Ive run a dehumidifier for 2 years after my 180 gallon tank raised the humidity to like 70%
now i get it to about 25% but now i get alot of static electricity and dust and it does heat my place up quite abit, its way better then keeping a window open.

Keins advice would be best im sure as he lives in a house and is a guru legend here on canreef, however as u already have mold, you may want to get an expert to ascertain whether its active or growing elsewhere.

The HRV is no doubt the more expensive solution, however, in addition to managing the moisture problem it also brings fresh air into the house while minimizing heat loss. That also goes for the summer when you've got the air conditioning on and it's hot outside too...