I built my coop last year without knowing I should have a vent. Pretty mild December so far so I want to do this weekend. The problem is I didn't know I needed or should have a vent when I built the coop so there is not really a lot of room above the roosts to put a vent that wouldn't just cause a cold draft. Can I vent effectively underneath the roosts or will that cause a draft as well that would bother them?
For venting to be effective, it should be above roosting level. The moisture from their breath rises, as does ammonia from their droppings. Drilling a few holes, an inch or so in diameter, as close to the roofline as possible is better than no ventilation at all.
Edited by junebuggena - 12/11/15 at 8:41am
Don’t beat yourself up about not knowing. Many of us, including me, have made modifications to the coop to take care of things. A lot of times you don’t know how things will work out until you build it and use it. That’s just the way it is. A lot of coops, especially small ones you don’t walk into, can be fairly restrictive on height.
The way I determine height of the roosts is to determine the floor level, including any bedding, then set the nests. Next, put in the roost higher than the nest. Hopefully you have room for venting above the roosts. So, can you somehow lower the nests and roosts to open up more room vertically?
Roof vents or cupolas can move a lot of air. As long as it doesn’t get blocked by snow a ridge vent is also very good but you have to have a peaked roof for that to work. I like leaving the top of a wall open under an overhang if you can. Gable vents work great too if you have the height to use them.
When the wind is calm you rely on the difference in air temperature to move air. That’s when you need larger openings. The heat to power this can come from their breathing, fresh poop, your waterer if you heat your water, (all these provide moisture too) and if the coop is on the ground, the ground can act as a thermal mass and provide heat during cold snaps. Openings high and low can help if there is a temperature difference in the inlets. If there is no temperature difference, you don’t get any energy from this. You don’t want to create a wind tunnel where a breeze hits the birds when the wind is blowing.
When the wind is blowing you can get air movement in the coop from that. A breeze moving through the coop but not hitting the birds will stir the air up enough to cause good air to replace bad air without harming the birds. A gentle draft hitting the birds is not bad, it’s a stronger breeze hitting them that causes problems.
The Woods Coop design has openings at or below the chickens’ level, but the roosts have to be in a cul de sac where the wind does not hit them. This design is very effective in really cold weather but it’s not the same as just opening one wall up and putting the roosts on the far end. You have to be careful to not create a wind tunnel, but using something like this where something else like another building is blocking the wind might work.
I doubt all this typing is helping you much. It’s mostly theory and you have a practical problem to solve. Maybe it can give you some ideas.