Vertical sliding window / outward opening window

For the renovation of an old town house with a relatively small floor area (50 sqm per floor), I am considering, for the sake of practicality, deviating from the standard "windows opening inwards." I quite like the principle of American windows, which often open by sliding upwards. This way, I can open a window halfway, and no space is lost inside. I also find the principle of Scandinavian windows, which open outwards or rotate, quite interesting.

Does anyone have experience with this type of window? Apart from the more difficult access for cleaning, are there any safety reasons or energy-related reasons against them? Should I generally expect longer lead times when ordering, or does it ultimately not matter because all windows are custom-cut anyway?

My neighbors have Norwegian wooden windows, most of which open normally inward. The kitchen windows have a pivot mechanism (lever at the bottom in the middle, you push the window forward/outward and the top part of the window moves backward/inward) – I find that quite practical because your windowsill, which in kitchens is often full of herbs and stuff, does not always have to be cleared for ventilation. The two doors also open outward – with a "hold-open option," which is really great! But this only works if the areas above are covered (in this case a carport and veranda). The handles are all very unusual (tilt and fully open are reversed positions compared to ours).

We lived for many years in a half-timbered house with wooden sash windows, all of which opened outward. The advantage here again is decoration on windowsills, easy handling, nice appearance, great sense of space, and a feeling of more room inside – but: with small children it is very dangerous. If the handle is not fully closed (which happens because they tend to warp easily) or a little hand fiddles with it and you lean against the window, it can happen that the window opens. So we long secured all the risky windows with cable ties and rarely opened them. If you leave a window open and it rains, that is very bad for the wood over time and it no longer seals properly. That means: leaving it wide open at night is not possible if it might rain. You cannot tilt these windows because then rain would come in like into a funnel.

I now have wooden windows again, but normal ones. I really missed the tilt function, I like fresh air drafts in my house – that’s why we decided against a controlled residential ventilation system...

Sliding windows are still very common in the Netherlands. I would look for manufacturers/dealers there.

With small children, this is really dangerous. If the latch isn’t fully closed (this happens because they warp easily) or a little hand fiddles with it and you lean against the window, it can happen that the window pops open. So we secured all risky windows with cable ties for a long time and only rarely opened them. If you leave a window open and it rains, over time that is very bad for the wood and it no longer seals properly. Meaning: you can’t leave it wide open at night if it might rain. You can’t tilt these windows, because then water would run in like through a funnel.

Those are two good points, thanks! For ventilation, I’m planning a central ventilation system; I hope that I won’t have to ventilate permanently neither at night nor during the day (and I’ll also get a pollen filter with it).

Regarding safety, I tend to go for vertical sliding windows. Although the question is whether the bar in the middle at eye level is a no-go. In America, I never found that disturbing, but I also never lived in such rooms for more than a few days.

For the upper floors, there’s a fall protection outside on the facade anyway. When the windows are slid up, that also protects the teenagers in the house (but that also applies to classic windows).