1gal humidifier work for a 30"x16"x60" in a 600sq ft apt?

Hey folks I have a small grow going on in a cabinet that I built with some friends in a 110 yr old house. There are drafts and it seems as if the old wood sucks the moisture out of the air. My RH right now is 30-40% usually resting on the lower side 30. It's spring time where I live but the humidity hasn't changed too much since the changing of seasons. Last week the humidity was around 20%. My budget is super tight right now so i'm hitting up craiglist, offer up, etc. The 2-3 gal seems excessive as its for 2k sq ft and that's way too much. In the future that will be great but for right now it's not. the light i'm using is a HLG 288 and a 4" Vortex outtake fan. Thanks y'all!

If the exhaust fan runs continuously then your humidity will always be low if the humidifier is in the cabinet as fresh, dry air is always coming in. What you want to do is use the humidifier in the room outside the cabinet so properly moistened air is being drawn in and your humidity stays the same all the time.

It's not old wood sucking the moisture out of your air it's just dry air. I have the same problem here in northern Alberta where it's dry all the time except the summer and it's still a lot drier than coastal areas. Only 34% in my grow room right now at 67F. If I raised the tempurature the RH would go down to around 20. It's only 13% RH in my man cave atm so it's pretty dry here.