A great question! Besides changing your windows or having wall insulation. A curtain can make a huge difference to your room's temperature!To answer this question there are a few options. Firstly, you can team either a thicker fabric, such as a faux-wool, velvet or chenille with a thermal lining. Together, this creates a great barrier next to your window or door.
Furthermore, you can use interlining in between the thermal lining, or to cut on labour cost, use bonded thermal lining. These upgrades are extra thick and you can drastically save on your energy bill!