How to replace your furnace
When your furnace isn't to blame
If your home is too cold, the furnace isn’t necessarily the culprit. The following fixes are easier and less expensive than furnace repair or replacement. (As a bonus, many of these will also make your air conditioner more effective.)
Is your furnace getting power? Check for tripped circuit breakers or blown fuses.
Leaky ducts (the metal tubes that distribute heat throughout your home) can be sealed so that more hot air actually gets blown into rooms instead of seeping into the attic. The American Council for an Energy-Efficient Economy says sealing leaky ducts can improve efficiency by 15% to 20%; it will set you back a few hundred dollars, but that’s much cheaper than a new furnace.
Better insulation in your attic and walls will help your home retain heat.
New weather stripping around doors and windows will keep cold out and heat in.
Upgrading a manual thermostat to an electronic one can regulate your home’s heat more effectively and lower your energy bills.
Replacing a furnace’s dirty air filter can improve airflow.