I have another take. With my chickens two types of management are at play.
One group is kept outside, sometimes roosting isolated in trees with very little in the way of even windbreaks. Such conditions can be harsher than what birds from much further north experience when the latter are in some sort of enclosed structure, especially when multiple birds are cozy along a perch. With exception of frostbite issues effecting combs and wattles, they can survive if not thrive even during the coldest winters so long as they are in good weight, good feather, good health, and well nourished. With those birds the concept of draft is at best confusing or simply not relevant.
The other type of management involves production birds that are either growing or in lay. Those birds in production are much more sensitive to low temperatures. For birds growing, they are also in a more or less continuous turnover of feathers that are considerably less effective as insulation. Hens in lay are already devoting a large portion of their energy intake into egg formation. As they have to invest more energy in keeping warm, they reach a limit where egg production competes with staying warm so less can be invested in the actual eggs. Nutrition in the form of fat, protein and carbohydrates directed to eggs can not be metabolized to produce heat. That means when conditions get to point where heat loss exceeds a certain point, then production slows and and some point is arrested. I can see both with my production birds in less protected areas.
The keeping of birds in the coops and hen houses makes a huge difference where the ambient temperature is raised by birds themselves plus you have the cozy thing going on. That system has limits largely imposed by moisture buildup which requires ventilation to resolve. Increasing ventilation decreases temperature if outside air is really cold. If temperature reduction related to ventilation is great enough, then there a point where production benefits from adding heat to the system. The birds may not require the additional heat to stay alive, but their ability to produce can benefit.
OP, if you are after eggs and production drops off when temperatures get really low, then adding a heat source can be good so long as you control fire risk. The amount of heat is not that much, may be a few degrees above what it would be without additional heat will work. I will be honest and indicate I do not know what the minimum temperature that is needed to support good egg production is. It is not something I have really tried to a handle on thus far. I do know commercial egg producers supply heat as needed to optimize production by reducing feed needs and help keep birds in liquid water.
One group is kept outside, sometimes roosting isolated in trees with very little in the way of even windbreaks. Such conditions can be harsher than what birds from much further north experience when the latter are in some sort of enclosed structure, especially when multiple birds are cozy along a perch. With exception of frostbite issues effecting combs and wattles, they can survive if not thrive even during the coldest winters so long as they are in good weight, good feather, good health, and well nourished. With those birds the concept of draft is at best confusing or simply not relevant.
The other type of management involves production birds that are either growing or in lay. Those birds in production are much more sensitive to low temperatures. For birds growing, they are also in a more or less continuous turnover of feathers that are considerably less effective as insulation. Hens in lay are already devoting a large portion of their energy intake into egg formation. As they have to invest more energy in keeping warm, they reach a limit where egg production competes with staying warm so less can be invested in the actual eggs. Nutrition in the form of fat, protein and carbohydrates directed to eggs can not be metabolized to produce heat. That means when conditions get to point where heat loss exceeds a certain point, then production slows and and some point is arrested. I can see both with my production birds in less protected areas.
The keeping of birds in the coops and hen houses makes a huge difference where the ambient temperature is raised by birds themselves plus you have the cozy thing going on. That system has limits largely imposed by moisture buildup which requires ventilation to resolve. Increasing ventilation decreases temperature if outside air is really cold. If temperature reduction related to ventilation is great enough, then there a point where production benefits from adding heat to the system. The birds may not require the additional heat to stay alive, but their ability to produce can benefit.
OP, if you are after eggs and production drops off when temperatures get really low, then adding a heat source can be good so long as you control fire risk. The amount of heat is not that much, may be a few degrees above what it would be without additional heat will work. I will be honest and indicate I do not know what the minimum temperature that is needed to support good egg production is. It is not something I have really tried to a handle on thus far. I do know commercial egg producers supply heat as needed to optimize production by reducing feed needs and help keep birds in liquid water.
