Yesturday I made a DIY water heater. Works great. Maybe too well? The issue I noticed is that the coop iced up, walls, door windows.... Now I had the windows open, the top vents open...the thing is, we are running between 75% and 100% humidity....with subzero temps. I have tried opening up top vents only, windows only, both vents and window...the vents are cross vents, near the rooftop, and two windows, one facing east, one north. There wasn't any wind, for here anyway....still, once I shut up the coop for the night, because the way the guys installed one of the top vents...it blows right on them, on the roost...between the humidity, them, and the water heater, all the condensation froze the entire inside of the coop and Mr Roo got the tips of his comb and his wattles frostbitten. I have 3 roosts and of course, they pick the very top roost. I CAN remove that top roost, which would put them UNDER the air flow of the vents...I have the roosts set into floor joists for easy removal for cleaning...I am not using any liquid cleaning, just scraping the poop board and roosts, best I can with a putty knife...scrape poop board daily, if not more often....so quite a bit of poo, is manually removed from the coop. Replacing bedding, is not an option $$$ wise...they do a good job of turning it and I add, as needed, shavings and straw...the straw, in our climate, is a must for warmth. We have had -38 F real temps with some -18 F also...windchills have been awful also. What would you all suggest? I'm not very educated on how air flow works...one vent is under the eves, at about 6 1/2 foot high, north side. South side, is ON the eves, but is straight out ( close to 6 foot high ), instead of being under the boxed in rafters...the guys didn't make the back of the coop eves long/big enough, to have the vent go under it, like the north side... I hope this long description helps with understanding my setup. The pullets have small combs and wattles, and so far, no frostbite...they are hatchery BR's, spring hatch and getting 5 eggs a day. There are 14 pullets and 1 cockerel, in a 8 by 8 coop, with a 7 foot front ( north ) and 6 foot back ( south ) . South and west have no windows. South faces woods, so would not give any sun...east gives some sun...when we get it...west wall is still tar papered, so will absorb heat if there is sun...the walls are doubled, no insulation, and floor is doubled. Outside is shingled, but for that west wall. We ran into winter and could not finish that last wall... Any help/ideas/air flow info will be much appreciated!!! Thanks!