When it comes to getting optimal performance from an older home’s HVAC equipment, improvements span the spectrum from maintenance and tuneups to total system replacement. In between are several other steps homeowners and contractors can take to improve and extend the performance of the home’s existing systems. Below are several options to consider.

Decision Making

Carefully consider if upgrading an existing HVAC system is the appropriate choice. In many cases the costs associated with intervention beyond basic maintenance and cleaning do not reap adequate benefits compared to replacing the system with new equipment because new equipment often has higher efficiency and better performance.

For general assessment and decision-making, including useful decision trees for determining whether or not to replace an existing system, see the guide Pre-Retrofit Assessment of Existing HVAC Systems. For general information regarding HVAC system types, typical efficiencies, and capabilities, see Building America Best Practices Series Volume 14 - HVAC: A Guide for Contractors to Share with Homeowners. You can also search the Building America Solution Center for guides describing specific heating and cooling systems.

Maintenance and Repair

For general maintenance and repair, see the following resources:

• ACCA Standard 4: Maintenance of Residential HVAC Systems
• Heat & Cool Efficiently

Upgrades

In addition to general maintenance, there are several specific HVAC upgrades that can improve system performance, extend system life, or expand service. The upgrades below were included on this list because they were either deemed cost-effective due to energy savings, or reasonable interventions to improve or expand system capability, or necessary because of lifestyle or architectural changes. Each of these measures is further addressed in the guides linked here.

• Replace a PSC fan motor with an ECM drive - for energy savings and quiet variable-speed continuous operation for greater comfort. For more information, see the guide ECM Air Handler Fans.
• Replace burners in oil furnaces or boilers with a high-efficiency flame-retention-head oil burner for significant energy savings. For more information, see the guide Oil-Fired Boilers.
• Upgrade to a programmable thermostat – to automatically set back temperatures while away from home for energy savings. For more information, see the guide Thermostat Control.
• Add dehumidification – to control indoor humidity levels for improved comfort and to inhibit mold growth. For more information, see the guide Whole-House Dehumidification.
• Improve filtration by adding a high-MERV filter for improved indoor air quality. For more information, see the guides High-MERV Filter and Proper Installation of Furnace and Air-Handler Filters.
• Improve exhaust fans by adding a backdraft damper to prevent heat loss. For more information, see the guide Bathroom Exhaust Fans.
• Add whole-house mechanical ventilation to improve building air quality. For more information, see the guides Whole-Building Delivered Ventilation and Whole-House Ventilation Strategies for Existing Homes.
• Seal and/or insulate the duct system to improve the performance of your HVAC system, increase comfort, and reduce energy costs. For more information see the guides Sealed and Insulated Flex Ducts, Sealed and Insulated Metal Ducts, Sealed and Insulated Fiber Board Ducts, and Injected Spray Sealant for Existing Ducts.
• Improve balancing of ducted systems to improve energy savings and thermal control by confirming an adequate return path, resizing return grilles, or adding transfer grilles or jump ducts, or adding dampers in the supply or return ducts. For more information, see the guides Ducted Returns, Transfer Grilles, Jump Ducts, Pressure Balancing Supply and Return Ducts in Existing Homes.
• Add ductwork to extend space conditioning to added living space. For more information see the guide Compact Air Distribution.
• Add terminal units (e.g., a radiator/convector or additional ductless heat pump head) to extend space conditioning to added living space. For more information see the guides Mini-Split (Ductless) Heat Pumps, Gas-Fired Boilers, Oil-Fired Boilers, and Condensing Boilers.
• Add a dedicated system to independently heat or cool a new addition. For more information see the guide Mini-Split (Ductless) Heat Pumps.

Costs

The upgrades listed above vary widely in terms of costs and labor involved in installation.  If you are considering equipment replacement instead, while replacing HVAC equipment can be costly and labor-intensive, it often reaps large rewards in terms of energy cost savings and comfort.

Some upgrades that reduce energy use may qualify for local or federal rebates. Check for rebates and incentives on local utility websites and also at the following database:

Database of State Incentives for Renewables & Efficiency (DSIRE).