Why is shading particularly important in newly built houses?

Let's go back to the radiation. There is a so-called g-value. For single-pane glazing it is 0.8, for double-pane glazing it is 0.63, and for triple-pane glazing it is 0.55. So triple-pane glazing actually lets in the least solar radiation (summer and winter), but the difference is only marginal (12.7% less energy input through radiation).

(by the way, the g-value indicates what percentage of the radiation the glass lets through and thus enters the building.)

If you now make the windows 100% larger, but with triple-pane glazing only have 12.7% less energy input per area, then it gradually becomes clear why shading is more important in a new building. It’s simply the increased area of south and west-facing windows.

So just put roller shutters on all the south and west windows and enjoy the light from the east windows, which still let in more light than in an old building with tiny windows?

No, the conductive one

Both are correct when we consider the complete heat transfer inside-outside interests (indoor air - boundary layer - wall - boundary layer - outdoor air).

Did you air out over the weekend? If there is no wind and the temperature inside and outside is the same, then Sebastian is right... Practice beats the textbook

No practice beats physics or the textbook, as long as it is applied correctly. Another problem could be that heat is "captured" through the windows and stored in the walls, and therefore not released again so quickly when airing out.

That is exactly the problem - and precisely the practice.

That is the problem - and exactly the practice.

Yes, but this can also be explained physically if ALL factors are taken into account. It is not the case that physically it can only be 24 degrees, but hex hex, in practice it is then 27 degrees. If that is the case, simply not everything was considered. Whether one makes the effort or even finds someone who calculates every detail is another matter. This is where, quite rightly, the practitioners come in who can estimate from experience that this and that has to be done...

No practice beats physics or the textbook, as long as it is applied correctly. Another problem could be that you "catch" the heat through the windows and it is stored in the walls, and therefore not released so quickly when airing.

Well... yes and no. We were discussing insulation and not heat storage capacity. Materials with a low U-value generally have a low heat storage capacity. So the argument rather goes in the opposite direction.