I wish there were something that opens the windows automatically at the right time to keep the heat* and humidity out. I'm sure other people will have had that idea, too. But I haven't come across easy-to-use hardware controls. That's not even talking about the full optimal control problem, i.e. weather forecast, the heat capacity and heat permeability of the walls, and any cigarette smoke coming in.
*Air conditioning is hard to get permission for as a renter in Germany.
> I wish there were something that opens the windows automatically at the right time to keep the heat* and humidity out.
The latter part of your problem is a solved one. Weather forecasts and local conditions (from your own indoor/outdoor sensors) for the weather, heat capacity and permeability could be hardcoded or via helpers, cigarette smoke via air quality sensors. All of these can be integrated with Home Assistant.
All that is left is something to physically open/close the window, which should also be a solved problem.
*Air conditioning is hard to get permission for as a renter in Germany.