Mini Split for an Attic
An attic is the hardest room in the house to condition, and floor area understates it every time. The roof deck above you can sit far hotter than the outdoor air on a summer afternoon, so an attic room needs to be sized for the heat coming through the roof rather than for its square footage alone.
Systems for an attic conversion
Single-zone systems from 9,000 to 18,000 BTU. Size one step above what the floor area suggests unless the roof assembly is genuinely well insulated.
Zone Air® DIY 9,000 BTU 23 SEER2 115V Wall Mount Ductless Mini-Split Heat Pump AC & Heater with Pre-Charged Lineset - Up to 450 Sq Ft
Zone Air® DIY 9,000 BTU 24 SEER2 230V Wall Mount Ductless Mini-Split Heat Pump AC & Heater with Pre-Charged Lineset - Up to 450 Sq Ft
Zone Air® DIY 12,000 BTU 23 SEER2 115V Wall Mount Ductless Mini-Split Heat Pump AC & Heater with Pre-Charged Lineset - Up to 600 Sq Ft
Zone Air® DIY 12,000 BTU 24 SEER2 230V Wall Mount Ductless Mini-Split Heat Pump AC & Heater with Pre-Charged Lineset - Up to 600 Sq Ft
Zone Air® DIY 18,000 BTU 23.5 SEER2 230V Wall Mount Ductless Mini-Split Heat Pump AC & Heater with Pre-Charged Lineset - Up to 900 Sq Ft
Insulate before you size
This is the one recommendation that changes the outcome more than the equipment does. An attic room under a bare or lightly insulated roof deck gains heat all afternoon and keeps gaining it into the evening, because the roof holds what it absorbed. No system size fixes that — it only changes how long the unit runs and what it costs you.
Insulating the roof assembly and the knee walls, and air-sealing where the knee walls meet the floor, is usually cheaper than the difference between two system sizes and it improves every hour the room is occupied. If the conversion is still in progress, do the insulation first and size afterward.
How to size an attic room
Take the floor area, then account for the roof. A 300 sq ft attic bedroom under an insulated, ventilated roof behaves close to its size and takes 9,000 BTU. The same room under an uninsulated deck, with skylights or dormers facing the afternoon sun, behaves like a considerably larger space and is a 12,000 BTU job.
Sloped ceilings work in your favor on paper and against you in practice — the volume is lower than a flat ceiling of the same footprint, but the conditioned air pools at the peak away from where you sit. Mount the indoor head on a full-height wall where you have one, and run the room through the sizing calculator rather than trusting floor area alone.
Why ductless suits an attic
Attics are the classic room ductwork never reached. Extending a central system upward means finding a path for a supply and a return, and even where that is physically possible the attic is usually the last room on the run and the first to be starved. A ductless head puts the capacity in the room itself, with no duct losses through the very space that is overheating.
The install also happens to be well suited to a DIY job. The condenser sits at ground level outside and the line set runs down through a soffit, an exterior wall chase, or a closet — a longer run than a ground-floor room, but a straightforward one. Pre-charged line sets come in lengths up to 50 ft, which covers most two-storey drops.
What DIY Installers Say
As of 2026, the Zone Air single-zone range holds an average rating of 4.8 out of 5 across 84 verified customer reviews spanning 5 systems, with owners most often mentioning cooling performance, quiet operation, and energy savings.
Was hurrying to get this installed because our old ac unit went out and Zone Air expedited shipping for us at no additional cost. I would highly suggest purchasing from Zone Air!
on the Zone Air 9,000 BTU mini split →This was my first time installing anything HVAC related. I had done basic remodeling and electrical work in the past, but this was not hard at all.
on the Zone Air 12,000 BTU mini split →Installed our DIY unit in place of one of those portable AC units with the hose hanging out the window. This looks way better. Thanks!
on the Zone Air 9,000 BTU mini split →I put a Zone Air 9k DIY unit in my office. It's about 300 square feet, gets a lot of sun. The 9k unit has been cooled this room down great. I didn't expect to work so easily. Quiet too. I’ve had it turned on during every Zoom call the past few weeks and co workers said they can’t even here it!
on the Zone Air 9,000 BTU mini split →Read all 75 written reviews
The finished install looks good. Shipping was a little slow.
on the Zone Air 9,000 BTU mini split →I installed this in my living room, and it has handled the space well. The room feels cooler and more comfortable.
on the Zone Air 18,000 BTU mini split →For a DIY install, this was a good choice. It was manageable to set up, and the results have been excellent.
on the Zone Air 9,000 BTU mini split →For the money, this ductless system has been a strong purchase. It performs well and looks good installed.
on the Zone Air 9,000 BTU mini split →The install went smoothly from start to finish. Once it was on, it worked exactly how I hoped.
on the Zone Air 12,000 BTU mini split →The final install came out looking cleaner than I expected. It works well and does not look out of place.
on the Zone Air 18,000 BTU mini split →Overall, I had a really good experience with this. The install was manageable, and the system has worked great.
on the Zone Air 9,000 BTU mini split →For a ductless setup, this feels like a very good deal. It works well and looks much nicer than I expected.
on the Zone Air 12,000 BTU mini split →The installation was straightforward, and the result was exactly what I hoped for. The space is finally comfortable.
on the Zone Air 18,000 BTU mini split →My garage needed something with enough power to actually make a difference. This has handled the space really well.
on the Zone Air 12,000 BTU mini split →The setup was simple enough, and using it day to day has been easy. I mostly just set the temperature and forget about it.
on the Zone Air 12,000 BTU mini split →I was happy with how clean it looked after installation. It does not take over the room, and it works quietly in the background.
on the Zone Air 12,000 BTU mini split →The parts felt good out of the box, and the install was easier than I expected. After getting it running, the room cooled down fast and stayed comfortable.
on the Zone Air 18,000 BTU mini split →I took my time with the install and everything came together well. It fired up without any issues and has been running great since.
on the Zone Air 12,000 BTU mini split →I did not expect it to feel this solid for a DIY setup. It has been smooth, quiet, and much stronger than I thought it would be.
on the Zone Air 9,000 BTU mini split →Okay. I struggled installing it.
on the Zone Air 9,000 BTU mini split →This 9K unit has really surprised us - its been a great little unit. The customer support even helped us register the warranty. The high SEER rating has already saved us $80 over the past two months. My husband reckons the installation was easy enough with the pre-charged lineset. We're pretty impressed.
on the Zone Air 9,000 BTU mini split →We got a nice rebate from our utility because of the Energy Star certification. The unit has been running for 4 months now and our power bills have definitely gone down. The ECO mode is pretty effective and I love that I can control it from my phone. Installation with the included lineset was pretty straightforward.
on the Zone Air 9,000 BTU mini split →I installed this thing in my 400 sq ft garage workshop and its been a total game changer. The 115V plug-and-play was super convenient. Heats fine even below 0°F. The WIFI feature is a nice little touch and the quiet mode is actually quiet - without being annoying.
on the Zone Air 9,000 BTU mini split →We installed this in our home office and it keeps the room comfortable all year round. The heating surprised me - it worked fine even at 5°F outside. The only thing I'd say is that the remote could be a bit more intuitive - but once you get the hang of it, it's fine. Overall, it's a great value for what we paid.
on the Zone Air 9,000 BTU mini split →I installed this 12K BTU Wall Mount in my 600 sq ft home office and its been amazing. Super quiet on low settings - I didn't even know it was on during a video call. The heating works great even when its below zero outside. Installation was pretty easy with the pre-charged line set. My power bills have gone down noticeably since chucking the old window unit. Plus its just nice to be able to plug it into a standard 115V outlet.
on the Zone Air 12,000 BTU mini split →I swapped a window unit out for this 230V one and it's got a way higher efficiency rating than the 115V version I was used to. The 24 SEER2 rating really shows on our electric bill. Installation was pretty straightforward - we already had a 230V outlet from an old window AC around. Extremely quiet and cools the room fast.
on the Zone Air 12,000 BTU mini split →We added a 1200 sq ft family room and didn't want to take our existing HVAC out of commission. This 18K unit was the perfect solution. Heating and cooling are both excellent. The smart sleep mode is great - gradually adjusts temperature overnight so we wake up comfortable every morning. Installation with a 208V connection was straightforward for our electrician.
on the Zone Air 18,000 BTU mini split →After researching extensively, I chose this unit for the 23.5 SEER2 rating and the cold climate certifications. Three months in and it's been flawless. The variable speed operation keeps temperatures rock solid without the on/off cycling of cheaper units. We got an Energy Star rebate from our utility that covered a good chunk of the installation. Highly recommend!
on the Zone Air 18,000 BTU mini split →The mini split itself works fine, but I wasn't impressed with the manual. The diagrams are small. Because of this I did the drain hose wrong the first time and water started to collect in the hose. Still happy with the purchase now that it’s finished.
on the Zone Air 9,000 BTU mini split →The unit has been great, but I messed up thinking I could connect it to an existing bedroom breaker. That circuit also fed two other rooms, so I ended up having an electrician come out.
on the Zone Air 12,000 BTU mini split →Put this in a workshop that’s 550 square feet. Works good.
on the Zone Air 12,000 BTU mini split →Zone Air was recommended to us by a contractor friend. Half the cost of other quoted units and works even better! So glad we took his advice. I am super impressed.
on the Zone Air 9,000 BTU mini split →The indoor head is larger than I thought, glad we measured the wall first. So far, so good.
on the Zone Air 18,000 BTU mini split →Big thanks to Nate in customer service for helping me choose the 230 volt (power was already nearby) otherwise it would have been more work and more money. Overall it’s been great.
on the Zone Air 9,000 BTU mini split →Was choosing between MrCool and Zone Air. I chose Zone Air because they are trying to manufacture in the US, so far it is top notch. Happy to support USA manufacturing!
on the Zone Air 12,000 BTU mini split →The noise difference alone made this worth it.
on the Zone Air 12,000 BTU mini split →Great customer service and support. Worked with me to help me order over the phone.
on the Zone Air 12,000 BTU mini split →It has been comfortable, quiet, and simple to use. That is pretty much exactly what I wanted.
on the Zone Air 12,000 BTU mini split →For the price, it feels like a premium system. It runs smooth, looks clean, and performs really well.
on the Zone Air 9,000 BTU mini split →This has worked well for my smaller home. It provides steady comfort without taking up much space.
on the Zone Air 9,000 BTU mini split →It keeps the room comfortable throughout the day. I do not have to keep adjusting it constantly.
on the Zone Air 18,000 BTU mini split →This worked perfectly for my home addition. I did not want to add ductwork, and this solved the problem.
on the Zone Air 9,000 BTU mini split →So far, it has been very reliable. It starts quickly, cools well, and has not given me any problems.
on the Zone Air 18,000 BTU mini split →This was a smart upgrade for my house. The comfort improvement was immediate, and it has been working well.
on the Zone Air 9,000 BTU mini split →I put this in a converted garage, and it really finished the space. It feels like a normal room now.
on the Zone Air 12,000 BTU mini split →The controls are easy, and the unit seems efficient. I do not have to mess with it much once it is set.
on the Zone Air 18,000 BTU mini split →I put this in a shed office, and it made the space usable every day. Before that, the temperature was all over the place.
on the Zone Air 12,000 BTU mini split →It looks good on the wall and works exactly like I wanted. The airflow is strong, and the room cools evenly.
on the Zone Air 9,000 BTU mini split →I put this in a guest room, and it has been perfect. Guests can set the temperature how they like it, and the room stays comfortable.
on the Zone Air 9,000 BTU mini split →The air feels more even throughout the room now. I do not get the same hot spots I used to have.
on the Zone Air 9,000 BTU mini split →I like how simple it is. It does what it is supposed to do without being complicated.
on the Zone Air 18,000 BTU mini split →For its size, it puts out a lot of cooling. I was impressed by how quickly it handled the room.
on the Zone Air 9,000 BTU mini split →It runs quietly and keeps the room comfortable. Compared to what I had before, it feels much more efficient.
on the Zone Air 12,000 BTU mini split →I am very satisfied with it so far. It made the room more comfortable and has been simple to operate.
on the Zone Air 9,000 BTU mini split →It cools better than I expected for the size. The room gets comfortable fast and stays that way.
on the Zone Air 12,000 BTU mini split →This has been easy to use every day. It cools well, responds quickly, and does not need much attention.
on the Zone Air 12,000 BTU mini split →My basement used to feel chilly and uncomfortable. This helped make it feel like a real living space.
on the Zone Air 18,000 BTU mini split →I leave it running at night, and it has not bothered me at all. It keeps the room cool without waking me up.
on the Zone Air 12,000 BTU mini split →My upstairs bedroom used to be uncomfortable by the end of the day. This made it much easier to sleep and relax up there.
on the Zone Air 9,000 BTU mini split →The unit has more than enough power for my space. It cools quickly but still runs smoothly and quietly.
on the Zone Air 12,000 BTU mini split →It has handled the hottest days better than I expected. The room stays cool even when the rest of the house feels warm.
on the Zone Air 12,000 BTU mini split →I got tired of dealing with window AC units, and this was a much better solution. It is quieter, cleaner, and cools better.
on the Zone Air 12,000 BTU mini split →Compared to my old AC, this is a big improvement. It is quieter, cools more evenly, and looks much better.
on the Zone Air 9,000 BTU mini split →This was one of those upgrades where I noticed the difference immediately. I wish I had done it sooner.
on the Zone Air 9,000 BTU mini split →So far, it has been very dependable. It runs quietly, keeps the temperature steady, and does not feel like it is using a ton of power.
on the Zone Air 18,000 BTU mini split →The room used to be the one place in the house nobody wanted to sit in. Now it is actually one of the more comfortable spots.
on the Zone Air 9,000 BTU mini split →I was surprised by how much cooling power it has. The space gets comfortable quickly and stays that way.
on the Zone Air 9,000 BTU mini split →I added this to my workspace, and it made a huge difference. I can spend hours out there now without getting uncomfortable.
on the Zone Air 18,000 BTU mini split →I like not having to switch between different systems depending on the season. It handles warm and cool days really well.
on the Zone Air 12,000 BTU mini split →I put this in a smaller space and it has been just right. It cools evenly without feeling too strong or uncomfortable.
on the Zone Air 12,000 BTU mini split →The cooling is strong, but what really surprised me was the noise level. Most of the time I barely notice it running.
on the Zone Air 18,000 BTU mini split →For what I paid, I’m really happy with it. It does the job well, looks nice on the wall, and feels like a good value.
on the Zone Air 12,000 BTU mini split →The first thing I noticed was how quickly the temperature changed. I can turn it on and feel the difference within a few minutes.
on the Zone Air 9,000 BTU mini split →Converted our garage to a home gym and this unit handles it perfectly. The 230V version was the way to go since we already had the wiring in place. The WiFi control is also a big plus - I can cool it down before my workout which is awesome.
on the Zone Air 12,000 BTU mini split →Attic mini split FAQ
What size mini split do I need for an attic?
Start from the floor area, then size up one step unless the roof is well insulated. A 300 to 450 sq ft attic room under an insulated, ventilated roof takes 9,000 BTU. The same room under a bare deck, or with skylights and dormers taking afternoon sun, is a 12,000 BTU job — and a large finished attic running 600 to 900 sq ft is 18,000 BTU territory. Run it through the sizing calculator rather than relying on square footage alone.
Will a mini split cool an unfinished attic?
It will struggle, and this is worth being straight about. An unfinished attic under a bare roof deck is not a conditioned space in any practical sense — it is a heat collector, and a mini split will run continuously trying to keep up while the roof keeps feeding it. If the plan is a usable room, insulation and air sealing are the first purchase and the mini split is the second. If the attic is staying unfinished storage, ventilation is a better investment than a heat pump.
Where do I put the outdoor unit for an attic install?
At ground level, on a pad or a wall bracket at the base of the house — not in the attic and not on the roof. The line set makes the run up, which is the main difference between an attic install and a ground-floor one. Pre-charged line sets come in lengths up to 50 ft, and the run should take the shortest practical path down through a closet, a soffit, or an exterior chase.
Can one attic mini split heat the room in winter too?
Yes, and attics often heat more easily than they cool — heat rises through the house and the room starts warmer than the floors below. These are heat pumps rated to keep producing heat down to -13°F, so the same system covers both seasons. The caveat is the same as for cooling: an uninsulated roof loses heat as fast as the system makes it, so insulation decides how well winter goes.
Can I install this mini split myself?
Yes. Every Zone Air system ships with the refrigerant sealed inside a pre-charged quick-connect line set, so the refrigerant circuit is never opened during installation — no vacuum pump, no manifold gauges, and no EPA Section 608 certification. A single-zone install typically runs four to eight hours: mount the indoor head, set the outdoor condenser, route and hand-tighten the line set, run the condensate drain, and make the electrical connection. Check local building codes, and hire an electrician if the job needs a new circuit.
Do I need a 240V circuit, or will a regular outlet work?
It depends on the size. Zone Air 9,000 and 12,000 BTU systems come in a 115V version that runs on a standard household outlet and a 15A single-pole breaker, so many installs need no new service at all. The 18,000 BTU system and every multi-zone system require 208-230V. If the space already has a 240V circuit for a dryer, welder, or shop tool, the harder half of the electrical work is done.
Is the line set included?
Single-zone wall mount systems ship with a 16 ft pre-charged line set in the box. Ceiling cassette systems, concealed ducted systems, and every multi-zone system are priced without the line set, which is bought per zone — from $229.99 for a 16 ft run, or $279.99 on the 18K line — so you only pay for the run lengths your layout actually needs. Longer runs are available at a length upcharge.
What warranty comes with the system?
Zone Air systems carry a 5-year parts warranty and a 7-year compressor warranty, with live technical support if you get stuck partway through an install. Installing the system yourself does not void the warranty — the pre-charged line set is designed for exactly that.