Questions on drafts and disinfectant

I think it might be a good idea to seal your concrete floor. And yes, you might want to disinfect it once a year. Certainly couldn't hurt.

Chickens can handle quite a bit of cold. But they need to be dry and out of drafts. Openings across from each other, so the breeze can go straight through, is what causes drafts. Drafts are good when it's hot, so I would leave all windows open when it's warm. You might want to close at least one window at the roost level, when it starts to get close to freezing, so you won't have a draft. I would definitely leave the high window open all year for ventilation.

 

if you disinfect with bleach, a one part bleach to 9 parts water mix is great. bare cement is cold in winter, i would put some hay/shavings/litter down. i would say any air movement below 75 at night would be a draft, in my opinion. If u cant make the whole coop air tight on the cool drafty nights, designate one corner and make it cozy, with perches, nest box, etc. i do all sorts of temporary things to my coops in the winter, using plastic, shavings, hay, rubbermaid boxes, caulk, spray foam, insulation board, etc, and in summer im trying to move as much air as possible with fans, moving chicken tractors to get more wind, and opening everything up. We go from 110 in the summer to snow on the ground for 5 days last winter.

 

Drafts are at floor level or across the roost. You need high ventilation-anything besides windows? If the air doesn't blow directly across the roost, you can leave a window open or cracked. Better to leave all windows cracked than to close them up tight, but you just don't want air blowing across them while roosting in winter.

 

If I had a concrete floor, I'd seal it at least, but I'd also cover it with a wooden floor and wood shavings.
Having a concrete floor or stepping stones under a wooden floor is an ideal situation; nothing can dig its way into your coop.
During spring, summer, and fall I leave the windows open to catch any cooling breeze that comes along.
During winter, I close all windows/doors/pop doors tightly, and make sure there's lots of ventilation at least two feet above the roost level.

 

No one has really addressed your ultimate question yet: when to close down the windows at roost level.

If it was me, I'd go ahead and do it with night time temps in the 40's. If you find it getting too warm in the coop during the daytime with the windows closed, you could always open them in the day and close them back down at night, right?

Chickens would probably be ok in drafty conditions at temperatures lower than the 40's, but why take any chances when it's so easy to eliminate the draft? That's my thinking, anyway.

Your 6.8 square feet of "other" ventilation should be plenty for 7 chickens, and keep humidity in your coop down below levels where frostbite becomes a problem. If you really want to keep an eye on humidity (other than using your nose and sniffing for ammonia levels), you can put one of those combination temperature/humidity sensors in your coop. I have a remote unit that lets me check the temperature and humidity of the coop from the comfort of my own bedroom. It's nice to have for those of us that tend to be worriers.

Unless you have a particular breed of chicken that's not cold hardy, your chickens will do fine even in a bitterly cold winter if they have a dry, draft free but adequately ventilated coop. They come with down coats, after all!

If you do use bleach as a disinfectant, let it dry and air out thoroughly before you return the chickens to the coop. Chickens, like other birds, have very efficient respiratory systems and are susceptible to airborne pollutants. I know that if you mix bleach and ammonia, you'll create chlorine gas (very toxic), but I'm not sure whether or not ammonia from chicken poop could cause the same chemical reaction. In any event, don't return the chickens to the coop until there is no more bleach smell.

Oh, forgot to include this excellent link on the subject of the winter coop:

https://www.backyardchickens.com/web/viewblog.php?id=1642-winter-coop-temperatures