I would avoid this too. They just need their normal diet. Feeding corn can lead to fat chickens and fat chickens live much shorter lives.
Make sure their crops are full before going to roost.
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It depends on your setup. I have fresh air coming in through the permanently open pop door seen below the poop boards. I have a second one on the south facing wall in the brooder room near the front of the coop.
The windows around the roosts are kept closed during winter and opened wide during summer. All the light coming in over the roosts is permanently open. There is also a ridge vent and a matching gable vent in the brooder room.
Post pictures of your coop for ideas on where and how to add ventilation or start a new thread in the Coop & Run Forum.