Does the sun reach your window? The light check for Vienna
Every listing says “flooded with light”. This calculates it — from the officially measured eaves heights of the neighbouring buildings, for every compass direction and for your floor.
A flat is viewed for twenty minutes, on one day, at one time. Whether the sun comes in at all in December is decided by the buildings opposite — and you cannot see that from inside the flat. Azima calculates it for one address: the real obstruction horizon around the house, the sun’s path across it, and what is left over at ground level and higher up.
Start the light check →How it works
What makes it different
Most sun tools work everywhere on Earth — and therefore have to talk about accuracy in the same words everywhere. They cannot admit, address by address, whether an official roof model exists there or whether a building was assumed to be three metres tall. Azima only covers Vienna, and that is precisely why it can put the sentence on the screen: how many of the shading neighbours stand there with an officially measured eaves height. Where that share is too thin, no number appears.
Frequently asked
How much direct sunlight does a flat in Vienna get?
It depends far less on the compass direction than on what stands opposite. In a narrow Gründerzeit lane a south-facing flat can be in shade by early afternoon, while a fourth floor in the same house keeps the sun for hours. The light check calculates the real obstruction horizon around one address — for every compass direction the height the sun has to clear — and compares it against the sun’s path for that day.
Which data is this based on?
Building heights come from the City of Vienna’s generalised roof model (LOD2.1, CC BY 4.0) — eaves and ridge, measured, not estimated. Where that is missing, an OpenStreetMap entry counts. Terrain comes from the Copernicus elevation model, the sun’s position from astronomy. Nothing is guessed.
What happens when the data is not good enough?
Then no number appears — only the reason and the coverage figure. An invented hour of sunshine is worse than no answer, because afterwards nobody believes the correct one either. This is the one thing most sun tools do not do: they always return a result.
Does the floor matter?
A lot. Sun maps stop at the house wall; here the calculation runs up the facade. In a deep lane the low winter sun never reaches the ground floor but still clears the neighbours’ roofs higher up — that difference is measured from the same real building heights, and the check says whether it exists at this address.
Is my address sent anywhere?
To OpenStreetMap, for the neighbouring buildings — and nowhere else. Nothing travels back to this site; the result stays on your device. You can check that in the network tab.
What does it cost?
Nothing. There is no account, no sign-up, no tracking.
Sources: City of Vienna — generalised roof model LOD2.1 (CC BY 4.0) · OpenStreetMap contributors (ODbL) · Copernicus elevation model · sun position calculated astronomically. This is a calculation, not an expert opinion: it says nothing about your curtains, the courtyard side or a balcony above your window.