I thought I would share with everyone who might be fighting mold in your coop like I have been for the past few weeks my latest fairly inexpensive discovery and hopefully, cure. Ours grew on the roof (inside) and in the corners near the roost poles mainly. We believe that the wood (new this last summer) probably had some spores in it already and the rest of the conditions - chickens + a wet and humid fall - just helped them along. We do have a fair amount of ventilation already, but we are adding more this weekend as a safeguard and planning to add a roof fan and another window this summer for more air flow. I also clean the roost pans every few days and add Stall Dry and DE almost daily to keep the moisture absorbed. After I killed and removed the mold using bleach water, then soapy water and letting it dry completely, I sprayed it down with Concrobium Mold Control we bought at Home Depot to try and prevent further growth, or at least impede it. It contains no bleach, no ammonia and no VOCs, and while still a chemical, it is about as safe as you can get. It is the EPA's recommended product for mold control in your home. I wish I had found it before I used the bleach, but next time...... This is the link if anyone is interested http://www.concrobium.com/atHome_howItWorks.php When the roof was completely dry, I hung 8 Damprid hanger bags (the kind you put in closets) from the rafters of my coop. They hang just high enough and are close enough together that the girls are not even interested in trying to fly up to them. I also nailed 4 of the sachets bags of Damprid in the corners (not puncturing the bags) to help the trouble spots. It is important not to puncture the bags and to make sure the bags you get do not have holes in them since the crystals are toxic if ingested. We had used these in a car a couple years ago that grew mold after a window was left down for a week, so I figured why not try them again. The only other choice was a dehumidifier and $200 was not in the budget this month plus I wasn't sure how that would really work in the coop. Immediately, the Damprid bags started working. The bags below them fill up with crystals as they start removing moisture from the air and sachets will slowly turn a darker shade of brown. They should continue to work about 60 days. The cost for all this - $40. Today, the humidity level is way down in the coop and the wood is dry. My plan this summer is to treat the wood again and then paint it using a kitchen and bath paint I use which contains anti mold and mildew agents. I hope this helps someone fighting mold this season. It is really bad right now in the Pacific NW and it doesn't seem like it is going to improve anytime soon. I know it was very frustrating for me because I know the health effects on chickens and with them all molting and fighting the mud and muck in the run, mold was the last thing we needed!