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Comment by Arn_Thor | Hacker News Reader

By coincidence I was walking around Paris today in 30+ degree heat. It was only really bearable in the shade, which the city has a lot of thanks to a good amount of trees lining the sidewalks. It was quite pleasant until we passed a convenience store and the heat and humidity of that part of the street immediately rose to oppressive levels. This was because an air conditioner for the store was venting into the street.

The effect is stark and incontrovertible. There is the heat being removed plus some heat from the compressor and fan. Everyone in public and private spaces will be better off if we reduce AC usage as much as possible in favor of other solutions

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It's not (just) the a/c in the store, it also has huge refrigeration units.

In Asia, 7-Eleven is famous for its chilled air, but also has the walls covered with refrigerators for cool drinks, and there may be freezers for meat, seafood and ice cream.

In Las Vegas they solve this by blowing cold air onto the sidewalk through an always-open door, thereby cooling passersby, and perhaps enticing a few to enter for a game of slots.

That doesn’t really solve the problem. They’re just dumping the waste heat on the back of the building where tourists aren’t walking. And producing more of that waste heat because they’re trying to condition a leakier building.

99% sure the parent post is sarcastic

No, I've personally witnessed this practice. Wide open doors pouring out cold air on a sweltering day really gets people to stop and shop.

They meant that the person acting like that was the solution was the sarcastic part. Everyone is in agreement that that’s what they do in Vegas.

In Paris small shops like that typically don't have a vent on the roof, so they need to vent heat to the street at pedestrian level. Easily solved, if people cared.

Venting up helps a little for the immediate surroundings but it adds to a layer of heat oppressing the city.

You're right, and now I realize that I missed the point of the comment I responded to.

Living near Paris, it annoys me whenever I look through my window and see the exit pipes of mobile AC units (like this one https://www.emoqui.fr/wp-content/uploads/2019/06/climatiseur...) running through the open windows of the opposite flat.

It annoys me whenever I see a single hose AC unit period.

It just makes no sense to me.

First, you are now pumping air from inside the building to outside. You aren't creating a vacuum inside, so all that means is somewhere else in the building the air is being replaced from the only place it can... from outside...

Second, the air you are pumping outside contains some of the air from the inside space that you just spent electricity cooling...

I use a mobile AC unit like this because it's really the only type of unit that will work in my apartment, but I use a dual hose unit. The unit has 2 air loops. Air from the room is drawn in from the back of the unit, heat is absorbed by the heatsink, and then cool air is blown out the front of the unit into the room.

Then to dissipate the absorbed heat as well as the heat from the electricity being consumed, air from outside is sucked in through 1 hose, runs through the other heatsink, and then is expelled back outside again from the other hose.

It just makes so much more sense, and if you can stick 1 hose in your window, it's really not that hard to stick 2.

Worthwhile noting that most single hose AC units can usually be converted into double-hose with some cardboard, hose, and a lot of duct tape.

It's worth doing too - you'll normally get almost the double the cooling effect from a double hose unit of the same wattage as a single hose one, just due to the fact you aren't wasting coolness out of the window.

If you do this, note that it's important to use extra large and short (insulated) hoses, simply because the blower fans in your unit aren't designed for so many yards of hose.

Unfortunately dual-hose ACs are not widely available. I just couldn’t find any when I was in the market. It’s single-hose only in my experience. Why this is I don’t understand. Had to buy one and try it to finally conclude that I was sane and society was crazy.

You want air changeover. Low changes/hr leads to high indoor co2 and is just in general bad for you.

"ASHRAE empirical research determined that "acceptability" was a function of outdoor (fresh air) ventilation rate and used carbon dioxide as an accurate measurement of occupant presence and activity. Building odors and contaminants would be suitably controlled by this dilution methodology. ASHRAE codified a level of 1,000 ppm of carbon dioxide and specified the use of widely available sense-and-control equipment to assure compliance. The 1989 issue of ASHRAE 62.1-1989 published the whys and wherefores and overrode the 1981 requirements that were aimed at a ventilation level of 5,000 ppm of carbon dioxide (the OSHA workplace limit), federally set to minimize HVAC system energy consumption. This apparently ended the SBS epidemic."

https://en.wikipedia.org/wiki/Sick_building_syndrome

Window mounted units which are the most common don't cycle air either. They have an inside the room loop and an outside the room loop.

Same with mini-split systems and central AC systems.

The vast majority of AC systems don't cycle air for their heat transfer.

Not saying that cycling fresh air isn't important, but I don't necessarily think it's the job of the heat pump to do that.

If the outside temperature is lower than inside then single hose is at least as good, as long as you open a window somewhere else so outside air rather than some other apartment’s air is sucked in

Single hose portables are bad in countries where air con is practically essential, but are fine or even desirable for countries where only a handful of % of people have AC - the purchases will be for use cases like attics and top floor apartments where inside can be easily hotter than outside

Why does this annoy you?

I can see why seeing someone else making poor choices wasting their own money, making their quality of life worse, and destroying our shared environment, could be upsetting.

In a way it's worse than seeing strip mining, or those people who fish with dynamite, or people who litter. At least all those people are benefiting from their environmental destruction.

Just the visible waste, especially as those AC units are running in flats with windows open

Some people aren't allowed (rental) or cannot afford built-in AC units. I've got a mobile one in my attic where I WFH because otherwise it gets to 30c+ and that's just unbearable.

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