Yes, you can use too much bubble wrap. If you overdo it with the wrapping, it can strain the top of your box and break open the taped seal, risking the chance that the contents of the box could fall out or break. Use enough wrapping to fully cover your item without compromising the security of your box.

Insulating windows without plastic is usually the better method. Outside of simply replacing your windows, you could buy cellular shades, which trap air between the window and the home, add a window film that blocks UV rays and traps heat, or cover your windows with a low-emissivity coating called “low-E.”

Insulating an unheated garage can still be worth it. For instance, insulating an attached garage can help with heat loss from your house in general, and it can also make it easier to store electronics in your garage without worrying about them being exposed to extreme temperatures.

If you use your detached garage as a workspace, insulation can still make a difference. Plus, you can use space heaters and a window unit AC to help condition the space while you work without installing heating.

You do not always need to remove old insulation before adding new. If the existing insulation is in good condition—not wet, physically damaged, moldy, or infested with pests—you can add new insulation directly on top of it for a compounding effect. You can also mix different types, such as adding blown-in insulation around existing fiberglass batts.

However, removal is recommended if the old insulation is compromised by water damage or pests. You should also remove it if you plan to install a different type of insulation, like switching from roll or batt insulation to spray foam. If the existing insulation is very old or damaged, you will likely get more benefit from removing it and starting fresh.