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Posted 06/18/2018 in Hvac

Unico System Air Conditioner -The Best HVAC for Your Old House

my old house fix blog on the unico system hvac for your old house

Updated: 05/10/2024

While outside temperatures climb, there’s nothing like a good air conditioner to keep you cool and comfortable. So, whether you are remodeling, restoring, or building an addition, The Unico System air conditioner may just be your best option for central air conditioning.




Because Unico addresses many of the drawbacks associated with conventional HVAC systems, like size, noise, and space constraints. So let’s face it, the last thing you want to do is add air conditioning, at the cost of unsightly dropped ceilings, soffits, bump-outs, and large floor registers. Most of all, these aspects can really detract, and kill a home’s historical significance, character, and charm. So, let’s explore why the Unico System air conditioner is a perfect fit for your house!

You don’t want to miss out on this info! See the Unico System “LIVE” below!


Have you been curious about how a Unico System air conditioner operates?  See the Unico System air conditioner in action, right here with My Old House”Fix”!!!

What is a Unico System Air Conditioner?

 The Unico System is characterized as a modular, small duct, high velocity (SDHV) system. Therefore, it is the perfect solution to increase indoor comfort with Old Houses, and where new construction doesn’t allow enough space required by traditional HVAC systems.

  • Modular in design, and saves space.

  • Can be located in the attic, basement or crawl space.

  • Small duct, high velocity (SDHV) system.

  • Overall, a more efficient system than traditional HVAC.

  • Learn more from Unico HERE.


The Unico System

The Composition of a Unico System Air Conditioner 

The Unico System consists of the following components and Unico System parts. However, unlike conventional HVAC systems, The Unico System has a smaller footprint, and a more modular design.


Photos: unicosystem.com

Unico System Air Handler

Depending on application, location, and space constraints, the Unico System air handler is fully flexible to be mounted horizontally, or vertically. In addition, its fully customizable, and modular design is perfect for heating and/or cooling. Finally, the Unico air handler is also compatible with most conventional condensers, and heat pumps.

  • Blower Module – The cabinet is galvanized steel and insulated.  Additionally,it consists of a direct drive blower wheel, and is available in single (full on/off speed) or variable (soft on/off) speed motors ( E. C motor only). Read more HERE.

  • Cooling Module – Indoor fan coil (refrigerant or chilled water coil) that integrates with an outdoor condenser (cooling only) or heat pump (heating and cooling), and distributes air to a network of small ducts.

  • Heating Module (optional)- Indoor fan coil (with hot water or heat pump) that integrates with an outdoor condensing unit.

  • Electric Duct Heater (optional) –  At up to 20 kWh, this optional , multi-staged duct heater mounts to the discharge end of the blower module, if additional heat is needed.

  • Humidifier (optional) – A humidifier module can be added for extra comfort in winter months.

  • Capacities: Cooling –  2 to 5 tons. Heating – 20K to 120K Btu.

  • Learn more from Unico at  Unico System Resources.

Photos: Unicosystem.com    Modular Air Handler                       E.C. Motor

Heating Module              Cooling Module

Duct Heater

Unico System Air Supply Plenum

This is the main air duct feed coming off the Unico System air handler.

  • One-fourth the size ( at 7 -10 inches) vs a conventional plenum (duct).

  • Less thermal loss and more efficient, thus easier to seal with its gasket connections.

  • Learn more from Unico HERE.

Photos: Unicosystem.com

Unico System Sound Attenuator and Supply Duct (branch ducts)

The Unico System consists of flexible aluminum and sound attenuating Unico ducts.

  • 2 – 2.5 inch (inside diameter) duct.

  • Factory insulated for thermal efficiency.

  • Nylon inner core and insulated for sound absorption.

  • Gasket connection for more efficient seal to the plenum. As a result, less tape equals less leaks!

  • Flexible, and can run over, or around construction obstacles.  

  • Learn more from Unico HERE

Photos: unicosystem.com

Unico System Supply Outlets and Covers

Used at the supply duct termination points –  floor, ceiling, and wall.

  • 5 inch face plate diameter.

  • 2 inch outlet.

  • Many options – Colors, material, and shapes (round, slotted).

  • Learn more from Unico HERE.


Outdoor Condenser or Heat Pump

The Unico System can integrate and work with most commercial condensers and condensing units.

  • Unico System I-Series Condenser.

  • Conventional, commercial off-the-shelf condensers.

  • Conventional, commercial off-the-shelf heat pumps.

  • Learn more from Unico HERE.

Why Install a Unico System Air Conditioner?

First of all, many people assume that  conventional HVAC systems are easier, cheaper, and provide good performance. However, newer technologies, such as the Unico system have many added benefits that many homeowners may be unaware of. Simply stated, other HVAC systems just cannot match the performance of the Unico System air conditioner.

Photo: unicosystem.com

Here’s why…

Unico System – Higher Comfort Level

Most noteworthy, the Unico System provides a higher level of comfort compared to the conventional HVAC competition.

  • Temperature – The conditioned air is supplied through a series of two inch diameter Unico ducts. This stream of air  entrails, and mixes with the room’s air. Therefore, this process of aspiration produces a more even temperature distribution in the room, compared to a conventional system. As a result, the temperature differential is no greater than 2 degrees throughout the home. See the comparison videos HERE

Photo: unicosystem.com

  • Draft-Free – Traditional HVAC systems distribute air unevenly, consequently dumping air into rooms, and creating drafts with uneven temperatures. While the Unico System uses a principle called aspiration, thus creating a gentle suction around itself. This action draws the room air into its stream of cooled air. As a result, the Unico System delivers even, draft free cooling – from room to room, and floor to ceiling (Unico, 2012).



 Photo: unicosystem.com

  • Optimized for Zoning (EC motor only)  – Most noteworthy, this feature  allows a motor speed adjustment, so the system does not over-speed when zone dampers are closed. 

  • Humidity – The Unico System air conditioner removes up to 30% more humidity than conventional HVAC systems! As a result, you can keep your thermostat a few degrees higher to achieve the same level of comfort. Therefore, Unico saves on energy costs (Unico, 2012).

  • Humidifier Compatibility – The Unico System can be combined with a humidifier, for added winter comfort.

  • Operation  – Soft-start and soft-stop (ACB and EC motors only), for quieter operation. The unit will slowly ramp up the motor from start, to full speed, and vice versa.

Photo: unicosystem.com

  • Noise – Whisper quiet! Unico System supply tubing is designed to be as quiet, and efficient as possible. It features a nylon inner core, and insulation that absorbs sound. Additionally, Unico air handlers are designed to isolate noise and vibration, as a result of closed cell insulation. Together, they bring decibels levels to the equivalent of a soft whisper. While you’ll feel the comfort Unico provides, you’ll hardly notice it’s running (Unico, 2012).

  • Compare the decibel levels HERE

  • Listen “LIVE” from My Old House”Fix”. Full operation to 0:08, then slow ramp down to off. CRANK UP THE VOLUME!

Live Unico System Demo

Unico System Size and Installation

  • Unico System – Fully modular and customizable for any application, whether heating, cooling, or both.

  • Reduced system size equals less footprint, logistical impacts, and challenges when installing.

  • Air Supply Plenum –  The size is one-fourth (at 7 -10 inches) less than conventional plenums (duct).

  • Sound Attenuating Supply Ducts – At 2 -2.5 inches in diameter, the Unico supply ducts can be run through new, or existing cavaties, such as floors, ceilings, and walls (unlike conventional metal duct).

  • Supply Outlet Covers – Low profile, small, and blend well with their surroundings, unlike conventional air duct registers.

Photos: unicosystem.com


                     Photos: unicosystem.com

Unico System Efficiency and Performance

Conventional, metal-ducted HVAC systems are known for air leaks! As a result, more duct tape, equals more leaks! The Unico System footprint is small, yet it delivers the same level of cooling as a conventional system, and three times its size (Unico, 2012).

  • Modular E.C. Air Handler – Quiet, uniform, predictable air mixing, and performance. The fully insulated cabinet contains closed cell insulation, and no exposed fiberglass. The E.C Air Handler is 2 decibels quieter, in addition, up to 30% more efficient than the standard motor. Read more HERE.


  •  S.M.A.R.T Control Board – The brains of the new air handler series. Yet, combined with the E.C. motor, it provides the highest level of indoor comfort. Read more HERE. 

Photos: unicosystem.com


  • Plenum and Supply Ducts – Unico ducts are smaller, quieter, and insulated with vapor barrier. As a result, the Unico ducts are more efficient than conventional metal HVAC ducts.

  • Insulation/leaks – Unico ducts are easier to seal (gaskets), and have less thermal loss (due to dual-layer insulation) than conventional HVAC systems. Less tape equals less leaks, and wasted energy!


Photos: unicosystem.com

  • Recommended for affordable LEED platinum certified homes (Unico, 2012).

  • Newer buildings, custom homes, and commercial applications benefit with a tighter, smaller, and more efficient Unico duct system. Furthermore, Unico provides an affordable path in achieving an energy efficient building (Unico, 2012).

Unico System Air Conditioner: A Good Fit For Old Houses.

As stated at the beginning, the last thing you want to do is add central air at the cost of unsightly dropped ceilings, soffits, bump-outs, and large floor registers. Consequently, this can have very lasting, and negative effects on your historic property.

 Photo: hornfolio.com


Size and Installation

  • Space Saving – Unico System components are small enough to fit in closets, attics, basements and/or crawl spaces.

Cold air return and supply pipes fit nicely inside existing wall cavities.


            Photo: Vivo Home

Supply duct small enough to pass through closets, etc

Allows for a “discreet” retrofit, with new HVAC installations.


Photo: Radiant Designs

  • Unico System parts and equipment are small enough to pass through most attic and ceiling access doors/openings.

  • Unico System flexible, sound attenuating supply ducts can be “fished” through floor, ceiling, and wall cavities with ease. Try that with metal duct!

Photo: Essex Co.

Photo: Savco House

Less Invasive Installation

  • Most noteworthy, the Unico System can uphold and maintain a home’s historical significance, character, and charm.

Photos: unicosystem.com

  • No need to “gut” the home to install Unico System air conditioning.

  • No HVAC ducts contained within unsightly bump-outs and soffits.


  • Older structures can be air conditioned and heated with a Unico System. This is accomplished without major renovations, or sacrifice of existing space. Because of its smaller size, the Unico System is popular with preservationists and homeowners,  for retrofitting older homes built before the advent of central heating and air conditioning (Unico, 2018)




Supply pipes are much smaller than metal duct


Supply pipes can pass through to multiple levels


Supply pipes are small enough to fit in tight spaces.


Cold air return and supply pipes fit nicely inside existing wall cavities.

Supply duct small enough to pass through closets, etc


Airhandler requires very little space.


Low profile outlets blend well


More Unico System Resources


Unico System Air Conditioner: Installation Tips

Lessons Learned

Lessons learned from the Unico System installation at The Eiting House.


Many HVAC pros will tell you that most “equipment” failures occur from an improper installation, and NOT the equipment. Make sure your contractor is familiar with Unico System, equipment, and installation procedures.

Furthermore, find qualified Unico contractors HERE https://www.unicosystem.com/contact/installing-contractors

The THREE most common Unico System issues:

  • 1) Improper refrigerant line length, and refrigerant charge/torque.

  • 2) Improperly sized equipment – Assess the ASHRE Schedule J, with the Unico “match-up” matrix.

  • 3) Electronic systems check (LED panel): Check dip switches, cables, and wires.

Long-term planning for easier installation: Try to plan a Unico System (or any HVAC project) with another large project. This is where a wall may be opened, or an addition may be built.

Make sure your contractor completes the Unico Installation Checklist

  • Bulletin 30-121.019CL.005

Make sure the contractor completes a Unico Warranty, Registration and Commissioning Reports (forms may have changed).

  • Bulletin 30-103.004

  • Bulletin 30-100

  • Float/Wet Switch for drip pan not supplied by Unico.

  • Supply duct size – 2 vs 2.5 inch: 2.5 inch requires less runs, with same noise level, but more air flow. 2.5 inch uses the new threaded outlets, but cannot be used with fiberglass duct board. Finally, you can mix 2 and 2.5 inch ducts if needed.

  • Supply duct length: Try to keep to 10 feet in length. Shorter than 6 feet is noisier.


  • Have a qualified Unico contractor install, and per Unico guidelines.

  • To properly size equipment:

    • 1)  Unico quick sizer (Unico Bulletin 40-20) or,

    • 2)  Use the ASHRE Schedule J


Photos: unicosystem.com


  • Ensure static pressure is correct, and within operating limits.

  • Adhere to distance limits between the Unico Air Handler (inside) and Condenser unit (outside)

    •  32 feet up/down.

    • 19 feet between indoor units (2 air handlers).

  • Adhere to refrigerant line length.

    • Units come pre-charged up to 98 feet.

    • With additional refrigerant charge  – 131 feet max.

  • Cut, debur, and properly torque the refrigerant lines. A flare nut and torque wrench  are required.

  • Pull a 500 micron, deep vacuum before allowing refrigerant into the lines.

  • Multiple cold air returns are best for maintaining temperatures, from floor to floor.

  • Air supply ducts: Add more runs for lower air flow (cfm) at the outlets = quieter operation.

    • Check  air flow at the outlets with a turbo meter.

    • Very low noise – 27dB, 8 outlets per TON.

    • Ultra low noise – 25 dB, 10 outlets per TON.

  • Keep air plenum 7 to 10 inches in diameter. The best style is “closed loop”.

  • Keep tee’s and elbows to a minimum.

  • Try to install outlets in ceiling and walls, resulting in better “aspiration” of air. 

  • Space supply ducts a minimum of 6 inches apart on the plenum, and 12 inches from the end cap.

  • Plenum: Ensure that there is at least 24 to  48 inches off the air handler, before the first tee, elbow, or supply duct.

  • Supply duct lengths should be kept to 10 feet in length. Every additional 5 feet = 10% capacity loss.

  • Insulate air handler mounting straps to prevent noise and vibration from transferring to living spaces.

  • Finally, make sure the ends of supply duct runs (just before they exit into rooms), have a gradual bend in the flexible pipe to reduce noise. Additionally, the bend should be greater than a 5 inch radius, and make the end look like a “question mark”.


WARNING – Too tight of a bend, WILL drastically increase sound levels!


  • Allow an inexperienced HVAC contractor to install a Unico HVAC System.

  • Allow contractor to skip the warranty, registration, and commissioning reports.

  • Skip proper system sizing, layout, and installation planning.

  • Ignore air supply plenum requirements and dimensions.

  • Ignore supply duct requirements and dimensions.

  • Tight supply duct bends (at the end of a run), increase system noise!

  • And finally, don’t ignore the system refrigerant line requirements – max length, and proper torque.


In conclusion, and contrary to common HVAC myths, air conditioning CAN be installed, or retrofitted into historic, difficult, and constrained structures. Most of all, The Unico System air conditioner is a perfect example of an HVAC system that meets small space requirements. Unico does this while delivering increased performance, and minimally impacting historic charm and character. So finally, just remember…you don’t have to “gut” your house to install a Unico HVAC System!



Best of luck, and keep on Fixing!   

Christopher Hewett My Old House Fix

For more info visit:  www.myoldhousefix.com

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