Is a venetian blind necessary on the east side?

If anything, it hits harder in the morning because the air is cleaner.

And it feels like the west sun is warmer when the house has heated up over the day.

Exactly, that's the difference: the evening sun adds to the heating of the day, while the morning sun follows the nighttime cooling.

Oh. So the morning sun doesn't add up, but the evening sun does? Cool, physics is being rewritten...

Not physics, but meteorology: before the morning sun, there was no warm phase of the day.

In a reasonably well-insulated and solid house, it makes no difference at what time of day the heat entered the house.

So for us, several points come together: 1. The east facade is even slightly oriented to the north 2. Our property is located on a south-facing slope that also rises to the east, meaning the morning sun is initially still "behind the mountain". 3. On the east side, there is a free plot of land that will presumably be built on at some point. Therefore the consideration to save the 3-4 TEUR...

Not the physics, but the meteorology: before the morning sun there was no warm phase of the day.

When the sun shines through the window at a certain angle and warms the floor / the room, it doesn’t matter whether it does so in the morning or in the evening. The outside temperature is irrelevant at first.