I suggest you start by reading these articles, written by a lady in Ontario.
Pat’s Big Ol' Ventilation Page
https://www.backyardchickens.com/web/viewblog.php?id=1642-VENTILATION
Pat’s Cold Coop (winter design) page:
https://www.backyardchickens.com/web/viewblog.php?id=1642-winter-coop-temperatures
Pat’s Big Ol' Mud Page (fixing muddy runs):
https://www.backyardchickens.com/web/viewblog.php?id=1642-fix-a-muddy-run
I don’t believe in magic numbers for chickens, whether that is space in the coop, in the run, on roosts, hen to rooster ratio, or about any other number we come up with. Each chicken has its own personality, each flock has its own dynamics, we have different flock make-ups, we keep them for different reasons, we have different climates, we manage them differently, the list of why different things work for different ones of us keeps going on and on.
I understand if you don’t have experience you need some numbers to start with. But please take these are general guidelines, not absolute required laws of nature. There is a general guideline of needing 4 square feet per full sized chicken in the coop plus 10 square feet per chicken in the run. This will keep most of us out of trouble most of the time, even with differences in climates and how we manage them. It is overkill for the absolute minimum that many of us need, but it’s a pretty good place to start.
If you manage them in a way and have a climate that allows them to be outside every day and they have access to that outside area pretty much any time they are awake, you can get by with quite a bit less than 4 square feet in a coop. But you are then committed to that way of managing them.
A couple of examples: If your management technique includes letting them out of the coop at daybreak, who do you find you can trust to do that when you are on vacation? If you plan ion giving them free access to the great outdoors, what do you do if you run into a predator problem? With mine, I can leave them locked in the coop or coop and run until I deal with the predator.
If you plan on having multiple roosters (probably not in your case) that works better if they have more room. If you plan on having a broody raise chicks with the flock, Mama needs room to work. If you plan to integrate chickens, that is a lot easier if they have plenty of room and I’d suggest additional roosts.
In general, I find the more space I give them the less hard I have to work (I clean my coop put every three years whether it needs it or not to put that stuff on the garden), the fewer behavioral problems I have with the chickens, and the more flexibility I have to deal with problems.
On the space question; no one ever complains about having too much space. Your chickens don’t need to be in a tiny cramped space to stay warm, not even in New Hampshire. They wear a down coat. They will stay warm enough in really cold weather. What they need is lots of good ventilation to get rid of the moisture and ammonia they can produce. Ammonia is lighter than air so you need a good opening above where they sleep to get rid of it. The danger from cold is not from a chicken freezing to death but is frostbite. High moisture levels can cause frostbite to the comb and wattles especially when the temperature is barely below freezing. If you have good ventilation, they can go a whole lot colder and not have any frostbite issues. Plenty of people in climates colder than yours don’t have any issues with frostbite because they have good ventilation. Some have claimed to have stopped frostbite by opening up the ventilation. How you do that without having a cross breeze blowing directly on them is to have the permanent ventilation opening over their heads when they are sleeping.
Further on the “chickens are cold” issue. I’ve seen chickens sleep outside in trees with the temperature around zero degrees Fahrenheit. These were single combed chickens, which are the ones that are supposed to be most susceptible to frostbite. They were not on top of a mountain on a bare limb of a dead tree squawking defiantly in the face of a blizzard. You’d only see that in a Disney movie. They were in a thicket in a protected valley where they could position themselves out of the direct wind. But they were outside where they had plenty of ventilation and were fine.
Something else on chickens and cold. Here is a photo taken when the air temperature was 4 degrees above zero Fahrenheit. I opened the pop door and let them decide what they wanted to do. They don’t like a cold wind and will seek protection if a cold wind is blowing. But as long as it is calm, they go about their business as if nothing is wrong.
Much building material comes in 4’ and 8’ dimensions. If you take this into account when planning your coop, you can often provide extra space with less cutting and less waste of materials for the same price.
That’s enough of the general stuff. There are some management issues. Do you plan to raise your dual purpose for meat or are you planning on getting the Cornish Cross, Cornish X, broilers, meaties, whatever you want to call them? If it is the broilers I suggest a separate coop for them. They are only going to be around for a couple of months at the most, they need a special diet, why go through an integration with them, and they are just messy.
If it is your own dual purpose, are you planning on using an incubator or a broody to hatch eggs? If you are planning on using a broody, there are some issues. As I said earlier, Mama needs extra room to work so go bigger than the absolute minimum. But you are taking a risk depending in a broody. Not all hens go broody at all and very few go broody when you want them too. If you really plan on eating 24 chickens a year, I think you need to plan on an incubator and raising them yourself.
Something else to consider with dual purpose birds. You probably will not want to process them until they are at least 4 months old and may want to go longer. They just grow a lot slower than the broilers. I don’t even consider processing on until they are at least 16 weeks old and prefer a few more weeks.
Then you have the issue of how you feed them. If you provide all they eat, it can get expensive. The broilers are much more efficient in converting feed to meat. But if you can provide good forage, they will eat a lot less. They will still eat a lot and how much forage they eat depends on the quality of the forage.
If you are planning on eating your dual purpose hatched from your eggs, I still suggest you consider a separate coop. Build you main coop bigger than you think you need it. That gives Mama room to work if you get a broody and she raises them with the flock. It also gives you flexibility if you decide to integrate some replacement layers when yours start to get old and production declines.
I don’t know how many you plan to raise at a time for the table. But I’d make a separate coop that can be used as a brooder and a grow-out coop. For the brooder, I suggest making it plenty big with decent ventilation up high and a good draft guard down low. Keep one are warm and let the rest cool down to ambient. Don’t worry how cold that ambient is as long as you keep one small area warm. This does a few things. You don’t have to worry about keeping the entire brooder a perfect temperature. Too much heat can kill them faster than them getting cold. By keeping one area warm and letting the rest cool off, they will find their comfort zone. Many people would be surprised how much time very young chicks spend in the colder areas of the brooder, only coming back to the heat when they need to warm up.
Allowing them to play in the cooler parts of the brooder also acclimates them. They feather out faster and can handle colder temperatures a lot better than chicks raised in a sauna.
I’d go bonkers trying to keep all of a brooder one perfect temperature. Let them do the work. A big brooder with heat on only one spot and the rest cooler takes the worry out of it as long as you keep the heat in that one spot.
I do something fairly similar to what you are talking about with my dual purpose chickens. My main coop is 8 x 12. I made it by boxing off the end of an existing shed so the 12’ was set. I just had to decide how wide to make it. My basic flock is 7 hens and one rooster but I practically never have that few. I currently have 28 in there of varying ages. Eleven are 11 week old chicks and most of the rest are pullets just waiting on freezer space and me to evaluate their laying so I know which few to keep.
I built a 3’ x 6’ brooder in the main coop, under the roosts so it doubles as a droppings board. The main reason the brooder is in the coop and not separate is that I have electricity already there.
I built a 4’ x 8’ grow-out coop separately. This is just a place with roosts and feed and water. I’ve kept as many as 17 in here until butchering age. Keeping that many in there does restrict my management options some for a short period. It doesn’t matter when they are fairly young but just as they are reaching butchering age it gets really crowded.
In between the two coops I have a 12’ x 32’ run, partitioned off in 24’ and 8’ sections that can be isolated or can be opened to use as one. Each section has a door to the outside. Because of predator problems I have electric netting around an area maybe 30‘ x 65’ for them to range in. I used to just let then totally free range but too many people drop dogs off out here in the country. I got tired of shooting dogs and losing chickens.
I move my chicks from the brooder to the grow-out coop at about 5 weeks age. I keep them in the coop only for a week or so, then let them out in the 8x12 run section for a couple of weeks. Once I’m comfortable that they are going into the coop to sleep at night and consider it home, I start to let them alternate with the rest in that electric netting area, chicks one day the adults the rest. Usually when they are about 8 weeks old, I let them all run together.
If a hen goes broody I always give her eggs to hatch. She raises them with the main flock and they sleep in the main coop.
I know this is really long but hopefully you can get something useful out of it. Good luck!!!
