You can certainly heat your coop if you want; nothing wrong with it. The only downside would be if you had a power outage during the winter and the birds weren't used to really cold weather-the situation zark mentioned. I also like to think my girls are fairly comfortable, so if the weather turned especially bitter, I might leave the heatlamp over the waterer on all night rather than a couple of hours in the morning. Between their own body heat and that lamp in the insulated coops, they'd be okay. I think we were just saying they would be fine without heat, but it is absolutely not wrong to want your birds to be comfortable.