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Comment by rsync | Hacker News Reader

"This needs some real data."

I agree and I, admittedly, have none.

I will say, however, that a deeper dive into these efficiencies would also have to take into account the production, distribution and installation costs (embedded pollution, not dollars) of several hundred little devices vs. a single plant that is integrated into each unit during building construction.

Even considering room by room optimization (turning off AC in living room while you sleep, etc.) it's hard to imagine this penciling out vs. operating + embedded costs ...

(and I still suspect that just the operating costs are higher, but your point is well taken ...)

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A common form of central heating, like burning fossils kind that delivers hot water over insulated pipes to each building, is more efficient in pretty much every way and is cheap to add during building construction than doing it individually. But it's not the case with a "central AC", it's less efficient, more expensive to add during building construction and operating costs are no better. Just think about it, you can't just deliver cold over a pipe and rely on air convection, like with heat, you need to literally move cold air into each room and make it individually adjustable. It's a ridiculously inefficient complicated expensive system requiring extra space and with installation costs higher than that of all AC units individually installed.

Could you have a split AC system with a big centralized compressor?

You could, but chilled water circulation is the more typical heat transfer medium in central, building-wide units. Water can carry a lot of heat, is cheap and readily available, non-polluting, non-toxic, easy to pump, easy to plumb, and liquid at temps convenient for heating and cooling.

The first apartment building I lived in in NY had this. The only downside was that if the board put off maintenance so long that one summer the cooling towers were busted, then they waited until may to start the project to replace them, then an early heat wave came, it could be darn uncomfortable for a week or two. (That did indeed happen, just like I told it.)

At least one building science expert (Joseph Lstiburek) reccomends a decentralized approach for HVAC, with tightly sealed individual units: https://www.buildingscience.com/documents/digests/bsd-110-hv...

Although I do wonder how that works with something like district heating/cooling systems, which seem to rely on centralized boilers and chillers to move thermal energy between buildings.

I was gonna say, the outlay of capital for a building-wide hydronic system and an evaporative tower, versus each owner be responsible for their AC, I can see why that would be possible.

Particularly if the building is older.

Also, I am curious why there are multiple single condensor units in lieu of multizone units...I guess it is financially easier to purchase one unit at a time.

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