If you’ll forgive the groan-inducing dad cliché, sometimes it really is the humidity, not the heat, that gets to you. Although you can set your AC to the lowest possible temperature, it won’t cool you down if there’s so much moisture in the air that your sweat can’t evaporate.Most people think of a dehumidifier as an appliance for drying out a damp basement. But technically speaking, it’s more similar to an air conditioner than people might realize.“Most residential dehumidifiers today still have the same parts under the hood that a window AC does,” explained Ross Bonner, co-founder and chief technology officer of Transaera, an industrial air conditioning company that uses a proprietary material to remove moisture from the air and improve efficiency. (Of all the total energy emissions related to global cooling, more than half go toward moisture removal. ) “At their core, they both work the same way — they draw the moisture out by cooling the air, then push out the heat.”In HVAC terms, the act of changing the air temperature is known as “sensible cooling.” By contrast, “latent cooling” refers to the moisture-removal part, or the process of changing between two states of matter, in this case turning water vapor into liquid water. Latent cooling works best when the cooling coils inside an air conditioner or dehumidifier reach the dew point, or the specific temperature when moisture in the air turns to liquid. If your AC is trying to handle a heavy load of both sensible and latent cooling at the same time, it can struggle to hit the dew point; even if your AC does a decent job of dropping the actual temperature, it could still leave the room feeling clammy, dank, and, well, generally unpleasant.And that’s why, on the worst of the dog days of summer, I drag the Frigidaire FFAD2234W1, our former smaller dehumidifier pick, up from the basement.