Cleaning it out will help drop the moisture too. I think you have great options for more airflow. I would fold down the tarp at the top edge. Just an inch below the top 2x4 will allow a lot more wet out.
My big coop is 8x14 with an 8 foot tall peak. I keep 24 birds in there. My vents are open soffits on both long sides. The only time I close them is if the wind is whipping or snow blowing in. I always have at least half of them open.
We get down to -20 but down to -5 is more common. I tell you this because we don't get frost bite here. Lots of good air in and bad air out.
Your area likely is more humid then mine so may be more of a challenge. Do you have thermometers with humidity meters available?
I keep a watch on my indoor compared to the outdoor. If I see much more then a 10% difference I change the shavings.
My big coop is 8x14 with an 8 foot tall peak. I keep 24 birds in there. My vents are open soffits on both long sides. The only time I close them is if the wind is whipping or snow blowing in. I always have at least half of them open.
We get down to -20 but down to -5 is more common. I tell you this because we don't get frost bite here. Lots of good air in and bad air out.
Your area likely is more humid then mine so may be more of a challenge. Do you have thermometers with humidity meters available?
I keep a watch on my indoor compared to the outdoor. If I see much more then a 10% difference I change the shavings.