Also put foil-backed insulation over any single-paned windows you don’t use. Or do what I did and cover only half the window if you still use the room occasionally.
And if you have an HOA that bans this, placing the insulation behind the blinds instead of directly on the window will do the trick and make it difficult to see what you did, especially if you keep the blinds closed or only open them partially and angled downward.
Also put foil-backed insulation over any single-paned windows you don’t use. Or do what I did and cover only half the window if you still use the room occasionally.
And if you have an HOA that bans this, placing the insulation behind the blinds instead of directly on the window will do the trick and make it difficult to see what you did, especially if you keep the blinds closed or only open them partially and angled downward.