An often underestimated and unknown problem is a bad ventilation in your loft. Because the fresh air can enter your loft, but then „drizzles“ on your pigeons, the upper airways of your pigeons will be heavily burdened. They will start to sneeze and will be sensitive for chlamydia and ornithosis. Then you will be giving treatments over and over again, but the problem will not be solved.
It is important that the fresh air that enters via the front side, will also be aspirated. The only right place for that is through the roof, via a pipe that stands out over the highest point of the roof. By the wind that blows along the pipe, the „dirty“ air will be aspirated.
To avoid draught, in a loft with a saddleback roof, you can make a ceiling over the pigeons‘ compartiments, up to the place where the pipe goes through the roof. So not a completely closed ceiling.
In lofts with a flat or sloping roof you can make an opening in the front and in the rear for air-refreshment. When you make this at the top of the wall, the pigeons will not be affected by draught, the current will flow over the pigeons. If need be, you can make a small piece of ceiling above the pigeons‘ compartments. If you also open a window at the front, the air will also flow up and out swiftly, normally it also will not reach the pigeons‘ compartments. You can make the airflow visible by, for example, light a smoke tablet in your loft. This way you will immediately see clearly how the airflow goes.