Factors influencing environmental temperature and humidity in intensive broiler houses during the post‐brooding period

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Abstract
Details are given of the environmental temperature and humidity conditions which occurred in 15 commercial houses containing broilers weighing between 1.4 and 1.8 kg. The relative humidity of these houses was related to climatic relative humidity. House relative humidity levels which were reduced by increased standards of thermal insulation, by background heating and by correct floor construction, did not fluctuate as widely when temperature and ventilation were controlled by thermostatically operated extraction fans as when the fans were manually controlled. The condition of the litter was correlated with house relative humidity; mean weekly relative humidity levels higher than 72 per cent saturated were associated with caking of the litter surface. During winter, house temperatures higher than 15° C. were achieved when the outside temperature fell to 0°C. or below only where the ventilation was automatically controlled and where the insulation contained an infill of at least 2.5 cm. thickness of mineral wool. In more poorly insulated buildings, similar temperatures were rarely achieved, even when background heating was provided throughout rearing. Studies of temperature gradients at floor level in broiler houses showed that these were partly due to large and non‐baffled air inlets whose air throughputs were affected by variations in wind speed and direction. Data of house temperatures in relation to windspeed suggest that air velocities through baffled inlets should be at least 150 m./min. at the point of greatest restriction to air flow. However, if air inlet velocities of this magnitude are used, careful design is necessary in order to prevent draughts at bird level. Observations are also presented on the incidence, causes and effects of structural condensation in broiler houses.