If it’s cold and the place isn’t that well insulated, adding humidity can lead to disastrous results.
The humidity will build up and cling to the windows, it can freeze breaking the seals, but it can also run off into the wall causing mold and damage to the framing and anything else.
You shouldn’t have the humidity above 35%rh below freezing, unless you have very specific reasons too (hard wood, piano, health) but be prepared for additional costs eventually in some form. Wheter it’s upgrading to allow the house to do it, fixing issues, or preventing damage.
Also, raising the humidity makes the air feel colder not warmer, so that’s just plain false.