How much temp improvement should a coop have

The smaller the coop the less temperature differential there will be between indoors and out (all other things being equal). Also, differences indoor vs out tend to be greater on colder nights than they are this time of year, for insulated coops anyhow.

One thing you can do is fiddle with the ventilation and see how much you can close down and still have it be adequate (i.e. not high humidity or stinky in there).

Many chickens do fine in pretty cold temperatures though, so if you've chosen your breeds wisely and keep the coop clean and dry and all that it is not necessarily *required* to have the coop much warmer than outdoors. (Although I think it's always handy to have the capacity to run a lamp just in case of unforseen circumstances, even though you do not plan on using it)

GOod luck, have fun,

Pat

 

chickens do well in cols weather for the most part. As long as they are draft free you should be ok with an insulated coop.