What are my best options for replacing the forced-air furnace in my small bungalow built in the 1920s? The furnace is at least 25 years old.

Asked by Edward Greene
Memphis, TN

I live in Memphis, TN. Plan on adding central air. The present unit is natural gas.


When it comes to replacing your existing HVAC system, you have a lot of options depending on location and budget.  Since you intend to add central air, your primary options include:

  • conventional gas-fired heating and a split-coil air conditioner (good),
  • an air-source heat pump (better), or
  • a geothermal system (best).

These options are listed as good, better, or best when considering energy efficiency.

Improve your home's performance first

What is equally as important in deciding what to install is to consider improving the thermal performance of your home. It makes little sense to install a highly efficient HVAC system in a dwelling that is inefficient. You'll save money, but you'll just waste energy more efficiently!

  • Upgrading the thermal envelope will not only improve the comfort and efficiency of your home but it will reduce the size of the equipment needed to service your home.
  • Oversized HVAC systems is a common problem in the industry. Make sure that your HVAC contractor completes heating and cooling load calculations for your home on a room-by-room basis. 
  • Contractors using a "rule of thumb" sizing method should be avoided at all cost.

Air source heat pumps

Air source heat pumps are a viable option in moderate, mixed temperature climates. Your local installer can determine if their equipment can handle 100% of your heating requirements.

  • If ambient temperatures routinely fall below 30 degrees Fahrenheit, you may require emergency backup heating.
  • Auxiliary heating is often provided by electric resistance heating elements. This is an expensive back up system.


If geothermal is in the budget, you'll want to make the thermal envelope improvements to your home prior to installation so the heating and cooling loads are kept to a minimum.

The smaller the system, the lower the installation cost.


For more information:

Read "What do you think about geothermal heating and cooling systems?" a Q&A answered by Rick Goyette.

Tagged In: heating cooling

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