How cold is to cold without a light at night?

[Gamecock]

My husband went out of his way to build a very nice coop. with removeable plexiglass windows on both sides, a nest for each hen, we will be able to lift up the top of the nest area to get eggs, he designed it carefully, but we still need to run wire for lighting , the chicks are 9weeks old and we bring them in at night for fear they will get to cold at night. Lows are in the 50s. They are getting to big for the brooder.

 

[gkeesling]

Temps on the 50's are not low at all for chickens that are fully feathered. You could leave them out in zero degrees at night if they coop didn't have a draft running through it. I put my first chicks out in the coop when they were 6 weeks old. I did have a red heat lamp in the coop that turned on at 32 degrees. I did that through January because the temps got down around -10 for a few days on and off. When the temps started getting consistently over 20 degrees I took the heat lamp out. My hens are now a year old. I won't use a heat lamp in the coop unless the temps get down below zero for a few days straight.

 

[Akane]

The main thing is the change in temperature. Even if they are old enough to withstand freezing they may die if they go from a 70F brooder to 50F outside. I killed a couple earlier this year because of that. They were more than old enough to withstand the cooler temps on the porch but inside it was an even 72F so outside with the temp being cooler and changes between day and night they became inactive and 2 died before we figured out why. You don't want to change the temp more than 5-10F at a time and wait for them to adjust and start running around not caring about the cold before lowering it again.