Question about ventilation and preventing drafts


In the Brooder
Nov 20, 2015
Ocean County, New Jersey
I have read through practically the entire thread concerning "Winterizing your Coop" and I am still a little confused. I understand the importance of venting your coop so humidity does not build up but were is the line between venting and preventing drafts. Some of the coops I have seen here have big vents that I would think would create drafts. I am just not sure what to do.

Where should they be placed?
How big should they be?
How does venting not cause drafts?

My coop is 4x4x4. (we only have 4 standard sized chickens and 1 bantam)
I have 1 window that is 10x18 (yes its small and we are replacing the whole coop making it taller with a window that is 36x36)
My husband drilled two 2.5 inch holes opposite the windows for ventilation over the summer. My outdoor run is 10 foot by 4 foot which is covered and they also have the 4x4 area under the coop. We have enclosed the run with plastic to prevent drafts and snow in the run.

I am installing a thermometer inside the coop which will give me the temp and humidity so I can monitor that...

Any help would be greatly appreciated.
I think one of the problems is that when people hear “draft” they think of holding a candle near a window in the house to see if there is any tiny air movement. That’s not what we are talking about. That kind of air movement is good in a coop, it replaces bad air with good. What we are talking about is a breeze strong enough to ruffle the feathers. They keep themselves warm by trapping tiny air pockets in their down. That trapped air provides insulation. If a breeze allows that air to escape then they can get cold. In the summer a breeze hitting them is fine, but not when you have your cold weather.

What you are trying to achieve is to set up ventilation without creating a wind tunnel that’s going to blast the chickens with a strong cold wind. There are different ways to do that but the easiest to me is to have openings above their heads when they are on the roost. Any breeze is over their heads but it creates enough turbulence to get some gentle air movement down low.

I understand why 4’x4’x4’ coops are so popular. Cut a sheet of plywood in half and you have two sides. You don’t need anything bigger for a small flock. But you have to be a bit careful how you set things up inside. To get ventilation over their heads the roosts can’t be very high. You may need to look at that.
I think of ventilation as warm air rising on its own rather than air blowing in. My 2 high vents are 8" by 3' long covered in hardware cloth and tucked under the eaves on opposite sides of the coop. I leave their pop door to the run open but the run is covered in plastic so there is no breeze blowing in the pop door. There is also another 12" by 12" hardware cloth opening in the access door. Due to the coop being tucked into the L shape of the house, that opening gets no wind.

So the chickens heat the air in the coop. The warmed air rises and goes out the high vents. Warm air can hold a lot more humidity than cold air so with the warm air the humidity also goes. As the air goes out the vents fresh new air will be drawn in through the pop door and the access door vent. It's subtle but that's what is needed to keep the air in the coop from getting too humid. I also have the roosts fairly low in the coop just in case a stray breeze might blow in the high vents. My coop is 5' high and the roosts are placed at 20" above the floor.

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