Air conditioning in a large, unenclosed space is quite costly and inefficient. Stations typically have passive ventilation (in most NYC stations along most of t

Air conditioning in a large, unenclosed space is quite costly and inefficient. Stations typically have passive ventilation (in most NYC stations along most of the length of the platform, plus entrances). And then there’s the massive tunnel that lies between stations. The London Underground (which is referenced in the article) did a lot of things, but they didn’t try to air condition the stations. They did in-station air circulation, active ventilation from surface air, heat exchange cooling from existing cool water sources, and heat re-capture to heat homes. Then, of course, more specific to NYC, is that it’s more worthwhile presently to spend money on making the trains run more smoothly (whereby passengers will spend less time in the station), as the system has major issues there (and not enough money as-is).