Heat loss and gain are from air infiltration. Protect the doors, windows, basement and furnace.
Use film kits and caulking and they will reward you. Windows are an easy area to insulate. Unless you have installed new windows, you are probably loosing heat through the glass and letting too much wind to infiltrate through poor seals.
Window shrink film kits return up to a 90% increase in R-value (resistance to heat loss) over a single-pane window. In an older home installing the kits could pay for themselves in one month plus the added value of having a more comfortable house. If new windows are not in your near future consider installing the film with a reusable tracking around the window.
Good old Mortite, reusable rope caulk can be applied in cracks around windows to seal wind, moisture and reduce sweating. Soft, non-hardening, easy to apply and easy to remove, Mortite has been used for over 50 years.
Foam strips and V tape stop air effectively. I think V tape lasts longer.
Switch and receptacle insulators are easy to install and reduce cold air in older homes without wall insulation. According to Frostking.com “By sealing every single socket and switch in the average home, a homeowner can save approximately 10% year round on their energy bills.”
An often forgotten area is the joist-ends in the basement. Cut 16-inch sections of fiberglass insulation (any thickness, but thicker is better) and stuff it between the floor joists around the perimeter of the house. Use the insulation full length on the walls that are parallel with the joists.
And use canned spray foam to close larger openings that let air out of your home.
Check the weather stripping around the door including the threshold. Just because a door is on a lower landing does not mean it’s not letting in a ton of cold air.
A bad door sweep lets a tremendous amount of air into your home.
Installing a programmable thermostat can save up to 15% a year on your heat bill. That number is reduced in harsher climates, which could include us, but savings are still there to be had. A reliable and easy to program thermostat can be purchased for less than $60 and installed by most homeowners.
And change that furnace air filter!