A mini-split condensor unit in a home's attic

Attic spaces are notoriously difficult to heat and cool. At the very top of a building, and often with little insulation, they can get far too hot during the summer and too cold during the winter.

The Occupational Safety and Health Administration (OSHA) recommends that temperatures be kept between 68 and 76°F in an office environment. It also recommends humidity be maintained between 20% and 60%.

The most comfortable temperature for your attic is largely personal preference. Still, if it gets a lot hotter or colder than the recommended range, you will find reduced enjoyment of the attic space.

Go far enough beyond that range, and you could even suffer health consequences. Therefore, it is crucial to make sure you have the proper heating and cooling solution for an attic space to keep you comfortable and healthy.

Mini-splits can be a great way to do this.

Is a Mini-Split a Good Option to Heat and Cool My Attic?

Yes, mini splits are a great option for efficiently heating or cooling an attic space. They don’t use ductwork, are extremely efficient, and can be left on all the time to maintain a certain temperature. They can provide 100% efficient heating down to 0°F, and cooling during the summer months.

What Is a Mini-Split?

Mini-splits are heating and cooling systems that can be installed in your home to maintain living areas at comfortable temperatures.

They are comprised of two separate units in different locations, with an outdoor component containing the compressor and indoor air handler units that blow conditioned air into the home. The two units are connected by refrigerant lines and electric cables that handle power and communications between them.

The exterior component of a ductless mini-split attached to a home's exterior brick wall

Refrigerant is pumped around the system to transfer heat from the cool side of the system to the warm side. Refrigerant is a unique gas with the right combination of thermodynamic properties to effectively transfer the heat energy around the mini-split heat pump system.

This transfer provides the heating or cooling effect. It is achieved by taking the refrigerant through a series of steps involving compression, expansion, condensation, and evaporation, which characterize the refrigeration cycle.

The refrigeration cycle makes it possible to use electrical energy to move heat energy against its natural inclination to flow from hot to cold.

We’ve already written an article you can read on the best and most affordable eco-friendly refrigerants available on the market.

Mini-split heat pumps move heat rather than generate heat directly as an electrical resistance heater would. This characteristic allows them to operate so efficiently, often transferring three or four times the amount of heat energy than the amount of electrical power put in.

Insulate Before Installing a Mini-Split

Mini-splits can be very effective at heating and cooling, but before jumping to that solution, it’s essential to ensure your attic is adequately insulated.

Attic spaces are difficult to heat because they are subjected to greater temperature extremes during the year. This exposure is partly because their surfaces (walls and ceilings) form the barrier between the outdoor elements and the living space and don’t benefit from the insulating effect of adjoining rooms.

They also get the sun’s full glare in the summertime, which heats the external-facing side of these surfaces and throughout. So by 10 am on a sunny summer’s day in Tennessee, you’ll feel the heat of the sun coming through the wood of your roof unless you have the proper insulation in place.

You have a few main options when it comes to insulation. The main ones include:

  • Rigid foam board insulation
  • Fiberglass insulation
  • Spray foam insulation

Let’s briefly look at the main features of each of these.

Rigid Foam Board Insulation

Stacked sheets of polyisocyanurate foam board insulation

Rigid foam board comes in panels that can easily be cut to size and are placed between the joists of your roof or wall studs.

It has very good R-values (typically 3.8-5 per inch of thickness) and is easy to work with.

Fiberglass Insulation

Fiberglass insulation typically comes in rolls, or batts, which are easy to transport and install. It’s also available in loose-fill form, but you need a mechanical blower to install loose-fill fiberglass insulation.

Fiberglass insulation being installed in the underside of a home attic ceiling, showing a beige fiberglass batt

Fiberglass insulation has lower R-values than rigid foam board insulation, but you can increase its insulating effect by placing additional layers.

Spray Foam Insulation

As its name suggests, spray foam insulation is sprayed into place between the joists in your home.

Foam insulation has a very high R-value and can serve as an effective seal, which is particularly important if you want to prevent warm air from escaping through your attic during the winter, and keep the cold, conditioned air inside during summer.

A picture of spray foam insulation covering the floor and wood studs in a wall.

For more information on the different types of insulation available and the pros and cons of each, why not read our article comparing rigid foam board and fiberglass insulation?

Use Blinds to Keep the Sun Out

It sounds obvious, but a lot of the unwanted heating of your attic space during the summer months will come from the sun.

Allowing the sun to shine through attic windows will heat that room. This effect is known as solar gain and can be greatly reduced using simple window coverings.

Drawing curtains during the day’s heat or using angled blinds to keep out the worst of the sun’s rays while still allowing daylight through is a great way to cut down on solar gain.

 Sometimes doing this alone is enough to prevent temperatures from becoming oppressive.

Installing a Mini-Split in Your Attic

Once you’ve ensured that your attic space is adequately insulated and reduced the effect of solar gain by fitting blinds, you are ready to get your mini-split installed and start enjoying the comfort of year-round temperature-controlled living.

Making additional space in your home livable in this way provides more space for you and your family to live and can also increase the value of your home. Worth doing in anybody’s book.

There are plenty of other ways to increase your home’s value, and we’ve covered some of them in other articles on our website. If you’re interested in increasing your home’s resale value by making energy efficiency improvements, you should read our article that covers this in detail.

Mini-splits don’t require ducts to be installed because they transfer heat between the indoor and outdoor units via the refrigerant lines instead of blowing air along ducts.

 This feature makes them far more efficient than traditional central air heating and cooling and less disruptive for retrofits.

The outdoor mini-split heat pump unit can be mounted on a stand or the wall of your home using a special bracket. The indoor air handler can generally be installed up to 98 feet from the outdoor unit, depending on the make and model of your system, which should provide enough flexibility for most homes.

Types of Air Handlers for a Mini-Split

The air handler, also called a head unit, is the unit that is installed in the room to be heated or cooled and is responsible for blowing the conditioned air into the room.

There are three main options to choose from for a mini-split air handler, including:

  • Wall-mounted
  • Ceiling-mounted
  • Floor-mounted

The wall-mounted units are by far the most popular and are a discreet way to get warm or cool air into your living space. 

A ductless mini-split in the corner of a room below the ceiling
A wall-mounted air handler component of a mini-split

However, they require sufficient circulation space above them for the air intake and must be installed on a vertical wall, which can be a problem in some attics. If a wall-mounted air handler is not suitable, or perhaps just not your preference, you could install a ceiling-mounted air handler.

Ceiling-mounted units generally take the form of a cassette, which is recessed into the ceiling and very subdued. Once installed, the only visible part of a ceiling cassette is a grill that lies flush with the ceiling itself.

A mini-split's ceiling-mounted air handler component

If you can use neither a wall-mounted or ceiling cassette air handler in your attic, your best bet is a floor-mounted unit. However, these tend to be a bit larger than the others and will take up floor space against your wall, limiting where you can put furniture.

Apart from those slight drawbacks, they will do an excellent job of providing heating and cooling for your attic reliably and quietly.

Final Thoughts: Installing a Mini-Split in Your Attic

Attics are complex spaces to keep cool in the summer and equally challenging to heat in winter. This is due to their exposed nature at the top of the house, surrounded on all sides by the great outdoors.

You can significantly improve attic comfort by installing adequate installation and keeping the sun’s glare at bay using blinds during those hot summer days. Provided your attic is appropriately insulated, a mini-split heat pump system is a choice option to heat and cool your attic.

Mini-splits are highly efficient and straightforward to install, providing reliable, cost-effective heating and cooling throughout the year.

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