I have a split air con Samsung SH09APG. It's a typical air con machine, with an inside and outside unit.

I was thinking it would be really useful if it allowed the outside air to come inside the house. Sometimes, you cannot open the window (noise outside, rain, ...), but it's still good to renew the air inside, to avoid lacking oxygen/stale air.

However, I couldn't see any way to make the outside air come inside. This confuses me, as I know these machines work by having large tubes hidden in the walls, to allow airflow between outside and inside.

There is a simple fan function, but I think it does not use outside air. Just pushes the air inside.

Even when I use it on cold mode (air con), I think it's not really using the outside air, but simply cools the air inside.

What am I missing, why is there no function to use outside air?

  • 1
    Unless your house if very well sealed, you're getting plenty of outside air into the house through all the small cracks and leaks everywhere. If there is any attic/soffit venting, then at a minimum, air is being drawn through the attic and it's pulling some amount of air through any little crack it can find in the ceiling or ceiling/wall joints. It's highly unlikely that you'll breathe enough O2 in and CO2 out that you'll cause yourself any danger.
    – FreeMan
    Sep 10, 2021 at 12:57
  • Ok, thanks for the comment. I was wondering indeed. The room is quite well sealed, but there is a gap under the door leading to the hallway. I don't really have a good sense of how much oxygen regeneration this creates. I sometimes hear people commenting that they sleep much better with the window open, and I thought maybe it came from having oxygen being renewed faster. I know that breathing air all night long will deplete the oxygen by only a very small percentage, but I don't know if the body feels strongly this small oxygen difference.
    – DevShark
    Sep 10, 2021 at 13:38
  • 1
    If you're talking about only one room (are you?) then it's likely that room is not sealed that well from the rest of the house (as you've noted). Houses need to breathe, just like people, so newly constructed/renovated houses that are tightly sealed will have air exchangers, but older houses will leak enough on their own that it's not a problem. Now, if you turn the gas stove on, but don't light the burner, you're going to have a problem in either case, but not from just breathing.
    – FreeMan
    Sep 10, 2021 at 13:44
  • Yes, it's just one room. You're right, it's not constructed to be perfectly sealed. It should probably be fine...
    – DevShark
    Sep 10, 2021 at 13:46
  • @FreeMan -- mostly, that older houses are designed to tolerate water leakage by way of using heat and air leakage to drive that water back out. Newer houses, because they can't have that much heat/air leakage (heat isn't so cheap now), rely instead on more explicit water management with flashings, drainage planes, and other such details Sep 10, 2021 at 23:31

3 Answers 3


Split machines do not have, normally, large tubes inside the walls.

The tubes between the inside unit (evaporator) and the outside unit (condenser) are only carrying refrigerant and so are small.

You would need a different system to replace the air inside with fresh air from outside with perhaps temperature and humidity control.

All the existing system does is to absorb heat from inside and reject it outside to control the internal temperature.

  • Oh, interesting. I got confused then. Thanks for your explanation.
    – DevShark
    Sep 10, 2021 at 10:42
  • Think the closest system you are looking for is an air ex-changer, but might be more than what you want. Usually comes with duck work, filters, and a heat exchanger. Might have one if your house is a newer well sealed type(R-2000 type).
    – crip659
    Sep 10, 2021 at 11:49
  • I see. Thanks for that. The house is a little old, and does not come with that. It seems indeed a little too complicated for me to do and I do not know any contractor that I trust in the area unfortunately :/
    – DevShark
    Sep 10, 2021 at 13:39

The system you chose is called a heat pump.

It is a specific kind of heat pump, called a mini-split heat pump.

Air conditioners have a hot side and a cold side. The hot side is outdoors, and makes the already-hot outdoors even hotter.

On a cool day wouldn't it be nice to switch them, and make the house warm and the outside cold(er)? Nothing need be moved, all it takes is a reversing valve to make the system work in the opposite direction.

Of course if you're in the USA, you know that air conditioners do not do that. That's because gas heat was always cheap and air conditioners weren't efficient enough to make that worthwhile.

Well, now they are. Your "air con" as you call it, is actually a heat pump, and it does do that.

You also have the "wide band" unit that will continue to make heat well below freezing. However it becomes less efficient the colder it gets, so there is a breakover point where it becomes cheaper to switch to gas heat. If you're using electric "toaster" heat, the breakover point is probably "never".

How can it pump heat from outside when the temperature is BELOW ZERO? That's easy, because "ZERO" is a lie. Real, actual zero is at -460 degrees Fahrenheit (or -273 celsius). So on a cold winter day indoors is only 20% hotter than outdoors. In absolute terms.

Air conditioners and heat pumps do not move air between inside and outside at all. That is usually unnecessary in older homes. The newest homes, which are that well-sealed, are built with special air exchangers.


You need a different, additional device.

You could just have an exhaust fan and an intake fan, but the efficient option is a Heat Recovery Ventilator (or the slightly different Energy Recovery Ventilator) which have an intake and exhaust fan combined with a heat exchanger (or a heat and humidity exchanger for the ERV) that helps to reduce the expenditure on conditioning the air that you bring in from outside, whether you are heating or cooling. There are multiple options with a range of efficiencies, price points, and operating noise levels. ...And operating temperature ranges (folks in the higher latitudes need good defrost controller performance, which folks in the lower latitudes may not need to consider.)

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