Conditioning your Cave
We small-scale cheese makers can dream of one day having a real "cave" or dedicated conditioning room, but alas for most of us it's not very likely to ever be a reality.
Thus our less expensive options:
Option 1 requires a lot of attention (exchanging ice packs) and option 2 is too cold for most cheeses to ripen properly. The last two are the best choices if you want to be able to maintain good conditioning targets.
Size and capacity differences aside, fridges, freezers and wine cellers have in common a cooling system, i.e. either a compressor (traditional heat pump) or thermo-electric module (solid-state heat pump). To cool the enclosure air must cycle through the cooling system and be exposed to coils or cooling fins that are much colder than the air passing over them.
This works fine if you have a keg of beer or wine bottles in the enclosure, but when you have exposed cheeses and want to keep them at a high humidity the cooling system will more often than not act as a de-humidifier.
Unless your ambient temperature surrounding your cave is lower than your target temperature (in which case you may want to consider a two-stage controller*) every time the cooling system runs de-humidification will occur.
The chart below is a good illustration of the "compressor" effect. This was %RH / Temp data I collected in my cave (converted fridge) during the summer of 2013. My cave is in a garage, and due to the warm environment the compressor cycled fairly often. My temperature controller was set for 55 deg. F with a 3 deg. differential and I was running a Cave Cube humidifier (without a controller).
Over the measurement period the temperature varied very close to the three degree differential. Also, the relationship between %RH and temperature (or more accurately, compressor run time) is clearly evident. Compressor runs: de-humidification takes place; Compressor stops: Cave Cube pumps humidity back into the cave.
Note: I had one of our "Cave Cube" humidifiers running at the time which helped to "pump" humidity back and allow the %RH to recover quickly after every compressor cycle.
There's no doubt that a strong correlation between temperature and %RH exists. This is why when you open the cave your humidity sensor may be low or decreasing when the compressor is on or high or increasing when off).
I had noticed this occurring for some time but thought it was due to the %RH sensor not correctly compensating for temperature changes. That may be part of it, but I did a couple of experiments that showed sensor drift is not a significant cause (I'll post this data in a second part soon).
So what does this mean for maintaining your target cave conditions? I personally don't think it's a problem as long as the average temperature and RH% are at or near your target. That said you may want to a little data gathering to understand how your cave is doing.