humidity

You do not want consistency if you plan on optimising growth; you could just hold at 50% day and night if you so choose for consistency. You need to consider other variables than just "what's best for growth. Vapor Pressure Deficit (VPD) is crucial for judging daytime transpiration because it quantifies the drying power of the air, directly influencing water movement and nutrient uptake. But there is no transpiration at night, VPD is 10x less effective. At night cellular respiration occurs. This means so long as carbon is being converted, the plant will be spitting out water vapor all night; this water doesn't come from the pot. Establishing a proper wet-dry cycle, with consistency, is key. Balance of water and oxygen in the root zone, encouraging robust growth. This cycle involves thoroughly watering the plants and then allowing the top layer of the growing medium to dry out before the next watering session. Generally speaking you want to add a little RH% daytime to really lock in the VPD if you want to optimize growth, 60-70%rh with warmish temps. Humidity is relative to temperature, so when temp drops 10F from lights off, relative humidity increases because colder air cant hold as much absolute moisture. Gas exchange will cease above 75%, and hardly any respiration will occur. Ideally, you want to use your nights to encourage evaporation, drop RH%, and incorporate some dry into the wet/dry cycle. I cannot express enough how important oxygen is at night. So no, don't want consistent unless its 50%, then its kinda just always somewhere in the middle, keeping RH% consistently high will eventually lead to hypoxia of rootzones and a breakdown of all internal function. Keeping consistently dry is not great either. 86F 70RH% days, 77F 45-55RH% nights, Its not fun having to refill everyday, but you only really need to RH during the day, anyone humidifying at night is doing it wrong unless you live in a barren desert.

Make sure you have the proper tools. But also you won't get perfectly stable humidity levels. It'll be a general range. It'll go up and down but as long as you're in your target range its fine. I would suggest following vpd and adjusting your humidity based on your temperature. I flower plants with humidity above 60 even though we were always taught not to do that but I get better results following vpd than adjusting my humidity depending on the stage my plants are

If you have a smart controller you can most likely automate it, with smart controller app or from home assistance if you can. and set the automation to run the exhaust fan on an of inside this range. a humidifier will help also.

There's not much you can do.. can exhaust to same room as tent to help maintain or increase humidity -- assuming the plants produce enough to do so. Or, if humidity is rising uncontrollably you can exhaust to an area not exchanging gase with the room encompasssing the tent, but this too depends on ambient humidity beiny at or below what you want in the tent. If these things don't magically pan out in your region's climate, then you need: Dehumidifier Humidifier I grow during the winter for specifically this reason. It's probably 30-35% RH, but adding moisture is much cheaper than removing it - and a lot less heat created - evaporation will actually have a cooling effect, dehum will have a heating effect. the lights and moisture from the canopy eventually balance out around where i need it with minimal dehumidification. My late summers are very high rh, so i avoid them.

Always have an outlet point if into a lung room make sure that room gets fresh air to give to the "box". Never have it too wet or too dry. Have fans circulating inside and have control every aspect of the environment be it cave man or iron man it's the same principle. Dragging air out of an area will also drag air into it so if you only have 1 extractor then sucking out is the best and try get it away from the fresh inlet.. Good luck

It’s like a thermostat but for RH with a RH probe instead of a thermometer plugged on ultrasonic mist maker soaking in a bucket with water. Look for ULTRASONIC MIST MAKER and HYGROSTAT