If you live in an older house or building, you probably have older windows that are not energy efficient. I purchased a Window Insulation Kit (3 pack) for about $5.00 from Home Depot. It comes with plastic, double sided tape & all you have to do is cover the window & then use a hairdryer to “seal” the plastic to the window. According to the kit there is an up to 90% energy difference.
Don’t cover up all of your windows! For safety’s sake you may want to leave at least one window in the kitchen open, as well as one of the common areas in the event of an emergency.
We’ll see next month if it actually makes a difference on the heating bill, but my bedroom is much more cozy now!!!