard or the municipal variant, a methodology appendix and a source list. The case officer assesses it as a stand-alone attachment alongside the building plan. That is something different from what SketchUp Shadows or Revit Solar Study deliver out of the box, namely a visualisation for use in the design. The visualisation is part of your design process; the report is part of the permit.

In almost all cases the municipality asks for a PDF report that reads like a Handel Bouwadvies or DGMR report. That means: a north arrow, a scale bar, side-by-side diagrams for the reference situation and the proposed situation, a sun-hour table to the minute, an explicit standard test and a separate appendix with all assumptions and sources. You have to build that format by hand in a reporting tool such as Word or InDesign, based on screenshots from your CAD tool. That is the structural time gap between “shadow visualisation in my model” and “report for the permit”.

The manual workflow: SketchUp or Revit to an auditable PDF

The steps an architecture firm goes through for a routine permit application for an extension, roof addition or small new build usually look like the table below. The hours are realistic estimates for an experienced building designer using SketchUp Pro or Revit 2024 with the built-in shadow tools.

According to the BNA guideline for advisory rates, the hourly rate for an experienced building designer sits between € 75 and € 150 excluding VAT. That means the manual workflow per permit application comes to € 300 to € 2,400 in architect fees, for the sunlight study alone. Outsourcing to an independent firm costs € 295 to € 535 with a turnaround of five to ten working days. Each design iteration requires a fresh cycle under both options.

What a permit report must contain at minimum

The municipality of Krimpen aan den IJssel has set out in its guideline the six sections a sunlight report must contain. This structure is used nationwide as the de facto standard, including in the advisory practice of Handel Bouwadvies, Blauwdruk Bouw and Bezonningsingenieur. According to the Administrative Jurisdiction Division of the Council of State (ECLI:NL:RVS:2023:172, Almelo) TNO standards based on such structural work are “not unusual” to apply. The six sections:

1. Introduction. Project name, address, client, applicant, scope and scale.
2. Assumptions. Chosen standard (light TNO, strict TNO, The Hague, Rotterdam, Krimpen), test dates, time intervals, coordinate system, reference situation (existing or maximum planning-permitted).
3. 3D sunlight diagrams. Side by side per test date and per hour. North arrow, scale bar, legend.
4. Quantification. A table of sun duration per measurement point, before and after the planned construction, delta in minutes.
5. TNO standard test. Explicit pass, near-miss or fail per measurement point, tied to the applied standard.
6. Conclusions and source list. A clear final conclusion, a list of the data sources used (3DBAG, BAG, AHN4), the software used, assumptions, a disclaimer.

The Voorburg ruling (ECLI:NL:RVS:2023:1329) shows where manual workflows go wrong: in that case a recently built roof addition on the neighbour’s house was missing from the municipal 3D model, which led to additional investigation at the applicant’s expense. Because 3DBAG is updated weekly on the basis of the current BAG registrations and AHN4 surveys, such an omission is structurally ruled out in an automated tool: by definition the model contains all construction registered at that moment.

Unit economics: what a sunlight study costs per project

How much you save per building application depends on the complexity of the job and the number of design iterations you go through with the client. The table below shows what a typical concerned-neighbour case (an extension) and a mid-sized new-build plot cost across three scenarios.

The real value is not only in the euro difference; iterating within the same client meeting changes the type of advisory relationship. You discuss three roof-type variants during the first conversation, the client chooses, and you move on. The traditional workflow forces a design proposal per iteration with a week’s wait. That not only slows delivery; it also narrows the design space, because as an architect you become more cautious about experiments that would mean calling the client back.

What Schaduwplan delivers specifically for architects

The core of the product proposition for building designers has four parts. One: automatic construction of the urban fabric from 3DBAG and AHN4, including roof shapes and ridge heights at LoD 2.2 level. Two: import of your own design via IFC (the BuildingSMART open standard), GLB or OBJ, placed on the correct national-grid coordinates. Three: a municipal standards library with presets for The Hague, Rotterdam, Eindhoven and Krimpen aan den IJssel plus custom-standard input. Four: automatic PDF generation following the Krimpen guideline, including a methodology appendix and a source list.

Schaduwplan works with one simple rate: € 29 per report, with no subscription or minimum purchase. For large firms or organisations with specific integration needs (API, BIM plugin, co-sign flow with a sworn expert) we build a business track on request — email [email protected]if that applies. For most architecture firms and freelance architects, the one-off rate of € 29 per report is enough.

When you should still hire a firm or expert witness

Honest about the limits: our tool covers the standard permit application and many more complex briefs, but not everything. In the following scenarios an independent firm or a sworn expert remains the sensible choice:

• High-rise above 40 m where wind simulations, nuisance exposure and shadow impact are combined at large scale. Firms such as DGMR, Peutz and Nieman are equipped for that.
• Large area developments where “maximum planning possibilities” must be used as the reference situation rather than the existing buildings. That requires a manual interpretation of the zoning plan or environment plan.
• Zoning-plan procedures where the plan itself is in dispute and an independent expert witness must give a statement at a hearing or in court.
• Listed monuments and protected townscapes and village scenes where a cultural-historical assessment requires a separate review.

In all other cases a Schaduwplan report is sufficient for the permit. And even in the exceptional cases named above, it serves as a starting point with which the follow-up firm can cut its intake by 50% or more.