How does ductless AC work and why do buildings still use air ducts?
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Ductless AC means having individual wall units on walls/compressors outside home
for each room vs. one larger compressor and much smaller air vents.
Ductless AC has thin pipes (usually copper) running to the outside unit. It is a good choice is you want to cool down one room or one apartment (and not the rest of the building), and do not want a window unit (which is noisy and takes up space).
Ducted AC has one huge AC unit at cooling down the air that is then distributed via ducts. It is also called Central Air. It costs less than putting individual units into several different rooms. It lets you heat the place from the It lets you put an air filter. It circulates the air around the entire building, so one open window mean fresh air in every room.
Ductless AC works by sucking in heat energy from the air within a space, transferring to a liquid or gas, and then pumping that fluid somewhere else (Typically outside the building) where the heat is released back to the air and the now cooler fluid is sent back into the space to suck up more heat. Back and forth endlessly. This type of system might also be able to be run in reverse, sucking in heat from out side and dumping in the space. This later system is called a “heat pump” and is very efficient and is what greener advocates are suggested we change our HVAC systems to.
One major problem with split systems (the ductless ac model) is they don’t exchange any actual air. So all the goobers and dust and stuff that people are breathing in / exhaling just stay in place. That’s especially in times of air borne communicable illnesses. It also means that CO2 levels will increase with all those breathing humans, just a few ticks higher CO2 is directly linked to poorer cognitive performance so that’s also bad. So ducted systems not only allow for air exchange to get rid of CO2 but also allow for things like filtration of air for quality.
So most modern office buildings will use a mixture of the above. They will have fresh air intake systems that create an exchange and filtration, to some nominal degree. Remember, you don’t want *full* exhaust of all your air because then you are heating/cooling all your air constantly that’s an energy hog. (You might want a 100% outside air system in things like labs…)
So we’re cutting a balance right now. Many buildings do something like a 70/30 exhaust split (you’re rebreathing 70% “old” air with 30% being constantly exchanged with outside) to minimize conditioning costs while also ejecting CO2 and minimizing things like everyone re-breathing each others breath goobers. Some specialty spaces like server rooms or big conference rooms will have supplemental local split systems to just provide heating/cooling.
But there are tons of ways of doing this, I’m in commercial construction (I build your offices) and since COVID at least there have been 1,001 “miracle” inventions to improve air efficiency, filtration and sanitation, and reduce energy costs. Many are being put in your offices right now, or since lockdown, and are potentially brilliant advances, but many are just snake oil being sold to land lords to attract tenants.
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