You need better windows then. NW Ontario they can maintain 35% when its minus 30CWell dry is a relative term, right? For me personally, the past couple of weeks have brought the coldest, driest air that I can ever remember. This has been a brutal beginning to February, so much so that I'm thinking of moving, lol. In order for my house to avoid condensation on the windows right now, I'd have to maintain an indoor RH of probably <20%. That's great for the house but horrible for us humans.
Ask any otolaryngologist about indoor RH during the heating months and they're going to tell you to definitely keep it above 30%, preferably no lower than 40%. So there's a conflict between the building scientists and the medical professionals. Some people can get away with temporary bouts of extremely low indoor RH. Others like me who have really bad vasomotor rhinitis, which seems to triggered by large swings in RH, temp, and barometric pressure, or those who have a house full of occupants with viral and bacterial upper respiratory infections, have little choice but to say to heck with the wooden casement windows - let 'em rot in winter, I'll fix 'em in the spring.
Windows really are the weak link in the building envelope, assuming everything else is properly sealed and insulated. Unfortunately, if you don't build, then you're stuck with whatever came with the house (usually inadequate even in new construction) and that will ultimately determine your indoor RH if you're absolutely committed to maintaining a condensate free interior.