I have my trees stored in a shed during the winter.
It has a heater set to 35 degrees
I have a exhaust and a fresh air intake fan set to run at 41 degrees
I run a 14” fan inside the shed 10 hours a day
My humidity is always very high, essentially the same as the outside or slightly lower.
Today the outside humidity is 81%
Inside the shed it is 70%
Should I be running a dehumidifier?
Or is matching the conditions outside more favorable?
I know nothing about greenhouse, cold house management and I am learning as I go.
My system is similar to yours (I install the fan in the spring and just open and close the door until then), although I run the fan 24 hrs/day. I don’t measure or worry about the humidity until it starts to look a bit low in the mid to late winter - i.e. things are starting to dry out - so I either water or shovel in some snow. On very cold nights I often have frost on the inside surface of the greenhouse. I feel that running the fan on cold nights is more important than during the day to keep the cold corners from freezing too hard. For the record I normally see some nights around 0F (-18C) or colder.
it looks like you live in an environment that gets colder winters causing you to store trees inside to avoid freezing them. relative humidity is a measure of how much moisture air can hold at various temperatures. relative humidity outside when it is in the 30s F is generally high because cold air cannot hold as much water as warm air can. If the relative humidity were to become low at these cold temperatures, the air may start “grabbing” water from your trees desiccating them. relative humidity will spike after you water and generally subside after a few hours. turning the air over in your shed by using an exhaust fan with a method of making up the air will serve to remove air that might be temporarily too humid. I don’t generally find issues with it but have an exhaust fan that is both triggered by high temperature and by high humidity to exhaust the space - I set the exhaust to go on at 90% RH. I wouldn’t try to use a dehumidifier as you are basically trying to air condition the shed with that. Likely will freeze up at cold temps. I would also run the circulating fan 24-7 and not point it on trees. look for signs of fungus, etc. indicating you have problems with air exchange or humidity. make sure you don’t have trees packed too tight so air circulation around them is limited. that can also be a problem. wouldn’t mess with it if your trees look fine.
