That makes sense if you want to ventilate their air anyway. After all you need to get rid of CO2 inside as well. Fun fact: You don't need to worry about the lack of oxygen in that context. If the oxygen level have dropped from from the normal 21% do 17% because the oxygen (O~2~) was magically removed you'll still be perfectly fine. But if those were converted into 4% CO2 that will make you sick.

Anyway: My point is that a dehumidifier is more often more efficient because it doesn't involve wasting warm air. It's also a fairly efficient heater. Dehumidifying, i.e. turning vapor into liquid means that you get the energy used for evaporation back. It's essentially sweating in reverse. With a typical dehumidifier that means you get about 2 Joules of heat for every Joule of electricity used.