I have been curing at a neighbors in the cold room under the front porch when the temps are below freezing as my curing chamber converted from a frig doesn't work well in my garage at that time. I installed a rack made from wire shelving at the unused end of the cold cellar and placed a tray with sand in it under the drying rack. I keep the sand wet to provide humidity in that area. Last winter I experienced some case hardening (easily fixed by vacuum packing and storing in the frig to equalize moisture) but this year I tried to increase the humidity by isolating the area with a tarp and adding a small humidifier to supplement the sand tray. The tarp does not extend to the floor or the ceiling so there is still some draft present.
The result so far has been promising. The temperature has been holding at 10C with RH 75-80%. The early made sausages are drying slowly and at 35% weight loss are holding their shape which I believe shows that the drying is even throughout. Time will tell. I aim for about 45% weight loss as I prefer the meat to be firm, but not shiny, when cut. I'll report back when drying is complete as to the success (or not!) of my trials.