system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why are airport ceiling so high?

ELI5 Why can't airports just be standard or double maybe triple height, why do they have to be so big?
gpt
I used to build airports, there are two main reasons—humans generate 500 BTU each of heat. There are smaller airports with plenums and oversized HVAC systems but you’d have to localize the HVAC systems for each gate instead of just using chilled water systems before flights. 

Taller ceilings help dissipate the heat around the entire building. Also, like someone else mentioned, airports are basically symbolic welcome mats to tourists & businesspeople alike so a great deal of expensive architecture goes into them. Some of the most expensive firms serve as the architects of record on them.