Ductless Mini-Splits vs. Central HVAC for Additions (Sunrooms, Garages & Basements)

Adding space? Compare ductless mini-splits vs. extending central HVAC. Costs, comfort, and when each option wins for Missouri homes.

When your addition is standalone (such as a sunroom, garage, or bonus room) or if your current system is nearing its capacity, opting for a ductless system is typically cleaner, quicker, and more efficient. Conversely, if your addition is seamlessly incorporated into the main design and your existing system has adequate headroom, extending your central HVAC can be a wise choice.


  • Is the new space physically far from existing ducts or separated (e.g., garage/sunroom)?
    yes→
    Go Ductless
  • Does your current system struggle on extreme days?
    yes→
    Go Ductless (avoid upsizing the whole house)
  • Is the new space small and used intermittently (workshop, hobby room)?
    yes→
    Go Ductless (zoned control saves money)
  • Is the addition fully integrated, and does your system have spare capacity?
    yes→
    Consider Central (extend supply/return + balance)


Real-World Scenarios 

  • July sunroom humidity: ductless systems aid in dehumidification and prevent short cycling. 
  • Detached or finished garage: ductless options eliminate the issue of dirty duct returns while providing targeted heating and cooling. 
  • Basement transformation: both avenues are viable—ductless for individualized temperatures, or central if ducts are nearby and returns are accessible.


Sizing & Placement Notes

  • Direct the indoor unit towards the longest dimension of the room. 
  • Refrain from directing airflow straight onto seating areas. 
  • For central extensions, include sufficient return-supply-only additions to balance hot and cold air.


Maintenance & Ownership

  • Ductless: clean washable filters monthly in peak season; annual professional cleaning of coils/fan(s).
  • Central: change filters on your home’s schedule; have professional inspection and cleaning twice a year.


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Thinking about a sunroom or garage comfort upgrade?
Request a free, no-pressure estimate from Johnson Heating & Cooling:

(636) 332-4141.

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