Why we build this
How much sun reaches your garden, through your windows, on your terrace? And will it stay that way when your neighbour builds, when you renovate, or when you are weighing up a new home? Until now that knowledge sat behind a consultancy wall of €400 and five working days — absurd, for what is essentially an arithmetic problem on public data.
Who builds this
In 2022 my partner and I bought a house with a sunny garden. Two years later, two apartment blocks went up further down the street — already visible in the zoning plan (bestemmingsplan) that was public at the time, only we had not found it. Since then we have lost a large share of our afternoon sun and privacy. With Schaduwplan that purchase might have looked different.
I build Schaduwplan because the data already exists — 3DBAG, Kadaster, AHN, zoning plans (bestemmingsplannen) — but it is scattered and hard to combine. A sunlight report from a consultancy costs hundreds of euros and takes days; it does not have to. Five minutes with the right sources side by side is enough for most decisions.
What prompted this
Since 2022, 3DBAG has provided LoD2 building models for the whole of the Netherlands, free of charge. AHN offers height data accurate to a few centimetres. The building blocks for a serious sunlight calculation are now available to everyone.
Since Ootmarsum 2013 and Almelo 2023, it is clear in administrative law: municipalities (gemeenten) must weigh substantiated objections. Without data, an objection rests on feeling. With data, it is factual.
A traditional sunlight study (bezonningsonderzoek) costs €330–€535 and takes five to ten working days. That effectively prices homeowners out of exercising their own rights. We think much of it is technical work, not consulting work.
Whose shoulders we stand on
The open Dutch data infrastructure is unique in the world. We lean on it heavily, and we want to acknowledge that openly — not bury it.
3DBAG
TU Delft 3D Geoinformation + 3DGI
LoD2 building models for the whole of the Netherlands, updated quarterly. The foundation on which every analysis rests.
View sourceKadaster (BAG)
Basisregistratie Adressen en Gebouwen
Address data, building register, parcel boundaries. Authoritative source for address lookup and building metadata.
View sourceAHN (4/5/6)
Het Waterschapshuis + Rijkswaterstaat + Ellipsis Drive
Actueel Hoogtebestand Nederland (the national height model). Height data from lidar, accurate to the centimetre. AHN4 nationwide via PDOK; AHN5/AHN6 per province via Ellipsis Drive.
View sourcesuncalc.js
Vladimir Agafonkin
Open-source library for sun-position calculations. The standard within the sunlight-analysis community.
View sourceHow we build
We build solely on Dutch open-data sources. No closed-source dataset that could disappear tomorrow. No vendor lock-in.
Every report states the norms used, source data, versions and a report ID. A third party can reproduce the calculation on schaduwplan.nl with the same input. That is what makes a sunlight report usable as evidence.
We read everything. For bug reports, feature requests, missing municipal norms or integration questions: [email protected].