Do you run A/C during lights on? if so... its acting just the same as a dehuey in terms of lowering R/H, its one of the fundamental principles of their operation... why do you think so much water gets dumped out of the drain line from an A/C?
Also... just because you might think your room is designed correctly and mine isn't.. consider that geographical location and climate have a LOT to play on that too, as does grow method.. If you live somewhere with low RH most of the year and grow in something soil-like, chances are you will have a lot less issues at all, than someone who lives in a high humidity location, growing hydro drip trays (or E&F) where a lot of extra evaporation occurs during lights-on.
Also... just because you might think your room is designed correctly and mine isn't.. consider that geographical location and climate have a LOT to play on that too, as does grow method.. If you live somewhere with low RH most of the year and grow in something soil-like, chances are you will have a lot less issues at all, than someone who lives in a high humidity location, growing hydro drip trays (or E&F) where a lot of extra evaporation occurs during lights-on.