I have a small brrom closet in my house, where i have a de-humidifyer hooked up to a hygrostat (like a thermostat, but with humidity) It switches on when RH rises above 52.5%, and off when it drops to 47.5. But that’s a relatively expensive setup. I think a lot of people get by with a small cupboard or the like thats heated slightly with a large lightbulb or the like.