I have a corner room in our house, in the summer it traps heat and in the Winter (like right now) it lets it all out. In the summer my room is regularly between 3 to 10 Celsius hotter than the rest of the house, and in the Winter it is usually the reverse, hovering around a 5 degree difference. I have three windows, one single one and two that serve to make a large double window. They are those idiotic non sensicle windows that open outwards and have to be hand cranked. All of them are broken, they cannot open, unless forced open (and I mean forced) and I hate having to get a ladder and climbing up two stories to forcefully close them, so they never open, and I have given up on any airflow and just use an air-purifier year round with just makes the room feel colder in the winter. I have currently put up plastic sheets around my Windows, and since the large window is facing the street and everyone can see into my room very well, especially at night, I just covered it with a large sheet (I tore down the stupid blinds that came with the house in a fit of rage over how idiotic and stupid and half broken they were). I can't fix the rest of this house (most studs range from 14" to 17" apart because the guy who built this place was an absolute fool) so I was wondering, since I have a bunch of this left over fiber glass insulation form when I worked on our basement, and I block my windows anyways, would putting it between the plastic which if it comes off, would only be to refresh the tape, and the Window itself, somehow help insulate it further? And even if it does help, is it safe to do in the place I spend probably around 90% of my time in, even with an air filter.
Edit: I live about 30 minutes south of Boston, MA. In the summer it gets fairly hot, average of about 26c (up to 35c, that is around the highest I've personally experienced during a heat wave) and is very humid (upwards of 90%) and in the Winter it gets very cold, below freezing usually and extremely dry.