You should consider an energy recovery ventilator. It blows in fresh outside air but it uses exhausted inside air to bring it up to the temperature of your home.
And this will work in a the apartment that OP is living in? Because that sounds like it might involve some invasive installation. If it's just a box one can plug in, maybe a vent hose, that would be great.
I'm surprised that there are no portable ERVs similar to portable AC units that just vent out a window. I have a small ERV in my shed/office that uses a single outdoor and indoor vent for combined intake/exhaust. (ie minimal ducting)
I’ve seen them in a form factor that resembles a short, shallow window air conditioner that you just close your window on top of and optionally lock into place with screws.
Some ERVs come in the shape of a cylinder, about 10cm x 30cm for use in apartments.
Yes, installation requires cutting a hole in the wall, but it is doable.
Yep. You are right. This is my main problem here -- not only the inside installation is extremely invasive. But the local laws basically prevent me from being able to make the large holes in the wall needed to pass the massive amounts of air.
