Your dream of a room addition, finished basement, or attic conversion is finally coming true. There’s just one problem – how do you heat and cool the area if expanding your existing HVAC system is cost prohibitive or impractical?

A ductless mini-split system may just be the solution you’re looking for. Although the technology has been around for decades, ductless systems have become more popular in recent years and for good reason. They’re less expensive, more energy efficient, offer individualized control, and can be added to spaces traditional heating and cooling cannot.

What Is a Ductless Mini-Split System?

A ductless mini-split system uses an outdoor compressor and condenser, but feeds each indoor air-handling unit through a conduit that works much like a heat pump. The indoor evaporating unit can be mounted to a wall or ceiling wherever you’re looking for individualized temperature control.

Proper Sizing Matters

For a mini-split system to efficiently maintain comfortable indoor temperatures, proper sizing is key. The system should have a British thermal unit (BTU) rating that matches the specifications of the room being heated and cooled. If the unit is too small, it will work too hard and run continuously trying (and failing) to heat or cool the space sufficiently. This will result in wasted energy and higher utility bills. The extra wear and tear will also cause the unit to age more quickly and require more frequent service.

On the other hand, a mini-split unit that is too large for the space can cause short cycling, meaning it will turn on and then off right away because it heats or cools the space too quickly. This, too, results in higher than necessary energy bills, more frequent repairs, and premature system failure. Short cycling also produces uneven temperatures and poor humidity control.

How to Size a Ductless Mini Split System

When sizing a mini-split, multiply the square footage of the room or area by 25 to determine the recommended BTU. This formula determines the correct amount of warm or cold air needed to ensure that an area is at a constant and comfortable temperature.

Follow these simple steps to determine the best size mini-split unit for your specific space:

  • Figure out the square footage of the room by measuring its length and width and multiplying the two numbers.

  • Convert the square footage to BTUs by multiplying by 25.

  • For example, if a room measures 22 feet by 18 feet, multiply the numbers to get 396 square feet. Then multiply 396 by 25 to get 9,900. A 10,000 BTU mini-split unit would be required for this size space.

Other Factors to Consider

When sizing a mini-split system, there are several other factors to consider besides a room’s size.

  • The climate outside can affect the temperature inside a home, therefore affecting the size of a mini-split.

  • If the ceiling height in a room is greater than the standard 8 feet, it is recommended to increase the BTU capacity of the mini-split.

  • Older homes with poor insulation require more power to heat or cool a room.

  • Newer homes with effective insulation will probably need fewer BTUs than normal for the same space.

  • The number of windows and doors, how leaky they are, and amount of direct sunlight heating a room affects mini-split sizing.

  • Stoves, ovens, and other sources of heat in a room play a role.

  • The number of occupants that typically occupy the space is also a factor.

To learn more about ductless mini-split systems or to request a free in-home comfort consultation and new system quote, contact Anthony’s Plumbing, Heating & Air Conditioning today.