In order to insulate a room, would it make sense to apply a layer of bubble wrap to my walls/ceiling? What about some other material like mylar or foylon? What major factors would affect the answer to this question? In particular, would the amount of sunlight coming into the room have a significant effect?
If yes, how much benefit would I get from <100% coverage, e.g. from missing some uneven spots on the wall or missing the ceiling?
(Context: I am already taking a number of steps to insulate my windows. I am also a renter of a second floor unit with somewhat irregular construction, which I take to mean that it is a hassle for me to modify the exterior or the inside of the wall and I cannot assume that "best practices" were followed in the construction process.)
Best Answer
I would select non-flammable insulating materials such as rock-wool, or fiberglass (fully puffed up; mashing it badly hurts its performance). To use these, you will need some sort of framing to hold it up. It can't just be taped to a wall.
It's not out of the question to frame a room inside a rental house; I've seen it done. However this is the wrong year to be buying lumber and building supplies: COVID shut down the logging and milling earlier this year, meanwhile everyone stuck at home has gone on a remodeling binge, meanwhile new-home construction remains a very strong market.
However, you really need to work the normal insulation priority list: sealing of doors and windows first, window treatments second, then walls pretty much last.