I've been wondering about ventilation. I have noticed on several chicken coops that that comes in the form of small windows towards the top of the coop. Do I need to worry at all that my ventilation windows will make it too cold for my birds in the winter time?
If you plan out your ventilation correctly it shouldn't be "too cold" - the issue isn't the actual temperature but drafts. Ideally you want to put much of your ventilation up high, well above the heads of roosting chickens, to let moist air rise up and out. Plus roof area is a great place to put in a lot of ventilation that will remain protected from most weather. You can do combinations of ridge, gable, soffit, under eave vents for that purpose.
You also need to take into account your location and how the wind flows in your area. Obviously you don't want large, open vents facing into prevailing winds. But you can use louvered covers or buffers to blunt that. Or just put the majority of your ventilation facing other directions.
I personally like windows for letting in both air and light. Windows that can close, especially awning style ones, are good for dealing with bad periods of weather.
DobieLover's coop has really good examples of ample ventilation in a colder climate.