A new furnace will just decrease that which we waste. Last, if you put in a new furnace, you should think about replacing your previous thermostat with one that's digital or digital programmable.
This Single Track Bypass Barn Door Hardware Kit allows two doors to over-lap each other so they are basically always connected, but one door can slide in front/behind the other almost all the way. This is a great solution for limited space that requires 2 doors. Suitable for applications with two doors on one track!