It’s common knowledge that heat rises. When the lower part of your house is nice and warm because your furnace is on, the warm air is rising up from your basement to your second floor, into the attic, and then out the roof.
Experts agree that the attic is arguably the greatest single heat loser in the home.
The only way to prevent this heat loss is to insulate. The beauty of good attic insulation is that it will also prevent cool air from escaping in the summer (when your air conditioner is chugging away).