The main role of winter ventilation strategies is moisture control. Because of that, the most important factor in monitoring air quality and ventilation success during the winter is relative humidity. Poultry houses are designed to be ventilated for relative humidity and moisture control. In cold weather, growers tend to under ventilate and slick over the litter. By controlling ammonia with an acidic litter treatment such as PLT® litter acidifier, houses can again be ventilated properly for relative humidity. The best time to measure relative humidity is in the mornings during brooding.
After 14-21 days, the need to vent heat from the house becomes the dominant factor in ventilation. It is important to keep relative humidity between 50-70%. Above 70% for more than 24 hours and the house will begin to become damp and the litter will slick over. Once this happens, the damage is done and difficult to correct. The litter will begin to generate greater amounts of ammonia and this combined with the high humidity will burn up a litter treatment within a matter of hours and cause a grower to burn more fuel later on to rid the house of excess ammonia. The increase in litter moisture will also allow for a bloom of bacteria, fungi, viruses, and coccidia, which can overwhelm even the best health programs. Drying the litter out then disseminates a large number of fungal spores throughout the house. If the relative humidity is below 50%, the dry air will begin to dehydrate the young chicks and will dry out their mucous membranes. This makes them more susceptible to respiratory disease and is similar to what happens to humans on a long airplane trip.
The easiest way to measure relative humidity is with a simple digital humidity meter or hygrometer. These are available from a large variety of sources and range from $15-100. Simply place the hygrometer on the feed line when you enter the house in the morning and let it sit for 10-15 minutes and take a reading. The hygrometers should not be left in the house because they easily become clogged with dust.
If the relative humidity is above 70% increase fan time by 15-30 seconds. If the relative humidity is below 50%, decrease fan time by 15-30 seconds. It’s that simple. Stationary humidity sensors connected to the house’s controller do not work well for very long and are not recommended.