Many Home Owners spend thousands to replace their Furnace or install a Heat Pump without first assessing the home.
A new 90% efficient Furnace / Heat Pump is not going to save you any money if the heat flows out and cold air flows in your home easily. In fact you would be throwing money away as there will not be enough savings to cover the expense over a reasonable amount of time.
A good example of energy transfer is to think of a Camping Cooler. If you buy a cheap Cooler without much insulation your ice will only last about a day, if you buy a good well insulated Cooler your ice will last about 3 days. Homes are very similar to this in energy transfer. A well sealed home will hold heat and keep out cold air much longer saving you money.