Emergency mylar/aluminium blankets are 5 for $12 +/-. Taping them in front on your blinds behind the drapes, reflects back over 90% of heat to lower furnace use by over 1/3 at least. With 15F, -9 C my house built in the early 1900s, old wooden windows, was losing 3 degrees F every 15 minutes. After I put these on the windows, it has not lost a single degree in over 3 hours and holding, with only a 300 watt electric heater, that was on before as well. This will cut your furnace cost by half or at least a third.
I use the window insulation kit. Used it in an old farm house. When you heat it with the hair dryer it shrinks and becomes tight and crystal clear.
Under 10 bucks. Duck brand.
Wow, great tip, thank you!
Dollar store for the space blankets?
Interesting. I remember reading about this concept in Mother Earth News, and in fact, placing the mylar inside the wall.