Ask experienced keepers what new builders get wrong most often and “not enough ventilation” comes up again and again. It’s counterintuitive: people seal coops to keep birds warm and end up making them sick. Here’s the principle that prevents it.
Why it matters more than warmth
Chickens are well-insulated and handle cold far better than damp. Inside a closed coop, they constantly release moisture (through breathing and droppings) and their manure gives off ammonia. With nowhere to go, that humid, ammonia-laden air does two things:
- Causes frostbite. Counterintuitively, frostbite is largely a moisture problem — humid air freezing on combs and wattles. A well-ventilated coop is a drier, less frostbite-prone coop.
- Damages airways. Ammonia buildup irritates and harms the respiratory system, opening the door to disease.
How to ventilate without chilling birds
The rule is simple: air exchange high, no draft low.
- Put vents up high — along the eaves or near the roofline, well above where birds roost. Hot, moist, ammonia-rich air rises and exits there.
- Keep roost-level air still. Birds should not have cold air blowing directly on them while they sleep. Solid walls at roost height, vented gaps above.
- Cover vents with hardware cloth, never leave them open to predators.
- Aim high on quantity. Around 1 sq ft of opening per 10 sq ft of floor is a starting point; more is usually better.
Get this one detail right and most “winter” coop problems — frostbite, dampness, respiratory illness — simply don’t appear. Pair it with our winterizing guide for the cold-season specifics.
Common questions
- How much ventilation does a chicken coop need?
- A common guideline is about 1 sq ft of vent opening per 10 sq ft of floor space, placed high up. Many experienced keepers go further, treating ventilation as something you can rarely overdo as long as it's above the birds and not blowing on them.
- What's the difference between ventilation and a draft?
- Ventilation is air exchange high up, near the roofline, that lets moisture and ammonia escape. A draft is cold air moving across the birds at roost level. You want lots of the first and none of the second.
- Should coop vents be open in winter?
- Yes. Closing the coop up tight in winter traps moisture and ammonia, which causes frostbite and respiratory problems. Keep high vents open year-round; manage cold by stopping low-level drafts, not by sealing the coop.