The short answer is – NO. Air conditioners, including mini-splits, don’t bring fresh air into the home. Instead, they pass indoor air through the air handler, where it’s “freshened up” before it’s returned to the room.
The approach is generally beneficial as it keeps out pollen and other impurities from the outside air. However, it also comes with a few drawbacks. The following is everything you need to know.
How the Mini Split Works
Mini-split air conditioners are unique air conditioning systems that comprise two distinct parts – an indoor air handler and an outdoor condenser. These two-part are connected via a refrigerant line set and electrical wires.
The air handler is installed inside the house, typically on an exterior wall. Meanwhile, the compressor unit installs outside the house but often on the same wall as the air handler. The refrigerant line set runs through the wall to connect the two components. Electrical wires connecting the two parts also run through the wall.
The cooling process is primarily fueled by refrigerant that runs from the indoor air handler to the compressor ad back.
When the system is set to cool during the summer, the indoor air handler draws the hot, sweaty air from your home and passes it over freezing-cold evaporator coils. At this point, heat exchange occurs. The refrigerant absorbs the heat from the air such that the air coming out of the other end is substantially cooler.
The cool air is then released back into the house via a separate set of vents on the air handler. In most cases, air enters the air handler from vents towards the bottom and leaves via vents located around the top. A fan inside the air handler helps to blow this air to the furthest corners of the room. The blowing action also helps to ensure even cooling throughout the room.
When it absorbs heat, the coolant changes from a high-pressure liquid to a low-pressure gas. This gas then travels outside to the compressor unit via the refrigerant lines, where it releases the heat and reverts to a high-pressure liquid.
This high-pressure liquid is then sent back to the air handler inside the house to absorb more heat. The process goes on and on until the room is sufficiently cool in line with the thermostat settings.
The reverse happens during the winter when the mini-split functions as a heat pump. When the cycling refrigerant reaches the outdoor unit, the condenser dumps whatever heat is available into it.
The refrigerant carries this heat and dumps it into the air passing through the evaporator. The now-warm air then passed back into the room and dispersed evenly with the help of the fan.
No Fresh Air
As you can see, the indoor air flows in a closed-loop. It can’t leave unless there’s a leak. Indeed, the air itself doesn’t even get past your walls. Whether it’s heat extraction or addition, it all happens at the air handler inside the house.
It means that fresh air doesn’t enter your house. Instead, a mini-split air conditioner merely adds or extracts heat to indoor air depending on the season. It doesn’t introduce fresh air from outside the house into the room.
It’s Both a Good and a Bad Thing
Most homeowners aren’t even aware that the AC doesn’t bring in fresh air inside the house. So, they won’t bother with the benefits and drawbacks. But if you’re concerned, closed-loop air cycling is good and bad in the following ways;
- Protection from external impurities
The main reason the mini split was designed as a closed-loop system is to keep impurities at bay. Think about all the dust and particles floating in the air outside your house. It can be a nightmare if you live near a busy highway or a processing plant. If the AC were to draw fresh air into the house, you’d also likely introduce a massive volume of such impurities into your home.
The closed-loop operation means that no impurities can enter your home from outside the house. This, to a great degree, protects you from potential health issues.
- “Fresh air” could be hotter air
Although air from outside the house is typically even fresher than inside, the two might not be at the same temperature. For instance, while the AC attempts to keep your indoor temperature at 75˚F, the temperatures outside could be as high as 90˚F. In hotter states, outdoor temperatures can rise as high as 100˚F or higher.
Allowing this fresh but hotter air to enter the home may derail your air conditioning progress. It negates the gains made and may force the air conditioner to work even harder.
- It protects the air conditioner
We’ve already mentioned that allowing fresh air from outside the house to enter the AC would introduce dirt, debris, and all kinds of unwanted particles into the house. But, before these particles get to the house, have you thought about how they would impact the air conditioner. Imagine allowing dust and smoke particles into the AC, for instance. You’d have malfunctions all the time.
Keeping the airflow in a closed-loop saves you from the potential repairs and replacements by keeping out dirt and debris.
- Indoor air can become stale
The biggest drawback to the closed-loop nature of air conditioners is that there’s no escape route for unwanted and harmful particles trapped inside the air conditioners. Unless the AC incorporates special mechanisms to extract and eliminate the particles, the cigarette smell and smoke from your heaters will remain inside the house for a long time.
For this reason, many mini-split systems have filters designed to trap unwanted particles. The filters vary from one manufacturer to the next. However, the best filters can even remove smoke odors and eliminate pollens.
Tips to Add Fresh Air in the Summer
If the lack of fresh air concerns you, there are things you can do about it. HVAC experts recommend the following;
Open the windows briefly but wide
Opening the window briefly every 2-3 hours allows you to draw fresh air into the home without significantly impacting indoor air temperature. You want to open them for just five minutes. However, open them as wide as possible.
Run the fan
Window fans can be invaluable here. The fans help to circulate air throughout the room, making you feel a cool breeze in the process. This may even allow you to raise the thermostat setting a little. Remember to set the fan to run in a counterclockwise motion in the summer.
Install an attic vent
Attic vents allow warm air to escape the house, allowing cool air to take its place. Since they’re installed in the attic, you don’t have to worry about losing substantial amounts of cool air as the denser cool air is often found at floor level. It’s best to let a professional install it.
Consider window vents
Window vents are small devices installed on the window or wall. Also known as trickle vents, these devices allow fresh air to circulate naturally through a room while allowing stale air to leave. They’re typically fitted to a window frame or between the glass and the frame.
There you have it. Although mini split air conditioners don’t bring in fresh air, it’s for your good. However, if the room feels stale, there are solutions, including room fans, attic vents, and window vents.