Many portable air conditioners are known to be problematic, and often reviled, for using a single hose to vent hot air outside. The problem with which, is that the air that gets pumped outside has to be replaced in your home, and that air is just going to come in from outside.
This cycle of pumping out hot air, and that being replaced with more hot air from outside, makes them less effective at cooling spaces, and you waste electricity running them more.
They do make two-hose models, which solve this problem by using a second hose to bring in outside air to exchange over the radiator before pumping it out again, resulting in no outside air being brought into the house.
Unfortunately these two-hose models are the significant minority, and unfortunately the impacts/benefits are nebulous. When all you know is that they’re ‘better’ but not really any information on how much better, it’s hard to justify buying a more expensive model.
I’ve had a single hose model for a few years to cool my basement office/workshop space, and have left it run as designed until now, knowing that it’s ‘less efficient’ but not putting really much thought into it. However, the wildfire smoke recently made me rethink trying to retrofit my unit into a two-hose operation, and try to reduce the amount of outside air (and pollutants) being pulled into the house.
I cut and taped a cardboard box to enclose the intake portion of the radiator, and fed in some 6″ ducting from the hardware store, which matches the ducting for the exhaust, and fed both hoses out through the window.
First impressions are that subjectively it does feel like it does a better job of cooling. I don’t feel like I have to run it as hard, or turn the set temperature down as low to get the room to where I want it. However, subjective data is easily biased, and also isn’t great for convincing others.
Fortunately I have both indoor and outdoor air quality (particulate) sensors, and the data shows a remarkable change.
We are looking at a 7 day graph window, and we can see in the Indoor graph, that for a large portion of the earlier part of the week, I have been fighting to keep air quality inside the house at a reasonable level, using box fans with filters, and occasionally running the central furnace on fan mode to pull air through the furnace filter as well.
The marked red line is where I modified the air conditioner to two-hose operation. After which we see a very significant drop off and better air quality inside the house without having to run the central furnace fan/filter. Meanwhile air quality levels outside remain well above an AQI of 100, so the improvement in indoor quality is not due to an improvement outdoors.
To me, this is pretty clear evidence just how much air this portable air conditioner was causing the house to exchange with the outdoors, and how much of an impact it can have on the efficiency of cooling the house, as well as in situations like mine where there is wildfire smoke, the air quality within the house.