It’s easy to install an HVAC system into a new construction, but it can be a challenge to fit one into an existing home. However, a mini-duct system is a less invasive option to add cooling to your space. In this guide, we’ll explain how to retrofit air conditioning using mini-ducts. We also have a video featuring This Old House’s plumbing and heating expert, Richard Trethewey, who explains the components and benefits of a mini-duct air conditioning system.
Components of a Mini-Duct System
The ducts of mini-duct systems are small and flexible, so they’re easier to squeeze into tight spots than traditional central air conditioning systems. Also called small-duct or high-velocity systems, mini-duct systems have several components, which include:
- Air handler unit
- Blower module
- Cooling coil
- Main supply trunk
- Round outlets or vents
- Small-diameter flexible ducts
How Mini Duct Air Conditioning Systems Works
In a mini-duct system, air is drawn in through a single return duct. HVAC technicians usually install the air handler, which has the cooling coil and blower in it, in an attic or basement. From there, the main supply trunk branches off into small, flexible ducts that you can route through walls, floors, and ceilings throughout the house. We’ll outline the steps the mini-duct system takes once you flip the switch to turn on your AC:
- Air intake: A single return duct pulls air from the living space into the system.
- Cooling process: That air passes through a filter and over the cooling coil in the air handler.
- Air distribution: A blower forces the cooled air through the main supply trunk.
- Room delivery: The air travels through small, flexible ducts to outlets in each room.
- Air circulation: High-velocity air flows from the outlets and distributes the cooled air throughout the room.
Advantages of Mini-Duct Air Conditioning
Slipping those small, flexible ducts through walls, floors, and ceilings with little structural impact isn’t the only benefit of a mini-duct system. Here are a few more advantages:
- Energy-efficient: They use more energy to move air than central AC, but they’re still more energy-efficient because they dehumidify spaces better, have less air leakage, and could offer zoned cooling.
- Improved comfort: These high-velocity systems distribute even temperatures, provide a quick cooling response, and have reduced drafts under their vents.
- Less noise: Mini-duct systems are quieter than traditional HVAC systems.
Installation Process for Mini-Duct Systems
We recommend you hire an HVAC technician to install your mini-duct system, but if you understand what it takes to add one to your home, you’ll know what to expect during the process.
Planning and Design
Your HVAC technician will need to assess your home’s cooling needs and structural layout, which includes:
- Evaluating electrical and condensate drain requirements
- Calculating cooling load requirements
- Determining optimal air handler location
- Planning duct routes and outlet placements
Air Handler Installation
If you don’t have an attic or basement, an HVAC professional will likely suggest placing the air handler in a closet space. They’ll confirm the designated space can support the unit’s weight, has proper ventilation, and is close to the electrical connections and condensate drain.
Ductwork Installation
This part of the process takes the most time. The HVAC technician will connect the air ducts to the air handler and outlets and also install the main supply trunk. They’ll seal and insulate the ductwork and route them through the home.
Outlet Placement and Installation
Once the ductwork is in place, they’ll add outlets to the ceilings or floors. Most technicians know to place the outlets in corners to circulate the air without creating uncomfortable drafts, but you can confirm their placement during the planning and execution phase if you’re not sure.
Considerations for Retrofitting with Mini-Ducts
Before committing to a mini-duct air conditioning system, there are a few things you might want to consider, which include:
Home Compatibility
Your home may not be compatible with a high-velocity system. Here are a few factors you’ll need to consider if you’re looking into adding one to your home:
- Available space for the air handler
- Existing insulation levels
- Home’s overall energy efficiency
- Structural limitations for duct routing
Cost Considerations
The cost to install a mini-duct system depends on your home size, system capacity, and how complex the installation is. It could cost more than some traditional AC options, but you might save since it doesn’t require major renovations or structural upgrades. You may also notice some utility savings since these systems are more energy-efficient.
Maintenance Requirements
You’ll have to perform regular maintenance on your mini-duct system so that it continues to run properly. This type of upkeep is typical of any HVAC system and includes:
- Air filter replacement
- Annual professional tune-ups
- Coil cleaning
- Duct inspection and cleaning
Consider Alternative Air Conditioning Solutions
There are other cooling solutions you can consider adding to your home if you’ve decided a mini-duct system isn’t right for you. Here are a couple of potential alternatives:
- Ductless mini-split systems: You can use these to cool your home without the need for extensive ductwork.
- Traditional central air: Central air might be a viable option if you aren’t concerned about structural modifications.
Our Conclusion
Mini-duct air conditioning systems are energy-efficient, quieter than other HVAC types, and don’t require many structural modifications. We recommend working with an HVAC technician to find the right cooling solution for your home, but no matter which one you choose, there are a few ways to reduce energy consumption and enhance your system’s performance. You can opt for programmable thermostats that cool only when it gets too warm inside a space, maintain your system, and make sure insulation is installed properly.
