I am extremely cold sensitive. We live in Chicago and moved from a well-insulated apartment to one with old windows and poor heating. New windows were prohibitively expensive, and were not allowed by the building. We got indows for all rooms. It has made an amazing difference. The temperature is up by several degrees, and I can no longer tell in what direction the wind is blowing! You can clearly feel the difference if you put your hand next to a window without the insert and then to one with the insert. I think the indows provide just as much insulation as new windows. The do require set up, and opening the windows is no longer so easy, but it is worth it. They also require storage space, if you are going to take them off during the summer. We also bought the storage sleeves.