When we place day old chicks, we have to make sure that the floor and the air is warm enough for the birds to be comfortable. We do not only need to heat the house, but we also need to ventilate. When we calculate the rate of ventilation, it turns out that we have to ventilate actually much more than we expect.

Theoretically, the rate of venilation that we need for exchanging oxygen and carbon dioxide is approximately 0,35 to 0,4 m3 of air per kg of live weight per hour. This means if we have placed 40.000 chicks of 40 grams, the theoretical ventilation would be 40.000 x 0.04 x 0.4 = 640 m3 of air per hour, which is a very low amount.

In reality we often need to ventilate much more to keep the carbon dioxide at an acceptable level. This is because we do not only have to ventilate for the birds, but we have to ventilate for the carbon dioxide used by the heaters as well. The heaters are producing much more carbon dioxide than the birds, and to keep the carbon dioxide at an accepable level, we often have to ventilate up to 5 times more than what the birds by themself require.

This makes the role of insulation of the house quite important. If the house is poorly insulated, we need to run the heaters more to keep up the temperature. If the heaters run more, they produce more carbon dioxide, and we have to venilate more to get rid of it. With that, we bring more cold air from outside into the house, the temperature drops because of that, and we need to use the heaters more, producing more carbon dioxide.

Systems with indirect heating do not produce carbon dioxide in the house, and they can deal with much lower levels of ventilation.

Ventilation during the first days after placement of the birds is not so much directed by the oxygen consumption and the carbon dioxide production of the birds, but much more by the heaters. The ventilation rate is therefore depending on the set up and the quality of the house, and not so much by the numbber of birds placed.