An empty remodeled basement of a home

A finished basement requires heating and cooling; therefore, you need an appropriate HVAC system. Since basements aren’t always a part of ducted HVAC systems, you may consider installing a ductless mini-split in yours.

Naturally, you may wonder whether mini-splits are suitable for basements.

Read on to learn more about how these HVAC systems function and if they are an ideal choice for basements.

Are Ductless Mini-Splits Well-Suited For Basements?

Ductless mini-splits are not only a good idea for basements but a fantastic option. A mini-split can heat and cool your basement, which can cover only one room or several areas. Mini-splits also dehumidify basements while increasing energy efficiency.

The only practical concern you or some homeowners may have is the drain line for mini-split heat pumps in basements. Luckily, you have at least three solutions to choose from to solve this issue. 

Why Ductless Mini-Splits Are a Good Idea for Basements

In general, basements aren’t ideal for every air conditioning system. For instance, your basement may not have a window. Even if there’s one or more, the space above the ground might be insufficient for a conventional window air conditioner.

The only way to heat and cool the basement with a central HVAC system is by installing new ducts. Unfortunately, extensive ductwork is both complicated and expensive. Besides, your HVAC system may already be at its peak capacity to heat, cool, and ventilate the rest of your house.

Therefore, ductless mini splits tend to become a default option for basements. Still, a ductless mini-split system is a pragmatic choice, even if the other options are available.

Here’s why:

Wall Mounted Mini-Splits Only Require a Small Hole

Mini-splits have different designs, but the most common style has an indoor unit that you mount on a wall. If you choose an exterior wall, this indoor unit requires only one three-inch (7.62 cm) hole – give or take – for the refrigerant or coolant coil to connect to the outdoor condenser.

A mini-split air handler in the corner of a room just below the ceiling with a vent installed

Also, the same hole is enough to route the drain line from the indoor or evaporator unit to the ground outside. However, a gravity-fed drain line setup works better if the indoor unit is installed above the ground level. Otherwise, you need one of the mechanisms that we’ll explain in greater detail later.

Unlike ducted HVAC systems, you don’t need elaborate ductwork, supply vents, return vents, etc., for mini-splits. All you need is just one small hole in the basement wall, and you can install an indoor mini-split unit using the bracket and fasteners in the box.

In contrast to window air conditioners, mini-splits don’t need a large opening through a wall or window for installation. Also, window air conditioners don’t work on interior walls. A mini-split indoor unit can be installed on an interior wall, and the lines can be routed as necessary. 

They Offer Zonal Heating and Cooling

Mini-splits provide both heating and cooling. You can choose a model or capacity to meet the specific requirement in your basement based on its size and purpose. Therefore, you can have meticulously planned and executed zonal heating and cooling.

Consider the following scenarios:

  • You may get a 0.75-ton (9,000 BTU) mini-split if your finished basement has only one small living area or room. 
  • You can choose a 1.5-ton (18,000 BTU) system if the basement has more than one room, and each can have a separate evaporator unit or indoor head. 
  • You can opt for a two-ton (24,000 BTU) unit if your basement has a living area, games room, gym, or home theater, with each zone having a separate indoor unit.

Each of the above setups requires only one exterior condenser outside your house. So, a basement can be fully covered with adequate heating and cooling. Plus, you can independently regulate the heat setting or temperature for every room or zone.

A ductless mini-split compressor on the external wall of a home

Therefore, you can heat or cool as little or as much of the basement as you want in real-time using only one outdoor compressor unit and single or multiple heads indoors. 

Mini-Splits Will Dehumidify Your Basement

Basements are relatively damp and sometimes excessively humid. Mini-split heat pumps regulate the relative humidity of a place while also heating or cooling the space you choose.

The evaporator units have a drain pan that collects indoor moisture. This drain line carries the water out of the indoor space. 

Therefore, your basement will be less vulnerable to mold growth and the unpleasantness of an unventilated space with a ductless mini-split.

They Can Increase Energy Efficiency

Ductless mini-splits are energy-efficient due to two main reasons.

  • First, you can heat or cool only one room if you want – the evaporator or indoor units of the other unoccupied spaces in your basement can be off. The condenser outside will still run for an evaporator or indoor unit and heat or cool only one room you select.
  • Mini-splits save or prevent 30% of energy lost through the ducts of central HVAC systems – of course, that approximate loss is for an entire house, not just one room. However, you cannot do much about the heating or cooling loss in those ducts.

Mini-splits don’t have this inherent energy loss problem. They don’t heat or cool air other than what’s circulating through its evaporator coils in the selected room or zone. Therefore, you benefit from significantly higher energy efficiency.

Why Mini-Splits May Not Be a Good Idea for Basements

The drain line is the most common issue with ductless systems in basements. If your indoor evaporator unit isn’t above ground level, you cannot use a gravity-fed drain line to route the condensate outside. However, this problem has more than one solution. 

A ductless mini-split condensate drain at the bottom of line near the compressor
Courtesy of Quality Heating and Sheet Metal Company, Inc.

The other issue is the size—not the unit outside but the one indoors. Your basement may not have sufficient headroom for an indoor evaporator unit mounted on the wall. Also, some homeowners may think a protruding console won’t suit their decor.

You can address both issues with the following solutions:

Use a Gravity-Fed Drain Line

Suppose the indoor evaporator unit is below the ground level in your basement. In that case, you must use a drain or outlet below the indoor unit.

Your basement is likely to have a floor drain. So, you can direct the condensate or water line from the indoor unit to this floor drain.

However, this drain could lead to a sump pit or sewer system. These two scenarios demand different installations of the drain line’s setup.

If the floor drain leads to a sewer system, you need a trap for the condensate line or pipe from the mini-split evaporator unit. This water trap inside the drain or condensate line will block foul odors from the sewer system. 

Also, it would help if you had a valve for the floor drain to protect the setup from sewer backflow. But the floor drain in your basement or plumbing system may already have such features. 

Many houses have a sump or sewer pit. You can use a basement floor drain leading to a sump pit without concern.

But, of course, you should already have a sump pump to move water up and out of your property. Likewise, if you have a sewer pit, you already have an ejector pump.

Therefore, you can use the floor drain in your basement to route the condensate from a ductless mini-split system. 

Install a Condensate Pump

Suppose you don’t want a gravity-fed drain line. Alternatively, the floor drain is not in an appropriate place for you to route the condensate from the position of the mini-split’s indoor unit. In these circumstances, you can use a condensate pump. 

 The head unit of a mini-split with condensate pump being installed at right
The head unit of a mini-split with condensate pump being installed at right

You can use only one condensate pump for multiple indoor evaporator units for a single ductless system. You can strategically install the condensate pump to get the water to a drain on the ground floor or route the line outside.

Ductless heat pumps don’t necessarily have a condensate pump inside the evaporator unit. But you’ll find a few models with a similar feature, bringing us to ponder the headroom or shoulder space issue and aesthetics or decor in a basement.   

Buy a Recessed System

Mini-splits can have wall-mounted evaporator units, recessed cassettes, and indoor heads you install along a floor. A recessed system or cassette is installed in the ceiling. So, the headroom or shoulder space issue is not a problem.

A ceiling with multiple ceiling-mounted mini-split air handler units installed

Also, recessed units, like cassettes, are installed flush with the ceiling. However, even if you get a wall-mounted unit, its aesthetics may not have unpleasant effects on the decor. Modern indoor evaporator units are pretty stylish, and many can complement your basement’s aesthetics. 

But let’s consider the possibility of an integrated condensate pump or something similar. For example, the Mitsubishi MLZ Series uses a recessed ceiling cassette as the indoor unit with a drain lift-up mechanism. 

You can watch this Mitsubishi Electric EZ FIT video on YouTube to see how it works:

Screenshot from a promo video for the Mitsubishi MLZ Series mini-split
Courtesy of Mitsubishi Electric Trane HVAC US

The drain lift-up mechanism for almost 20 inches (50 cm) vertically is probably sufficient for a cassette in your basement ceiling to use gravity for the above-ground line or hose.

Conclusion

Whichever you look at it, ductless mini-splits are a good idea for basements.

You have no comparable HVAC alternative for basements with as many benefits or conveniences as zonal heating and cooling. Also, ductless heat pumps are an excellent option for add-on installations. 

Sources

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