The attic is one of the most problematic HVAC areas in the summer. The immense heat that is generated in the attic can increase your cooling costs by several $100/year. It’s basically a hot and humid mess on top of your house. That’s why it’s smart to install an attic air conditioner.
Here’s the deal:
The attic usually has no ductwork. In most cases, you can’t use the central air conditioner in the attic. That limits your choices of an attic air conditioner to ductless split systems and room air conditioners.
Which type of air conditioner is best for the attic?
This is the key question you need to answer before getting an attic air conditioner. On top of installation difficulty, you also have to think about the energy efficiency, how many BTU you need, as well as the need for heating in the winter (mini splits are perfect for this).
There are 4 types of AC units you can install in the attic, namely:
- A split system. Those are ductless mini split air conditioners (that can also provide heating in the winter).
- Portable air conditioner.
- Window air conditioner.
- Through-the-wall air conditioner.
All of these units have their pros and cons. We are going to look into which air conditioner type is the best for the attic. Further on, you will also find a list of specific AC models that you can get and install yourself to adequately cool your attic.
Before we look at the pros and cons and the best attic air conditioner, let’s look at what we want from a perfect attic air conditioner:
What To Look For In Attic Air Conditioner? (5 Key Features)
As we know, you can’t use ducted AC in an attic without ductwork. Split system and room air conditioners will have to do.
Here are 5 key things you need to think about before choosing an attic air conditioner:
- How many BTU AC unit you need for the attic? It’s important to adequately size an air conditioner for your attic. Usually, you follow the DOE’s ’20 BTU per sq ft of living space’ rule of thumb. However, this simple rule presumes you have an 8 ft ceiling. Attic usually has a variable ceiling height; from 0 ft to up to 14 ft. Sun exposure and insulation parameters also need to be accounted for. In general, most attics need a 10,000 BTU to 15,000 BTU cooling output. Example: If you use a 20 BTU per sq ft rule, a 10,000 BTU AC will adequately cool an up to 500 sq ft attic and 15,000 BTU AC will cool an attic with up to 750 sq ft in square footage.
- How to pick an energy efficient AC for the attic? You want to minimize the costs of cooling your attic. That’s why you have to check an EER and SEER rating of attic AC units. Any unit with an above 10 EER rating is considered energy efficient. Units with a 12+ EER rating like #1 MRCOOL DIY-12-HP-115B25 in the list below are the true cost-saving air conditioner.
- How difficult it is to install an attic air conditioner? If you have to call an HVAC company to install an AC, you are looking at a $500+ installation cost. The best air conditioners for the attic are the ones you can install yourself.
- What is the expected lifespan of the attic air conditioner type? Mini splits might be the most costly but they last 15-20 years. Portable AC units might be cheaper but they last 5-10 years. You have to take the expected lifespan of the AC into account.
- Brand reputation is important. As with choosing any AC, the brand is important. In general, good and recognizable brands make durable attic AC units (that last 10+ years) and less-known brands have questionable durability.
With all this in mind, let’s look at all 4 types of air conditioners for the attic one by one. We will start with arguably the best type of attic air conditioner: the split system.
Ductless Mini Split AC For Attic (Best Type Of Attic AC)
Without the ducted option, the best you can do is a ductless mini split air conditioner. In fact, these mini splits are slowly but steadily replacing central air-cons because they are more energy efficient and reliable than central AC systems. They also need a lot less handling and obviously require no ductwork.
Every mini split consists of an outdoor unit, indoor unit, and refrigerant lines that connect the two units and close off the refrigerant cycle. In the attic, you install the indoor air handler, make a small refrigerant hole through the outer wall or through the roof, and install the outdoor unit outside.
This type of attic air conditioner is preferred due to several advantages over room air conditioners for attic (portable, window, thru-the-wall), namely:
- Mini splits are the most energy efficient type of attic air conditioner. Some of them even have above 12 EER rating (Energy Efficiency Ratio) and can run at 20+ SEER rating. Such high energy efficiency ratios will dramatically lower the running cost of attic air conditioning.
- Longest lifespan. Mini splits typically last for 15 to 20 years. That’s for 10 years more than portable AC units and 5 years more than the window air conditioners. While the upfront cost of mini split is higher, the mini split will last a lot longer and will pay for itself in energy savings due to incredibly high energy efficiency.
- Mini splits are the quietest. If you don’t spend a lot of time in the attic, this is not all that important. If you live in the attic, however, you want the quietest attic air conditioner. Mini split ACs have the compressor – the primary source of noise – located outdoors. That means that the indoor air handler will generate much less noise; it’s not uncommon to see a mini split with below 40 dB indoor noise levels. Portable and window AC units are much loader, typically generating 55 dB of noise or more.
- Mini splits can provide heating in the winter as well. The refrigerant cycle of every mini split can be reversed with by just flipping the switch. That’s how you can adequately heat an attic in the winter. As you can see, all mini splits AC are basically mini split heat pumps for the attic. You transfer heat; in the summer, they transfer the cool air indoors, and in the winter, they transfer the warm air indoors.
- Easier-than-expected installation. Installation can be a bother. Mini splits, however, require only a small hole for refrigerant lines. Compared to the through-the-wall air conditioners which need a big hole and portable or window AC units that require a window, installing a mini split AC in the attic is relatively easy.
With all these advantages mini splits have, we must not forget about the cons as well. As everybody knows, the biggest con is the upfront cost. Most portable and window AC units for the attic cost about $500. Attic mini splits can cost up to $1,500 and you have to pay extra for installation.
That’s why it’s smart to invest in a DIY mini split. With some technical skills, you can follow the step-by-step installation process found in the manual. The installation kit is included. The best example of a DIY mini split for the attic is the #1 MRCOOL DIY-12-HP-115B25 found in the list below.
Mini splits are the best option for an attic air conditioner. Let’s look at other options as well; these include standard room air conditioners like portable AC units and window AC units as well as through-the-wall AC units for the attic.
Portable Air Conditioner For Attic (Cheaper Option In Short Term)
One of the most popular choices for attic air conditioning are portable AC units. More people are familiar with these basic portable AC units, we know how to install them, and they are less expensive than the better mini splits.
To install a portable AC unit in the attic, you will have to carry the 30-50 lbs unit to the attic. You just plug it in 110/120V standard outlet and press ‘On’ and get the air conditioning.
The tricky part here is how to vent a portable air conditioner in the attic. Without exception, you have to vent a portable AC through a window. This can be a regular window or, in the case of an attic, a roof window.
With most portable AC units, you get:
- Extendable hose (up to about 60 inches). This is a 4″ to 6″ hose you have to install through a window.
- Window seal for portable AC. After you vent a hose out of the window, you have to seal the window opening. For that, you use these window kits that are, honestly, quite bothersome to set up.
Portable AC units are not as energy efficient as mini splits or even window AC units. They typically have about an 8.5 EER rating. Some of the more efficient attic portable AC units have a 10+ EER rating.
The best thing to do is to opt for a dual-hose portable air conditioner for the attic. The dual-hose units have very high energy efficiency (they can rival window AC units in this) and you don’t get the negative pressure problem as you do with the standard single-hose unit.
Portable air conditioners cost anywhere from $300 to $700. The price depends on the cooling efficiency, capacity (measured in BTU/h), brand, and reliability.
In general, you can get a dual-hose 14,000 BTU portable AC with a 10+ EER rating for about $500. The #2 Whynter ARC-14S in the table below is an excellent example of a durable dual-hose portable air conditioner for the attic.
Window Air Conditioner For Attic (Good Option If You Have Right Size Window)
A window AC unit is a good option for attic air conditioning. They are, in general, cheaper than portable and mini split ACs, have a very good energy efficiency (better than portable AC, worse than mini split), and can be installed quite easily.
Of course, not everybody will be able to install a window air conditioner in the attic. Attic spaces usually have smaller roof windows that cannot support window AC. Installing a window AC on an inclined and narrow window is extremely difficult and impossible in most cases.
If you have a standard and wide enough (15+ inch length) window, you can opt for an attic window AC unit. In terms of energy efficiency, look for units with a 10+ EER rating. This will keep the attic air conditioning running costs low.
In all cases, make sure that you will actually be able to install a window air conditioner on the attic window. If you have an inclined roof window, mini split AC units and portable AC units are a much better option.
Special Option: Through-The-Wall Or Through-The-Roof Air Conditioners For Attic
A special type of air conditioner for the attic is the so-called through-the-wall AC unit, or in this case, the through-the-roof AC unit. These air conditioners are installed through the wall (or through the roof). That means they can be a good option as an air conditioner in an attic without windows or an attic with inclined roof windows.
Specs-wise, they have a lower cooling capacity than mini splits, portable, or window air conditioners. They also have a lower energy efficiency (EER rating below 10 EER). Nevertheless, they provide a solution for attics that are harder to vent otherwise (via window).
The installation process is a bit tricky. You will have to use power tools to make a hole in the wall if your attic has an adequate wall. Otherwise, you will have to make a special hole in the roof. Now, making a hole in the roof is not the easiest task in the world and should be done by a professional. This, of course, incurs additional installation costs.
With all these types of ACs for the attic evaluated, you now have a little bit of insight on which type of air conditioner is the best for your attic.
For additional help, LearnMetrics has prepared a list of the specific air conditioner models that are best equipped to cool an attic in the summer. Here is the full list with spec-by-spec comparison:
4 Best Air Conditioners For Attic (By AC Type)
Based on the pros and cons analysis and spec-by-spec comparison, you can pick the right air conditioner for your attic. If you need a bit of help, you can use the comments below and we’ll try to help you out.
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