coop ventilation

Exploring Insulation and Ventilation Options

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Now that winter is officially here, if you haven’t already (and you really should have done by now!) you need to look at insulation for your coop. This is a place where everyone seems to ‘know’ the answer and yet there are a lot of wrong answers. I’m hoping to clear up some of the confusion in this area for everyone. There are a few things that you MUST do.

Have a DRY coop

Currently a good portion of the US is rainy and wet and expected to stay so for a few months. Add cold to that and you can have some very unhealthy chickens.

The cold, wet air can encourage illnesses of the head and lungs such as flu, cold, bronchitis, cough, or some of the more ‘official’ sounding chicken diseases like coryza (a bacterial cold bug). But more than just illnesses, the damp conditions will breed a horde of fungi and molds that can be very dangerous or even fatal for your flock. To prevent this, start by removing anything that can serve as a breeding ground for mold or fungus inside the coop.

  • Hay and straw usually come with their own types of molds and fungi so if they start to get damp, scrape and dump it. In wet weather I usually don’t even bother putting it in the coop to begin with.
  • Water dishes that have been repeatedly filled but never washed. Slimy mold tends to build up and then the hens are actively drinking it. Yuck.
  • In places where it is often rainy (like the Pacific Northwest) or has a long rainy season (Florida and the low areas) it’s best to make a coop that does not have insulation between the walls because unless you spray it with nasty chemicals that can outgas into your coop, it’s going to get damp and because of lack of air circulation it will stay damp which turns into mold and mildew. Possibly even the dreaded black mold that is guaranteed to get into the lungs of your flock and YOU!


So let’s say that in the summer your coop has good airflow, catches the breezes just right, and stays nice and dry even in the rain. Your hens are happy and productive, giving you a lot of eggs because you also give them good feed and access to fresh water and insects.

Then winter comes . . .

This same coop that worked so well during the summer months becomes a nightmare. It doesn’t keep the drafts out completely. The plastic you put up over it catches the wind and frequently rips pieces of the coop or blows away. Your hens are freezing cold and huddled together so tightly that you don’t think you could pry them apart with a stick. The water is frozen in the dish.

What do you do?


So your hens are warm and cozy. They’ve snuggled up together against a big hay bale to keep warm and there are enough hens to generate heat that prevents them from getting cold in the 20F temperatures outside. But the air grows moist from a combination of spilled water, ammonia fumes from the chicken waste, and no ventilation. Soon the hay bale wilts and the fungal spores start to grow from inside. Even the walls themselves are growing mold and mildew from the moist conditions. The chickens start to get sick from the damp, moldy air and the fumes from their own waste.

Or you could take those warm, cozy hens you started with and keep them that way by making sure there is a good airflow from bottom to top (cool air comes in on the bottom and carries away the air that is too moist or too warm up through the roof). You can use hay bales if you want, but keep in mind that they carry a lot of fungi and molds so it’s critical to keep the air the perfect balance between moist and dry or you’ll have problems. We’ve already explored how the the temperature variations can cause problems, as well as the moisture, but try taking some additional steps to keep your flock safe in the very likely event that you aren’t perfect and will never have the perfect balance of temperature and moisture.

  • When you do seasonal cleaning, spray the walls with a light solution of vinegar and lemon, lavender, or thyme oil (thyme oil was the original Lysol…). This will help prevent mold and mildew.
  • Paint the interior of your coop at seasonal cleaning time with mold and mildew resistant paint. They have a low VOC paint that is safe for animals and humans.
  • Put a couple of drops of apple cider vinegar in your chicken water to help combat mold or fungal growth where the water gets spilled.
  • Stay on top of chicken waste, especially in the winter.
  • If you serve your flock a hot mash or peelings for a treat, make sure they eat it all and if they don’t make sure it’s cleaned out of the coop within two days.

There are several options for insulation that work for coops depending on your needs. If you live in a hot, dry area then the type of insulation you need is drastically different from someone who lives in a cold, damp climate.

HOT & DAMP (Florida, Coastal South, etc) Insulation isn’t needed, but ventilation is a must to prevent mold and fungus.
HOT & DRY (Southwest US) Insulation isn’t needed as much. Focus on keeping flock hydrated.
COLD (or COOL) & DAMP (Pacific Southwest) Light insulation since temperatures rarely go below 25F. Ventilation is important to prevent illness, mold, and fungus.
COLD & DRY (Midwest states) Insulation required, ventilation type depends on amount of chickens in coop. May need additional heat source, but usually a heated water dish will provide enough warmth unless you have very few chickens or a very large coop.
EXTREME COLD (Upper Midwest, Canada) Insulation required, ventilation depends on amount of chickens in coop. Will certainly need additional heat source.

Roll insulation works really well, but to prevent mold problems inside the walls where I can’t see it, I like to use a safe roll insulation like bamboo or recycled denim. I’m not really concerned that way if the hens peck at it a little. Just staple it up on the walls, then cover the walls with cut to fit chicken wire or micromesh.

Until later,

Photo by: fishermansdaughter

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6 thoughts on “Exploring Insulation and Ventilation Options

    • Rob, if you look at the chart up above it covers the 5 basic types of climate. I’m in Kentucky, which is a mid-atlantic state or a midwest state OR a southern state depending on your map (although I’m a Southern boy myself, thanks!). Anyway, the climate here changes from one side of the state to the other so you really have to just look at the information I put up there and use your best judgment as to which one applies to you. For instance, if you live in Greenland and you could use the extreme cold suggestions from Canada.

  1. Thanks for the write up John! This is our first winter with our flock so this advice comes at the right time. Our barred rock hens don’t seem to mind the temperatures with their natural insulation. They continue to roost and chase everything that moves as normal. I think the point of your article is the damp environment and the dangers presented, aka, black mold (OH NO). Yes, the whole coop and run seems to be continually damp, even down here in Texas! Welcome to January. The steps presented to prevent mold and fungi buildup are welcome to this newbie. BTW, the eggs are the best we ever ate, and for the cost of compost scraps and some chicken feed no regrets here!

    San Marcos, Texas

    • Yes, that was the main point to keep safe conditions. And if you want some stuff about feeding your flock, flip back through the old blog posts here. A lot of information about that here.

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