Ventilation rates and gaseous emissions from naturally ventilated dairy houses

The ventilation rate, the emissions of ammonia (NH3) and methane (CH4), the temperature and the relative air humidity were determined in four naturally ventilated dairy houses with an eave to ridge ventilation. Additionally different climatic data (wind velocity, wind direction, temperature, relative air humidity) were measured in the outside area. The houses differed mainly with respect to their size, the livestock, and the manure removal system. By means of a stepwise regression the influence of the climatic data on the ventilation rate and the emission was estimated. Depending on the building design, 73-84% of the ventilation rate could be explained by the climatic values. Here, the wind velocity was of outstanding importance. The emissions varied from 113-322 g [NH3] h(-1) and 749-2946 g [CH4] h(-1), respectively. The measurement of the ventilation rate was carried out by a tracer decay method. In order to improve the exactness of the procedure, a system was developed for evenly dosing of a tracer gas at the air inlets and obtaining an air sample at the outlets by the use of calibrated glass capillaries. (C) 2003 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd.