When to Install a Ductless Air Conditioning System

Mini split in room near ceiling

What’s the Difference Between a Ducted and Ductless Air Conditioning System?

Air conditioners provide cool air through two forms of delivery: ducted or ductless systems. The majority of homes in the U.S. are built with air ducts made from sheet metal that run from the main air conditioning unit to each room in the house. The ducts are hidden in walls and air is delivered to each room through vents. In ductless systems, the refrigerant from the outdoor condensing unit is sent directly to an air handler located on the wall or ceiling of a particular room.

While a ductless system can have several benefits, many homeowners with existing ductwork will be better off from a financial and comfort perspective by using a ducted system.

Benefits of Ductless Air Conditioning System

  • Easy for a contractor to install (no ductwork)
  • Some flexibility in location of air handler
  • Ability to cool the home by specific zones
  • Quiet when operating

Concerns with Ductless Air Conditioning System

  • Reduced overall indoor air circulation and increased humidity can lead to comfort and air quality problems
  • Appearance of the air handler on a wall or ceiling in each room
  • Higher cost of ownership for a whole-home solution if your home already has central AC
  • External refrigerant lines which could cause energy losses and aesthetic concerns
  • Serviceability and ease of repairs could be a problem as the unit gets older

When to Consider Installing a Ductless Air Conditioning System

While we don’t recommend a ductless system for most homes, there are several situations where a ductless system should be considered over a traditional ducted one. These include:

  • Room additions or adding cooling to a garage or work space
  • Cooling smaller, older homes without existing ductwork
  • When space is at a premium and ducts won’t fit
  • When replacing a less efficient window/room air conditioner

The bottom line on Ductless Air Conditioning Systems

Your comfort, humidity and long-term reliability should all be factors in making a smart decision. As with any important HVAC question, it makes sense to talk with a professional. Contact a reputable licensed contractor who can explain the many options and variables when it comes to selecting the best solutions for your needs.

If you’re considering a ductless system, comment below and tell us some of the reasons it appeals to you!

For more information on ductless systems, click here.


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38 thoughts on “When to Install a Ductless Air Conditioning System

  1. Great post! For ductless air conditioning systems your comfort, humidity and long-term reliability should all be factors in making a smart decision. Thanks.

  2. I currently have a central heating and air system. it will need to be replaced in the next couple of years. My house is not very large but the living room gets hotter than any other area of the house (Birmingham, Alabama). It only has one vent and its behind the couch, there is really no good place to add another vent. I have thought about adding a ductless unit to supplement the living room…. any thoughts?

  3. This article, while several years old, was quite helpful to me and I would love to get some thoughts from you.

    I am in South Louisiana, just west of New Orleans, surrounded by just as much water. Design temps are 92F dry, 80F wet and 33F cold. We probably run AC for maybe 300 days a year, the heater for 30 and actually have pleasant weather in the balance (April and October/November).

    My house is 40+ years old, 1-1/2 story ranch (cape cod style), 2,450 SF. The insulation, where exists, is in bad shape. The duct work is undersized at even in worse condition. The home has two central A/C units, a 1-1/2 ton upstairs installed directly in front of a 5-ton for downstairs…both 20 years old. Because the house is a 1-1/2 story, you cannot fit both HVAC units and be code compliant. Additionally, the limited attic space, especially accommodate the stairway and dormers, does not permit properly sized and properly insulated ductwork. I have contemplated re-insulating the house to the current non-vented attic configurations recommended in the current codes for homes in Zone 2 with humid climates. However, to do this, both HVAC systems and all duct work needs to come out. I have tried to “patch” the duct work as a DIY homeowner, however the job is way too big and there are too many sections of ductwork that are compromised. Much of it now sits on the attic floor where condensation has rusted the sheet metal work.

    I have spoken to a couple of AC contractors who have told me to just fix the existing duct work and just put new AC variable speed AC systems and let the system balance the heat load. I find this answer unacceptable as this is my home, not just another contract to me. My parish has adopted the latest building codes and requires permits and design review for all mechanical work. Have run the Manual J and Manual D numbers and I know the new duct work will not fit. I also know you cannot fit two AC systems with returns and duct, into my attic space and maintain the code compliant access. As it is now, getting access to the 5 ton unit reminds me of the nursery song about over the mountains (1-1/2 ton hvac) and through the woods (mixed duct work, hanging electrical wires draped on duct work and roof rafters). Clearly will NOT be acceptable to current day code officials.

    I have also considered a single large system with zoned duct work. More reputable HVAC contractors seem to favor this approach. I still run into issues with ductwork access and placement due to required sizes. Also, because of layout, I would need 5 zones. This approach still requires everything to come out, repair insulation, then put everything in.

    So my plan was to install ductless systems throughout the house. I would install 4 each 9K or 12K ceiling cassettes in my large living area (1,000 SF) and 4 small 6k units in each bedroom (1,350 SF upstairs) and two 6k units in my garage (450 SF currently no HVAC but within my building envelope). Ten mini units is quite a lot of copper! Mitsubishi has a line where a common copper line can be run to a central location and the splitter box connects to and communicates to individual units. The setup requires two compressors. Once this is done, the two HVAC units and all duct work can come out. Now I can do the insulation upgrades to the home.

    The final act would be to install a small air handler and gas furnace for the whole home which would also include fresh air exchange and common dehumidifier – this would help with air distribution, overall comfort and the ducts will fit! The furnace would be a 40k/28k dual stage. Based on Manual J, if I upgrade the insulation for the house to current standards, this would be adequate for the entire house.

    Now I understood the mini-splits were more efficient at dehumidification. Your write up above states the opposite, or did I mis-understand?

    I understand my approach will be more expensive than conventional but I think it would be more efficient by eliminating the old duct work, associated pressures and losses. I do have full access for routing copper lines and drain lines (all condensate pumps to plumbing stacks, all accessible). More importantly, this approach seems like it is better code compliant without getting into major structural renovations.

    Unfortunately, I have found HVAC contractors recommendations are highly biased by the manufacturers they sell/service and are not always the best for the application. This is the most frustrating part of the industry. As an engineer, I am not allowed to operate with blinders, so Im instead am hoping to identify the best product line, then find the best contractor.

    I appreciate your input.

      • Brad, Your reply to this man stinks. It’s a cop-out.
        It reminds me of the Wal-Mart associate answer when a customer asks them if they have any more of an item so they say “everything we have is on the shelves”. Having worked on their computer systems in the back of the stores, I know that story line is a lie.

  4. Hello – I have a bilevel home with a one zone central air. The downstairs family room is not keeping as cool as in previous years. I had service performed and they do not see any issues with the unit. They said it may be an issue with vents but do not see anything on the surface. Would you recommend us upgrading to ductless or upgrading with ducts. I assume with ducts they would need to tear holes in walls/ceiling.

    • Here are a few thoughts. Has the load changed on that space? This could be caused by adding or removing doors, walls windows, etc., or removing shade trees, changes in insulation (settling) among other things. If the load has changed (increased) then you might need more capacity (a larger system) to keep up with changing demand. If it continues to be a problem you could add a small mini-split to the space that needs additional cooling and keep your whole home system as well. This is a pretty common practice for people with spot cooling needs. Hope this helps.

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